Cephalometric analysis of Malay children with and without unilateral cleft lip and palate

80% 40% K 80% 40% C 80%� 40% M 80% 40% Y 80% 40% K 80% 40% C 80%� 40% M 80% 40% Y 80% 40% K 80% 40% C 80%� 40% M 80% 40% Y 80% 40% K 80% 40% C 80%� 40% M 80% 40% Y 80% 40% K 80% 40% C 80%� 40% M 80% 40% Y 80% 40% K 80% 40% C 80%� 40% M 80% 40% Y 80% 40% K 80% 40% C 80%� 40% M 80% 40% Y 80% 40% K 80% 40% C 80%� 40% M 80% 40% Y 80% 40% K 80% 40% C 80%� 40% M 80% 40% Y 80% 40% K 80% 40% C 80%� 40% M 80% 40% Y 80% 40% K 80% 40% C 80%� 40% M 80% 40% Y 80% 40% K 80% 40% C 80%� 40% M 80% 40% Y 80% 40% K 80% 40% C 80%� 40% M 80% 40% Y 80% 40% K 80% 40% C 80%� 40% M 80% 40% Y 80% 40% K 80% 40% C 80%� 40%

ContentsOriginal articles109 Indirect bonding – do custom bases need a plastic conditioner? A randomised clinical trial

Peter Miles113 The effect of morphine on orthodontic tooth movement in rats

Mohammad S.A. Akhoundi, Ahmad Reza Dehpour, Mahsa Rashidpour, Mojgan Alaeddini, Mohammad JavadKharazifard and Hassan Noroozi

119 Initial and fatigue bond strengths of chromatic and light-cured adhesivesJune M.L. Lee, George Georgiou and Steven P. Jones

127 A comparative assessment of the forces and moments generated at the maxillary incisors between conventional andself-ligating brackets using a reverse curve of Spee NiTi archwireIosif Sifakakis, Nikolaos Pandis, Margarita Makou, Theodore Eliades and Christoph Bourauel

134 Bond strengths and debonding characteristics of two types of polycrystalline ceramic bracketsKatia Lemke, Xiaoming Xu, Joseph L. Hagan, Paul C. Armbruster and Richard W. Ballard

141 Skeletal and dental changes after rapid maxillary expansion: a computed tomography studyAhmed Ghoneima, Ezzat Abdel-Fattah, Francisco Eraso, David Fardo, Katherine Kula and James Hartsfield

149 Strength of attachment between band and glass ionomer cementElahe Vahid Dastjerdie, Houman Zarnegar, Mohammad Behnaz and Massoud Seifi

153 Lip - tooth relationships during smiling and speech: an evaluation of different malocclusion typesRoozbeh Rashed and Farzin Heravi

160 Effects of orthodontic treatment and premolar extractions on the mandibular third molarsMevlut Celikoglu, Hasan Kamak, Ismail Akkas and Hüsamettin Oktay

165 Cephalometric analysis of Malay children with and without unilateral cleft lip and palateLillybia Emily Ebin, Norzakiah Mohamed Zam Zam and Siti Adibah Othman

171 Factors contributing to stability of protraction facemask treatment of Class III malocclusionYan Gu

178 Effects of rapid-slow maxillary expansion on the dentofacial structuresNihat Kilic and Hüsamettin Oktay

184 Shear bond strengths of buccal tubes Kathiravan Purmal and Prema Sukumaran

Case reports189 The effect of a Clark twin block on mandibular motion: a case report

Catherine O’Shea, Andrew Quick, Gillian Johnson, Allan Carman and Peter Herbison195 Orthodontic treatment of a transmigrated mandibular canine: a case report

Göksu Trakyalı, Sule Kavaloglu Çıldır and Nüket Sandallı 201 Non-surgical treatment of mandibular deviation: a case report

Abdolreza Jamilian and Rahman Showkatbakhsh

Editorial206 Effective orthodontics

Michael Harkness207 Retirement of Michael Harkness

Craig Dreyer

Letter208 Optimal force

Felix Goldschmied

General209 Book reviews 220 In appreciation 223 Calendar216 Recent publications 222 New products 224 Index

AustralianOrthodontic JournalVolume 26 Number 2, November 2010

Australian Orthodontic Journal Volume 26 No. 2 November 2010

28001_aoj_ortho_jnl_26.2_dec 15:06:24 10-11-08 Black Yellow Magenta Cyan Sect 1 Back

Introduction

The advent of the direct bonding of orthodonticattachments to the etched enamel surface in the mid-1960s by Newman1 was a major advance in ortho-dontic treatment. In 1972 Silverman et al.2 describeda method of indirect bonding which involved place-ment of the brackets on a plaster model and thentransfer of the attachments to the patient’s mouth bymeans of a tray. In 1979, Thomas3 refined this tech-nique by bonding the brackets to the model withcomposite resin, thereby creating a custom base,which reduced the flash and facilitated the clean-up.Direct bonding of brackets is still the most popularmethod of attaching brackets to teeth, but indirectbonding is increasing in popularity. In 1990, 7.8 percent of practitioners used indirect bonding, whereasby 2008 the number had increased to 13.2 per cent.4

Initially, bond failure rates for indirect bonding (13.9per cent) were high compared with direct bonding(2.5 per cent).5 However with modifications andimprovements to the technique, the two methods

now have similar bond strengths and failure rates.6–8

As with any orthodontic procedure it is desirable for the technique to be effective and efficient. Withindirect bonding, goals include minimising bond failures while also keeping laboratory and clinicalprocedures to a minimum. There are several recom-mended adhesives and bonding protocols, but limited clinical evidence to support their use. Thevalidities of in-vitro studies of bond strength havebeen questioned which is exemplified by a clinicaltrial revealing that the failure rate of the adhesive wasseven times that reported as being satisfactory in anin-vitro study.9–12 For this reason prospective clinicaltrials are preferred.

Light-cured flowable adhesives and plasma and LEDlights have reduced the handling times for indirectbonding. Clinical trials of indirect bonding havereported that light-cured adhesives have comparablebracket failure rates to chemically-cured adhesives.13,14

In the clinical studies, the composite resin custombases were lightly microetched in the laboratory and

© Australian Society of Orthodontists Inc. 2010 Australian Orthodontic Journal Volume 26 No. 2 November 2010 109

Indirect bonding – do custom bases need a plasticconditioner? A randomised clinical trial

Peter MilesPrivate practice, Caloundra, Queensland, Australia

Aim: To compare the clinical failure rates over six months of indirectly bonded brackets with and without methyl methacrylatemonomer (MMM) conditioned custom bases.Methods: Thirty-six consecutive patients satisfying the selection criteria were randomly assigned to two groups in a split-mouthstudy design. In Group 1, the maxillary right and mandibular left quadrants were indirectly bonded after the custom bases had been conditioned with MMM. The brackets bonded to the teeth in the contralateral quadrants were not conditioned. In Group 2, the custom bases on the brackets indirectly bonded to the teeth in the maxillary left and mandibular right quadrantswere conditioned and the brackets in the contralateral quadrants were not conditioned. Over the 6-month observation periodall loose brackets were recorded, and the data were compared with a Wilcoxon signed ranks test.Results: Of the 828 brackets placed, six with the MMM conditioning came loose (1.4 per cent failed) compared with five inthe Control group (1.2 per cent failed). The difference was not statistically significant (p = 0.74).Conclusion: These results indicate that conditioning custom bases with methyl methacrylate monomer is an unnecessary stepwhen indirectly bonding brackets.(Aust Orthod J 2010; 26: 109–112)

Received for publication: November 2009Accepted: February 2010

Peter Miles: [email protected]

MILES


then 10 minutes prior to bonding painted withmethyl methacrylate monomer (MMM), which isbelieved to improve adhesion between the base andthe bonding composite.15 Other studies have usedplastic conditioners, such as Enhance AdhesionBooster (Reliance Orthodontic Products, Ithaca, IL,USA) or the unfilled resin Orthosolo (Ormco, Glen-dora, CA, USA) to improve the bond strength.16,17

The only laboratory study evaluating the condition-ing of custom bases found that the highest bondstrengths were achieved when the custom bases weremicroetched.18 Conditioning microetched custombases with Orthosolo resulted in lower bond strengths,particularly if too much resin was applied.19 The evidence suggests that painting a custom base withsome form of plastic conditioner is an unnecessaryprocedure and may even lead to a higher clinical failure rate. With these thoughts, it was decided to compare the clinical failure rates of indirectlybonded brackets with and without conditioned custom bases.

Materials and methods

Forty subjects were prospectively selected from theprivate orthodontic practice of the author for thisrandomised clinical trial. All subjects were informedof the purpose of the study and all agreed to partici-

pate. Subjects were randomly assigned to one of twogroups in blocks of even numbers to ensure that eachgroup had the same number of subjects. Subjectswere excluded if one arch was to be treated, if all teeth(first molar to first molar) could not be bonded at theinitial visit or if the number of teeth was asymmetric.After the enrolment period had ended, it was foundthat four subjects should have been excluded as allbrackets could not be bonded at the initial visit so thetotal number of subjects was 36 (Figure 1). All sub-jects (17 in Group 1, 19 in Group 2) completed thetrial. There were 21 females and 15 males and themean age of the subjects was 14.2 ± 1.5 years. A total of 828 brackets was placed (Maxilla: N = 406;Mandible: N = 422).

The custom bases on the brackets bonded to the teethin the maxillary right and mandibular left quadrants(from first molar to central incisor) were painted withMMM (Orthocryl, Dentaurum, Pforzheim, Ger-many) 10 minutes prior to bonding, whereas no con-ditioning agent was applied to the bases bonded tothe teeth in the contralateral quadrants. In Group 2, the custom bases on the brackets indirectly bond-ed to the teeth in the maxillary left and mandibularright quadrants were conditioned and the brackets inthe contralateral quadrants were not conditioned. Inboth groups the same prescription of precoated

Randomised(N = 40)

Enr

olle

dA

lloca

tion

Fol

low

-up

Ana

lysi

s

Allocated to Group 1 (N = 20)Received allocated intervention (N = 17)

Allocated to Group 2 (N = 20)Received allocated intervention (N = 19)

Lost to follow-up (N = 0)

Analysed (N = 19)Excluded from analysis (N = 0)

Lost to follow-up (N = 0)

Analysed (N = 17)Excluded from analysis (N = 0)

Figure 1. Study design.

brackets (APC II adhesive, 3M Unitek, Monrovia,CA, USA) was used to form the custom bases and allcustom bases were microetched in the laboratory.

After etching the enamel with conventional phos-phoric acid etch for 20–30 seconds, the teeth wererinsed with water and thoroughly dried. A moistureinsensitive primer MIP (3M Unitek, Monrovia, CA,USA) was applied to the teeth prior to bonding andall brackets were bonded indirectly using the flowableadhesive, Filtek Flow (3M ESPE, St Paul, MN, USA).The laboratory and clinical techniques have beendescribed previously.13,14 The only variations fromthis technique were that a flexible inner tray was usedand the hard outer tray was omitted. The flexible traycontaining the brackets was seated with light fingerpressure and the tip of the curing light, to ensure intimate contact between the custom bases and theteeth prior to curing the bonding adhesive.

If the brackets interfered in the occlusion, a compos-ite resin bite plane or wedge (Herculite XRV, KerrCorporation, Orange, CA, USA) was built up on thepalatal surfaces of the maxillary incisors or, if this wasnot suitable, on the buccal cusps of the lower molars,to prevent any contact with the lower brackets. A0.014 inch thermally active NiTi wire (G & H,Greenwood, IN, USA) was the initial archwire. Thenormal wire sequence used after 10 weeks was a0.016 x 0.022 inch thermally active NiTi wire (G &H, Greenwood, IN, USA) and after an additional 10weeks a 0.016 x 0.022 inch stainless steel wire (G &H, Greenwood, IN, USA) was placed as the workingwire. The number of loose brackets over six monthswas recorded for all subjects. Only the first occasion abracket was dislodged was used in the analysis. The data were analysed using a Wilcoxon signedranks test.

Results

Of the 828 brackets placed, a total of 11 bracketscame loose during the study (Table I). Of thesebrackets, six had the MMM applied to the custombases and five brackets were not conditioned. Thefailure rates for the brackets with conditioned anduntreated bases were 1.4 per cent and 1.2 per cent,respectively (p = 0 .74).

In the maxillary arch, three brackets from the MMMquadrants were dislodged, compared with four brackets from quadrants with no monomer applied tothe custom bases (p = 0.71). In the mandibular arch,three brackets from the MMM quadrants failed,compared with one bracket in the non-treated quadrants (p = 0.32).

Discussion

One of our primary goals as orthodontists is to pro-vide quality, evidence-based treatment in an efficientmanner for our patients. Based on the results of thisstudy, the conditioning of custom bases with MMMis an unnecessary step: it did not result in fewer failedbrackets. This result is supported by an in-vitro studywhich suggested that conditioning custom bases withOrthosolo was an unnecessary step when indirectbonding, but microetching the bases was extremelyimportant.18 The present clinical study and the in-vitro study referred to used brackets precoated witheither APC or APC II adhesive from the same manu-facturer (3M/Unitek, Monrovia, CA, USA). Adhesivesfrom other manufacturers may have different compo-sitions and bonding strengths so the results from thepresent study may not be applicable to these adhesives.

Other clinical findings relevant to the effectivenessand efficiency of indirect bonding have been published. Light-cured custom bases are reported toresult in significantly higher bond strengths andlower bracket failure rates than heat-cured compositeresin custom bases.20,21 Another clinical trial foundthat microetching the enamel prior to conventionaletching did not significantly affect the bracket failurerate when indirect bonding, indicating that this is anunnecessary procedure.22 Clinical studies of adhesiveshave found the chemically-cured Maximum Cure(Reliance Orthodontic Products, Ithaca, IL, USA)and light-cured Filtek Flow (now available asTransbond Supreme LV; 3M Unitek, Monrovia, CA,USA) have lower clinical failure rates than the

DO CUSTOM BASES NEED A PLASTIC CONDITIONER?

Australian Orthodontic Journal Volume 26 No. 2 November 2010 111

Table I. Bracket failures over the 6-month observation period.

Total brackets (N = 828) Failed Failure (Per cent) p

Total - Conditioned (N = 414) 6 1.4Total - Not conditioned (N = 414) 5 1.2 0.74Maxilla - Conditioned (N = 203) 3 1.5Maxilla - Not conditioned (N = 203) 4 2.0 0.71Mandible - Conditioned (N = 211) 3 1.4Mandible - Not conditioned (N = 211) 1 0.5 0.32

MILES


chemically-cured Sondhi Rapid Set (3M Unitek,Monrovia, CA, USA).12,14 Although the delaybetween the manufacture of the custom bases and thebonding of the brackets may vary from a few days tothree weeks, delays up to 30 days have no effect onthe bond strength.23 Long delays between impressiontaking and placement of the brackets should beavoided as minor tooth movement could compromisethe fit of the transfer trays and brackets to the teeth.

The bracket failure rates in this study (1.4 and 1.2 percent) were at the low end of the range reported in previous studies of indirect bonding (1.4 to 13.9 percent).5–7,12,14,20 The use of composite bite wedges toprevent the teeth from contacting the brackets mayexplain the lower failure rates in the present study asnot all previous studies used wedges to disclude theteeth.6,5,12,14 To determine if the wedges contributedto the lower failure rate will require further investiga-tion. The findings of the present study indicate thatconditioning custom bases with MMM can be omit-ted without sacrificing bracket retention. Indirectbonding is an effective clinical technique with a lowclinical failure rate over six months. The efficiency ofthe technique can be improved by eliminating unnec-essary procedures, such as conditioning the custombases.

Conclusions

Conditioning custom bases with methyl methacrylatemonomer had no influence on the bracket failurerate.

The bracket failure rates in this study (less than 1.5per cent) were low when compared with the litera-ture, indicating that the method of indirect bondingemployed in the present study is an effective clinicaltechnique.

Occlusal wedges may contribute to bracket retentionby protecting brackets from occlusal trauma.

Corresponding author

Dr Peter Miles10 Mayes AvenueCaloundra Qld 4551AustraliaEmail: [email protected]

References1. Newman GV. Epoxy adhesives for orthodontic attachments:

a progress report. Am J Orthod 1965;51:901–12.2. Silverman E, Cohen M, Gianelly AA, Dietz VS. A universal

direct bonding system for both metal and plastic brackets.Am J Orthod 1972;62:236–44.

3. Thomas RG. Indirect bonding: simplicity in action. J ClinOrthod 1979;13:93–106.

4. Keim RG, Gottlieb EL, Nelson AH, Vogels III DS. 2008JCO Study of orthodontic diagnosis and treatment proce-dures, Part 1: Results and trends. J Clin Orthod 2008;42:625–40.

5. Zachrisson BU, Brobakken BO. Clinical comparison ofdirect versus indirect bonding with different bracket typesand adhesives. Am J Orthod 1978;74:62–78.

6. Read MJ, O’Brien KD. A clinical trial of an indirect bond-ing technique with a visible light-cured adhesive. Am JOrthod Dentofacial Orthop 1990;98:259–62.

7. Aguirre MJ, King GJ, Waldron JM. Assessment of bracketplacement and bond strength when comparing direct bond-ing to indirect bonding techniques. Am J Orthod 1982;82:269–76.

8. Hocevar RA, Vincent HF. Indirect versus direct bonding:bond strength and failure location. Am J OrthodDentofacial Orthop 1988;94:367–71.

9. Eliades T, Brantley WA. The inappropriateness of conven-tional orthodontic bond strength assessment protocols. EurJ Orthod 2000;22:13–23.

10. Swartz ML. Limitations of in vitro orthodontic bondstrength testing. J Clin Orthod 2007;41:207–10.

11. Klocke A, Shi J, Kahl-Nieke B, Bismayer U. Bond strengthwith custom base indirect bonding techniques. AngleOrthod 2003;73:176–80.

12. Miles PG, Weyant RJ. A clinical comparison of two chemi-cally-cured adhesives used for indirect bonding. J Orthod2003;30:331–6.

13. Miles PG. Indirect bonding with a flowable light-curedadhesive. J Clin Orthod 2002;36:646–7.

14. Miles PG, Weyant RJ. A comparison of two indirect bond-ing adhesives. Angle Orthod 2005;75:1019–23.

15. Hickham JH. Predictable indirect bonding. J Clin Orthod1993;27:215–18.

16. Polat O, Karaman AI, Buyukyilmaz T. In vitro evaluation ofshear bond strengths and in vivo analysis of bond survival ofindirect-bonding resins. Angle Orthod 2004;74:405–9.

17. Swartz M. Bond strength of a universal orthodontic bondingagent. Clinical Impressions 2005;14:14–16.

18. Thompson MA, Drummond JL, BeGole EA. Bond strengthanalysis of custom base variables in indirect bonding tech-niques. Am J Orthod Dentofacial Orthop 2008;133:9.e15–20.

19. Waugh RL. Optimizing bond retention. ClinicalImpressions. 2005;14:27.

20. Miles PG. A comparison of retention rates of brackets withthermally-cured and light-cured custom bases in indirectbonding procedures. Aust Orthod J 2000;16:115–17.

21. Klocke A, Shi J, Kahl-Nieke B, Bismayer U. Bond strengthwith custom base indirect bonding techniques. AngleOrthod 2003;73:176–80.

22. Miles P. Does microetching enamel reduce bracket failurewhen indirect bonding mandibular posterior teeth? AustOrthod J 2008;24:1–4.

23. Klocke A, Tadic D, Vaziri F, Kahl-Nieke B. Custom base pre-aging in indirect bonding. Angle Orthod 2004;74: 106–11.

Introduction

During orthodontic tooth movement a series of com-plex changes occur in the alveolar bone cells and periodontal ligament. These changes are mainly con-trolled by osteoblasts and osteoclasts in a processcalled ‘coupling’.1 Factors such as certain drugs/medication taken during orthodontic treatment caninterfere with the remodelling mechanisms and affecttooth movement.2–4 The same drugs can be used in experimental studies to explore some of the mechanisms controlling tooth movement.

Non-steroidal anti-inflammatory drugs (NSAIDs),which are taken for pain control during orthodontictreatment, prevent the conversion of arachidonic acidto prostaglandins and so reduce the amount of tooth

movement.5,6 Opioids, which are categorised asexogenous and endogenous, can also interfere withbone metabolism.7,8 Opioid receptors (mu, delta andkappa) can be found in the cells of the central nerv-ous system and in other cells,4,7,9,10 and opioid recep-tors in osteoblast-like cells are connected with thestructure and metabolism of bone.4,11

Opioids may either increase or reduce the rate oftooth movement. For example, endogenous opioidsinteract with nitric oxide in cholestatic rats andincrease the rate of tooth movement, but exogenousopioids taken for pain relief (e.g. acetaminophencodeine) may have an entirely different effect.12–14 Arecent study of Iranian high school and universitystudents reported that 91 per cent resorted to self-medication to relieve pain and acetaminophen


The effect of morphine on orthodontic toothmovement in rats

Mohammad S.A. Akhoundi,* Ahmad Reza Dehpour,† Mahsa Rashidpour,+ MojganAlaeddini,+ Mohammad Javad Kharazifard+ and Hassan Noroozi+

Departments of Orthodontics* and Pharmacology,† and the Dental Research Center,+ Tehran University of Medical Sciences, Tehran, Iran

Objectives: To investigate the effect of morphine as an exogenous opioid on orthodontic tooth movement. Naltrexone will beused as an opioid antagonist to confirm the results.Methods: Forty rats were randomly divided into four equal groups. The first group received no injection; the second groupreceived daily injections of morphine; the third group received daily naltrexone-morphine injections and the fourth group dailyinjections of naltrexone-normal saline. The left first maxillary molar in each rat was tipped mesially with a NiTi closed coilspring. The rats were sacrificed after 14 days and the maxillae fixed, sectioned serially and examined histologically.Results: The greatest amount of tooth movement occurred in the Control group and the least amount of tooth movement in theMorphine group. Tooth movement in the Morphine group was significantly different from the other three groups (p < 0.05). The differences in tooth movement in the Control, Morphine-naltrexone and Naltrexone-saline groups were not statistically significant (p > 0.05). No statistically significant histological differences were found.Conclusions: Morphine reduced orthodontic tooth movement in rats. This effect was reversed by the opioid antagonist, naltrexone, which had no effect on tooth movement.(Aust Orthod J 2010; 26: 113–118)

Received for publication: April 2009Accepted: February 2010

Mohammad S.A. Akhoundi: [email protected] Reza Dehpour: [email protected] Rashidpour: [email protected] Alaeddini: [email protected] Javad Kharazifard: [email protected] Noroozi: [email protected]

AKHOUNDI ET AL


codeine was the most commonly used analgesic.15

Since orthodontic treatment can be painful andpatients may resort to self-medication we decided toinvestigate the effect of morphine, an exogenous opioid, on tooth movement in the rat. We used nal-trexone, an opioid antagonist, which binds opioidreceptors in a non-selective manner, to confirm theaction of morphine on tooth movement.16

Materials and methodsAnimalsForty male Wistar rats between 200 and 250 g bodyweight were used. The animals were housed in plasticcages, with a 12/12 hour light-dark cycle. They werefed soft laboratory food to minimise any discomfortfrom the appliances and to reduce the risk of an appliance being dislodged or deformed.12 The experi-mental protocol was approved by the EthicsCommittee of Tehran University of Medical Sciences.

The animals were weighed on the day the applianceswere placed and immediately before death. All animals had an orthodontic appliance consisting of aNiTi closed coil spring ligated to the left maxillaryfirst molar and both upper incisors. The rats wererandomly divided into four equal groups. The firstgroup received no injection, the second groupreceived a daily injection of morphine (5mg/kg bodyweight), the third group received a daily injection ofnaltrexone (20 mg/kg body weight)-morphine (5 mg/kg body weight) and the fourth group received

a daily injection of naltrexone (20 mg/kg bodyweight)-normal saline. All injections were adminis-tered intra-peritoneally at 24-hour intervals for 14days.17

Orthodontic appliance and measurementof tooth movementEach rat was anaesthetised with an intra-peritonealinjection of chlorpromasine (30 mg/kg body weight)and ketamine (50 mg/kg body weight). The maxillaryleft first molars were tipped mesially using 6 mm0.006 x 0.022 inch NiTi closed coil springs for 14days.12 The springs were anchored at the ends with0.010 inch stainless steel ligature wires tied to the leftmaxillary first molars and the upper incisors (Figure 1).The molar ligature wires were passed between the firstand second molars and tied around the cervical mar-gins of the first molars. The anterior ligature was tiedaround the incisors and secured in shallow groovescut into the labial and distal surfaces of the incisors,close to the gingival margins. A small amount oflight-cure composite resin was placed over the liga-ture wires to protect the wires from damage. Eachspring was activated about 1 mm to deliver a 60 gmesial tipping force and it was not reactivated duringthe course of the study.18,19 After insertion of theappliance, the crowns of the lower incisors werereduced 1.5 mm to prevent the incisors from cuttingthe ligature wires.

Mesial movement of the first molar was measured atthe start and end of the experiment with a filler gaugeinserted between the first and second maxillary leftmolars. The initial distance between the molars waszero in all animals. The final measurement was car-ried out following decapitation, but before the appli-ances were removed and potential relapse of the firstmolar into the space between the molars. All meas-urements were repeated twice by the same operator,who was blinded to the treatment each rat hadreceived. The intraclass correlation coefficient (ICC)between the two sets of measurements was .984.

Histological evaluationThe maxillae were fixed in 10 per cent formalin for10 days and decalcified in 5 per cent formic acid for 4 days. The decalcified maxillae were embeddedin paraffin and parasagittal serial sections of themesial roots of first molars cut and stained withhaematoxylin and eosin.20

Figure 1. Schematic view of the appliance.

From each tooth, six sections that showed the fullwidth of the root from the cemento-enamel junction(CEJ) to the apex were examined under an OlympusBx-41 light microscope (Figure 2). Root resorptionand the width of the periodontal ligament (PDL) sur-rounding the mesio-buccal root were evaluated withthe aid of an eyepiece graticule with the accuracy of10 µm. The number of resorption lacunae and theirmaximum depths were used to determine the amountof root resorption (Figures 3 and 4). The latter weremeasured using the method described by Sekhavat etal.21 Apparent ‘roughness’ of the dentine or cementum

was considered as resorption. Thus, each section pro-duced a number representing resorption and themean of the six representative sections determinedthe amount of resorption affecting a tooth. The number of osteoclasts was also used to determinebone resorption.

The width of the PDL was measured on the mesialand distal surfaces of the root in the most coronal andapical regions.22 All sections were measured twice bythe same operator and the mean of the two measure-ments used in all subsequent calculations.

EFFECT OF MORPHINE ON ORTHODONTIC TOOTH MOVEMENT


Figure 2. Parasagittal section of the mesio-buccal root of an upper first molarin the Morphine group. The tooth was moved from right to left. Originalmagnification x40.

Figure 3. Resorption lacunae on the mesial surface of the mesio-buccal rootof a first molar in the Morphine group. Original magnification x100.

Figure 4. An osteoclast (circled) on the mesio-buccal root of a specimen inthe Morphine group. Original magnification x200.

Morphine Naltrexone-saline

Toot

h m

ovem

ent

(mm

)

Naltrexone-morphine ControlGroups

.3

.2

.1

0.0

Figure 5. Tooth movement in the groups. Means and SD bars are shown.

AKHOUNDI ET AL


Statistical analysisDifferences between the groups were analysed by theone-way ANOVA followed by Tukey post-hoc testsfor multiple comparisons. The statistics were analysedwith SPSS 11.5 software. Probability values < 0.05were considered as statistically significant.

Results

There were no statistically significant differences inthe mean overall weights of the groups. All firstmolars showed evidence of tooth movement (Table I).Among the groups, the Control group showed great-est mesial movement (Mean: 0.170 mm) and theMorphine group (Mean: 0.081 mm) the least mesialmovement (Figure 5). The first and second molars inthe Morphine group were significantly less separatedthan the molars in the other three groups (p < 0.05).The differences between the Control, Morphine-naltrexone and Naltrexone-saline groups were not statistically significant (p > 0.05).

Osteoclasts were found lining the bone on the mesialsurfaces of the roots in all groups, but there were nostatistically significant group differences in the number of osteoclasts (p > 0.05). Although the resorp-tion lacunae in mesial roots in the Morphine groupwere fewer and shallower than the lacunae in theother groups, the differences were not statistically significant (p > 0.05). There were no significant dif-ferences in the widths of the PDL on mesio-apical,disto-apical, mesio-coronal and disto-coronal areas ofthe mesio-buccal root (p > 0.05).

Discussion

We determined the magnitude of tooth movement inrats administered morphine, an exogenous opioid, bymeasuring separation of the maxillary first and secondmolars following mesial movement of the first molar

with a simple orthodontic appliance. We found thatmorphine (an exogenous opioid) reduced the amountof tooth movement and this effect was reversed bynaltrexone. We found no differences in tooth move-ment between the groups that received naltrexoneeither with morphine or with saline, or the Controlgroup, which suggests that the naltrexone did not affect tooth movement. Our histological methodsfailed to disclose supporting differences in the number and depths of resorption lacunae or thewidth of the PDL.

Previous studies have shown that opioids affectosteoblasts and bone remodelling.4,7 Since there arethree opioid receptors (mu, delta and kappa) onosteoblast-like cells (MG-63), the high concentrationof morphine, as an agonist of mu receptor sites, pre-vented the synthesis of osteocalcin, which is a markerof osteoblastic activity.7 Rosen et al. suggested theexistence of opioid receptors in osteoblasts and con-firmed the presence of specific mRNA of kappareceptors in rat osteoblasts.4,23

Our results can be compared with a study of the roleof opioid systems on orthodontic tooth movement incholestatic rats.12 Endogenous opioids in cholestasicanimals may interfere with bone remodelling byaffecting osteoblast-like cells and, in turn, increasingthe rate of orthodontic tooth movement.12 In theseconditions, endogenous opioids interacting withnitric oxide were thought to be responsible for theincreased rate of orthodontic tooth movement.24,25 Inthese studies, naltrexone blocked the increase inendogenous plasma opioids and inhibited the rate oforthodontic tooth movement, whereas we found it had no effect on the rate of tooth movement. Itappears that endogenous and exogenous opioids havequite different effects: endogenous opioids increasetooth movement and exogenous opioids reduce it.Part of the answer may lie with the strength and/or

Table I. Molar separation over 14 days.

Group N Mean SD SE 95% CI Minimum Maximum

(mm) Lower Upper

Morphine 10 0.081 0.029 0.009 0.060 0.102 0.05 0.15Naltrexone - morphine 10 0.164 0.069 0.022 0.114 0.214 0.10 0.30Naltrexone - saline 10 0.162 0.061 0.019 0.119 0.205 0.08 0.25Control 10 0.170 0.089 0.028 0.106 0.233 0.10 0.35

dosage of the opioid used. For instance, codeine is arelatively weak opioid, but morphine and heroin arestrong opioid agonists, and pentazosine is an agonist-antagonist opioid. The latter appears to work as akappa agonist and mu antagonist.9

We measured tooth movement 14 days after appli-ance activation, because the period for completion ofthe bone remodelling cycle is 10–14 days.12,18,26

Although we found a difference in macroscopic toothmovement between the groups there was no statisti-cally significant group difference in the number ofosteoclasts or the maximum depths of the resorptionlacunae. One view of the difference in tooth move-ment is that morphine reduces the activity of osteo-clasts rather than reducing the number of osteoclasts.Our methods did not enable us to confirm or refutethis notion. Future studies should investigate the histological changes over longer periods of time, usehistological methods able to detect smaller changes incell activity and investigate different dosages of morphine.27,28

Our results, which demonstrated that morphinereduced tooth movement in a small laboratory ani-mal, cannot be extrapolated to humans. The resultssuggest that a clinical trial of tooth movement in sub-jects using opiate-based analgesics should be initiatedto determine if small pharmacological doses affectorthodontic tooth movement.

Conclusions

1. Morphine reduces the rate of tooth movement in rats.

2. This effect was reversed by administering the opioidantagonist, naltrexone, which had no effect on ortho-dontic tooth movement.

3. Further studies are needed to investigate the effectsand modes of action of morphine and other opiateson tooth movement in rats and man.


Dr Hassan NorooziDental Research CenterFaculty of DentistryTehran University of Medical SciencesTehranIranTel: +98 21 88986677Fax: +98 21 88986688Email: [email protected]

References1. Newman M, Takei H, Carranza F. Carranza’s clinical perio-

dontology. 9th ed. 2002;47.2. Adachi H, Igarashi K, Mitani H, Shinoda H. Effects of top-

ical administration of a bisphosphonate (risedronate) onorthodontic tooth movements in rats. J Dent Res 1994;73:1478–86.

3. Yamasaki K, Miura F, Suda T. Prostaglandin as a mediator ofbone resorption induced by experimental tooth movementin rats. J Dent Res 1980;59:1635–42.

4. Rosen H, Metzer E, Benzakine S, Bar-Shavit Z. Functionalopioid receptors on skeletal cells. J Bone Miner Res 1997;12:(suppl).411.

5. Zhou D, Hughes B, King GJ. Histomorphometric and bio-chemical study of osteoclasts at orthodontic compressionsites in the rat during indomethacin inhibition. Arch OralBiol 1997;42(10–11):717–26.

6. Chumbley AB, Tuncay OC. The effect of indomethacin (anaspirin-like drug) on the rate of orthodontic tooth move-ment. Am J Orthod 1986;89:312–14.

7. Peréz-Costrillón JL, Olmos JM, Gomez JJ, Barrallo A,Riancho JA, Perera L et al. Expression of opioid receptors inosteoblast-like MG-63 cells, and effects of different opioidagonists on alkaline phosphatase and osteocalcin secretionby these cells. Neuroendocrinology 2000;72:187–94.

8. Hall TJ, Jagher B, Schaeublin M, Wiesenberg I. The anal-gesic drug buprenorphine inhibits osteoclastic bone resorp-tion in vitro, but is proinflammatory in rat adjuvant arthritis.Inflamm Res 1996;45:299–302.

9. Pleuvry B J. Opioid mechanisms and opioid drugs.Anaesthesia and intensive care medicine 2005;6:30–4.

10. Brownstein MJ. A brief history of opiates, opioid peptides,and opioid receptors. Proc Natl Acad Sci U S A 1993;90:5391–3.

11. Rico H, Costales C, Cabranes JA, Escudero M. Lower serumosteocalcin levels in pregnant drug users and their newbornsat the time of delivery. Obstet Gynecol 1990;75:998–1000.

12. Nilforoushan D, Shirazi M, Dehpour AR. The role of opioidsystems on orthodontic tooth movement in cholestatic rats.Angle Orthod 2002;476–80.

13. Saper JR, Lake AE. Continuous opioid therapy (COT) israrely advisable for refractory chronic daily headache: limit-ed efficacy, risk, and proposed guidelines. Headache 2008;48:838–49.

14. Minai-Tehrani D, Minoui S, Sepehre M. Inhibitory effect of codeine on sucrase activity. Drug Metab Lett 2009;3:58–60.

15. Sedighi B, Ghaderi-Sohi S, Emami S. Evaluation of self-medication prevalence, diagnosis and prescription inmigraine in Kerman, Iran. Saudi Med J 2006;27:377–80.

16. Farid W.O, Dunlop S.A, Tait R.J, Hulse G.K. The effects ofmaternally administered methadone, buprenorphine andnaltrexone on offspring: review of human and animal data.Curr Neuropharmacol 2008;6:125–50.

17. Brudvik P, Rygh P. The repair of orthodontic root resorp-tion: an ultrastructural study. Eur J Orthod 1995;17:189–98.

18. King GJ, Fischlschweiger W. The effect of force magnitudeon extractable bone resorptive activity and cemental crater-ing in orthodontic tooth movement. J Dent Res 1982;61:775–9.

19. Igarashi K, Woo JT, Paula H. Effect of a selective cyclo oxygenase-2 inhibitor on bone resorption and osteoclasto-genesis in vitro. Biochem Pharmacology 2001;63:523–32.

EFFECT OF MORPHINE ON ORTHODONTIC TOOTH MOVEMENT


20. Leiker BJ, Nanda RS, Currier GF, Howes RI, Sinha PK. Theeffects of exogenous prostaglandins on orthodontic toothmovement in rats. Am J Orthod Dentofacial Orthop 1995;108:380–8.

21. Sekhavat AR, Mousavizadeh K, Pakshir HR, Aslani FS.Effect of misoprostol, a prostaglandin E1 analog, on ortho-dontic tooth movement in rats. Am J Orthod DentofacialOrthop 2002;122:542–7.

22. Tengku BS, Joseph BK, Harbrow D, Taverne AA, SymonsAL. Effect of a static magnetic field on orthodontic toothmovement in the rat. Eur J Orthod 2000;22:475–87.

23. Rosen H, Polakiewiez RD, Benzakine S, Bar-Shavit ZB.Proenkephaline A in bone-derived cells. Proc Natl Acad SciUSA 1991;88:3705–9.

24. Namiranian K, Samini M, Mehr SE, Gaskari SA, RastegarH, Homayoun H et al. Mesenteric vascular bed responsive-ness in bile duct-ligated rats: roles of opioid and nitric oxidesystems. Eur J Pharmacol 2001;423:185–93.

25. Nahavandi A, Mani AR, Homayounfar H, Akbari MR,Dehpour AR. The role of the interaction between endoge-nous opioids and nitric oxide in the pathophysiology ofethanol-induced gastric damage in cholestatic rats. FundamClin Pharmacol 2001;15:181–7.

26. Gameiro GH, Nouer DF, Pereira-Neto JS, Urtado MB,Novaes PD, de Castro M et al. The effects of systemic stresson orthodontic tooth movement. Aust Orthod J 2008;24:121–8.

27. Rozisky JR, Dantas G, Adachi LS, Alves VS, Ferreira MB,Sarkis JJ, Torres IL. Long-term effect of morphine adminis-tration in young rats on the analgesic opioid response inadult life. Int J Dev Neurosci 2008;26:561–5.

28. Zarrindast MR, Ebrahimi-Ghiri M, Rostami P, Rezayof A.Repeated pre-exposure to morphine into the ventral pallidum enhances morphine-induced place preference:involvement of dopaminergic and opioidergic mechanisms.Behav Brain Res 2007;181:35–41.

AKHOUNDI ET AL


IntroductionA clinically effective bonding adhesive should providea secure bond between an orthodontic attachmentand the tooth surface during treatment, but thenallow removal of the attachment at the end of treatment without damaging the enamel. The searchfor the ideal bonding material in orthodontics hasbeen the focus for much research and development,

leading to the introduction of newer bondingmaterials to the market. In addition to any new properties, an adhesive must also retain the strengthsfound in current adhesives used by clinicians for it to be a viable substitute. The process of developing a new bonding agent relies on effective ex vivo laboratory studies which are commonly carried outprior to clinical trials, although comparisons


Initial and fatigue bond strengths of chromaticand light-cured adhesives

June M.L. Lee, George Georgiou and Steven P. JonesUCL Eastman Dental Institute, London, United Kingdom

Aim: To compare the initial and fatigue shear bond strengths of a chromatic adhesive with a light-cured adhesive in an ex vivolaboratory study.Methods: Hydroxyapatite discs were used as the bonding substrate. They were produced by cold uni-axial compression at 20 tons, sintered at 1300 °C and embedded in epoxy resin before grinding and polishing. One hundred and fifty upper leftcentral incisor brackets were bonded to the discs with Transbond PLUS Color Change (3M Unitek, Monrovia, CA, USA) whileanother 150 similar brackets were bonded with Transbond XT (3M Unitek, Monrovia, CA, USA). Seventy-five brackets fromeach group were subjected to cyclic loading (5000 cycles at 2 Hz) at 50 per cent of the mean bond strength in a DartecSeries HC10 Testing Machine. Initial (unfatigued) and fatigued bond strengths were determined by applying a shear force atthe bracket-substrate interface using a custom-made metal jig in an Instron Universal Testing Machine. One-way ANOVA withBonferroni post-hoc correction and two-way ANOVA were used to analyse the differences between the initial and fatigue meanshear bond strengths of the adhesives. The survival and bond reliability of both adhesives were evaluated with the Kaplan-Meier and Cox regression analyses.Results: The initial mean shear bond strength for Transbond PLUS Color Change (16.72 MPa) was higher than Transbond XT(15.11 MPa), but this was not statistically significant (p = 0.109). The fatigue mean shear bond strength for Transbond XT(15.87 MPa) was similar to that of Transbond PLUS Color Change (15.33 MPa), and the difference was not statistically significant (p > 0.999). There were no significant differences when the effects of the material (p = 0.264) or fatiguing (p = 0.512) were considered separately, but in combination, the effect on bond strength was statistically significant (p = 0.026). The survival analysis showed that both adhesives demonstrated similar survival patterns in the unfatigued andfatigued states. Analysis of the material type and fatiguing showed no effect on the survival pattern for both adhesives (p = 0.098).Conclusions: There were no statistically significant differences between the mean initial (unfatigued) and fatigue bond strengthsof Transbond XT and Transbond PLUS Color Change under laboratory conditions. A survival analysis for both resins with andwithout fatigue loading exhibited similar behaviour with respect to their survival patterns. Although this may imply that under clinical conditions the two adhesives could behave similarly, the clinical extrapolation of these results should be interpreted withcaution.(Aust Orthod J 2010; 26: 119–126)

Received for publication: February 2010Accepted: March 2010

June M. L. Lee: [email protected] Georgiou: [email protected] P. Jones: [email protected]

LEE ET AL


between laboratory studies can be fraught with difficulties due to variations in their methodologyand protocols. This has led to the emphasis on theimportance of standardised test parameters and protocols.1,2

During fixed appliance therapy, patients may be at asignificant risk of developing white spot lesions if oralhygiene is suboptimal.3,4 Chromatic adhesives weredeveloped to aid the removal of flash adhesive duringbonding, since it has been suggested that the removalof flash may reduce plaque accumulation and theincidence of enamel demineralisation. These adhes-ives may either be photochromatic, where the adhesive turns clear on exposure to the curing light;or thermochromatic, where the adhesive turns clearabove 32 ºC and then reverts to its original colourbelow 32 ºC to allow complete removal at debond-ing. Transbond PLUS Color Change adhesive (3MUnitek, Monrovia, CA, USA) is a light-activated photochromatic composite resin that changes from apink-coloured resin to a tooth-coloured resin uponcuring. The manufacturer claims that the colourchanging property aids bracket positioning and flashclean-up around brackets, although this was not sup-ported by a typodont study which found that the useof chromatic adhesive did not result in improvedremoval of excess adhesive and that significantamounts of adhesive flash remained after bonding.5There is limited published data relating to the bondstrength of this material.6,7

Ex vivo laboratory bonding studies have traditionallyused extracted human premolar teeth as the bondingsubstrate and the shear bond strengths of bracketsbonded to human enamel has been reported to be inthe range of 15–20 MPa.8–10 The use of extractedhuman teeth has potential disadvantages whichinclude the inconsistencies of crown contour andmorphology, presence of surface defects and restor-ations, variations in fluoride mineralisation, coupledwith an increasing difficulty in collecting suitableteeth for adequate sample sizes and problems relatedto the storage and sterilisation of human teeth. A pre-vious study considered alternative substrates for themineral phase of enamel, thereby introducing a bio-mimetic approach to laboratory bond strength test-ing. The use of cold-pressed commercially availablepure hydroxyapatite powder has been recommendedas an alternative substrate to enamel for comparativelaboratory studies.11,12

Fatigue can be defined as ‘degradation of materialssubjected to a number of load changes, with a ten-dency to fracture under cyclic stress’. Fatigue failure isa phenomenon whereby stress values well below theultimate tensile or shear stress of a material can pro-duce premature fracture, because microscopic flawsgrow slowly over many cycles of stress.13 The struc-ture eventually fails after being repeatedly subjectedto loads that are so small that one application appar-ently causes no damage. Fatigue may be caused bythermal insults or by mechanical means. During fixedappliance therapy, bonded attachments may be sub-jected to repeated loading from masticatory forces orvia the archwires. These forces vary in frequency,duration and magnitude, and when repeated overlong periods of time may eventually result in struc-tural or fatigue failure. It is important that whenselecting a particular bonding material for clinicaluse, the fatigue resistance of the material is con-sidered, as it will affect the durability of bondedattachments throughout the course of treatment.14

The conventional method for comparing two bond-ing adhesives has been a comparison of their initialbond strengths. However, fatigue testing is a moreappropriate test to investigate the survival and dura-bility of the bonding adhesive in the mouth, since thelife expectancy of an adhesive is influenced by cyclicloading from occlusal forces. Fatigue failure could bea factor in predicting the bond strength and eventu-ally the long-term survival of the bonding adhesive ina clinical environment.15

This study was designed to compare the initial (unfatigued) and fatigue bond strengths of TransbondPLUS Color Change with Transbond XT in a labora-tory setting. The results of this study will form afoundation for future in vivo clinical trials.


Circular hydroxyapatite discs were manufacturedfrom commercially available hydroxyapatite powderCaptal R (Plasma Biotal Ltd., Tideswell, UK) bycold-pressing at 20 tons in a hydraulic press. Thesewere sintered at 1300 ºC in a furnace, allowed to coolto room temperature overnight and then embeddedin acrylic resin before being polished to a standardprotocol. The manufacturing and polishing protocolshave been described in detail.11,12

A small pilot study confirmed that a sample size of 75 per test group would provide 80 per cent power

(α = 0.05). Three hundred upper left central incisor,Victory Series stainless steel brackets (3M Unitek,Monrovia, CA, USA) were bonded to the hydroxyap-atite discs with either Transbond XT (N = 150) orTransbond PLUS Color Change (N = 150) adhesives.The hydroxyapatite discs were etched with 35 percent ortho-phosphoric acid gel prior to bonding,using a standardised bonding protocol.11,12 Fourbrackets were bonded peripherally on each disc inorder to allow the disc to be used for four separateshear tests. These were bonded in two stages usingonly opposing pairs of brackets at any one time toavoid dislodging the other brackets during testing.

The Instron Universal Testing Machine 4505(Instron Limited, High Wycombe, UK) was used tocarry out the shear bond strength testing of the bonded brackets. During testing each hydroxyapatitedisc was held securely in place in the machine with aspecially constructed metal jig (Figure 1). The load

cell used for shear bond testing was 1 kN, at a cross-head speed of 1 mm per minute. Shear force wasapplied to the bracket-disc interface until the bracketfailed. The maximum load at failure was recorded inkilonewtons (kN) and then converted to shear bondstrength in megapascals (MPa) by dividing the maxi-mum load at failure by the cross-sectional surface areaof the bracket base.

Fatigue loading of bonded orthodontic brackets wascarried out in the Dartec Series HC10 (Zwick/Roell,Herefordshire, UK). The cyclic mode of loading inthis machine is designed to simulate repetitiveocclusal forces to which the orthodontic bracketswould be exposed intra-orally. The cyclic load appliedwas 50 per cent of the mean bond strength suggestedby the pilot study. The loading cycle was 5000 cycleswith the load applied in the form of a sine wave at afrequency of 2 Hertz (Figure 2). Once the fatiguecycle was completed, the bracket was then sheared to

SHEAR BOND STRENGTHS OF TWO ADHESIVES


Figure 1. Jig mounted in Instron for bond strength testing, showing twoopposing brackets in position.

Figure 2. Jig mounted in Dartec Series HC10 for cyclic fatigue loading,showing two opposing brackets in position.

LEE ET AL


failure in the Instron machine in order to determinethe bond strength after fatigue cyclic loading.

As suggested from the sample size calculation, 75brackets bonded with Transbond XT Light CureOrthodontic Adhesive and 75 brackets bonded withTransbond PLUS Color Change Adhesive weresheared to failure without fatigue loading (initialbond strength test) and the same number of bracketsfor both adhesives were sheared to failure after fatigueloading.

A modified Kaplan-Meier survival curve was pro-duced by plotting the cumulative survival probabilityagainst the bond strength to failure for the bondedbrackets. This is a useful survival analysis tool todetermine the bond reliability and survival probabil-ity at specific loads. A Cox regression analysis wasused to investigate the simultaneous effect of a number of explanatory variables on survival.

Results

The mean shear bond strengths for all test groups aresummarised in Table I. The data were found to benormally distributed and so parametric analyses werecarried out. The mean differences in the shear bondstrengths between the test groups were comparedwith a one-way ANOVA adjusted with the Bonfer-roni post-hoc correction for multiple comparisons.Transbond PLUS Color Change had a higher meanshear bond strength (16.72 MPa) than Transbond XT(15.11 MPa), but this was not statistically significant

(p = 0.109). Transbond XT had a higher mean shearbond strength after fatiguing (15.87 MPa) thanTransbond PLUS Color Change (15.33 MPa), butagain this was not statistically significant (p > 0.999).Fatiguing produced no statistically significant differ-ences in shear bond strength for either adhesive(Transbond PLUS Color Change: p = 0.248;Transbond XT: p > 0.999).

A two-way ANOVA was used to investigate the influ-ence on bond strength of changing a single variable(the composite type or the introduction of fatigue),and whether there were any interactions when thecomposite type and fatigue were combined. Therewere no statistical significances when consideringeither the composite resin (p = 0.264) or the effect offatiguing on the bonded brackets (p = 0.512). How-ever, when composite type and fatigue were analysedin combination, the effect on bond strength was statistically significant (p = 0.026).

Figures 3 and 4 show modified Kaplan-Meier survivalplots for unfatigued brackets and fatigued bracketsrespectively, for both composite resins. The Y-axisrepresents cumulative survival, such that a survival of 1.0 is 100 per cent survival, and 0.25 represents 25 per cent survival. Horizontal lines are drawn tohighlight 25, 50 and 75 per cent survival. The profileplots for all test groups were comparable and this was confirmed by the Cox regression analysis thatfound no statistical significance between all the variables on the survival of the brackets. There were

Initial (Unfatigued)

Bond strength (MPa)

9.00 12.00 15.00 18.00 21.00 24.00

Cum

ulat

ive

surv

ival

1.0

0.8

0.6

0.4

0.2

0.0

Composite resin Composite resin

Fatigued

Bond strength (MPa)

6.00 9.00 12.00 15.00 18.00 21.00 24.00

Cum

ulat

ive

surv

ival

1.0

0.8

0.6

0.4

0.2

0.0

Figure 3. Kaplan-Meier plot for unfatigued brackets. Figure 4. Kaplan-Meier plot for fatigued brackets.

Transbond Plus

Transbond PlusTransbond XT

Transbond XT

no statistically significant differences between the sur-vival plots when considering the effects of the mater-ial (Transbond XT versus Transbond PLUS ColorChange, p = 0.184), initial bond strength versusfatigue bond strength (p = 0.290) or the interactionbetween material and fatigue status (p = 0.098).

Discussion

The bonding technique used in this study was carriedout in a dry field area following the manufacturer’sinstructions. A strict bonding protocol was adheredto for each bracket to ensure that every attempt wasmade to standardise the variables during the bondingprocess.1,2 Polishing the enamel surfaces of the teethwith pumice is a common clinical practice before acidetching commences. It is also a common procedure inlaboratory studies that have used human or animalteeth in bond strength testing. In this study, thehydroxyapatite discs were not pumiced because thedisc surfaces had been ground and polished followinga meticulous protocol to produce a uniformly pol-ished surface. These surfaces were not covered by anorganic pellicle which has been shown to cause poorbonding to enamel surfaces intra-orally.16 Pumicingthe hydroxyapatite surfaces would have offered noadvantage and instead could become an unnecessaryvariable in this comparative bonding study.

One of the parameters in bond strength testing,which shows large inter-study variation, is the rate offorce application as determined by the crossheadspeed of the testing machine. Previous work hasshown that varying the crosshead speed between 0.1mm/min and 5.0 mm/min did not significantlyinfluence either the debonding forces or the mode offailure of the bonded brackets.17 In this study, acrosshead speed of 1.0 mm/min was used which fellwithin the previously proposed acceptable range andpermitted an acceptable laboratory time per test. Theload application chosen to debond the brackets was ashearing mode as this has been described to more

closely resemble the occlusal forces exerted on bondedbrackets intra-orally.18–20 For the purpose of thisstudy, a custom-made jig was used to hold theembedded hydroxyapatite discs firmly while the slid-ing blade directed the applied force vertically and asclose as possible to the hydroxyapatite – adhesiveinterface.11,12 The placement of the samples in the jigwas carried out with great care to ensure that thedirection of the applied force and the point of appli-cation of the force were consistent in all the samples.This is important because changes in the location ofthe applied force can cause significant differences inshear bond strength measurements and the failurepattern of the bond.21

The cyclic loading of the bonded brackets to simulatefatigue was carried out using a Dartec Series HC10,which is a hydraulic stress and strain testing machine.The fatigue load applied to the brackets was an esti-mation based on the initial bond strength from thepilot study. No standard force level or specific fre-quency of force application has been established torepresent the forces to which bonded orthodonticbrackets are subjected during a course of treatment.In this study, the fatigue load was set at 50 per cent ofthe mean bond strength and loaded for 5000 cycles,so that brackets were not debonded during fatiguing.This was deemed to be adequate to represent masti-catory forces ranging from 40 to 120 N.18 This tech-nique of testing the shear bond strength after a fixednumber of fatigue cycles mirrored that of a previousstudy.22

In order for meaningful comparisons to be madebetween different studies, the materials and method-ology of the studies should be identical.1 Theseshould include parameters such as the type of bracket and resin used, as well as the bonding andtesting protocols. In this current study, the methodsemployed in the fabrication of the hydroxyapatitediscs, the bonding and debonding protocols weresimilar to two reported studies.11,12



Table I. Shear bond strength values (MPa) for test groups.

Group N Mean 95% CI SD Minimum Maximum SE

Transbond XT Initial 75 15.11 14.13, 16.10 4.29 8.26 24.19 0.49Transbond PLUS Initial 75 16.72 15.87, 17.56 3.66 9.13 23.91 0.42Transbond XT Fatigued 75 15.87 14.85, 16.89 4.42 7.54 24.85 0.51Transbond PLUS Fatigued 75 15.33 14.38, 16.29 4.15 7.75 22.97 0.48

The mean initial (unfatigued) bond strength value forTransbond XT bonded to hydroxyapatite was foundto be 15.11 MPa. This was lower than the valuefound in previous studies.11,12 However, the meanshear bond strength of Transbond XT in the presentstudy still lies within the accepted range of 15–20MPa for shear bond strength of brackets bonded toenamel.8–10 Although the methodology was identical,the differences between the bond strengths from thisstudy and previous studies may reflect the fact that thebrackets used were from different manufacturers.11,12

The mean initial bond strength for Transbond PLUSColor Change was found to be 16.72 MPa. There arelimited studies in the literature on the bond strengthof Transbond PLUS Color Change and to date thereis no published study of this bonding adhesive tohydroxyapatite to enable reliable comparison with thefindings of this study. In the studies that have inves-tigated the bonding strength of Transbond PLUSColor Change, the substrate, the bonding conditionsand protocols were diverse. Bonding in dry and wetconditions with various primers on bovine enamelwas used in one study,7 while human premolarsbonded in a dry field have been reported in another.6

The manufacturer claims that the bond strength ofTransbond PLUS Color Change is comparable to theconventional bonding adhesive Transbond XT. In thisstudy, the difference in bond strengths between thetwo adhesives was not statistically significant (p = 0.109). This supported the findings of Vicente etal. who found no significant difference between thebond strengths of these two adhesives when bondingwas performed in dry conditions with no contamina-tion.7 However, when Transbond PLUS ColorChange was used in wet conditions with moisture tolerant or self-etching primers, the bond strengths

were significantly higher than Transbond XT. It wassuggested by the authors that this could be due to alower content of hydrophobic (Bis-GMA) monomerin Transbond PLUS Color Change and the additionof polyethylene glycol dimethacrylate which rendersit less sensitive to wet conditions.7

It has been postulated by researchers that the meanbond strength values of bonded brackets after fatigueloading would be lower compared to the unfatiguedbrackets. This was based on the assumption thatfatigue loading may cause, or at least influence theprocess of mechanical failure of the substrate-adhe-sive-bracket interfaces. In this study there were nostatistically significant differences in bond strengthfor either adhesive following fatiguing (TransbondPLUS Color Change: p = 0.248; Transbond XT: p > 0.999).

The two variables, composite resin and fatigue load-ing, were analysed using a two-way ANOVA to inves-tigate whether these variables influenced the shearbond strength of the bonded brackets. When thecomposite resin type alone was tested, it did not showa significant effect on the bond strength (p = 0.264).This suggested that the differences in the materialtype, which may include factors such as composition,physical and chemical properties of the materials perse, did not influence the shear bond strength. Thiswas also demonstrated when fatigue loading wasanalysed in isolation (p = 0.512) suggesting thatfatigue alone did not significantly affect the shearbond strength. However, when ANOVA analysed thetwo variables in combination, the interaction betweenthe material type and fatigue loading was found to bestatistically significant (p = 0.026). This may implythat the interaction could influence the bond strengthby acting synergistically.

LEE ET AL


Table II. Survival percentiles for all test groups.

25 per cent 50 per cent 75 per cent

Initial/Fatigued Composite Resin Estimate SE Estimate SE Estimate SE

Initial Transbond XT 18.67 0.966 14.64 0.534 11.50 0.852Transbond PLUS 19.57 0.629 16.96 0.654 14.50 0.960Overall 19.29 0.454 15.86 0.601 12.84 0.550

Fatigued Transbond XT 19.01 0.462 17.04 0.953 11.90 0.523Transbond PLUS 18.67 0.832 15.17 0.554 11.55 0.344Overall 18.89 0.426 15.43 0.865 11.74 0.291

Overall Overall 19.01 0.308 15.78 0.502 12.02 0.319

Survival analysis, such as the Weibull or Kaplan-Meier analysis, has been proposed by previousauthors for orthodontic bond strength studies to pro-vide more information for the clinician on the sur-vival and reliability of the bonded brackets.1,23 Theseanalyses focus on the bond strength values at thelower end of the range (tail end of the distribution)which are more critical in the assessment of the prob-ability of failure of the bonded bracket. This helps clinicians to evaluate whether a particular bondingsystem might perform safely and successfully whenused clinically. The shear bond strength data fromthis study was subjected to a modified Kaplan-Meiersurvival analysis. The estimated bond strengths at the25 per cent, 50 per cent and 75 per cent survival per-centiles for all test groups are shown in Table II. Forbrackets that were bonded with Transbond XT andnot fatigued, at an estimated shear force of 11.50MPa, 75 per cent of the brackets survived while 75per cent of unfatigued Transbond PLUS ColorChange survived a higher shear force of 14.50 MPa.When the brackets bonded to Transbond XT weresubjected to fatigue loading, the mean shear force for75 per cent survival was estimated to be 11.90 MPaand for Transbond PLUS Color Change, 11.55 MPa.This suggests that the probability of survival andbehaviour of the fatigued brackets bonded with eithertype of adhesive are similar at the lower end of theshear force range.

Although laboratory findings should be extrapolatedto the clinical environment with caution, a number ofclinical implications can be considered from thiscomparative study. There was no significant differ-ence between the mean initial shear bond strengthsfor Transbond XT and Transbond PLUS ColorChange. This suggests that the changes in con-stituents associated with the colour change materialhave resulted in no deterioration in bond strengthperformance. Neither material demonstrated signifi-cant differences in mean shear bond strength as aresult of the fatigue process used in this study. Thecyclic forces used may be considered as representativeof the nature of loads produced by intra-oral mastica-tory forces. Both materials resisted these cyclic forcesadequately and did not demonstrate significantlylower bond strengths as a result of fatigue. This sug-gests that the materials should resist intra-oral fatigueequally, with neither adhesive demonstrating superiorperformance over the other. The equality in perform-

ance of the two adhesives was reflected in the similar-ity of the Kaplan-Meier survival curves and lack ofsignificant difference shown by the Cox regression. Inorder to confirm the findings of this laboratory study,it would be beneficial to follow this up with an invivo clinical trial.

Conclusions

There was no statistically significant differencebetween the mean initial (unfatigued) bond strengthsof Transbond XT and Transbond PLUS ColorChange (p = 0.109).

There was no statistically significant differencebetween the fatigue bond strengths of Transbond XTand Transbond PLUS Color Change (p > 0.999).

There were no statistically significant differencesbetween the initial and fatigue bond strengths foreither Transbond XT (p > 0.999) or Transbond PLUSColor Change (p = 0.248).

A survival analysis for both composite resins with andwithout fatigue loading exhibited similar behaviourwith respect to their survival patterns (p = 0.098).

In a laboratory setting, the shear bond strength ofTransbond PLUS Color Change, a new chromaticadhesive, was comparable to Transbond XT in bothfatigue and unfatigued conditions. Although this mayimply that under clinical conditions the two adhe-sives could behave similarly, the clinical extrapolationof these results should be interpreted with caution.

Acknowledgments

The authors would like to acknowledge the supportof Professor David Moles from the Biostatistics Unitand Professor Jonathan Knowles of the BiomaterialsDepartment, UCL Eastman Dental Institute. We alsowish to thank 3M Unitek (UK) for generously donat-ing the materials used in this study.


Dr S. P. JonesOrthodontic UnitUCL Eastman Dental Institute 256 Gray’s Inn RoadLondon, WC1X 8LDUnited KingdomTel: (+44 0) 20 7915 1068Fax: (+44 0) 20 7915 1238Email: [email protected]



References1. Fox NA, McCabe JF, Buckley JG. A critique of bond

strength testing in orthodontics. Br J Orthod 1994;21:33–43.

2. Bishara SE, Soliman M, Laffoon J, Warren JJ. Effect ofchanging a test parameter on the shear bond strength oforthodontic brackets. Angle Orthod 2005;75:832–5.

3. Gorelick L, Geiger AM, Gwinnett AJ. Incidence of whitespot formation after bonding and banding. Am J Orthod1982;81:93–8.

4. Travess H, Roberts-Harry D, Sandy J. Orthodontics. Part 6:Risks in orthodontic treatment. Br Dent J 2004;196:71–7.

5. Armstrong D, Shen G, Petocz P, Darendeliler MA. Excessadhesive flash upon bracket placement. A typodont studycomparing APC PLUS and Transbond XT. Angle Orthod2007;77:1101–8.

6. Endo T, Ozoe R, Shinkai K, Aoyagi M, Kurokawa H, KatohY, Shimooka S. Shear bond strength of brackets rebondedwith a fluoride-releasing and recharging adhesive system.Angle Orthod 2009;79:564–70.

7. Vicente A, Mena A, Ortiz AJ, Bravo LA. Water and salivacontamination effect on shear bond strength of bracketsbonded with a moisture-tolerant light cure system. AngleOrthod 2009;79:127–32.

8. Buonocore MG, Matsui A, Gwinnett AJ. Penetration ofresin dental materials into enamel surfaces with reference tobonding. Arch Oral Biol 1968;13:61–70.

9. Gilpatrick RO, Ross JA, Simonsen RJ. Resin-to-enamelbond strengths with various etching times. Quintessence Int1991;22:47–9.

10. Barkmeier WW, Shaffer SE, Gwinnett AJ. Effects of 15 vs 60second enamel acid conditioning on adhesion and mor-phology. Oper Dent 1986;11:111–16.

11. Imthiaz N, Georgiou G, Moles DR, Jones SP. Comparison ofhydroxyapatite and dental enamel for testing shear bondstrengths. Aust Orthod J 2008;24:15–20.

12. Jones SP, Cheuk GC, Georgiou G, Moles DR. Comparisonof fluoridated apatites with pure hydroxyapatite as potentialbiomimetic alternatives to enamel for laboratory-based bondstrength studies. Aust Orthod J 2009;25:12–18.

13. Daskalogiannakis J. Glossary of Orthodontic Terms.Chicago: Quintessence Publishing Company, Inc., 2000;112.

14. Moseley HC, Horrocks EN, Pearson GJ, Davies EH. Effectsof cyclic stressing on attachment bond strength using glassionomer cement and composite resin. Br J Orthod 1995;22:23–7.

15. Scherrer SS, Wiskott AH, Coto-Hunziker V, Belser UC.Monotonic flexure and fatigue strength of composites forprovisional and definitive restorations. J Prosthet Dent2003;89:579–88.

16. Gwinnett AJ. Bonding of restorative resins to enamel. IntDent J 1988;38:91–6.

17. Klocke A, Kahl-Nieke B. Influence of cross-head speed inorthodontic bond strength testing. Dent Mater 2005;21:139–44.

18. Reynolds IR. A review of direct orthodontic bonding. Br JOrthod 1975;2:171–8.

19. Tavas MA, Watts DC. Bonding of orthodontic brackets bytransillumination of a light activated composite: An in vitrostudy. Br J Orthod 1979;6:207–8.

20. Lopez JI. Retentive shear strengths of various bondingattachment bases. Am J Orthod 1980;77:669–78.

21. Klocke A, Kahl-Nieke B. Influence of force location inorthodontic shear bond strength testing. Dent Mater 2005;21:391–6.

22. Hashim NA. Fatigue of a new fluoride-releasing compositebonding agent. MSc. Thesis, University of London 2005.

23. Brantley WA, Eliades T, Litsky. Chapter 2: Mechanics andmechanical testing of orthodontic materials. In: BrantleyWA, Eliades T, eds. Orthodontic Materials: Scientific andClinical Aspects. Stuttgart, New York: Thieme, 2001; 43–5.

LEE ET AL


Introduction

Self-ligating bracket usage has been on the rise overthe last two decades due to their claimed greater clin-ical efficiency. These brackets present a fourth wall,which converts the slot into a tube. Two main typesof self-ligating brackets have been developed: activebrackets that possess a spring clip which presses

against the archwire and passive brackets whose clipsdo not exert any forces on the archwire, but just close the slot. Several studies have been conducted totest the friction, force and torque delivery by thesebrackets with inconclusive results.1–7

It has been postulated that self-ligation increasesintra-slot wire play, which reduces the generated


A comparative assessment of the forces andmoments generated at the maxillary incisorsbetween conventional and self-ligating bracketsusing a reverse curve of Spee NiTi archwire

Iosif Sifakakis,* Nikolaos Pandis,† Margarita Makou,* Theodore Eliades± andChristoph Bourauel+

Department of Orthodontics, National and Kapodistrian University of Athens, Greece,* Private practice, Corfu, Greece,† Department ofOrthodontics, Aristotle University of Thessaloniki, Greece ± and the School of Dentistry, Rheinische Friedrich-Wilhelms University of Bonn,Germany+

Objectives: To compare the intrusive forces and labio-palatal moments generated at the maxillary incisors by a 0.017 x 0.025inch reverse curve NiTi wire using self-ligating and conventional brackets.Methods: Ten 0.017 x 0.025 inch reverse curve NiTi archwires were used with each of the following 0.022 inch bracket systems: Titanium Ortho (Ormco/Sybron, CA, USA), In-Ovation R (GAC International, NY, USA) and Damon System 3MX(Ormco/Sybron, CA, USA). The wires were inserted on bracketed maxillary Frasaco models, with segmented maxillary incisors. Simulated intrusion from 0.0-1.0 mm was performed on the Orthodontic Measurement and Simulation System, whichrecorded the intrusive forces and the labio-palatal moments at 0.05 mm increments. The data were analysed with the ANOVAand Scheffe tests. Results: The intrusive forces were significantly different between all bracket types. The highest force was recorded with the conventional Titanium Orthos brackets (8.2 N), followed by the Damon 3MX brackets (6.3 N) and the In-Ovation R brackets(5.5 N). The moments were found to be significantly different between the conventional and the self-ligating brackets, but notbetween the two types of self-ligating brackets. The highest moments were recorded with the self-ligating brackets (16.6-16.9N/mm), followed by the conventional brackets (10.8 N/mm).Conclusions: The intrusive forces exerted on the maxillary incisors by a 0.017 x 0.025 inch reverse curve NiTi archwire duringthe final 1 mm of levelling are very high and beyond the necessary intrusive force level for these teeth. Lower intrusive forces,but higher labio-palatal moments, were recorded with the self-ligating brackets.(Aust Orthod J 2010; 26: 127–133)

Received for publication: December 2009Accepted: May 2010

Iosif Sifakakis: [email protected] Pandis: [email protected] Makou: [email protected] Eliades: [email protected] Bourauel: [email protected]

SIFAKAKIS ET AL


forces.1 However, other research failed to show thisdifference.2 Recently, Pandis et al. have demonstratedforce differences between different directions of dis-placement, when applied to the mandibular teeth.3,4

The authors concluded that these differences in forcelevel between conventional and self-ligating bracketsfollow a complex pattern and seem to be influencedby many factors including the method of ligation,bracket width, archform and tooth position: eachcontributing with variable weightings depending onthe specific characteristics of the dental arch and thewire.

The torque expression of these brackets has also beenevaluated, but the results were again inconclusive.5–7

Active self-ligating brackets are expected to be moreeffective in torque expression than passive ones, afinding that was confirmed in vitro by Badawi et al.5Other in-vitro research concluded that the generatedmoments depend on the direction of movement andthe examined tooth.6 In a clinical trial, self-ligatingbrackets seem to be as efficient as conventional bracketsin delivering torque to the maxillary incisors.7

Reverse curve NiTi archwires are commonly used instraight-wire mechanotherapy of deep-bite cases. Thelow modulus of elasticity of the NiTi wires promisesa reduction in the magnitude of the intrusive forces.However, to date there is a lack of evidence on thequantitative assessment of forces and moments gener-ated from continuous rectangular reverse curve NiTiarchwires on the maxillary incisors. By using self-

ligating brackets with these wires it might be possibleto apply biologically acceptable intrusive forces tothese teeth.

The aim of this study was to compare the intrusiveforces and torquing moments generated at the maxil-lary incisors by a continuous 0.017 x 0.025 inchreverse curve NiTi wire and three different brackettypes: an active self-ligating bracket, a passive self-ligating bracket and a conventional bracket.

Material and methodsExperimental apparatus and configurationThe Orthodontic Measurement and SimulationSystem (OMSS) is a measuring system developedspecifically for investigating biomechanical issues inorthodontics and its set-up and applications havebeen described in detail.8,9 It has been used for the in-vitro evaluation of different intrusion mechanics.8,10

The simulation of tooth movement with the OMSSis conducted using two measuring tables comprisinga 6-axis positioning table and a 6-component force-torque sensor, monitored by a personal computer.Each sensor consists of a central element with fouraxes. A strain gauge (HBM 6/350LY43) is fixed toeach side of the axes, resulting in 16 strain gauges,which are electrically connected to form eight half-bridges. The OMSS programme running on thecomputer, written in ‘C’ language, calculates theforce-torque vectors acting on the centre of resistanceand with a mathematical model, the resulting vectorsin the movement of the teeth. The system allows theregistration of the complete force-torque vectors during the movement of the tables along a specifiedpath.8,10

In this study, an acrylic replica of an upper Frasacomodel (Franz Sachs and Company GmbH, Tettnang,Germany), with a levelled and aligned dental arch,was used for the intrusion simulation. This modelwas split into an anterior segment, comprising thefour incisors and a posterior segment, which includ-ed the canines and the posterior teeth. Each of thesemodel segments was mounted on the positioningtables of the OMSS with an appropriate adaptor(Figure 1). Three different bracket systems with0.022 inch slots were evaluated separately. In eachcase, new brackets and tubes were bonded on theteeth up to the first molars. The brackets were bonded on the centre of each tooth mesio-distallyand at the suggested height with the aid of a Unitek

Figure 1. The acrylic Frasaco model mounted on the positioning tables ofthe OMSS. Conventional brackets were bonded on the teeth up to the firstmolars.

bracket positioning gauge (3M Unitek, MN, USA).Before every evaluation, the complete levelling of theattachments in every segment as well as between thetwo segments was ensured with the aid of a straight0.019 x 0.025 inch stainless steel archwire. This arch-wire was ligated to the two segments and they wereboth mounted on the positioning tables of theOMSS. The system was adjusted with the straightwire in place and all forces/moments generated werenullified.

In the absolute measurement mode, the dental archwas initially levelled. During the measurement pro-cedure the anterior segment was intruded to 1.0 mmand the forces/moments generated in the sagittalplane in the anterior segment were measured in 0.05mm steps.

MaterialsThe following brackets were evaluated, as regard tothe forces/moments generated at the anterior maxil-lary segment (Table I): Titanium Orthos(Ormco/Sybron, CA, USA), In-Ovation R (GACInternational, NY, USA) and Damon System 3MX(Ormco/Sybron, CA, USA).

Ten reverse curve NiTi 0.017 x 0.025 inch archwires,each one taken at random from a different package(NI-TI Preformed Archwires, Ormco, CA, USA),were used in each type of bracket and each of the wirespecimens was evaluated three times. During the

measurement cycle, the wires were not cinched back.The overall measurement set-up was installed in atemperature chamber (VEM 03/400, Vötsch Hereus,Germany) at a constant temperature of 37 °C, whichreasonably approximated the intra-oral temperature.8,11

In the conventional brackets, the wires were ligatedby the same person with 0.010 inch metal ligatures.

This study evaluated the intrusive and labio-palataltorque components of the reverse curve archwires ligated in different bracket types, hence only measure-ments of the intrusive forces (Fx) and the momentsMy (labio-palatal torque) were used. The other forces(Fy, Fz) and moment vectors (Mx, Mz) are greatlyaffected by factors such as proper adjustment of theanterior segment relative to the posterior segment andproper archwire insertion. Since these factors intro-duce unnecessary variability, the components Fy, Fz,Mx, Mz were adjusted to zero.

Statistical analysisDescriptive statistics presenting the mean and stan-dard deviation of the intrusive forces and momentsper bracket type were calculated (Tables II and IV).The force and moment values of all wire specimens at1.0 mm of intrusion were statistically analysed usingone-way analysis of variance (ANOVA) with force ormoment serving as the dependent variable and bracket system being the explanatory variable (TablesIII and V). Post-hoc pairwise comparisons were

REVERSE CURVE NITI FORCE SYSTEM


Table I. Bracket specifications.

Bracket type Titanium Orthos In-Ovation R Damon 3MX

Slot size (inches) 0.022 x 0.028 0.022 x 0.028 0.022 x 0.027Slot width (mm) U1 3.54 2.93 2.65

U2 2.66 2.77 2.65U3 3.35 2.96 2.65

Tip U1 5 5 5(Degrees) U2 9 9 9

U3 10 13 6Torque U1 15 12 12 (Degrees) U2 9 8 8

U3 0 –2 0Rotation U1 0 0 0 (Degrees) U2 0 0 0

U3 0 4 0Slot composition - Stainless steel Stainless steelClip composition - Cobalt chromium Stainless steel

SIFAKAKIS ET AL


performed using the Scheffe test at the 0.05 errorrate. All statistical analyses were performed with Stata10.1 statistical software (College Station, TX, USA).

Results

Table II summarises the mean intrusive forces at 1.0mm of intrusion for each bracket system tested. Thehighest force was recorded with the conventionalbrackets (8.2 N), followed by the Damon 3MX (6.3N) and the In-Ovation R (5.5 N) system (Table II).ANOVA showed statistically significant differencesbetween the forces generated by the bracket systems(Table III). Figure 2 depicts the range of intrusionforces (Fx) per bracket type and vertical displacementfrom 0.0–1.0 mm (0.05 mm increments).

The mean labio-palatal moments (torque) developedin the anterior segment are shown in Table IV. Theconventional brackets exerted the lowest moment(10.8 N/mm), followed by the self-ligating brackets(16.6–16.9 N/mm). ANOVA indicated significantdifferences in the moments generated by the conven-tional and the self-ligating brackets, but not betweenthe two types of self-ligating brackets (Table V).Figure 3 depicts the bucco-lingual moments (My) perbracket type and displacement for a range of 1.0 mm(0.0–1.0 mm), in 0.05 mm increments.

Discussion

Continuous reverse curve 0.017 x 0.025 inch NiTiarchwires, with or without torque, might be useful tocomplete intrusion of maxillary incisors in deep-bitemalocclusions because they deliver an intrusive forceand a labio-palatal moment on the anterior teeth. Itwas initially suggested that the magnitude of the force applied during intrusion of the four upper incisors could be as high as 1–1.6 N12,13 and thatsome light rectangular wires with low moduli of elasticity could be used even during the early stages oftreatment,14,15 but recently van Steenbergen et al.demonstrated that only 0.4 N of force is necessary tointrude the four maxillary incisors at the same rate asdouble the magnitude.16 In comparison, the intrusiveforces measured in this study are very high and thisdiscourages the use of a continuous reverse curve0.017 x 0.025 inch NiTi archwire in an unlevelleddental arch, regardless of the type of bracket. Withonly 1 mm simulated intrusion of the incisor seg-ment, the intrusive forces were 5.5–6.3 N for the self-ligating and 8.2 N for the conventional brackets.When using a continuous arch, such as the reversecurve NiTi archwire used in this study, the force magnitude on the anterior segment is primarily deter-mined by the dimensions and curvature of the wireand the distance between the canine and lateral

Table II. Intrusion force for each bracket at 1 mm wire displacement.

Intrusion force (N)

Bracket type Mean SD Tukey grouping*

Titanium Ortho 8.2 0.5 AIn-Ovation R 5.5 0.2 BDamon System 3MX 6.3 0.3 C

* Means with same letter are not significantly different at the 0.05 level

Table IV. Intrusion moment (torque) results for each bracket at 1mm wiredisplacement.

Moments (N/mm)

Bracket type Mean SD Tukey grouping*

Conventional 10.8 2.7 AIn-Ovation R 16.9 1.0 BDamon System 3MX 16.6 1.2 B

* Means with same letter are not significantly different at the 0.05 level

Table III. Intrusion force versus bracket type.

Intrusion Sum of df Mean F p*force (N) squares square

Betweengroups 38.177 2 19.088 132.68 0.000

Withingroups 3.884 27 0.144

Total 42.061 29 1.450

* ANOVA

Table V. Moments (torque) versus bracket type.

Intrusion Sum of df Mean F p*force (N) squares square

Betweengroups 235.982 2 117.991 35.71 0.000

Withingroups 89.219 27 3.304

Total 325.200 29 11.214

* ANOVA

80%40%K80%40%C80%�40%M80%40%Y80%40%K80%40%C80%�40%M80%40%Y80%40%K80%40%C80%�40%M80%40%Y80%40%K80%40%C80%�40%M80%40%Y80%40%K80%40%C80%�40%M80%40%Y80%40%K80%40%C80%�40%M80%40%Y80%40%K80%40%C80%�40%M80%40%Y80%40%K80%40%C80%�40%M80%40%Y80%40%K80%40%C80%�40%M80%40%Y80%40%K80%40%C80%�40%M80%40%Y80%40%K80%40%C80%�40%M80%40%Y80%40%K80%40%C80%�40%M80%40%Y80%40%K80%40%C80%�40%M80%40%Y80%40%K80%40%C80%�40%M80%40%Y80%40%K80%40%C80%�40%

incisor brackets.17 Clinically, the moments created bythis statically indeterminate force system are expectedto tip the teeth rapidly, but in a rather unpredictablemanner.15,18

The highest intrusive force was recorded by theTitanium Orthos brackets (8.2 N), followed by theDamon 3MX (6.3 N) and the In-Ovation R (5.5 N)system. These forces are applied to the gingival wall ofthe slot and they depend upon the wire deflection,the size of the span, the superelasticity of the wire andthe ability of the wire to slide distally. The variable inthis experiment was the bracket type. The width ofthe slot is different between brackets, so the inter-bracket distance between the cuspid and the lateralincisor is significant in determining the magnitude ofthe intrusive force. This distance was smaller in thecase of Titanium Orthos (by 0.7 mm with Damon3MX and by 0.3 mm with In-Ovation R). Howeverinter-bracket distance alone is not a reliable predictorof force magnitude during archwire engagement.3Although the Damon 3MX brackets had the smallestwidth, they exerted higher intrusive forces than theIn-Ovation R brackets, possibly underlining theimportance of ligation mode on force levels, i.e. theflexibility of the active clip in the case of the In-Ovation R bracket offers the wire the possibility tomove more easily through the neighbouring bracketslots. Longitudinal mechanical stress in the wire isbalanced and thus forces in neighbouring brackets arereduced. A reduction in the second order force levelshas been noted for self-ligating systems in comparison

with conventional brackets.3,4 This finding could beattributed to the increased play of wires in the slotand the lack of obstacles arising from the contact of aligature outside the wings.

Resistance to sliding at the bracket-wire interface represents a combination of friction produced by theligation method and wire-bracket binding as well aswire notching.19,20 The force values measured withthe OMSS testing unit were influenced by friction at the bracket-wire interface. Passively ligated self-ligating brackets produce less frictional resistancethan actively ligated systems,21,22 and the higher thefriction at the bracket-wire interface, the lower is theforce released by the system to produce bracket alignment.19,23 In the experimental model used here,significant binding can be expected at the mesialaspect of the canine brackets and at the distal aspectof the lateral incisor brackets but, in contrast to fric-tion, this phenomenon is similar for conventionaland all types of self-ligating brackets.22 Notchingappears to be more prevalent when hard ceramicbrackets are opposed by soft metallic wires anddepends, in part, on the frequency and forces of mastication.23

The conventional brackets used in this study showedthe lowest torquing values (10.8 N/mm), about 65per cent of the values recorded for the self-ligatingbrackets (16.5–16.9 N/mm). Currently, studies com-paring torquing moments and effectiveness of torquecorrection between conventional and self-ligating systems are scarce. It seems that neither the bracket



Figure 2. Graph depicting the mean intrusion force (Fx) per bracket type and level of intrusion for a range of 1.0 mm (0.0–1.0 mm) in 0.05 mmincrements.

Figure 3. Graph depicting the mean labio-palatal moments (My) per bracket type and level of intrusion for a range of 1.0 mm (0.0–1.0 mm) in0.05 mm increments.

8

6

4

2

0

Forc

e (N

)

0 .2 .4 .6 .8 1Displacement (mm)

20

15

10

5

Forc

e (N

mm

)

0 .2 .4 .6 .8 1Displacement (mm)

Conventional Damon In-Ovation R

Conventional Damon In-Ovation R

Conventional

In-Ovation R

Damon

Conventional

In-Ovation R

Damon

28001_aoj_ortho_jnl_26.2_dec 15:06:24 10-11-08 YellowMagentaCyanBlack Sect 3 Back

system nor archwire predominantly affects the gener-ation of torque during the correction of vertical andhorizontal malalignments. Hence it is the initialmalalignment that is primarily responsible for theresulting torque movement in such a levelling situation.2 Further research revealed that in thebucco-lingual direction, a light round copper NiTiarchwire exerted higher rotating moments into theself-ligating systems compared with the conventionalbrackets.3 Again, this might be explained by the rigid-ity of the self-ligating clips, acting as a rigid barrier,whereas the elastic ligatures in the case of the con-ventional brackets offer some flexibility and thusreduce the force couple generated in the bracket slot.This was obvious in the moments generated in thehorizontal plane during rotational correction of teethwith a 0.014 x 0.025 inch copper NiTi.6

Active self-ligating brackets may be more effective intorque expression than the passive ones, due to areduction in the amount of archwire play in thebracket slot by the active ligating mechanism.5,21 Butin the case of a 0.019 x 0.025 inch stainless steel wire,torque starts to be expressed at an angle of 15 degreesof torsion for Damon brackets compared with anangle of 7.5 degrees for In-Ovation brackets.5 Thisdifference was not recorded in the present study, sincethe wire used was of smaller cross-section and lowertorsional stiffness.

According to the specifics of the OMSS force-torquetransducers, described by Bourauel et al.,8 the resolu-tion for the force measurements is 0.02 N and for thetorque measurements is 0.5 N/mm. In the configura-tion used in this study, these values are of minorimportance, since the standard deviations of the pres-ent measurements are much higher than the resolu-tion. The experimental set-up used in this study is amodel that approximates the clinical situation whereforces and moments are exerted by an archwire ontobrackets. The actual force system acting on the teethwill probably vary, because of the presence of perio-dontal ligament, whose mechanical properties affectthe transmission of the force system. The OMSS isbased on the principle of the two-tooth model andapproximates the clinical situation of initial toothmovement within the periodontal space. It does notaccount for factors such as intra-oral aging and influ-ence of saliva, which influence the forces andmoments experienced by teeth over time.Additionally, it has not yet been possible to predict

the centre of resistance of the four incisors, and theintrusion of these teeth should be carefully monitoredin order to avoid side effects. Further investigation ofintrusive biomechanics using different bracket typesof the same width would expand the conclusions ofthis study. Another suggested area for future researchwould be the evaluation of the intrusive forces ofbrackets and wires from different manufacturers, tak-ing into account differences between the actual andstated dimensions of the materials.

Conclusions

A comparison of three different bracket systemsrevealed that a continuous 0.017 x 0.025 inch reversecurve NiTi archwire exerted very high intrusive forceson the upper incisor segment. Conventional brackets(Titanium Orthos) exerted 30 per cent higher forcesin comparison with the Damon 3MX brackets and49 per cent higher forces in comparison with the In-Ovation R brackets.

Differences were detected between the two self-ligating systems in labio-palatal torquing momentsgenerated at the maxillary incisors, but the conven-tional brackets showed the lowest torque, about 65per cent of the values recorded for the self-ligatingbrackets.


Dr Theodore Eliades57 Agnoston HiroonNea Ionia, 14231GreeceTel. (+30) 2102 717555Fax: (+30) 2102 717867Mob: 306932 340 955Email: [email protected]: www.orthodontix.gr

References1. Berger JL. The influence of the SPEED bracket’s self-ligat-

ing design on force levels in tooth movement: a comparativein vitro study. Am J Orthod Dentofacial Orthop 1990;97:219–28.

2. Fansa M, Keilig L, Reimann S, Jäger A, Bourauel C.The lev-eling effectiveness of self-ligating and conventional bracketsfor complex tooth malalignments. J Orofac Orthop 2009;70:285–96.

3. Pandis N, Eliades T, Bourauel C. Comparative assessment offorces generated during simulated alignment with self-ligat-ing and conventional brackets. Eur J Orthod 2009;31:590–5.

SIFAKAKIS ET AL


4. Pandis N, Eliades T, Partowi S, Bourauel C. Forces exertedby conventional and self-ligating brackets during simulatedfirst- and second-order corrections. Am J Orthod Dento-facial Orthop 2008;133:738–42.

5. Badawi HM, Toogood RW, Carey JP, Heo G, Major PW.Torque expression of self-ligating brackets. Am J OrthodDentofacial Orthop 2008;133:721–8.

6. Pandis N, Eliades T, Partowi S, Bourauel C. Moments gen-erated during simulated rotational correction with self-ligat-ing and conventional brackets. Angle Orthod 2008;78:1030–4.

7. Pandis N, Strigou S, Eliades T. Maxillary incisor torque with conventional and self-ligating brackets: a prospectiveclinical trial. Orthod Craniofac Res 2006;9:193–8.

8. Bourauel C, Drescher D, Thier M. An experimental appara-tus for the simulation of three-dimensional movements inorthodontics. J Biomed Eng 1992;14:371–8.

9. Drescher D, Bourauel C, Thier M. Application of the ortho-dontic measurement and simulation system (OMSS) inorthodontics. Eur J Orthod 1991;13:169–78.

10. Sifakakis I, Pandis N, Makou M, Eliades T, Bourauel C.Forces and moments generated with various incisor intru-sion systems on maxillary and mandibular anterior teeth.Angle Orthod 2009;79:928–33.

11. Moore RJ, Watts JT, Hood JA, Burritt DJ. Intra-oral tem-perature variation over 24 hours. Eur J Orthod 1999;21:249–61.

12. Burstone CR. Deep overbite correction by intrusion. Am JOrthod 1977;72:1–22.

13. Ricketts RM, Bench RW, Gugino CF, Hilgers JJ, SchulhofRJ. Bioprogressive therapy. Denver: Rocky MountainOrthodontics, 1979:p.189. Page no is correct

14. Burstone CJ. Variable-modulus orthodontics. Am J Orthod1981;80:1–16.

15. Kapila S, Sachdeva R. Mechanical properties and clinicalapplications of orthodontic wires. Am J Orthod DentofacialOrthop 1989;96:100–9.

16. van Steenbergen E, Burstone CJ, Prahl-Andersen B,Aartman IH. The influence of force magnitude on intrusionof the maxillary segment. Angle Orthod 2005;75:723–9.

17. Halazonetis DJ. Ideal arch force systems: a center-of-resist-ance perspective. Am J Orthod Dentofacial Orthop 1998;114:256–64.

18. Burstone CJ, Koenig HA. Force systems from an ideal arch.Am J Orthod 1974;65:270–89.

19. Baccetti T, Franchi L, Camporesi M, Defraia E, Barbato E.Forces produced by different nonconventional bracket orligature systems during alignment of apically displacedteeth. Angle Orthod 2009;79:533–9.

20. Burrow SJ. Friction and resistance to sliding in orthodon-tics: a critical review. Am J Orthod Dentofacial Orthop2009;135:442–7.

21. Budd S, Daskalogiannakis J, Tompson BD. A study of thefrictional characteristics of four commercially available self-ligating bracket systems. Eur J Orthod 2008;30: 645–53.

22. Thorstenson GA, Kusy RP. Comparison of resistance to slid-ing between different self-ligating brackets with second-order angulation in the dry and saliva states. Am J OrthodDentofacial Orthop 2002;121:472–82.

23. Kusy RP, Whitley JQ. Friction between different wire-brack-et configurations and materials. Semin Orthod 1997;3:166–77.



Introduction

In orthodontic practices today, there is a strongdemand for ceramic brackets due to the fact thatapproximately 20 per cent of all orthodontic patientsare adults.1,2 With the change in the treatment population there is a greater demand for aestheticorthodontics.3 Ceramic brackets are more aestheticand retain important physical properties such astorque control.4

Many new ceramic brackets have been introduced tothe profession; however, the bonding characteristics

of all have not been tested. The first generationceramic brackets had chemically-bonded ceramicbases.5 Several studies have shown that these bracketshad significantly higher bond strengths comparedwith conventional metal brackets6–8 and bond failureoccurred at the enamel-adhesive interface.8–10

Because these brackets were more rigid and brittle,complications such as enamel fracture, cracks andflaking occurred during mechanical removal.5,11

Consequently, tooth damage was a concern to manypractitioners. Furthermore, the debonding forceoften resulted in ceramic fragments remaining on the

Australian Orthodontic Journal Volume 26 No. 2 November 2010 © Australian Society of Orthodontists Inc. 2010134

Bond strengths and debonding characteristics oftwo types of polycrystalline ceramic brackets

Katia Lemke,* Xiaoming Xu,† Joseph L. Hagan,+ Paul C. Armbruster± and Richard W. Ballard±

Private practice, Kissimmee, Florida,* Department of Comprehensive Dentistry and Biomaterials,† School of Public Health+ andthe Department of Orthodontics,± Louisiana State University Health Sciences Center, New Orleans, LA, United States of America

Objectives: To compare the shear bond strengths and modes of failure of three orthodontic brackets: a polycrystalline ceramicbracket, a collapsible polycrystalline ceramic bracket and a metal bracket.Methods: Ninety extracted human premolar teeth were selected and examined at x3 magnification for any enamel defects.Three types of brackets and one orthodontic adhesive were used. One half of the sample was tested in a universal testingmachine to determine the shear bond strength. The other half was debonded with the appropriate pliers and the tooth surfaceexamined at x5 magnification. The site of failure was scored with the modified Adhesive Remnant Index (ARI). Teeth with an ARIgrade of zero were examined in a SEM to determine any enamel fracture. Results: No statistically significant differences in bond strength among the samples were found (p > 0.159). The modes of fail-ure after debonding with pliers were predominantly at the bracket-adhesive interface. The mean shear bond strength of theClarity bracket was 10.78 ± 2.74 MPa, the InVu bracket was 12.43 ± 2.40 MPa and the metal bracket was 11.89 ± 1.83MPa. There were significant differences in the mean rank of the ARI grade between the three groups (p = 0.006). The Clarityand InVu (p = 0.011) and the Clarity and metal brackets (p = 0.005) were significantly different, but there was no differencebetween the InVu and metal brackets (p = 0.187). Conclusions: All three samples had similar bond strengths. The risk of ceramic fracture on debonding was greatest for the InVuceramic bracket. (Aust Orthod J 2010; 26: 134–140)

Submitted for publication: January 2010Accepted: May 2010

Katia Lemke: [email protected] Xu: [email protected] Hagan: [email protected] C. Armbruster: [email protected] W. Ballard: [email protected]

BOND STRENGTHS AND DEBONDING CHARACTERISTICS OF CERAMIC BRACKETS


teeth, which then had to be removed with a bur: a procedure that could be stressful to both patientand clinician.12 To address this problem, differentmethods of bracket removal were introduced in orderto minimise enamel damage.

Initially, the instruments used to debond ceramicbrackets applied heavy shear-torsion forces that couldcause enamel fractures and/or cracks.13 Swartz sug-gested that the debonding force should be applied bya sharp-edged instrument on opposite sides of theenamel-adhesive interface, so that failure occurredthrough the adhesive rather than at the adhesive-enamel interface.8 Storm suggested that there wouldbe less enamel damage if ceramic brackets weredebonded with a rotational motion using a specially-designed instrument.14 Alternative methods ofdebonding ceramic brackets included ultrasonic, elec-trothermal and laser techniques.11,15

In order to serve the increasing demand for ceramicbrackets and improve their physical and bondingproperties, a second generation ceramic bracket witha mechanical base was introduced in 1991.16,17 Thesebrackets had significantly lower bond strengths andcaused less enamel fracture than the first generationbrackets, but special debonding instruments wereneeded and the tie wings frequently fractured duringdebonding.17 Several studies reported that mechani-cally retained brackets had adequate bond strengthsand there was minimal enamel damage duringdebonding.15,18,19

A third generation of ceramic brackets was intro-duced in 1997. The Clarity collapsible bracket (3MUnitek, Monrovia, CA, USA) incorporated a vertical

groove designed to produce a consistent mode of fail-ure during debonding.6 The Clarity bracket, which isa polycrystalline, mechanically retained ceramicbracket with a metal-lined archwire slot, requires aspecial plier for optimal debonding.20 The InVubracket (TP Orthodontics, La Porte, IN, USA) isanother polycrystalline ceramic bracket with, accord-ing to the manufacturer, a fracture point on themechanical polymer base that should flex duringdebonding. According to the manufacturer, the mainadvantages of the InVu bracket are its aestheticappearance and ease of debonding, which can bedone with a ligature cutter. The bond strength anddebonding characteristics of InVu brackets have notyet been reported.

A shearing force delivers a higher debonding forceand transmits more force to the enamel than the forceapplied by bracket removal pliers.12 For this reason,we investigated the shear bond strength and theAdhesive Remnant Index (ARI) after debonding withbracket removal pliers. We also compared the shearbond strengths of a polycrystalline ceramic bracket, acollapsible polycrystalline bracket and a metal bracket after debonding with bracket removal pliers,and the modes of failure of the brackets at the enamel-adhesive-bracket interfaces.


Ninety extracted human maxillary first premolarswere selected for bonding. The teeth were kept in dis-tilled water at 37 °C for 48 hours. All teeth wereexamined under x3 magnification to screen for anyenamel fractures prior to the research, and teeth withvisible fractures were excluded from the study. Theteeth were mounted in acrylic before testing in theInstron 5566 universal testing machine (InstronCorporation, Norwood, MA, USA) (Figure 1). Thebrackets tested were the Clarity collapsible poly-crystalline bracket, the InVue polycrystalline ceramicbracket and, as a control, the Miniature Twin metalbracket (3M Unitek, Monrovia, CA, USA). Allbrackets were maxillary first premolar brackets with0.022 x 0.028 inch slot size and mechanical retentionbases (Figure 2). Transbond XT Light Cure Adhesiveand Primer were used (3M Unitek, Monrovia, CA,USA). The teeth were pumiced, etched with 37 percent phosphoric acid for 20 seconds, rinsed withwater and then air dried for 5 seconds. The primerwas rubbed on the tooth surface and each tooth then

Figure 1. Tooth mounted in acrylic in the Instron machine.

received a two second air blast. Adhesive was appliedto the bracket base, and the bracket was placed on thebuccal surface of each premolar tooth. Excess resinwas carefully removed. The brackets were cured for10 seconds with an Ortholux LED curing light (3MUnitek, Monrovia, CA, USA). The samples werestored in distilled water at 37 °C for 48 hours.

Forty-five teeth (N = 15 per group) were bonded withClarity ceramic brackets, InVu ceramic brackets andMiniature Twin metal brackets, respectively. Theshear bond strengths were tested using the Instronuniversal testing machine at a crosshead speed of 1 mm/minute. This technique is frequently used inthis type of research.21 The average surface areas ofthe bases were 12.45 mm2 for the Clarity ceramicbrackets, 16.13 mm2 for the InVu ceramic bracketsand 9.08 mm2 for the metal brackets. The shear bondstrength values in MPa were obtained by dividing themaximum load (N) by the base area (mm2).

In the other 45 teeth, the brackets were removed withpliers, as recommended by the respective manufac-turers (Figure 3). The locations of failure were exam-ined in all 45 teeth with a Nikon Microphot SAmicroscope at x5 magnification. The amount ofresidual adhesive was assessed according to the modi-

fied Remnant Index (ARI).22 This index has fourgrades, ranging from 0 to 3 (0, no adhesive left ontooth; 1, less than half of the adhesive left on tooth;2, more than half of the adhesive left on tooth; 3, alladhesive left on tooth with distinct impression of thebracket base). An additional grade of 4 was added forsamples that had ceramic material left on the teeth.This method is frequently used to quantify theamount of adhesive left on the tooth. The teeth withan ARI score of 0 were evaluated with a SEM at x35magnification. One operator performed the entireexperiment.

ANOVA was used to determine whether or not therewere significant differences in the mean shear bondstrengths between the three groups (Clarity, InVu andthe Miniature Twin metal brackets). The Kruskal-Wallis test was used to determine if there were signif-icant differences in the mean rank of the ARIbetween the three groups. Post-hoc pairwise compar-isons were made using the Wilcoxon-Mann-WhitneyU test with a Bonferroni correction (adjusted α =0.017). The Weibull modulus (m), was computed tocompare brackets’ variabilities in tension at failure,where m is the slope coefficient obtained fromregressing ln(ln(1/survival probability)) on ln(shear

LEMKE ET AL


(a) (b) (c)

Figure 2. (a) Clarity polycrystalline bracket base. (b) InVu polycrystalline bracket base. (c) Miniature Twin (metal) bracket base.

Table I. Shear bond strengths of ceramic and metal brackets (MPa).

Bracket N Mean SD Maximum Minimum

Metal 15 11.89 1.83 15.63 8.5Clarity 15 10.78 2.74 15.60 7.08InVu 15 12.43 2.40 16.08 7.78

ANOVA, p = 0.159

Table II. Weibull moduli (m) and 95 per cent confidence intervals andadjusted R2.

Bracket m (95% CI) Adjusted R2

Metal 6.42 (5.42 – 7.42) 0.94InVu 5.15 (4.68 – 5.61) 0.98Clarity 4.03 (3.34 – 4.73) 0.92



bond strength). A high value of m indicates that thetensile strength of the material is defined more pre-cisely than a material with a small m value.23

Results

The mean shear bond strengths are given in Table I.The mean shear bond strengths of the Clarity, Invuand metal brackets were 10.78 ± 2.74 MPa, 12.43 ±2.40 MPa and 11.89 ± 1.83 MPa, respectively (p = 0.159). The Weibull analysis showed that themetal bracket had the highest m value and thus itsfailure could be defined in a more narrow range, fol-lowed by the InVu bracket and then the Claritybracket (Table II).

The modes of failure during debonding with plierswere predominantly between the bracket and theadhesive. There were significant differences in themean rank of the ARI between the three groups (p = 0.006). Pairwise comparisons revealed that therewere significant differences in mean rank between the

Clarity and InVu brackets (p = 0.011) and betweenthe Clarity and metal brackets (p = 0.005), but therewas no significant difference in mean rank betweenthe InVu and metal brackets (p = 0.187). The major-ity of the Clarity brackets had an ARI score of 3. TheARI scores for the metal brackets were also mostlywithin the adhesive: only one metal bracket failed atthe adhesive and enamel interface. The InVu bracketfailures were more toward the extreme scores, beingeither 0 and 1 or 3 and 4. In six out of 15 InVu brack-ets the brackets fractured. When debonding with pli-ers, three InVu and one metal bracket debondedbetween the enamel and the adhesive. These fourteeth were examined in the SEM to determine ifenamel fracture had occurred. There were no enamelfractures of the teeth bonded with the three InVubrackets, but there was a small fracture on the toothbonded with the metal bracket (Figure 4). An exam-ination with the SEM at a magnification of x250 con-firmed our findings (Figure 5). The ARI scores afterdebonding are shown in Table III.

(a) (b)

Figure 3. (a) Clarity debonding pliers. (b) Plier used to debond the InVu and metal brackets.

Table III. Comparison of ARI of ceramic and metal brackets when removed with pliers.

ARI grade Clarity vs InVu Metal vs Clarity Metal vs InVu

Bracket N 0 1 2 3 4 p p p p

Metal 15 1 3 2 9 0 0.0060.005

Clarity 15 0 0 3 11 1 0.006 0.187

Invu 15 3 5 0 1 6 0.0060.011

Grade: 0, no adhesive left on tooth; 1, less than half of the adhesive left on tooth; 2, more than half of the adhesive left on tooth; 3, all adhesive left ontooth with distinct impression of the bracket base; 4, ceramic left on toothBecause there was a statistically significant difference, pairwise analysis was used to compare the differences between the samplesSignificant values in bold

}} }

LEMKE ET AL


Discussion

While determinations of shear bond strength are fre-quently reported, one should remember that this typeof force is not always the force applied to a bracketduring function or debonding in vivo. In the labor-atory, shear bond strength is tested by applying a unilateral load at the bracket-adhesive interface, andprovides an acceptable method to compare the bondstrengths of different brackets.24 Retief reportedenamel fractures on debonding with bond strengthsof 13.73 MPa, leading Bishara and Fehr to suggestthat bond strengths lower than 12.75 MPa would besafe for the enamel.11,25 The mean shear bondstrength of the Clarity brackets reported byTheodorakopoulou et al. was 21.67 MPa, which ismuch higher than the previously reported values of10.4 and 13.27 MPa.20,26 Webster et al. evaluated thebond strengths of metal brackets bonded to enamelwith Transbond XT adhesive and found that, underideal conditions, the mean shear bond strength was ashigh as 26.9 ± 6.9 MPa, but when the XT primer wascontaminated with artificial saliva, the bond strengthwas 23.7 ± 5.3 MPa.27 These values are higher than

those reported by Theodorakopoulou and coworkers,although metal brackets were used.26 Bishara et al.tested the bond strength of Clarity ceramic bracketsbonded to enamel with Transbond XT adhesive andreported a value of 10.4 ± 4.1 MPa.28 We used thesame adhesive and found similar results. Mundstocket al. also used Clarity ceramic brackets withTransbond XT adhesive and reported a slightly high-er bond strength value of 13 ± 5.39 MPa.20 In agree-ment with Bishara et al., we found no significant dif-ferences between the forces needed to debond Clarityand metal brackets.6

In-vitro studies have shown that acceptable bondstrengths can be achieved for collapsible ceramicbrackets and removal of the bracket should not causeany enamel fracture.6,20,26 Liu noted enamel fracturein four out of 20 specimens with Inspire brackets andfive out of 20 for both the Clarity and the metalbrackets after shear bond strength testing: six out of14 of these fractures occurred below the bracketbonding areas.21 Our results indicated that debond-ing collapsible ceramic brackets with pliers is a safemethod of bracket removal: we found only two

(a) (b)

(c) (d)

Figure 4. SEM photomicrographs. (a) InVu bracket, specimen 2. (b) InVu bracket, specimen 10. (c) InVubracket, specimen 12. (d) Metal bracket, specimen 12. Original magnification x35.

enamel fractures when removing the InVu and onetooth with an enamel fracture in the Clarity group.Several studies confirm our finding of a high inci-dence of ARI scores of 3 (all adhesive on the enamel)with the Clarity bracket.20,26,28 Three InVu bracketsfailed at the adhesive-enamel interface, five had anARI of 1 and six InVue brackets fractured.

In our study, the modes of failure of the Clarity andmetal brackets during debonding with pliers werepredominantly at the bracket-adhesive interface,whereas 40 per cent of the InVu brackets fractured. Ina clinical setting, it is harder and takes longer toremove ceramic remnants from the enamel thanadhesive remnants. With some methods of removingceramic remnants there is a chance of overheating theteeth and possible pulpal damage.29

Conclusion

There were no statistically significant differences inthe shear bond strengths among the three brackettypes. The mode of failure with pliers was predomi-nantly at the adhesive-bracket interface in all threesamples. No enamel fractures occurred in the teethbonded with either ceramic bracket. The Clarity col-lapsible ceramic brackets had similar bond strengthand near-zero bracket failure rate compared with themetal brackets, while the InVu ceramic brackets hada higher failure rate than metal brackets.


Dr Richard W. BallardLSUHSC School of Dentistry1100 Florida Avenue (Box 230)New Orleans, LA, 70119United States of America

Tel: +504 941 8245Fax: +504 941 8410Email: [email protected]

References 1. Keim RG, Gottlieb EL, Nelson AH, Vogels DS. 2009 JCO

Orthodontic Practice Study. Part 1. Trends. JCO 2009;43:625–34.

2. Scott P, Fleming P, DiBiase A. An update in adult ortho-dontics. Dent Update 2007;34:427–8, 431–4, 436 passim.

3. Rosvall MD, Fields HW, Ziuchkovski J, Rosenstiel SF,Johnston WM. Attractiveness, acceptability, and value oforthodontic appliances. Am J Orthod Dentofacial Orthop2009;135:276 e1–12.

4. Sinha PK, Nanda RS. Esthetic orthodontic appliances andbonding concerns for adults. Dent Clin North Am 1997;41:89–109.

5. Birnie D. Ceramic brackets. Br J Orthod 1990;17:71–4.6. Bishara SE, Olsen ME, Von Wald L. Evaluation of debond-

ing characteristics of a new collapsible ceramic bracket. AmJ Orthod Dentofacial Orthop 1997;112:552–9.

7. Wang WN, Li CH, Chou TH, Wang DD, Lin LH, Lin CT.Bond strength of various bracket base designs. Am J OrthodDentofacial Orthop 2004;125:65–70.

8. Swartz ML. Ceramic brackets. J Clin Orthod 1988;22:82–8. 9. Odegaard J, Segner D. Shear bond strength of metal brackets

compared with a new ceramic bracket. Am J OrthodDentofacial Orthop 1988;94:201–6.

10. Chaconas SJ, Caputo AA, Niu GS. Bond strength of ceram-ic brackets with various bonding systems. Angle Orthod1991;61:35–42.

11. Bishara SE, Fehr DE. Ceramic brackets: something old,something new, a review. Semin Orthod 1997;3:178–88.

12. Bishara SE, Fonseca JM, Fehr DE, Boyer DB. Debondingforces applied to ceramic brackets simulating clinical conditions. Angle Orthod 1994;64:277–82.

13. American Association of Orthodontists. Summary of AAOceramic bracket survey. The Bulletin Supplement 1989;7(4)(Winter).

14. Storm ER. Debonding ceramic brackets. J Clin Orthod1990;24:91–4.

15. Bishara SE, Trulove TS. Comparisons of different debondingtechniques for ceramic brackets: an in vitro study. Part I.Background and methods. Am J Orthod Dentofacial Orthop1990;98:145–53.

16. Redd TB, Shivapuja PK. Debonding ceramic brackets:effects on enamel. J Clin Orthod 1991;25:475–81.

17. Forsberg CM, Hagberg C. Shear bond strength of ceramicbrackets with chemical or mechanical retention. Br J Orthod1992;19:183–9.

18. Viazis AD, Cavanaugh G, Bevis RR. Bond strength ofceramic brackets under shear stress: an in vitro report. Am JOrthod Dentofacial Orthop 1990;98:214–21.

19. Eliades T, Viazis AD, Eliades G. Bonding of ceramic bracketsto enamel: morphologic and structural considerations. Am JOrthod Dentofacial Orthop 1991;99:369–75.

20. Mundstock KS, Sadowsky PL, Lacefield W, Bae S. An invitro evaluation of a metal reinforced orthodontic ceramicbracket. Am J Orthod Dentofacial Orthop 1999;116:635–41.

21. Liu JK, Chung CH, Chang CY, Shieh DB. Bond strengthand debonding characteristics of a new ceramic bracket. AmJ Orthod Dentofacial Orthop 2005;128:761–5; quiz 802.



Figure 5. Small fracture found on a tooth bondedwith a metal bracket. Original magnification x250.

LEMKE ET AL


22. David VA, Staley RN, Bigelow HF, Jakobsen JR. Remnantamount and cleanup for 3 adhesives after debracketing. AmJ Orthod Dentofacial Orthop 2002;121:291–6.

23. Burrow MF, Thomas D, Swain MV, Tyas MJ. Analysis oftensile bond strengths using Weibull statistics. Biomaterials2004;25:5031–5.

24. Armstrong S, Geraldeli S, Maia R, Raposo LH, Soares CJ,Yamagawa J. Adhesion to tooth structure: a critical review ofmicro bond strength test methods. Dent Mater 2010;26:e50–62.

25. Retief DH. Failure at the dental adhesive-etched enamelinterface. J Oral Rehabil 1974;1:265–84.

26. Theodorakopoulou LP, Sadowsky PL, Jacobson A, LacefieldW Jr. Evaluation of the debonding characteristics of 2ceramic brackets: an in vitro study. Am J OrthodDentofacial Orthop 2004;125:329–36.

27. Webster MJ, Nanda RS, Duncanson MG Jr, Khajotia SS,Sinha PK. The effect of saliva on shear bond strengths ofhydrophilic bonding systems. Am J Orthod DentofacialOrthop 2001;119:54–8.

28. Bishara SE, Olsen ME, VonWald L, Jakobsen JR.Comparison of the debonding characteristics of two innova-tive ceramic bracket designs. Am J Orthod DentofacialOrthop 1999;116:86–92.

29. Vukovich ME, Wood DP, Daley TD. Heat generated bygrinding during removal of ceramic brackets. Am J OrthodDentofacial Orthop 1991;99:505–12.

Introduction

Rapid maxillary expansion (RME) is a routine ortho-dontic procedure used to normalise a constrictedmaxillary dental arch. It increases the width of themaxillary dental arch by separating the maxillae at themidpalatal suture and allows the maxillary andmandibular dental arches to match transversely.1,2

Traditionally, two-dimensional planar radiographicimages have been used to identify specific anatomiclandmarks from which vertical and anteroposterior

skeletal and dental dimensions can be measured.Within the past few years, three-dimensional (3-D)radiographic images have been used for the same purposes with many advantages.

Computed tomography (CT) allows fast and preciseacquisition of multiple thin slices and has the poten-tial for multiplanar, 3-D reconstruction. These capabilities greatly increase the utility of CT as a diagnostic method. It also facilitates precise measure-ments to evaluate surgical and orthodontic outcomes,


Skeletal and dental changes after rapid maxillaryexpansion: a computed tomography study

Ahmed Ghoneima,*† Ezzat Abdel-Fattah,* Francisco Eraso,† David Fardo,± KatherineKula† and James Hartsfield+

Department of Orthodontics, Al-Azhar University Faculty of Dental Medicine, Cairo, Egypt;* Department of Orthodontics and Oral FacialGenetics, Indiana University School of Dentistry, Indianapolis, Indiana, United States of America;† Department of Biostatistics, University ofKentucky College of Public Health, Lexington, Kentucky, United States of America± and the Department of Oral Health Science, University ofKentucky College of Dentistry, Lexington, Kentucky, United States of America+

Objectives: To investigate the skeletal and dental changes induced by rapid maxillary expansion, using computed tomography(CT) scans and three-dimensional (3-D) reconstructed images.Methods: Twenty patients (Mean age: 12.3 ± 1.9 years) who required rapid maxillary expansion as a part of their compre-hensive orthodontic treatment underwent pretreatment (T1) and post-treatment (T2) CT scans. The T2 – T1 differences betweenselected skeletal and dental measurements on the coronal CT and 3-D volumetric images were compared using the Wilcoxonsigned ranks test.Results: At T2 the Maxillary alveolar width (4.5 ± 3.5 mm) was greater than the Maxillary base width (1.7 ± 0.9 mm). Thegreatest transverse dental change was in the Intermolar width (6.3 ± 2.1 mm and 2.7 ± 1.9 mm at the crown and the apex,respectively). On the 3-D volume, significant increases occurred in the Bicondylar width (1.2 ± 1.3 mm), Bimaxillo-mandibularwidth (2.1 ± 2.3 mm) and the Maxillary width (2.5 ± 1.6 mm). The greatest change in the dental measurements was in theMaxillary first molar width (6.4 ± 0.1 mm). The Maxillary central incisor angle decreased significantly (-7.9 ± 8.4 mm), indi-cating an increase in the distance between the apices of the central incisors. Conclusion: Volumetric 3-D CT scanning provides a useful method for assessing skeletal and dental changes after rapid maxil-lary expansion. Although significant increases occurred in most skeletal and dental measures, it appears that dental tippingexplains most of the expansion.(Aust Orthod J 2010; 26: 141–148)

Received for publication: December 2009Accepted: June 2010

Ahmed Ghoneima: [email protected] Abdel-Fattah: [email protected] Eraso: [email protected] Fardo: [email protected] Kula: [email protected] Hartsfield: [email protected]

GHONEIMA ET AL


for example, following rapid maxillary expansion.3,4

Diagnosis and treatment planning are more preciseand predictable with the use of CT technology incombination with the available software. Clinicianscan take advantage of 3-D planning for many appli-cations.5 For all these reasons, CT has become anacceptable, accurate and readily accessible tool fortoday’s clinical practice.

Multislice CT is a powerful craniofacial measurementtool with several advantages: true volumetric 3-D representation of the hard and soft tissues of theskull; real-size (1:1 scale) and volumetric 3-Dcephalometric analysis; and high accuracy and relia-bility with no superimposition of anatomic structures.6Therefore, the aim of this prospective, clinical studywas to investigate the changes in the craniomaxillarycomplex and dental arches after rapid maxillaryexpansion using multislice CT scans and 3-D reconstructed images.

Material and methods

The study included 20 patients (Mean age: 12.3 ± 1.9years; Age range: 8–15 years) with bilateral posteriorcrossbites who required RME prior to comprehensiveorthodontic treatment. The exclusion criteria included: presence of a premature contact; previousorthodontic or orthopaedic treatment; systemic dis-ease; congenital abnormality; TMJ disorder; carious,gingival and/or periodontal lesions; and a metallicrestoration(s). The study was approved by the EthicalCommittee of the Dental Faculty, Al-AzharUniversity, Cairo, Egypt, and the parents of eachpatient gave their informed consent.

The Hyrax appliance design was used, which requiredbanding either the maxillary first premolars or themaxillary first primary molars and the maxillary firstpermanent molars (Figure 1). The appliance screwwas activated two quarter turns twice per day untilthe palatal cusps of the maxillary first molars contact-ed the buccal cusps of the mandibular first molars.The appliance was left in situ as a passive retainer forthree months, after which it was removed.

The multiplanar spiral CT machine (X vision EX,General Electric ‘GE’ Corporation Medical SystemsCompany, NY, USA) was used to obtain pre-RME(T1) and post-RME (T2) CT images. The latter weretaken the day after the Hyrax appliance was removed.

Figure 1. Hyrax appliance.

Figure 2. Coronal diagrams showing the landmarks and measurements. A, Molar level: 1-2, line tangent to the base of the nose; 3-4, Maxillarybase width; 5-6, Intermolar width (apex); 7-8, Maxillary alveolar width; 9-10, Intermolar width (crown); 11 and 12, Right and Left molar angula-tions. B, Premolar level: 1-2, line tangent to the base of the nose; 3-4, Interpremolar width (apex); 5-6, Interpremolar width (crown); 7 and 8, Right and Left premolar angulations. C, Canine level: 1-2, line tangent to the base of the nose; 3-4, Intercanine width (apex); 5-6, Intercanine width (crown); 7 and 8, Right and Left canine angulations.

The CT scans were performed at 120 kV and 20 mA(low dose), with a scanning time of 2 s/section. Themachine’s perpendicular light beams were used tostandardise the head position in all three planes,allowing comparison of the images before and afterexpansion. The scans were taken with the patients inthe supine position and the palatal plane perpen-dicular to the floor. Each subject was positioned sothat the longitudinal light beam passed through thecentre of glabella and the philtrum, and the transverselight beam passed through the lateral canthi of theeyes. One-millimetre thick axial sections were made parallel to the palatal plane.

The digital images (Imaging and communications inmedicine, DICOM) were assessed and measuredusing the InVivoDental Imaging software pro-gramme (Anatomage Incorporated, San Jose, CA,USA). Multiplaner reformatting and 3-D post-processing of the DICOM images were carried outwith the software used to create the 3-D volumetricskull models. Linear and angular parameters weremeasured to the nearest 0.1 mm and 0.1 degree

respectively, on both the coronal sections of the CTimages and on the 3-D volumetric scans (Figures 2 to 6).7,8

The Maxillary base width (MBW) and Maxillaryalveolar width (MAW) were measured on the coronalsections that included the furcations of the maxillaryfirst permanent molars. The same procedure wasrepeated for the T2 measurements. The amounts ofskeletal expansion at the Maxillary base and theMaxillary alveolar process and dental expansion at theIntermolar, Interpremolar and Intercanine widths atthe crowns and root apices were the differencesbetween the T1 and T2 widths (T2 minus T1).Positive values indicated expansion.

Dental angulations were measured on the coronalsections as the angles between the line tangent to thebase of the nose (representing the lower limits of thenasal cavity on the right and left sides, respectively)and lines passing through the buccal cusps and theapices of the palatal roots of the maxillary first per-manent molars, through the buccal cusps and apices

SKELETAL AND DENTAL CHANGES AFTER RAPID MAXILLARY EXPANSION


Figure 3. CT coronal images. A: 1, Maxillary base width; 2, Intermolarwidth (apex); 3, Maxillary alveolar width; 4, Intermolar width (crown). B: 1 and 2, Right and Left molar angulations; C: 1, Interpremolar width(apex); 2, Interpremolar width (crown); D: 1 and 2, Right and Left premolarangulations; E: 1, Intercanine width (apex); 2, Intercanine width (crown); F: Right and Left canine angulations.

Figure 4. Frontal diagram showing the landmarks and measurements: 1-2, Bilatero-orbital width; 3-4, Bicondylar width; 5-6, Bizygomatic width; 7-8, Bizygomatico-mandibular width; 9-10, Bimaxillo-mandibular width; 11-12, Maxillary width; 13-14, Bigonial width; 15-16, Biantegonial width;17-18, Maxillary central incisor apex width; 19-20, Maxillary first intermo-lar width; 21-22, Maxillary central incisor mesial width; 23-24, Maxillaryintercanine width; 25-26, Mandibular intercanine width; 27-28, Mandibularfirst intermolar width; 29, Maxillary central incisor angle.

GHONEIMA ET AL


of the first premolars, and the cusp tips and apices ofthe canines. The same procedure was repeated for theT2 measurements. An increase in the value (T2 – T1)indicated buccal tipping of the maxillary dental arch.

From the 3-D volume of each patient, 14 distancesand one angle were measured at T1 and T2. Toimprove the reliability and validity of the measure-ments of the 3-D volume, the selected skeletal anddental landmarks were defined on each model by twoinvestigators. The following skeletal landmarks wereused: Latero-orbitale point – the intersection of thelateral wall of the orbit and the greater wing of thesphenoid (the oblique line); Condylion – the super-ior point of the condyle; Zygomatic point – the mostlateral point of the zygomatic arch; Zygomandibulare– intersection between the lower margin of the zygo-matic bone and the lateral contour of the mandibularramus; Maxillomandibulare – the intersectionbetween the lower margin of the maxilla and themedial contour of the mandibular ramus; Maxillare –the depth of the concavity of the lateral maxillarycontour, at the junction of the maxilla and the zygo-matic buttress; Gonion – the gonial angle of themandible; Antegonion – the antegonial notch.

The following dental landmarks were located on the3-D volume: Maxillary first molar – the most

prominent lateral point on the buccal surface of themaxillary first molar; Mandibular first molar – themost prominent lateral point on the buccal surface ofthe mandibular first molar; Maxillary central incisormesial – the most mesial point of the maxillary central incisor crown; Maxillary central incisor apex –the tip of the root apex of the maxillary central incisor; Maxillary central incisor edge – the incisaledge of the maxillary central incisor, centred medio-laterally. The amount of dental expansion was deter-mined as the difference between the T1 and T2widths. For the Maxillary incisal angle, a positivevalue for T2 – T1 indicated flaring of the maxillarycentral incisors crowns, while a negative value indi-cated flaring of the maxillary central incisor apices. Inaddition, the buccal aspects of all involved teeth werescanned to determine if the roots fenestrated ordehisced the buccal cortical plate.

Statistical analysesAll parameters were measured twice by the sameexaminer with a fortnight between the measure-ments.9 The errors were assessed by Dahlberg’smethod and the intra-examiner reliability wasassessed with the intraclass correlation coefficient(ICC). Since the data were not normally distributed,the change in each variable was tested with theWilcoxon signed rank test.

Results

We found no statistically significant differencesbetween the first and second measurements and highintra-examiner reliability (ICC > .97). The Dahlbergvalues fell between 0.13 mm for the Maxillary centralincisor width at T1 and 0.91 mm for the Maxillo-mandibular width at T2, and 0.38 and 0.88 degreefor the Maxillary central incisor angle at T1 and T2,respectively. The majority of the ICC values were .98

Figure 5. 3-D volume. A: 1, Bilatero-orbital width; 2, Bicondylar width; 3, Bizygomatic; 4, Bizygomatico-mandibular width; 5, Bimaxillo-mandibularwidth; 6, Maxillary width; 7, Bigonial width; 8, Biantegonial width. B: 1, Maxillary central incisor apex width; 2, Maxillary first intermolarwidth; 3, Mandibular first intermolar width; 4, Maxillary central incisormesial width. C: 1, Maxillary intercanine width; 2, Mandibular intercaninewidth.

Figure 6. 3-D volume. The Maxillary central incisor angles before (A) andafter (B) RME.

and .99 and only four values (Maxillary alveolarwidth T1; Mandibular first molar width T1 and T2;Maxillary central incisor mesial width T1) had anICC of .97, confirming the reliability of our methodof measurement. The results are given in Tables I and II. The changes T2 minus T1 are the overalltreatment effect.

All skeletal and dental measurements on the coronalCT sections increased significantly from T1 to T2,indicating that the appliance had expanded the max-illary dentition and upper facial skeleton (Table I).The increase in Maxillary alveolar width was 4.5 ±3.5 mm, which was greater than that seen at theMaxillary base width (1.7 ± 0.9 mm).

Greater transverse changes occurred at the molarcrowns than the molar apices (Intermolar crownwidth: 6.3 ± 2.1 mm: Intermolar apical width: 2.7 ±1.9 mm). In addition, the right and left molars weretipped buccally 7.2 ± 4.2 degrees and 6.3 ± 4.7degrees, respectively. Dental tipping was not identicalon the right and left sides. The premolar and caninewidths also increased and the premolars and caninestipped buccally, but to a lesser degree than the molars.

There were nine significant increases in 3-D volumebetween T1 and T2 (Table II). The Bicondylar width,Bimaxillo-mandibular width and the Maxillary widthincreased between 1.2 and 2.5 mm. The greatest

increase in the linear measurements was seen in theMaxillary first intermolar width (6.4 ± 0.1 mm). TheMaxillary intercanine width (3.3 ± 0.9 mm),Maxillary central incisor apex width (3.4 ± 0.4 mm),Mandibular first intermolar width (1.7 ± 1.8 mm)and Mandibular intercanine width (0.6 ± 0.9 mm)also increased significantly. The Maxillary centralincisor angle reduced significantly from T1 to T2 (-7.9 ± 8.4 mm), indicating that the distance betweenthe root apices increased (Figure 6).

Discussion

Rapid maxillary expansion appliances are used toobtain a normal transverse relationship between themaxilla and the mandible and to relieve crowding inmild cases. The magnitude of the expansion variedgreatly in different individuals and at different partsof the craniomaxillary complex. We found theMaxillary alveolar width increased more than theMaxillary base width and that the amount of skeletaland dental tipping gradually increased from the ante-rior region to the molar region. Technical advances inCT have increased its utility as a diagnostic aid and asa method of evaluating the treatment outcome. SinceCT can be used for multiplanar 3-D reconstructionsand as it has few artifacts and superimposed struc-tures (both of which can hinder measurement),



Table I. Comparison of the T1 and T2 measurements on the coronal CT sections (N = 20).

T1 T2 Change p

Mean SD Mean SD Mean SD

Maxillary base width (MBW, mm) 59.7 2.7 61.5 2.6 1.7 0.9 0.01Maxillary alveolar width (MAW, mm) 52.8 4.0 57.3 4.1 4.5 3.5 0.01Intermolar width (crown, mm) 50.3 3.4 56.6 3.6 6.3 2.1 0.01Intermolar width (apex, mm) 29.3 2.2 32.0 2.8 2.7 1.9 0.01Interpremolar width (crown, mm) 40.6 2.9 46.6 3.2 6.0 2.6 0.01Interpremolar width (apex, mm) 26.5 3.3 29.2 3.6 2.8 1.7 0.01Intercanine width (crown, mm) 31.4 5.0 34.5 4.4 3.1 2.0 0.01Intercanine width (apex, mm) 23.5 3.3 25.9 3.0 2.4 1.4 0.01Right molar angulation (degrees) 118.9 5.6 126.0 4.7 7.2 4.2 0.01Left molar angulation (degrees) 119.5 7.5 125.9 6.6 6.3 4.7 0.01Right premolar angulation (degrees) 107.6 5.1 114.1 5.2 6.5 3.4 0.01Left premolar angulation (degrees) 110.0 6.5 115.5 6.4 5.5 4.2 0.01Right canine angulation (degrees) 100.5 7.8 105.6 6.6 5.1 5.1 0.01Left canine angulation (degrees) 100.7 9.2 104.1 6.8 3.5 4.3 0.01

Statistically significant at p < 0.01

evaluation of the skeletal and dental changes afterrapid maxillary expansion is possible. In addition, thenew software added to the CT workstation providesreproducible images over time, thereby increasing thepossibility of a longitudinal investigation.6

In the present study, all linear and angular measure-ments on the coronal sections increased significantly,indicating that RME increased the transverse dimen-sions of the maxillae. The increase in the Maxillarybase width, however, was considerably less than theincrease in the Maxillary alveolar width. This findingis in agreement with previous studies conducted onfrontal cephalograms,10–15 with the use of implants,16

and on CT scans.17–20 Despite the heterogeneoussample regarding age, sex and amount of expansion,Krebs reported similar outcomes, with a meanincrease in intermolar distance three times larger thanexpansion at the zygomatic processes.16 Wertz andDreskin reported a 2.5 mm widening of the maxillarybase compared with a 6.5 mm increase in the inter-molar distance.10

Our results also showed that the greatest increase inthe width of the dental arch occurred opposite thefirst molars and the effect gradually decreased towardsthe canines, indicating that the posterior dentitionunderwent the greatest expansion as a result of RME

therapy. This was further confirmed by our findingon the 3-D volume, that the greatest variation in thelinear measurements was found in the Maxillaryintermolar width. The increase in the Intermolarwidth reflects the total amount of dental and dento-alveolar expansion produced by the appliance.

In agreement with Garrett et al.,19 we found thatRME tipped the maxillary teeth buccally with thegreatest effect at the first permanent molars, indicat-ing increased alveolar bone bending posteriorly. Inthis regard, when tooth movement becomes the mostsignificant response to expansion, care should betaken not to cause a fenestration or dehiscence in thecortical plate overlying the buccal roots of the firstmolars. We used the 3-D data to examine the corticalplates from the canines to the first molars, and wefound no cases with alveolar fenestration.

The results from the coronal sections were confirmedby measurements of selected skeletal and dentalparameters on the 3-D volumes. Skeletal parameterssuch as Bicondylar width, Bimaxillo-mandibularwidth and Bimaxillary width increased significantly,whereas the Bilatero-orbital width, Bizygomaticwidth, Bizygomatico-mandibular width, Bigonialwidth, and Biantegonial width did not change, presumably because the latter were located some

GHONEIMA ET AL


Table II. Comparison of T1 and T2 measurements on the 3-D volumes (N = 20).

T1 T2 Change t p


Bilatero-orbital width (mm) 85.0 4.2 85.1 4.2 0.1 0.1 1.96 0.06Bicondylar width (mm) 91.8 6.8 92.9 6.6 1.2 1.3 4.20 0.01Bizygomatic width (mm) 113.6 5.0 113.7 5.0 0.0 0.1 1.63 0.12Bizygomatico-mandibular width (mm) 94.2 6.9 94.2 6.8 0.1 0.1 2.26 0.04Bimaxillo-mandibular width (mm) 77.3 9.7 79.3 9.8 2.1 2.3 4.05 0.01Maxillary width (mm) 56.2 4.2 58.7 3.7 2.5 1.6 7.16 0.01Bigonial width (mm) 83.8 5.7 83.8 5.7 0.0 0.1 2.60 0.02Biantegonial width (mm) 77.4 5.3 77.5 5.3 0.0 0.1 1.33 0.20Maxillary central incisor apex width (mm) 5.5 1.7 8.9 4.1 3.4 0.4 3.82 0.01Maxillary first intermolar width (mm) 49.7 3.5 56.1 3.6 6.4 0.1 29.59 0.01Mandibular first intermolar width (mm) 51.0 2.6 52.7 2.7 1.7 1.8 4.41 0.01Maxillary central incisor mesial width (mm) 0.5 0.8 0.9 1.3 0.4 1.5 1.32 0.20Maxillary intercanine width (mm) 30.9 3.7 34.2 3.8 3.3 0.9 16.50 0.01Mandibular intercanine width (mm) 26.6 1.9 27.2 2.2 0.6 0.9 2.89 0.01Maxillary central incisors angle (degrees) 10.3 5.3 2.4 10.5 -7.9 8.4 4.20 0.01

Statistically significant at p < 0.01

distance from the maxillae and not directly affectedby the expansion. In addition, the Mandibular firstintermolar and Mandibular intercanine widthsincreased significantly following RME although therewas no appliance in the mandibular arch during thistime, confirming that RME indirectly expands themandibular dental arch.2,8,13,21

When we compared the radiographic and clinicalfindings we found that the median maxillarydiastema closed at the end of active expansion as thecentral incisor crowns tipped mesially. This wasaccompanied by a significant reduction in the anglebetween the central incisors and an increase in thedistance between the incisor apices, while the dis-tance between the mesial surfaces of the central incisors did not change significantly.

Compared to current cephalometric methods, CTscans and 3-D reconstructed images provide a morecomprehensive and accurate assessment of the dentaland skeletal changes associated with RME.Furthermore, the use of CT scans for diagnosis andfollow-up is becoming accepted by clinicians as a sub-stitute for conventional cephalometry, but analysis oflong-term data and a larger clinical series will be nec-essary to determine the application of this method inthe clinical practice. Future studies will examine thelong-term treatment effects of RME on this group ofsubjects.

Conclusions

RME produced a significant overall increase in maxillary transverse dimensions, with increasingmagnitude from the base of the maxilla to the dentalarch.

Although significant increases occurred in most skeletal and dental parameters, it appears that bonebending and tipping might explain most of theexpansion. The amount of tipping graduallyincreased from the anterior region to the molarregion.

Computed tomography is an effective and reliablemethod for evaluating the changes induced by RME.It also allows multiplanar and volumetric 3-D reconstruction of the image and a comprehensiveevaluation of changes in the skeletal and dental structures. In addition, the volumetric images allowbetter examination of the treatment outcomes thanconventional methods.

Acknowledgments

The authors would like to thank Dr Ayman Kamelfor his skilled radiographic and technical assistance,Dr Ashraf El-Bedwehi for his critical advice and Mr George Eckert for the statistical assistance.


Dr Ahmed GhoneimaDepartment of Orthodontics and Oral FacialGeneticsIndiana University School of Dentistry1121 W. Michigan St. RM 270BIndianapolis, IN 46202United States of AmericaTel: (+317) 278-1653Fax: (+317) 278-1438Email: [email protected]

References1. McNamara JA. Maxillary transverse deficiency. Am J Orthod

Dentofacial Orthop 2000;117:567–70.2. Bishara S, Staley R. Maxilary expansion: clinical implica-

tions. Am J Orthod Dentofacial Orthop 1987;91:3–14.3. Goldenberg D, Alonso N, Goldenberg F, Gebrin E, Amaral

T, Scanavini M, Ferreira M. Using computed tomography toevaluate maxillary changes after surgically assisted rapidpalatal expansion. J Craniofac Surg 2007;18:302–11.

4. Baumrind S, Carlson S, Beers A, Curry S, Norris K, Boyd R.Using three-dimensional imaging to assess treatment out-comes in orthodontics: a progress report from the Universityof the Pacific. Orthod Craniofac Res 2003;6:132–42.

5. Scarfe W, Farman A, Sukovic P. Clinical applications ofcone-beam computed tomography in dental practice. J CanDent Assoc 2006;72:75–80.

6. Swennen G, Schutyser F. Three-dimensional cephalometry:Spiral multi-slice vs cone-beam computed tomography. AmJ Orthod Dentofacial Orthop 2006;130:410–16.

7. Podesser B, Williams S, Bantleon H, Imhof H. Quantitationof transverse maxillary dimensions using computed tomog-raphy: a methodological and reproducibility study. Eur JOrthod 2004;26:209–15.

8. Baccetti T, Franchi L, Cameron C, McNamara JA. Treatmenttiming for rapid maxillary expansion. Angle Orthod 2001;71:343–50.

9. Suomalainen A, Vehmas T, Kortesniemi M, Robinson S,Peltola J. Accuracy of linear measurements using dental conebeam and conventional multislice computed tomography.Dentomaxillofac Radiol 2008;37:10–17.

10. Wertz R, Dreskin M. Midpalatal suture opening: A nor-mative study. Am J Orthod 1977;71:367–81.

11. Frank S, Engel G. The effects of maxillary quad-helix appli-ance expansion on cephalometric measurements in growingorthodontic patients. Am J Orthod 1982;81:378–89.

12. da Silva Filho O, Montes L, Torelly L. Rapid maxillaryexpansion in the deciduous and mixed dentition evaluatedthrough posteroanterior cephalometric analysis. Am JOrthod Dentofacial Orthop 1995;107:268–75.



13. Cameron C, Franchi L, Baccetti T, McNamara JA. Longterm effects of rapid maxillary expansion: a posteroanteriorcephalometric evaluation. Am J Orthod Dentofacial Orthop2002;121:129–35.

14. Lamparski D, Rinchuse D, Close J, Sciote J. Comparison ofskeletal and dental changes between 2-point and 4-pointrapid palatal expanders. Am J Orthod Dentofacial Orthop2003;123:321–8.

15. Davidovitch M, Efstathiou S, Sarne O, Vardimon A. Skeletaland dental response to rapid maxillary expansion with 2-versus 4-band appliances. Am J Orthod Dentofacial Orthop2005;127:483–92.

16. Krebs A. Midpalatal suture expansion studies by the implantmethod over a 7-year period. Rep Congr Eur Orthod Soc1964:40;131–42.

17. Garib D, Henriques J, Janson G, Freitas M, Coelho R.Rapid maxillary expansion-tooth tissue-borne versus tooth-borne expanders: a computed tomography evaluation ofdentoskeletal-effects. Angle Orthod 2005;75:548–57.

18. Podesser B, Williams S, Crismani A, Bantleon H. Evaluationof the effects of rapid maxillary expansion in growing chil-dren using computer tomography scanning: a pilot study.Eur J Orthod 2007;29:37–44.

19. Garrett B, Caruso J, Rungcharassaeng K, Farrage J, Kim J,Taylor G. Skeletal effects to the maxilla after rapid maxillaryexpansion assessed with cone-beam computed tomography.Am J Orthod Dentofacial Orthop 2008;134:8e1–8.e11.

20. Ballanti F, Lione R, Fanucci E, Franchi L, Baccetti T, CozzaP. Immediate and post-retention effects of rapid maxillaryexpansion by computed tomography in growing patients.Angle Orthod 2009;79:24–9.

21. Adkins M, Nanda R, Currier G. Arch perimeter changes onrapid palatal expansion. Am J Orthod Dentofacial Orthop1990;97:194–9.

GHONEIMA ET AL


Introduction

Band retention is essential for successful and effectiveorthodontic treatment.1,2 Furthermore, plaque reten-tion under loose bands can result in carious lesions ina few weeks.3 The consensus is that bands cementedwith glass ionomer cements are retained longer, andless decalcification occurs under a loose band thanunder bands cemented with either zinc phosphate orzinc silico-phosphate cements.4,5–7

Band retention is improved when the band is well-adapted to the tooth, if it is rigid and if the anatomi-cal surface is roughened. A luting agent should sealthe gap between the band and tooth, reduce the riskof caries should the band loosen and be easilyremoved at the end of treatment. Although one in 10bands cemented with glass ionomer cements can beexpected to fail over the course of orthodontic treat-

ment, glass ionomer cements generally fail at thecement-band interface, leaving a protective layer ofcement on the tooth.4,5,8,9

Bond strength, which is the load required to dislodgean attachment from the surface of a tooth, is used asa guide to the retention of a band in vivo. A highbond strength is assumed to translate into a highband retention rate. The retention of a band isdependent on the properties of the cement and factorsthat influence mechanical retention of the band.

In this preliminary in-vitro study, we aim to deter-mine the strength of attachment between a stainlesssteel pad and glass ionomer cement. We excluded thecontributions to band retention made by surface treat-ment of the anatomical surface of the band material,such as microetching, and mechanical locking of anintact band on the tooth.


Strength of attachment between band and glassionomer cement

Elahe Vahid Dastjerdie,* Houman Zarnegar,† Mohammad Behnaz† and Massoud Seifi*

Department of Orthodontics, Dental School, Shahid Beheshti University of Medical Sciences* and Private practice,† Tehran, Iran

Aim: To determine the strength of attachment between plain stainless steel band material and glass ionomer cement.Methods: Seventy-five extracted upper premolars, free of visible structural defects, were used. The teeth were divided randomlyinto three groups and embedded in acrylic resin blocks. A short length of plain, stainless steel band material with a weldedstainless steel standard edgewise 0.022 inch bracket was adapted to the buccal surface of each tooth. The bracket-stainlesssteel pads were then cemented to the teeth with either Bandtite (Group 1), Granitec (Group 2) or Ariadent (Group 3) glassionomer cement and stored in an incubator at 37 °C for 30 days. The shear bond strengths of the specimens were measuredand compared.Results: The mean shear bond strengths (SBS) were significantly different: Bandtite 0.7331 ± 0.056 Mpa; Granitec 0.3869 ±0.047 Mpa; Ariadent 0.2931 ± 0.033 Mpa (ANOVA, p < 0.001). Tukey HSD post-hoc tests also showed significant differ-ences between Bandtite and Granitec, Bandtite and Ariadent, and Granitec and Ariadent (p < 0.001). All specimens failed atthe band-cement interface.Conclusion: The highest and lowest SBS were related to Bandtite and Ariadent cements, respectively. All cements had bondstrengths less than the range of bond strengths considered to be clinically acceptable for bonded orthodontic attachments.Mechanical factors are important for band retention.(Aust Orthod J 2010; 26: 149–152)

Received for publication: January 2009Accepted: June 2010

E. Vahid Dastjerdie: [email protected]. Zarnegar: [email protected]. Behnaz: [email protected]. Seifi: [email protected]

DASTJERDIE ET AL



Seventy-five extracted upper premolars were used inthis in-vitro study. The teeth were caries-free, had norestorations, no visible dentinal or enamel defects andwere not malformed. They were stored in normalsaline before the experiment. Soft tissue and blooddebris were removed by washing the teeth with waterand the crowns were cleaned with a fluoride-free pro-phylaxis paste and rubber cup. Following cleaning, theteeth were randomly assigned to three groups: Group1, Bandtite (American Orthodontics, WI, USA) atrue glass ionomer cement containing silicon oxide,calcium fluoride, aluminium oxide, barium sulfate,aluminium phosphate, aluminium fluoride, poly-acrylic acid and water; Group 2, Granitec (Ortho-Technology, FL, USA) a true glass ionomer cementcontaining fluoro-alumina-silica glass as a powderand an aqueous solution of polyacrylic acid as the liquid; Group 3, Ariadent (ApadanaTak, Tehran,Iran) a true glass ionomer cement containing fluoro-silicate as a powder and an aqueous solution of poly-acrylic acid as the liquid.

The teeth were embedded in acrylic resin blocks(Acropars, Tehran, Iran) to within 2 mm of thecemento-enamel junctions, placed in water to dissi-pate heat from the polymerising resin and then storedin normal saline for 24 hours.

Standard 0.022 inch slot, edgewise brackets(Dentaurum, Ispringen, Germany) were welded toshort lengths (5 x 7 mm) of 0.006 inch thick stainlesssteel band material and adapted to the buccal surfaceof each tooth. The band material was not micro-etched. The cements were mixed according to themanufacturers’ directions, loaded on the stainlesssteel pads, pressed on the dry buccal surfaces of theteeth with a burnisher and left undisturbed for 15minutes. The specimens were transferred to distilledwater and stored in an incubator with 100 per centhumidity and a temperature of 37 °C for 30 days.

The teeth were mounted in an Instron UniversalTesting Machine (Model 1195, Instron Ltd, HighWycombe, England) with the aid of a purpose-builtjig. A shear force was applied to each bracket slot bya length of 0.021 x 0.025 inch wire welded to a 2 x20 mm wide stainless steel blade at a crosshead speedof 0.5 mm/min. The groups were compared with aone-way analysis of variance and Tukey post-hoc multiple comparison tests.

Results

The observed force at fracture (N) was divided by themean area of the band material surface (35 mm2) toobtain the shear bond strength in megapascals (MPa).The results are given in Table I. The SBSs were:Group 1, Bandite, Mean: 0.7331 ± 0.056 MPa,Range: 0.63-0.83 MPa; Group 2, Granitec Mean:0.3869 ± 0.047 MPa, Range: 0.3-0.47; Group 3,Ariadent Mean: 0.2931 ± 0.033 MPa, Range:0.23–0.36.

The one-way ANOVA revealed a significant differ-ence in the SBS (p < 0.001). Tukey post-hoc tests alsoshowed significant differences between Bandtite andGranitec, Bandtite and Ariadent, and Granitec andAriadent (p < 0.001).

Discussion

We set out to determine the strengths of attachmentbetween the cement, the tooth and a plain stainlesssteel pad. Previous studies have shown what appearsto be a threshold in the shear-peel band strength ofmicroetched orthodontic bands.10,11 A coarse factory-etched surface aided retention, while a finer in-officepattern reduced the shear-peel band strength toalmost half that of the factory-etched band. Weaimed to exclude any contribution to retention byeither surface treatment of the anatomical surface of aband or by mechanical locking of the band on thetooth. As expected, the bond strengths of all threecements were markedly less than the bond strengthsof composite resins used to bond orthodontic attach-ments to teeth, and the strength of attachmentbetween an intact band and the tooth.12 We were sur-prised that the cement remained attached to the plainstainless steel pads for 30 days and at least 0.23 MPawas required to dislodge the pads from the teeth.

Of the cements tested, Bandtite had the highest shearbond strength (approximately 10 per cent of the clin-ically acceptable range for individual bonded attach-ments) and Ariadent the lowest bond strength.Following debonding, no remnants of cementremained on the band material and no specimensfailed cohesively. We are at a loss to explain the dif-ferences between the cements and postulate that thedifferent particle sizes, moisture contamination dur-ing storage, the powder/liquid ratio, solvent concen-tration, mixing procedure and different acidities mayhave contributed to our findings.4,8

Glass ionomer cements are mixtures of an acid, fre-quently an aqueous solution of polyacrylic acid, andan acid soluble calcium fluoro-alumina-silica powder.During bonding, polyacrylic acid reacts with theenamel, replacing phosphate and/or calcium ionsfrom the enamel and the cement bonds to the toothand, in our study, the band material.13 As a rule glassionomer cements with higher concentrations of acidand thinner films produce stronger bonds to enam-el.14 As the companies did not provide full infor-mation of the composition of their cements, we canonly speculate that different concentrations of poly-acrylic acid, different solubilities and powder:liquidratios may be responsible for the different strengths ofattachment between the cements and the stainlesssteel pad.

The ideal luting agent should fill the gap between theband and the tooth for the length of treatment andoffer some protection from decay should the bandloosen. It could be argued that cohesive failure or fail-ure at the band-glass ionomer cement interface ispreferable, as an intact cement film and release of fluoride ions from the cement protect the tooth fromdecay. The thickness of the cement layer is also animportant factor that may compromise the bondstrength at the cement-tooth interface. Thick layersof cement are more prone to dissolve in fluids overtime and influence the longevity of the bond betweenthe band and the tooth.2,3 Thin cement films, of theorder of 13–19 µm, produce strong bonds.15,16

Although we did not measure the thickness of thecement layer, we used well-adapted 7 x 5 mm stain-less steel pads and held them in place for 15 minuteswhile the cement set.

The debonding sites for all cements occurred at theband-cement interfaces and intact cement layersremained attached to the teeth. The specimens were

stored in distilled water, not saliva, for 30 days andwere not subjected to the temperature changesencountered in the mouth. Nor were they subjectedto the corrosive effects of some foods and drinks or to physical stress: factors that may promote early loosening and failure at the tooth-cement interface.

Conclusions

The glass ionomer cements failed at the cement-padinterface and all had bond strengths below the valueconsidered to be clinically acceptable for a bondedattachment. The importance of mechanical factorsfor band retention is stressed.

Acknowledgments

The authors wish to thank Dr Mina Mahdian forhelp revising and editing the manuscript.


Dr Elahe Vahid Dastjerdie Dental SchoolShahid Beheshti University of Medical SciencesEvin 1983969411TehranI.R. Iran

Tel/Fax: +98 21 2242 1814Email: [email protected]

References1. Millett DT, MacCabe JF, Bennett TG, Carter NE, Gordon

PH. The effect of sandblasting on the retention of firstmolar orthodontic bands cemented with glass ionomercement. Br J Orthod 1995;22:161–9.

2. Fricker JP. A 12-month clinical comparison of resin-modi-fied light-activated adhesives for the cementation of ortho-dontic molar bands. Am J Orthod Dentofacial Orthop 1997;112:239–43.

3. Melrose CA, Appleton J, Lovius BB. A scanning electronmicroscopic study of early enamel caries formed in vivobeneath orthodontic bands. Br J Orthod 1996;23:43–7.

STRENGTH OF ATTACHMENT BETWEEN BAND AND GLASS IONOMER CEMENT


Table I. The shear bond strengths of glass ionomer cements.

Group N Mean (MPa) SD Range SE 95 per cent CI

Upper Lower

Bandtite 25 0.73 a,b 0.05 0.63 – 0.83 0.010 0.75 0.70Granitec 25 0.38 a,c 0.04 0.30 – 0.47 0.009 0.40 0.36Ariadent 25 0.29 b,c 0.03 0.23 – 0.36 0.006 0.30 0.27

ANOVA, p < 0.001Tukey HSD test, groups with the same letters were significantly different from each other at p < 0.001

DASTJERDIE ET AL


4. Durning P, McCabe JF, Gordon PH. A laboratory investiga-tion into cements used to retain orthodontic bands. Br JOrthod 1994;21:27–32

5. Norris DS, McInnes-Ledoux P, Schwaninger P, Weinberg R.Retention of orthodontic bands with new fluoride–releasingcements. Am J Orthod 1986;89:206–11.

6. Clark RJ, Phillips RW, Norman, RD. An evaluation of sili-cophosphate as an orthodontic cement. Am J Orthod 1977;71:190–6.

7. Kvam E, Broch J, Nissen-Meyer IH. Comparison between azinc phosphate and a glass ionomer for cementation oforthodontic bands. Eur J Orthod 1983;5:307–13.

8. Shaver RL, Siegel IA, Nicholls JI. Effect of ultrasonicZnPO4 cement removal on band adhesion and cement solu-bility under orthodontic bands. J Dent Res 1975;54:206–11.

9. Stirrups DR. A comparative clinical trial of a glass ionomerand a zinc phosphate cement for securing orthodonticbands. Br J Orthod 1991;18:15–20.

10. Grabouski JK, Staley RN, Jakobsen JR. The effect ofmicroetching on the bond strength of metal brackets whenbonded to previously bonded teeth: an in vitro study. Am JOrthod Dentofacial Orthop 1998;114:452–60.

11. Aggarwal M, Foley TF, Rix D. A comparison of shear-peelband strength of 5 orthodontic cements. Angle Orthod2000;70:308–16.

12. Millett DT, Duff S, Morrison L, Cummings A, GilmourWH. In vitro comparison of orthodontic band cements. AmJ Orthod Dentofacial Orthop 2003;123:15–20.

13. Sturdevant CM, Roberson TM, Heymann HO, SturdevantJR. The Art and Science. 3rd edn. St Louis: Mosby, 1995:263–7.

14. Bagheri J. Glass ionomer cements. (D. Wilson). 1st edn.Astane Ghods Razavi Publishing Co. 1373:289–310.

15. Craig R, Powers J. Restorative Dental Materials. 11th edn.St. Louis: Mosby, 2002:614–16.

16. Zachrisson BU. Direct bonding in orthodontic treatmentand retention: a post-treatment evaluation. Eur J Orthod2007;29 (suppl.1):128–34.

Introduction

Psychological studies have shown that facial attrac-tiveness affects the way an individual is regarded byothers. Infants considered to be unattractive by thegeneral population and their own mothers tend to beperceived more negatively than attractive infants.1The attractiveness halo extends from home to school.It can affect teacher – student and student – peer relations and academic attainment.2 The benefits ofphysical attractiveness also extend to the workplace,where attractive individuals tend to fare better thanunattractive individuals with regard to perceived jobqualifications, hiring decisions and future career success.3 In modern society, a pleasant smile is an

advantage in job interviews, social interactions andeven in the selection of a spouse.3–5

An unattractive dental appearance during childhoodcan lead to teasing by age peers that may result in aprofound psychological impact, which may continueinto adult life.6–8 Both adolescent patients and theirparents expect orthodontic treatment to improve oraland dental function, health and aesthetics and toenhance self-confidence and the quality of their sociallife.9,10 Needless to say, the goal of modern ortho-dontics is to improve the quality of life which, in part,is achieved through the enhancement of the patients’smile and facial appearance. Oral health related quality of life (OHRQoL) has been defined as ‘the


Lip - tooth relationships during smiling and speech: an evaluation of different malocclusion types

Roozbeh Rashed and Farzin HeraviDepartment of Orthodontics, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran

Background: Few studies have focused on the impact of malocclusion on lip – tooth relationships during smiling and speech.Aim: To evaluate the impact of different malocclusions on lip – tooth relationships during smiling and speech, using videoimages. Methods: One hundred and three subjects with Class I (N = 31), Class II division 1 (N = 26), Class II division 2 (N = 16)and Class III malocclusions (N = 30) were asked to repeat the same sentence and then smile in front of a video camera. Nineframes were extracted from each subject’s video clip: at rest, posed smile, unposed smile and during the pronunciation of thesounds: ‘che’, ‘fa’, ‘se’, ‘chee’, ‘tee’ and ‘mee’. On each frame, up to 10 parameters describing the lip – tooth relationshipswere measured. Results: In all frames, there were no statistically significant differences in the upper central incisor display ratios among the malocclusion groups (p > 0.05). The buccal corridor ratio in the posed and unposed smiles did not differ significantly amongthe malocclusions (p > 0.05). The most frequently visible last maxillary tooth was the first premolar in the posed smile, and thesecond premolar in the unposed smile. In each malocclusion group, the upper central incisor display ratio varied significantlyamong the nine frames and the buccal corridor ratio during the unposed smile was less than the ratio during the posed smile;although this was only significant in the Class II division 2 subjects. The smile arc was similar in all malocclusions.Conclusions: In each malocclusion the upper central incisor display ratio varied significantly among the nine frames. In eachgroup, the buccal corridor ratio during the unposed smile was less than that during the posed smile, but only the Class II division 2 group was significantly different. The smile arc did not differ among the malocclusions.(Aust Orthod J 2010; 26: 153–159)

Received for publication: December 2009Accepted: June 2010

Roozbeh Rashed: [email protected], [email protected] Farzin Heravi: [email protected]

RASHED AND HERAVI


absence of negative impacts of oral conditions onsocial life and a positive sense of dentofacial self-confidence’. Thus, orthodontic treatment shouldcarefully consider the patient’s facial appearance andparticularly his/her smile. Patients will not be satis-fied with the treatment outcome if aesthetics are sacrificed for the sake of a good occlusion, even if allthe functional goals are met. Improvement in facial aesthetics is a powerful motivation for seekingtreatment.11

Lip – tooth relationships during speech and smilingare important aspects of facial aesthetics. However,few studies have focused on lip – tooth relationshipsduring speech and only one study has considered theimpact of malocclusion on these relationships duringspeech and smiling. Our aim was to evaluate the lip –tooth relations in subjects with different types of malocclusion, using video images taken during smiling and speech.

Material and methodsSubjects and video recordingThe experimental sample consisted of 37 male and 66female subjects who presented for orthodontic treat-ment. The mean ages of the male and female subjectswere 19.0 ± 6.7 years and 18.1 ± 4.9 years, respec-tively. Of the 103 subjects, 31 had a Class I mal-occlusion, 26 a Class II division 1 malocclusion, 16 aClass II division 2 malocclusion and 30 a Class IIImalocclusion.

The study was explained to each participant and/orhis/her parent or guardian and all agreed to partici-pate in the study. The subjects were seated facing amirror positioned two metres in front of them. Toobtain the natural head position (NHP), each subjectwas asked to pitch his/her head up and down until apositon of balance was obtained and to look at thereflections of their eyes in the mirror.

Video images were captured by means of a video camera recorder (Sony Video Camera Recorder,Model CCD-TR311E, Sony Corporation, Japan)mounted on a tripod 1.5 metres in front of each sub-ject, and aimed at the mouth. Each subject was thenasked to repeat a sentence which included words con-taining the sounds: ‘che’, ‘fa’, ‘se’, ‘chee’, ‘tee’ and‘mee’. The subject was then asked to smile voluntar-ily (posed smile) and spontaneously (unposed smile),while the movements of the lips were recorded. Aftercalculating the magnification of the recorded images,a vernier caliper was used to measure the width of anupper central incisor.

The captured images were then downloaded to a per-sonal computer. Using the Windows Movie Makersoftware (Windows XP Professional, Microsoft Cor-poration, USA), nine frames were extracted from eachvideo clip: the subject at rest, during the posed smile,during the unposed smile and during pronunciationof the sounds: ‘che’, ‘fa’, ‘se’, ‘chee’, ‘tee’ and ‘mee’.

Measurements were made using a software pro-gramme designed by the author and called ‘Smile

Figure 2. (a) Maximum upper central incisor display. (b) Outer commissure width (smile width). (c) Inner commissure width. (d) Visible maxillary dentition width.

Figure 1. Smile Analyzer software. This picture shows five windows for theoperators’ use, and the patient’s personal information, loading the desiredimage, measuring the desired parameter (here, the width of the right uppercentral incisor) and the table of measured variables.

Analyzer’ (Figure 1). In this software, all measure-ments were saved in the integrated database, andcould be transferred to other Windows-based soft-ware, such as Microsoft Excel or SPSS.

Measured parametersFor each subject, the height and width of an uppercentral incisor was measured on a frame that showedall of the central incisor crown, and the height-to-width ratio calculated (Figure 2). The followingmeasurements were taken from a representative framewith the subject at rest:

1. Maximum upper central incisor display and the upper central incisor display ratio. These are thepercentage and ratio of the crown height on theframe.

2. Gingival display of the upper central incisor. Theamount of gingival tissue displayed above the longaxis of the incisor, in millimetres.

3. Interlabial gap.

4. Philtrum height.

5. Left and right commissure heights. The distancesbetween the outer commissures and a horizontal linepassing through the subnasal point.

In addition to the first three parameters measured onthe ‘at rest’ frame, the following parameters weremeasured on representative frames of the posed andunposed smiles (Figures 2 and 4):

1. Smile width or outer commissure width, as delin-eated by the outermost confluences of the vermilionborders of the lips at the corners of the mouth,12 andthe smile index, that is, the smile width divided bythe smile height (interlabial gap).13

2. Inner commissure width (the inner commissure isformed by the mucosa overlying the buccinator muscle where it inserts with the orbicularis oris muscle fibres at the modiolus).12

3. Visible maxillary dentition width, which is the dis-tance between most lateral left and right points of themaxillary dentition during smiling.13

4. Left and right buccal corridors, measured from theinner commissure to the last visible maxillary tooth.This measurement was divided by the visible maxil-lary dentition width. The result was a ratio of themaxillary teeth while smiling, minus the buccal corridor. For example, 0.92 means that the maxillarydentition occupied 92 per cent of the inner inter-commissure width. Therefore, the buccal corridorwould then occupy 8 per cent (100 minus 92 percent) of the smile.14

5. Smile arc, which may be in one of three forms:consonant (i.e. parallel), flat or reverse.15

6. Most posterior maxillary tooth visible. In case of a discrepancy between the two sides, the most posterior tooth was entered.14

For the frames in which the subject was speaking thefollowing were measured:

1. Maximum upper central incisor display and theupper central incisor display ratio.

2. Gingival display of the upper central incisor.

3. Interlabial gap.

Statistical analysisStatistical analyses were performed with SPSS 15.0for Windows (SPSS Inc., Chicago, IL, USA). One-

SPEECH AND SMILE CHARACTERISTICS IN DIFFERENT MALOCCLUSIONS


Figure 3. Frequency distribution of the last visible maxillary tooth duringposed and unposed smiles.

Figure 4. (a) Posed smile. (b) Unposed smile. In an unposed smile, despitethe greater smile width, because the lips are stretched more, a larger part ofthe modiolus becomes visible and the inner commissures get more distinctand closer to each other. Thus, the buccal corridor ratio during an unposedsmile is less than that of a posed smile.

60

50

40

30

20

0

Posed Unposed

Lateral

Canine

1st Premolar

2nd Premolar

1st Molar

RASHED AND HERAVI


way ANOVA and paired-t tests were used to analysethe parametric data and the nonparametric tests: theFriedman, Wilcoxon, Mann-Whitney and Kruskal-Wallis were used to analyse the quantitative data. Thequalitative data were analysed with the chi-squaredtest. A significance level of 0.05 was used for all tests.

Results

The mean upper central incisor display ratio or theper cent of the visible crown height was 23 per centat rest, 78 per cent during the posed smile and 99 percent during the unposed smile. On average, the high-est ratio of incisor display during speech occurredduring the pronunciation of ‘che’ or ‘chee (70 percent) and the lowest ratio during pronunciation of‘mee’ (47 per cent).

Using Tjan et al.’s classification of incisor display dur-ing the posed smile, we found 41.7 per cent of thesubjects had an average smile, 13.6 per cent had ahigh smile and 44.7 per cent a low smile.16 There

were fewer subjects with high smiles in all of the mal-occlusion groups, although there was no statisticallysignificant difference in the type of smile among themalocclusion groups (p = 0.12). When incisor displayin the boys and girls were compared, 12.1 per cent ofthe girls and 16.2 per cent of the boys had a highsmile, but the difference was not statistically signifi-cant (p = 0.76).

There was no statistically significant difference in theupper central incisor display ratio among the mal-occlusion groups (p > 0.05). However, this ratio wassignificantly different among nine frames taken atrest, during the posed and unposed smiles, and for the frames taken during the speech exercises (p < 0.001). When frames of the speech exercises werepaired up, the pairs were statistically different (p <0.001), except for the ‘che’ - ‘chee’ and ‘fa’ - ‘se’ pairs.

We found a significant positive correlation betweenthe upper central incisor display ratio during the posedand unposed smiles (Spearman rank correlation:

Table I. Comparisons of the buccal corridor ratios.

Class I Class II div 1 Class II div2 Class III p*Mean (SD) Mean (SD) Mean (SD) Mean (SD)

Posed smile 0.13 (0.06) 0.14 (0.07) 0.18 (0.07) 0.14 (0.08) 0.14Unposed smile 0.12 (0.06) 0.13 (0.08) 0.14 (0.06) 0.13 (0.07) 0.68p† 0.27 0.77 0.04 0.50

* One-way ANOVA† Paired t-test, significant value in bold

Table II. Frequency distributions of the smile arc during posed and unposed smiles.

Unposed smile arc Total

Non definable Consonant Flat Reverse

Posed smile arc Non definable Number 4.0 6.0 5.0 2.0 17.0% of total 4.4 6.6 5.5 2.2 18.7

Consonant Number 0.0 24.0 8.0 0.0 32.0% of total 0.0 26.4 8.8 0.0 35.2

Flat Number 0.0 3.0 23.0 3.0 29.0% of total 0.0 3.3 25.3 3.3 31.9

Reverse Number 0.0 0.0 2.0 11.0 13.0% of total 0.0 0.0 2.2 12.1 14.3

Total Number 4.0 33.0 38.0 16.0 91.0% of total 4.4 36.3 41.8 17.6 100.0

Contingency coefficient: .716, p < 0.001

r = .59, p < 0.001). Furthermore, during speech, thehighest positive correlation was between ‘chee’ and‘tee’ (r = .92, p < 0.001) and the lowest correlationwas between ‘che’ and ‘mee’ (r = .69, p < 0.001). Apositive correlation was found between the uppercentral incisor display ratio during the posed smileand pronunciation of ‘chee’ (Pearson correlation coef-ficient: r = .60, p < 0.001).

Although the buccal corridor ratio was greater duringthe posed smile than during the unposed smile, thedifference was not statistically significant (p > 0.05),except for subjects with a Class II division 2 maloc-clusion (p = 0.04) (Table I). This ratio did not differsignificantly among the malocclusion groups (p > 0.05).

A significant positive correlation was found betweenthe interlabial gap at rest and incisor display duringthe posed smile (r = .41, p < 0.001). Within each mal-occlusion group, the smile indices during the posedand unposed smiles also varied significantly (p < 0.05). However, neither during the posed nor during the unposed smile was this difference significant among the malocclusions (p > 0.05).

Table II depicts a significant contingency in the smilearc type between the posed and unposed smiles(Contingency coefficient: .716, p < 0.001). Thismeans that the smile arc was the same among theposed and unposed smiles in about 70 per cent of the subjects.

As shown in Figure 3 during the posed smile, themost frequently visible last maxillary tooth was thefirst premolar, whereas during the unposed smile itwas the second premolar.

Discussion

Undoubtedly, patients expect to have an attractiveand pleasing appearance at the end of orthodontictreatment. Important components of an attractiveface are an attractive smile and appropriate lip – toothrelationships during speech: both contribute to socialinteraction. We measured the upper central incisordisplay ratio and found no gender difference in thetype of smile in our Iranian sample. Other investiga-tors have reported higher smile lines in women thanin men, selected from non-Iranian groups.17–19 Wefound that the upper central incisor display ratio inyoung adult Iranians during speech and a smile didnot differ significantly among the malocclusions,although we reported that male subjects with Class

III malocclusion displayed less of their upper incisorsduring speech and smile than subjects with Class Iand Class II malocclusions.20 Age-related and ethnicvariations in lip – tooth relationships may exist, aswhite North American adolescents with a Class Iskeletal pattern had different lip – tooth relationshipsbetween a posed smile and articulation of ‘chee’.21

A possible explanation for the similarity in the upperincisor display ratio among the malocclusions is thatthe soft tissues contribute more to incisor displaythan the underlying skeletal form.21 At present, wehave no effective method of classifying dynamicmovements of the lips that will allow us to investigatedifferences in lip – tooth relationships.

The upper incisor display ratio differed significantlyamong the nine frames because each facial animationresulted from different soft tissue movements. Duringa posed smile, the lip commissures move more superiorly and laterally compared with lip movementduring pronunciation of ‘chee’.21 We found positivecorrelations between incisor display during the posedsmile and during the pronunciation of ‘chee’ andbetween pronunciation of ‘chee’ and ‘tee’.

These findings lend support to the belief that soleconsideration of the lip – tooth relations in smilingmay be misleading. Observing the patient duringnormal speech gives the most valuable aesthetic infor-mation for planning treatment. Tooth display duringsmiling cannot provide the same information, sincethe upper lip is raised by three different musclegroups when a person is smiling.22 In addition, cer-tain consonant sounds may be more reproduciblethan smiles.23 Consonant sounds are certainly lan-guage – specific and, hence, not universal. Moreresearch is needed to relate speech sounds to theamount of incisor exposure. In social interactions,people mostly talk to each other rather than justexchanging smiles, thus making the consideration oflip – tooth relationships during speech of primeimportance. However, such analysis of the patient’sspeech is not possible unless dynamic records areobtained before treatment. It is also necessary todefine specific words or letters which represent thepatient’s lip – tooth relationships. This area is fertileground for further research.

No study has assessed the buccal corridor spaces indifferent malocclusions. In our study, the buccal cor-ridor ratio both during the posed smile (p = 0.14) and



the unposed smile (p = 0.68) did not differ signifi-cantly among the malocclusions. This may be due tospecific soft tissue features in each malocclusion, suchas the thickness of the lips, the amount of lip move-ment, the position and movement of the modiolus.24

An important and interesting observation in thisstudy was that the buccal corridor ratio during anunposed smile was less than that during a posed smile(although this difference was only significant in ClassII division 2 subjects). As Ackerman and Ackermanstated, the buccal corridor should be measured fromthe inner rather than the outer commissures.12 In anunposed smile, despite the greater smile width,because the lips are stretched more, a larger part ofthe modiolus becomes visible and the inner commis-sures become more distinct and closer to each other (Figure 4). Burstone attributed the variability ofthis space among different types of smiles to the buccinator muscle.23

We found a positive correlation between the inter-labial gap at rest and the upper incisor display ratioduring the posed smile. This confirms the notion thatthe interlabial gap at rest may be a good estimate of incisor display during a smile, underlining the impor-tance of taking the interlabial gap into account during treatment planning.13,25,26 We also found thatthe smile index differed significantly between theposed and unposed smiles, and attribute this to vari-ability of soft tissue movements and different smilewidths (i.e. outer commissure width) and smileheights (i.e. interlabial gap). Isiksal and his colleaguesreported that the smile index had little impact onsmile aesthetics.13 In nearly 70 per cent of our subjects, we found the smile arc was the same duringthe posed and unposed smiles, which suggests that if a consonant smile is present during a posed smile before and/or after treatment then a conson-ant smile during an unposed smile will be similarlyaffected.

In agreement with Maulik and Nanda,14 we foundthat the most frequently visible last upper teeth werethe first and second premolars during the posed andunposed smiles, respectively. It is believed that themuscles of facial expression may account for morethan 10,000 visible facial configurations and at least18 different types of smile.27 We found that the upper central incisor display ratio was significantlydifferent among the nine frames we used, which sup-ports our proposal that dynamic records should be an

integral part of orthodontic diagnosis and treatmentplanning.21,26,28,29

Conclusions

There was no significant difference in the upper central incisor display ratio among the malocclusiongroups.

The buccal corridor ratio during posed and unposedsmiles did not differ significantly among the mal-occlusion groups.

In each malocclusion group, the buccal corridor ratioduring an unposed smile was less than that during aposed smile, but only in the Class II division 2 groupthe difference was significant.

The smile arc did not differ significantly among different malocclusions.

Acknowledgment

This research was supported by a grant from Vice-Chancellor for Research, Mashhad University ofMedical Sciences.


Associate Professor Farzin Heravi Department of Orthodontics and Dental ResearchCenterSchool of DentistryMashhad University of Medical SciencesMashhadIranTel: +98 511 8419814Fax: +98 511 8423073Email: [email protected]

References 1. Langlois JH, Ritter JM, Casey RJ, Sawin DB. Infant attrac-

tiveness predicts maternal behaviours and attitudes. DevPsychol 1995;31:466–72.

2. Clifford M, Walster E. The effects of physical attractivenesson teacher expectation. Sociol Educ 1973;46:248–58.

3. Hosoda M, Stone-Romero EF, Coats G. The effects of phys-ical attractiveness on job-related outcomes: a meta-analysisof experimental studies. Personnel Psychol 2003;56:431–62.

4. Buss DM, Schmitt DP. Sexual strategies theory: an evolu-tionary perspective on human mating. Psychol Rev 1993;100:204–232.

5. Stevenage SV, McKay Y. Model applicants: the effect offacial appearance on recruitment decisions. Br J Psychol1999;90:221–34.

6. Shaw WC, Meek SC, Jones DS. Nicknames, teasing, harass-ment and the salience of dental features among school children. Br J Orthod 1980;7:75–80.

RASHED AND HERAVI


7. Helm S, Kreiborg S, Solow B. Psychosocial implications ofmalocclusion: a 15-year follow-up study in 30-year-oldDanes. Am J Orthod 1985;87:110–118.

8. Kilpeläinen PV, Phillips C, Tulloch JF. Anterior tooth position and motivation for early treatment. Angle Orthod1993;63:171–4.

9. Gosney MB. An investigation into some of the factors influ-encing the desire for orthodontic treatment. Br J Orthod1986;13:87–94.

10. Cunningham SJ, O’Brien C. Quality of Life andOrthodontics. Semin Orthod 2007;13:96–103.

11. Jacobson A. Psychological aspects of dentofacial aestheticsand orthognathic surgery. Angle Orthod 1984;54:18–35.

12. Ackerman MB, Ackerman JL. Smile analysis and design inthe digital era. J Clin Orthod 2002;36:221–36.

13. Is iksal E, Hazar S, Akyalçın S. Smile aesthetics: perceptionand comparison of treated and untreated smiles. Am JOrthod Dentofacial Orthop 2006;129:8–16.

14. Maulik C, Nanda R. Dynamic smile analysis in youngadults. Am J Orthod Dentofacial Orthop 2007;132:307–15.

15. Sarver DM. The importance of incisor positioning in theesthetic smile: the smile arc. Am J Orthod DentofacialOrthop 2001;120:98–111.

16. Tjan AH, Miller GD, The JG. Some esthetic factors in asmile. J Prosthet Dent 1984;51:24–8.

17. Vig RG, Brundo GC. The kinetics of anterior tooth display.J Prosthet Dent 1978;39:502–504.

18. Mikami I. An evaluation of the functional lip posture.Shigaku 1990;78:339–76.

19. van der Geld PA, van Waas MA. The smile line, a literaturesearch. Ned Tijdschr Tandheelkd 2003;110:350–4.

20. Heravi F. Assessment of lip line in different malocclusionswith video images. World J Orthod 2005;6:50–1.

21. Ackerman MB, Brensinger C, Landis JR. An evaluation ofdynamic lip-tooth characteristics during speech and smile inadolescents. Angle Orthod 2004;74:43–50.

22. Rubin LR. The anatomy of a smile: Its importance in thetreatment of facial paralysis. Plast Reconstr Surg 1974;53:384–7.

23. Nanda R, Burstone CJ. JCO Interviews: Part 1 FacialEsthetics. J Clin Orthod 2007;41:79–87.

24. Jacobs RM, Brodie AG. The analysis of perioral muscularaccommodation in young subjects with malocclusion. AngleOrthod 1966;36:325–34.

25. Peck S, Peck L, Kataja M. The gingival smile line. AngleOrthod 1992;62:91–100.

26. Frindel F. Sixteen keys for building a youthful smile. OrthodFr 2003;74:83–102.

27. Ekman P, Davidson RJ, Friesen WV. The Duchenne smile:emotional expression and brain physiology II. J Pers SocPsychol 1990;58:342–53.

28. Sarver DM, Ackerman MB. Dynamic smile visualization andquantification: part 1. Evolution of the concept and dynam-ic records for smile capture. Am J Orthod DentofacialOrthop 2003;124:4–12.

29. Tarantili VV, Halazonetis DJ, Spyropoulos MN. The spon-taneous smile in dynamic motion. Am J Orthod DentofacialOrthop 2005;128:8–15.



Introduction

Third molars are more frequently impacted than anyother tooth in the dental arches. Incomplete eruptionof mandibular third molars may be accompanied byinfection, pain, cysts, tumours, caries and root resorp-tion of the second molars.1–3 The prevailing view isthat extraction of lower second premolars followed byorthodontic treatment improves the positions andangulations of unerupted third molars so that somethird molars erupt fully.

Factors under the control of the clinician include thepremolar extracted and the mechanics used e.g. ClassII traction vs molar uprighting. First premolar extrac-tions are thought to provide less space for uneruptedthird molars and nonextraction treatment the leastamount of space. A number of biological factors alsoplay a part in determining whether a third molarbecomes impacted or whether it erupts into position.Some of these include: growth in the length of

mandible, the direction of condylar growth, the pattern of eruption of the mandibular dentition, thepath of eruption of the third molars and the retromolar space.4–6

Previous studies have investigated the angulations ofthe mandibular third molars after either second molaror first premolar extractions, but there have been fewreports of the effects of different premolar extractionson the positions and angulations of the mandibularthird molars.7,8 The aims of this study were to inves-tigate the effects of orthodontic treatment and premolar extractions on the inclinations of themandibular third molars and the space available fortheir eruption, and to compare these changes with anonextraction group.


This retrospective study used the standardisedpanoramic radiographs of 54 subjects (20 males,


Effects of orthodontic treatment and premolarextractions on the mandibular third molars

Mevlut Celikoglu,* Hasan Kamak,* Ismail Akkas† and Husamettin Oktay±

Departments of Orthodontics* and Oral and Maxillofacial Surgery,† Faculty of Dentistry, Ataturk University, Erzurum, Turkey, and Departmentof Orthodontics, Faculty of Dentistry, Medipol University, Istanbul, Turkey±

Background: The space available for an unerupted mandibular third may depend on the choice of premolar extracted. Aims: To investigate the effects of orthodontic treatment and premolar extractions on the inclinations of the mandibular thirdmolars and the space available for their eruption, and to compare these changes with a nonextraction group.Methods: The pre- and post-treatment panoramic radiographs of 54 subjects (20 males, 34 females) were used. Eighteen ofthese subjects had the four first premolars extracted, 16 subjects had four second premolars extracted and 20 subjects weretreated nonextraction. Changes in the inclinations and spaces available for the unerupted third molars were compared.Results: In the nonextraction group the third molars uprighted approximately 1 degree and in the second premolar extractiongroup the third molars uprighted 10 degrees. The spaces available for the third molars increased significantly in the first andsecond premolar extraction groups as compared with the space available in the nonextraction group. Conclusions: Orthodontic treatment and extraction of the second premolars improved the inclinations of unerupted third molarsand the space available for their eruption into the arch. The changes in inclination and eruption space were less marked following first premolar extractions. (Aust Orthod J 2010; 26: 160–164)

Received: February 2010Accepted for publication: July 2010

Mevlut Celikoglu: [email protected] Kamak: [email protected] Akkas: [email protected] Oktay: [email protected]

EFFECTS OF PREMOLAR EXTRACTIONS ON MANDIBULAR THIRD MOLARS


34 females) treated in the Department ofOrthodontics, Ataturk University. All subjects hadClass I skeletal and dental relationships with moder-ate anchorage requirements (crowding between 6 and9 mm) prior to orthodontic treatment. Eighteen sub-jects (7 males, 11 females) had four first premolarsextracted (Group I), 16 subjects (6 males, 10 females)had four second premolars extracted (Group II) and20 subjects (7 males, 13 females) had nonextractiontreatment (Group III). The subjects were age-matched at the start to ensure that each group started with the same potential for resorption on theanterior border of the ramus.

All subjects were treated with upper and lowerstraight-wire appliances for at least 24 months andthe second molars were not banded or bonded.Mechanics that could either hold or tip the lower firstmolars distally (e.g. uprighting bends, lingual arches)or mesially (e.g. Class II elastics) were not used.

All pretreatment panoramic radiographs were takenwithin one month prior to the start of the ortho-dontic treatment. The post-treatment radiographswere taken either on the day the active orthodontic

appliances were removed or within two weeks ofdebonding. All radiographs were taken by an experi-enced X-ray technician using an orthopantomograph(Planmeca Proline CC 2002, Helsinki, Finland) witha magnification factor of 1.2.

The outlines of the mandible, nasal septum, hardpalate and the mandibular second and third molarswere traced. The outline of the nasal septum wasbisected and a horizontal reference plane (RP) was drawn perpendicular to the midline bisector andthrough the outline of the hard palate. The anglesbetween RP and the long axes of third molar budsand the distances between the most distal points ofthe second molars and the right and left Z pointswere measured on the pre- and post-treatment filmsby the same investigator (Figures 1 and 2). Threeweeks after the first set of measurements, 30 filmswere randomly selected, remeasured and intraclasscoefficients were calculated to estimate the methoderrors. The coefficients for all measurements fellbetween .92 and .96, and were considered acceptable.

The changes in the eruption spaces and inclinationsof the third molars to RP were compared with one-way ANOVA and Tukey post-hoc tests. The significance level was set at p < 0.05 for all tests.

Results

The subjects’ ages ranged from 14.20 to 15.20 yearsand the observation periods from 2.04 to 2.30 years.As there were no statistically significant gender differ-ences in either the mean ages or the observation periods, the data for the males and females were

Z point

7

8

Z point

Reference plane (RP)

ANS

Nasal septum

Z point2

2

7

1 1

RIGHT LEFT

78 8

Figure 1. Definition of Z point: the constructed point on the retromolar outlineand the bisector of the angle between the tangents to anterior border oframus and superior surface of the body of mandible.

Figure 2. 1, third molar angulation to the reference plane (RP); 2, eruptionspace measured between the Z point and the most distal point on the outlineof the second molar.

combined (Table I). The pretreatment angulations ofthe mandibular third molars and the pretreatmentspace available for their eruption among the groupswere also compared and no statistically significant differences were found (Table II).

The Group I third molars uprighted approximately 4degrees, the Group II molars uprighted 10 degreesand the angulations of the Group III molarsunchanged (Table II). Only the difference betweenGroup II and III was statistically significant.

Extraction of the first premolars resulted in 3 mm of space for the unerupted third molars, and extrac-tion of the second premolars provided 5 mm additional space for the third molars. The eruptionspace in Group III was less than 1 mm. There weresignificant group differences in the eruption spaces(Table II).

Discussion

Measurements of third molar angulations on lateralcephalograms may be biased due to the difficulty inmeasuring the angulations of the molars on super-imposed images, but these problems can be overcomeif 60-degree cephalometric films are used.9–14 Theangulations and positions of the third molars can beaccurately measured on panoramic radiographs pro-viding the same equipment is used for the entirestudy.15–19 We used panoramic radiographs takenwith the same equipment. Although some previousinvestigators have used the occlusal plane and/or themandibular plane as the reference planes to assess thechanges in the angulation and position of the thirdmolars during orthodontic treatment, the occlusalplane may change during treatment and the mandib-ular plane may be affected by remodelling.5,16,17,20–23

CELIKOGLU ET AL


Table I. Comparisons of the pretreatment ages and periods between the pre- and post-treatment radiographs.

Sex N Mean age SD p Observation SD p(years) period (years)

Group I Male 7 14.76 1.59 0.574 2.09 0.19 0.365Female 11 14.20 2.22 2.30 0.58

Group II Male 6 14.57 0.85 0.215 2.13 0.28 0.980Female 10 15.17 0.96 2.13 0.24

Group III Male 7 14.73 1.15 0.177 2.04 0.11 0.311Female 13 15.37 0.87 2.15 0.27

Group I 18 14.42 1.97 0.264 2.22 0.47 0.615Group II 16 14.94 0.94 2.13 0.24Group III 20 15.15 0.99 2.12 0.23

Group I: first premolar extraction; Group II: second premolar extraction; Group III: nonextraction

Table II. Comparisons of the pre- and post-treatment angulations and positions of the mandibular third molars.

Group Pretreatment p* Post-treatment Mean difference P† P† P†Mean ± SD Mean ± SD ± SD Group Group Group

I vs II I vs III II vs III

Third molar I 45.22 ± 8.98 0.188 49.44 ± 11.93 4.22 ± 9.44angulation II 43.13 ± 8.18 53.03 ± 10.34 9.91 ± 11.26 0.123 0.433 0.006(degrees) III 40.43 ± 6.78 41.30 ± 7.04 0.88 ± 2.08

Third molar I 6.69 ± 3.03 0.167 9.78 ± 2.57 3.08 ± 1.31eruption space II 5.00 ± 3.66 10.31 ± 2.80 5.31 ± 2.39 0.000 0.000 0.000(mm) III 4.85 ± 2.98 5.28 ± 3.00 0.43 ± 0.73

Group I: first premolar extraction; Group II: second premolar extraction; Group III: non-extractionSignificant values in bold * ANOVA † Tukey HSD test

EFFECTS OF PREMOLAR EXTRACTIONS ON MANDIBULAR THIRD MOLARS


The palatal plane is a more stable option to theseplanes as it is not usually affected by orthodontictreatment.23 The treatment mechanics, in this study,were not so complex as to cause the palatal plane totip. Our subjects had skeletal Class I malocclusionstreated by levelling and aligning the arches and closing the extraction spaces.

Some orthodontists24–26 believe that extraction of thesecond molars will improve the angulation of thethird molars and will cause their eruption into thearch. According to some authorities, the mandibularthird molars upright between 7 and 10 degrees fol-lowing extraction of either the first or secondmandibular premolars.8,10,11,13,15 We found less than7 degrees uprighting in our first premolar extractiongroup (4 degrees), but a similar amount of uprighting (10 degrees) in our second premolar extraction group.In the nonextraction group, there was no change inthe angulation of the third molars.

The greatest increase in eruption space for the thirdmolars was found in the second premolar extractiongroup and the smallest increase in the nonextractiongroup. As the additional space for the third molars inthe nonextraction group was less than 1 mm, mesialmovement of the first and second molars in the second and, to a lesser extent, first premolar extrac-tion groups must have been responsible for increasingthe eruption space, and not growth changes in theretromolar area as claimed by Capelli.9

The third molars erupt between 17 and 21 years ofage, but their roots are not fully formed until 18 to 25years of age. Because our subjects were less than 20years of age at the end of treatment we could notdetermine the final outcome of the third molars. It isquite possible that some third molars in unfavourablepositions at the end of treatment may erupt into posi-tion and that some molars with favourable positionsand angulations may become impacted.10 In a recentstudy, the prevalence of third molar impaction wasfound to be 40 per cent for the nonextraction groupand 22 per cent for the first premolar extractiongroup.10 As expected, low rates of third molarimpaction occur following first and second molarextractions.18,21,27,28 The closer an extraction is to animpacted/unerupted third molar the less likely the third molar will become impacted.20 Thirdmolars that become impacted may be useful replace-ments for heavily filled and carious first or secondmolars.13

The types of the mechanics used during treatmentappear to have an important bearing on eruption ofmandibular third molars. Mechanics that move thefirst and second molars mesially are likely to createspace for unerupted third molars, and mechanics thathold or tip the first or second molars distally are like-ly to result in unerupted third molars becomingimpacted. In the present study, Class II elastics werenot required since the subjects had Class I skeletaland dental relationships with moderate anchoragerequirements. Although we did not randomly allocateour subjects to the groups or match the subjects’ thirdmolar eruption status, we attempted to reduce selec-tion bias by matching the ages of our subjects in thegroups at the outset.

Conclusions

1. Orthodontic treatment and extraction of the secondpremolars improved the inclinations of uneruptedthird molars and the space available for their eruptioninto the arch.

2. The changes in inclination and eruption space wereless marked following first premolar extractions.

3. Nonextraction treatment had little effect on thepositions and angulations of the third molars.

Acknowledgment

We would like to express our sincere gratitude to Professor Zekeriya Aktürk for his help with the statistical evaluation.


Dr Mevlut CelikogluDepartment of OrthodonticsFaculty of DentistryAtaturk UniversityErzurum, 25240TurkeyTel (Bus.): +90.442.231 1820 Fax: +90.442.236 0945 Email: [email protected]

References1. Halmos DR, Ellis E, 3rd, Dodson TB. Mandibular third

molars and angle fractures. J Oral Maxillofac Surg 2004;62:1076–81.

2. Polat HB, Ozan F, Kara I, Ozdemir H, Ay S. Prevalence ofcommonly found pathoses associated with mandibularimpacted third molars based on panoramic radiographs inTurkish population. Oral Surg Oral Med Oral Pathol OralRadiol Endod 2008;105:41–7.

CELIKOGLU ET AL


3. Celikoglu M, Miloglu O, Kazanci F. Frequency of agenesis,impaction, angulation and related pathologies of third molarteeth in orthodontic patients. J Oral Maxillofac Surg 2010;68:990–5.

4. Kaplan RG. Some factors related to mandibular third molarimpaction. Angle Orthod 1975;45:153–8.

5. Saysel MY, Meral GD, Kocadereli I, Tas ar F. The effects offirst premolar extractions on third molar angulations. AngleOrthod 2005;75:719–22.

6. Bjork A, Jensen E, Palling M. Mandibular growth and thirdmolar impaction. Acta Odontol Scand 1956;14:231–72.

7. Dierkes DD. An investigation of the mandibular thirdmolars in orthodontic cases. Angle Orthod 1975;45:207–12.

8. Guo XH, Qian YF, Feng QP. Effects of different premolarextraction on lower third molar eruption. Shanghai KouQiang Yi Xue 2007;16:370–3.

9. Capelli J, Jr. Mandibular growth and third molar impactionin extraction cases. Angle Orthod 1991;61:223–9.

10. Kim TW, Artun J, Behbehani F, Artese F. Prevalence of thirdmolar impaction in orthodontic patients treated nonextrac-tion and with extraction of 4 premolars. Am J OrthodDentofacial Orthop 2003;123:138–45.

11. Erdem D, Ozdiler E, Memikoglu UT, Bas pinar E. Thirdmolar impaction in extraction cases treated with the Beggtechnique. Eur J Orthod 1998;20:263–70.

12. Behbehani F, Artun J, Thalib L. Prediction of mandibularthird-molar impaction in adolescent orthodontic patients.Am J Orthod Dentofacial Orthop 2006;130:47–55.

13. Artun J, Thalib L, Little RM. Third molar angulation dur-ing and after treatment of adolescent orthodontic patients.Eur J Orthod 2005;27:590–6.

14. Richardson ME. The early developmental position of thelower third molar relative to certain jaw dimensions. AngleOrthod 1970:226–30.

15. Jain S, Valiathan A. Influence of first premolar extraction onmandibular third molar angulation. Angle Orthod 2009;79:1143–8.

16. Larheim TA, Svanaes DB. Reproducibility of rotationalpanoramic radiography: mandibular linear dimensions andangles. Am J Orthod Dentofacial Orthop 1986;90:45–51.

17. Elsey MJ, Rock WP. Influence of orthodontic treatment ondevelopment of third molars. Br J Oral Maxillofac Surg2000;38:350–3.

18. Bayram M, Ozer M, Arici S. Effects of first molar extractionon third molar angulation and eruption space. Oral SurgOral Med Oral Pathol Oral Radiol Endod 2009;107:14–20.

19. Olive RJ, Basford KE. Transverse dento-skeletal relation-ships and third molar impaction. Angle Orthod 1981;51:41–7.

20. Ay S, Agar U, Biçakçi AA, Kös ger HH. Changes in mandib-ular third molar angle and position after unilateral man-dibular first molar extraction. Am J Orthod DentofacialOrthop 2006;129:36–41.

21. Cavanaugh JJ. Third molar changes following second molarextractions. Angle Orthod 1985;55:70–6.

22. Staggers JA, Germane N. Clinical considerations in the useof retraction mechanics. J Clin Orthod 1991;25:364–9.

23. Nanda RS. Reappraising “Wits”. Am J Orthod DentofacialOrthop 2004;125:18A.

24. Gaumond G. Second molar germectomy and third molareruption. 11 cases of lower second molar enucleation. AngleOrthod 1985;55:77–88.

25. Huggins DG, McBride LJ. The eruption of lower thirdmolars following the loss of lower second molars: a longi-tudinal cephalometric study. Br J Orthod 1978;5:13–20.

26. Rindler A. Effects on lower third molars after extraction ofsecond molars. Angle Orthod 1977;47:55–8.

27. Orton-Gibbs S, Crow V, Orton HS. Eruption of third per-manent molars after the extraction of second permanentmolars. Part 1: Assessment of third molar position and size.Am J Orthod Dentofacial Orthop 2001;119:226–38.

28. Gooris CG, Artun J, Joondeph DR. Eruption of mandibularthird molars after second-molar extractions: a radiographicstudy. Am J Orthod Dentofacial Orthop 1990;98:161–7.

Introduction

The incidence of cleft lip, cleft palate and combin-ations of both conditions in Malay children is 1 in941 live births.1 Unilateral cleft lip and palate(UCLP) is the most common type of cleft lip andpalate deformity. Children with repaired cleft lip andpalatal deformities have an irregular dental arch, aClass III malocclusion, a retrusive maxillae and, to alesser extent, a retrusive mandible. Some of childrenwith UCLP also have a marked facial deformity andmasticatory dysfunction.2–8 Lateral cephalometricanalysis is a convenient method to appraise the post-

surgery craniofacial morphology of children withUCLP, and serial cephalometric records enable theimpact of treatment on the growing face to beassessed. As there have been no cephalometric studiesof the Malay children with UCLP, we aimed to inves-tigate the craniofacial morphology of Malay childrenwith repaired UCLP and compare the data with non-cleft Malay children.


Twenty Malay children (12 boys, 8 girls; Mean age:10.5 ± 1.79 years) with UCLP who attended the


Cephalometric analysis of Malay children withand without unilateral cleft lip and palate

Lillybia Emily Ebin,* Norzakiah Mohamed Zam Zam† and Siti Adibah Othman†

Oral Health Division, Federal Government Administrative Centre, Putrajaya* and the Department of Children’s Dentistry and Orthodontics,Faculty of Dentistry, University of Malaya,† Malaysia

Objective: To investigate the craniofacial morphology of Malay children with repaired UCLP and compare the data with non-cleft Malay children.Methods: Twenty Malay children with repaired UCLP (12 boys, 8 girls; Mean age: 10.5 years) and 20 normal Malay children (8 boys, 12 girls; Mean age: 9.72 years) were recruited from the Combined Cleft Lip and Palate Clinic and theDepartment of Children’s Dentistry and Orthodontics, Faculty of Dentistry, University of Malaya, Malaysia. Lateral cephalometricradiographs were taken with the head orientated parallel to the floor. Thirty-one linear and angular variables were measured onthe lateral cephalometric radiographs with Dolphin Imaging Software Version 10.0 (Dolphin Imaging, Chatsworth, CA, USA).The data were analysed with the Mann-Whitney U test and the level of significance was set at p < 0.05.Results: In the UCLP group, the girls had deeper overbites than the boys (p = 0.011), and in the Control group the girls had asignificantly more acute cranial base angle (NSBa, p = 0.017) and a less protrusive lower lip (LL-E line, p = 0.21). The datafor the boys and girls were combined. Subjects in the UCLP group had a more acute cranial base angle, shorter and moreretruded maxillae and were more skeletal III than the subjects in the Control group. In the UCLP group, the upper and lowerincisors were less proclined than in the Control group, the interincisal angle was more obtuse and the overjet reduced by 6mm. There were no significant facial height differences. The nasolabial angle (Col-Sn-UL) was significantly more obtuse and theupper lip relative to the E line more retrusive in the UCLP group. There was no significant difference between the groups infacial heights or the maxillo-mandibular planes angle.Conclusion: Malay children with repaired UCLP have small, retrusive maxillae. The mandible in this group of children was ofnormal size and position, relative to the cranial base. Pressure from the repaired upper lip may be responsible for the retrudedmaxillae, retroclined incisors and obtuse nasolabial angle.(Aust Orthod J 2010; 26: 165–170)

Received for publication: December 2009Accepted: July 2010

Lillybia Emily Ebin: [email protected] Mohamed Zam Zam: [email protected] Adibah Othman: [email protected]

EBIN ET AL


Combined Cleft Lip and Palate Clinic at theUniversity of Malaya were selected for this study. Thefollowing criteria were used for selection:

1. Children between 7 and 13 years of age.

2. Repaired, non-syndromic complete unilateral cleftof the lip and palate. Primary surgical repair of the lipwas carried out at 3 months of age and palatal surgeryat 9 months of age.

3. No major orthodontic treatment and/or orthog-nathic surgery prior to the cephalometric examina-tion. Subjects had palatal expansion with a quadhelixappliance prior to the alveolar bone graft

4. Second generation Malay.

Twenty non-cleft subjects (8 boys, 12 girls) wereselected from the patients receiving dental treatmentin the Department of Children’s Dentistry andOrthodontics, Faculty of Dentistry, UniversityMalaya. The subjects in the Control group were 9.72± 1.70 years of age. The following selection criteriawere used:

1. Children between 7 and 13 years of age.

2. No facial clefts and/or other facial abnormality.

3. Skeletal Class 1 malocclusion or mild skeletal ClassII malocclusion with either well-aligned arches ormild crowding. The arch length discrepancy was lessthan 4 mm.

4. No previous orthodontic treatment.

5. Second generation Malay.

Ethical and written approvals for this study wereobtained from the Research Committee of the DentalFaculty of the University Malaya and from the partic-ipants and their parents. A questionnaire was used toconfirm that all parents and grandparents were Malayand there had been no inter-racial marriages.

Radiographic proceduresAll lateral cephalometric radiographs were taken withthe same machine with the Frankfort horizontalplane parallel to the floor, with the lips in a relaxedposition and the teeth in the retruded contact position. Thirty-one linear and angular variables weremeasured directly on the radiographs with DolphinImaging Software Version 10.0 (Dolphin Imaging,Chatsworth, CA, USA). The landmarks identified onthe cephalometric films are shown in Figure 1.5All measurements were carried out by the same investigator.

Statistical analysisTen lateral cephalometric radiographs were selectedrandomly from the UCLP and Control groups,measured and remeasured a month later by the sameinvestigator. Reproducibility was determined usingthe intraclass correlation coefficient (ICC). The resultdemonstrated that the method was highly reliable forthe majority of measurements (Cronbach’s alphavalue > 0.8), except for Li-MP and Ar-Go, whereCronchbach’s alpha values were 0.57 and 0.70,respectively. Since the Cronchbach’s alpha valuesexceeded 0.4, Li-MP and Ar-Go were considered tohave acceptable reproducibilities.

A Mann-Whitney U test was used to determine ifthere were gender differences in each group or if thechildren in the UCLP and Control groups differedfrom each other. All calculations were made using theStatistical Package for the Social Sciences (SPSS 12.0for Windows) and the level of significance was set atp < 0.05.

Results

There were only three gender differences in bothgroups. In the UCLP group, the girls had deeperoverbites than the boys (p = 0.011), and in theControl group the girls had a significantly more acute

Figure 1. Cephalometric landmarks.

cranial base angle (N-S-Ba, p = 0.017) and a less pro-trusive lower lip (LL-E line, p = 0.21) than the boys(Table I). In light of the few differences, data for theboys and girls were combined.There were 12 statistically significant differencesbetween the UCLP and Control groups. Subjects inthe UCLP group had a more acute cranial base angle(N-S-Ba, N-S-Ar), shorter and more retruded

maxillae (ANS-PNS, S-N-A) and were more skeletalIII (A-N-B, A-N-Pg) than the subjects in the Controlgroup. In the UCLP group, the upper and lower incisors (Ui-Mxp, Li-Mp) were less proclined than inthe Control group, the interincisal angle (Ui-Li) wasmore obtuse and the overjet (OJ) reduced by 6 mm.There were no significant facial height differences.The nasolabial angle (Col-Sn-UL) was significantly

CEPHALOMETRIC ANALYSIS OF MALAY CHILDREN WITH UCLP


Table I. Comparisons of the skeletal, dental and soft tissue variables in Malay boys and girls with and without unilateral cleft lip and palate.

UCLP group (N = 20) Control group (N = 20)

Variables Male Female p Male Female pMean Mean Mean Mean

Dentoskeletal measurementsN-S-Ba (degrees) 128.2 126.2 0.355 131.4 128.0 0.017N-S-Ar (degrees) 124.2 120.7 0.203 126.5 124.9 0.616S-Ar (mm) 35.1 31.9 0.105 30.7 31.7 0.562S-N (mm) 64.0 60.8 0.643 61.4 59.6 0.247SNA (degrees) 77.0 79.5 0.113 81.5 83.4 0.463SNB (degrees) 77.8 80.9 0.280 76.9 79.5 0.263SNpg (degrees) 78.2 80.3 0.487 76.5 79.5 0.142S-Ar-Go (degrees) 145.0 149.4 0.355 145.5 144.7 0.758A-N-B (degrees) -0.9 -1.4 0.877 4.6 4.0 0.396A-N-pg (degrees) -1.2 -0.8 0.877 4.9 4.1 0.396SN-Mxp (degrees) 8.8 5.8 0.123 8.8 7.0 0.121MMPA (degrees) 22.0 38.4 0.123 25.1 25.8 0.121N-ANS (mm) 47.7 45.1 0.487 45.0 44.5 0.512ANS-Me (mm) 62.7 59.2 0.487 58.4 57.6 0.728N-Me (mm) 109.3 103.4 0.758 101.1 100.4 0.616S-Go (mm) 72.9 66.8 0.396 66.1 66.8 0.643Ar-Go (mm) 41.3 37.6 0.700 39.4 37.7 0.512ANS-Me/N-Me (per cent) 55.9 55.9 0.758 55.2 55.2 0.616S-Go/N-Me (per cent) 66.4 64.6 0.537 65.3 66.5 0.396Ui/Mxp (degrees) 105.3 104.4 0.700 112.0 113.9 0.375Li/Mp (degrees) 90.3 88.6 0.728 98.2 96.4 0.537Ui/Li (degrees) 140.1 138.7 0.396 124.7 123.8 0.969OJ (mm) -3.0 -3.2 0.728 3.1 3.1 0.537OB (mm) 0.7 4.1 0.011 2.1 2.7 0.296ANS-PNS (mm) 45.4 43.4 0.787 43.4 45.0 0.758Ar-Go-Me (degrees) 123.1 124.1 0.969 121.7 122.6 0.817Go-Me (mm) 60.7 60.8 0.908 57.7 59.5 0.563

Soft tissue measurementsCol-Sn-UL (degrees) 88.5 85.6 0.700 100.9 105.4 0.247Pn-N’-Sn (degrees) 18.4 19.7 0.375 17.9 18.1 0.699UL-E Line (mm) -1.4 -1.6 0.589 3.4 1.2 0.076LL-E Line (mm) 2.9 4.3 0.440 3.9 1.7 0.021

Significant values in bold

EBIN ET AL


more obtuse in the UCLP group. The upper lip relative to the E line was more retrusive than in theControl group.

Discussion In agreement with previous studies, we found themaxillae in children with UCLP were more retrusivethan the maxillae in the non-cleft children.2–7,9 Many

authorities attribute most or all of the deformity tothe contraction of scar tissue following surgery. Thisview is supported by the findings that children withUCLP had normal maxillary growth before palatalsurgery and that unoperated subjects with UCLP hadnormal anteroposterior maxillary growth.3,10 The S-N-A angle in our UCLP subjects was 4.7 degrees lessthan S-N-A in the non-cleft subjects, but maxillary

Table II. Comparisons of the skeletal, dental and soft tissue variables in Malay children with and without unilateral cleft lip and palate.

UCLP group (N = 20) Control group (N = 20)

Variables Mean SD Mean SD p

SkeletalN-S-Ba (degrees) 127.3 4.7 129.3 3.5 0.038N-S-Ar (degrees) 122.8 4.9 125.6 4.1 0.022S-Ar (mm) 33.8 7.6 31.3 2.2 0.194S-N (mm) 62.7 10.3 60.3 2.6 0.310S-N-A (degrees) 78.0 3.3 82.7 3.8 0.000ANS-PNS (mm) 44.6 7.9 45.4 2.9 0.030S-N-B (degrees) 79.0 5.1 78.4 3.7 0.839S-N-Pg (degrees) 79.1 5.0 78.3 4.3 0.705S-Ar-Go (degrees) 146.8 8.0 145.0 5.8 0.766Ar-Go-Me (degrees) 123.5 8.1 122.3 7.5 0.588Go-Me (mm) 60.7 12.0 58.8 7.0 0.715A-N-B (degrees) -1.1 3.9 4.2 1.5 0.000A-N-Pg (degrees) -1.1 4.3 4.4 2.3 0.000S-N-Mxp (degrees) 7.6 5.1 7.7 2.4 0.685MMPA (˚) 26.9 6.0 25.5 5.0 0.245N-ANS (mm) 46.7 7.7 44.7 2.2 0.925ANS-ME (mm) 61.3 10.9 57.9 4.5 0.850N-Me (mm) 106.9 17.8 100.7 4.5 0.903S-Go (mm) 70.4 14.5 66.5 5.6 0.914Ar-Go (mm) 39.8 8.3 38.4 5.6 0.989ANS-Me/N-Me (per cent) 55.9 2.4 55.2 2.2 0.291S-Go/N/Me (per cent) 65.7 4.9 66.0 4.0 0.507

DentalUi/Mxp (degrees) 105.0 6.9 113.1 5.7 0.001Li/Mp (degrees) 89.6 8.1 97.1 5.8 0.003Ui/Li (degrees) 139.5 10.7 124.1 8.5 0.000OJ (mm) -3.1 3.3 3.1 0.9 0.000OB (mm) 2.1 2.9 2.4 1.4 0.304

Soft tissueCol-Sn-UL (degrees) 103.6 9.7 87.3 15.6 0.001Pn-N’-Sn (degrees) 18.9 2.9 18.0 1.7 0.159UL-E Line (mm) -1.5 2.7 2.1 2.4 0.000LL-E Line (mm) 3.5 2.8 2.6 2.0 0.180


length in the UCLP subjects was only 1 mm shorterthan maxillary length in the non-cleft subjects.Bearing in mind that the subjects in our study werenot randomly allocated to their respective groups andthat we did have longitudinal records, we were unableto say how much of the deformity in our UCLP sub-jects was due to the morphogenetic pattern (i.e. earlydevelopmental disturbance of the maxillary growthdue to the cleft) and how much was due to scar tissuecontraction following surgery.4

We found small, but statistically significant, reduc-tions in the saddle angle (N-S-Ba, N-S-Ar) in theUCLP group as compared with the Control group.This finding differs from several previous studies5–7

that reported cranial base angulation was increased incleft subjects, and in other studies that it did not dif-fer significantly from non-cleft groups.9,10 Someinvestigators have argued that post-surgical scarring isunlikely to affect the cranial base, and have attributeddifferences in the size and angulation of the limbs ofthe cranial base to genetic influences.

Subjects with Class III malocclusions, with and with-out cleft palates, tend to have a smaller cranial baseangle that may contribute to the mandibular prog-nathism.11–13 Although our UCLP subjects wereskeletal III (the mean ANB angle was –1.1 degrees),the skeletal relationship appears to be due to maxil-lary retrognathism, as demonstrated by the S-N-Aangle and short maxillae rather than the size and/orposition of the mandible relative to the cranial base. In agreement with Dogan et al.7 we found no statistically significant group differences in thelength of the cranial base (S-N, S-Ar). Furthermore,the anterior and posterior vertical heights of ourUCLP subjects were similar to those in our non-cleftgroup.

The upper and lower incisors were retroclined, theinterincisal angle obtuse and the overjet significantlyless in the UCLP group as compared with theControl group. Pressure from the repaired upper lip isgenerally considered to be the most likely cause of theupper and lower incisor retroclination and the nega-tive overjet.3,5,7,8 In agreement with others, anincreased nasolabial angle (Col-Sn-UL) and retrusiveupper lip relative to the E line accompanied the retru-sive maxillae in the UCLP group. Again pressurefrom the repaired upper lip is believed to be responsi-ble for the upper lip changes in this group.3 On theother hand, the projection of the nose, as indicated by

the Pn-N’-Sn angle, was not significantly differentbetween the groups.

Conclusions

Malay children with repaired UCLP have small,retrusive maxillae.

The mandible in this group of children was of normalsize and position, relative to the cranial base.

Pressure from the repaired upper lip may be respons-ible for the retruded maxillae, retroclined incisors andobtuse nasolabial angle.

Acknowledgments

We would like to express our gratitude to DrMarhazlinda Jamaludin for her statistical help andMrs Zuraini Ghazali from the Cleft Lip and PalateAssociation of Malaysia (CLAPAM). This study wassupported by grant from the Institute of PostgraduateStudies, University Malaya, Grant number(PPP)/P0217/ 2007A.


Dr Siti Adibah OthmanDepartment of Children’s Dentistry andOrthodonticsFaculty of DentistryUniversity of Malaya50603 Kuala LumpurMalaysiaEmail: [email protected]: +6 03 79674567Fax: +6 03 79674530

References 1. Oral Health Division, Ministry of Health, Malaysia.

National Oral Health Survey of School Children 1997.Ministry of Health, Malaysia; 1998, p 30.

2. Hayashi I, Sakuda M, Takimoto K, Miyazaki T. Craniofacialgrowth in complete unilateral cleft lip and palate:aroentgenocephalometric study. Cleft Palate J 1976;13:215–37.

3. Smahel Z, Müllerová Z. Craniofacial morphology in uni-lateral cleft lip and palate prior to palatoplasty. Cleft PalateJ 1986;23:225–32.

4. Ross RB. Treatment variables affecting facial growth in com-plete unilateral cleft lip and palate. Part 7: An overview oftreatment and facial growth. Cleft Palate J 1987;24:71–7.

5. Semb G. A study of facial growth in patients with unilateralcleft lip and palate treated by the Oslo CLP Team. CleftPalate Craniofac J 1991;28:1–21.

6. Öztürk Y, Cura N. Examination of craniofacial morphologyin children with unilateral cleft lip and palate. Cleft PalateCraniofac J 1996;33:2–36.

CEPHALOMETRIC ANALYSIS OF MALAY CHILDREN WITH UCLP


7. Dogan S, Onçag G, Akin Y. Craniofacial development inchildren with unilateral cleft lip and palate. Br J OralMaxillofac Surg 2006;44:28–33.

8. Bishara SE. The influence of palatoplasty and cleft length onfacial development. Cleft Palate J 1973;10:390–8.

9. Bishara SE, Sierk DL, Huang KS. A longitudinal cephalom-etry study on unilateral cleft lip and palate subjects. CleftPalate J 1979;16:59–71.

10. Mars M, Houston WJ. A preliminary study of facial growthand morphology in unoperated male unilateral cleft lip andpalate subjects over 13 years of age. Cleft Palate J 1990;27:7–10.

11. Hopkin GB, Houston WJ, James GA. The cranial base as anaetiological factor in malocclusion. Angle Orthod 1968;38:251–5.

12. Moss ML. Correlation of cranial base angulation withcephalic malformations and growth disharmonies of dentalinterest. N.Y. State Dent J 1955;24:452–4.

13. Moss ML. Malformations of the skull base associated withcleft palate deformity. Plast Reconstr Surg 1956;17:226–34.

EBIN ET AL


Introduction

The treatment options for Class III malocclusionsinclude orthopaedic treatment, camouflage treatmentwith comprehensive fixed orthodontic appliances andorthognathic surgery. Early orthopaedic treatmentmay include chin cup therapy to inhibit forwardmandibular growth, facemask therapy to protract themaxillae and treatment with a functional regulator.1–3

The timing of early orthopaedic treatment dependsto some extent on the nature and severity of the skele-tal discrepancy and the amount of facial growthremaining. Some clinicians are convinced that early orthopaedic treatment is often a waste of timeand resources because the correction relapses, whileothers believe that treatment in the mixed dentitionwill eventually normalise a skeletal Class III disharmony.4–9

It is generally agreed that the treatment option chosen should address the patient’s particular skeletaland/or dentoalveolar discrepancy. In populationgroups with Class III malocclusions predominatelydue to maxillary skeletal retrusion, early treatmentwith a protraction facemask may be an effectivemethod of treatment.10–15 The major concern of pro-traction facemask treatment for this type of mal-occlusion is that the treatment may not be stable inthe long-term and, eventually, surgical correction willbe required. Obviously, it would be helpful to be ableto identify patients with Class III malocclusions thatare likely to be stable in the long-term following earlyorthopaedic treatment with a facemask.

The aim of the current study was to identify the craniofacial features that contribute to long-term stability of protraction facemask treatment. This


Factors contributing to stability of protractionfacemask treatment of Class III malocclusion

Yan GuDepartment of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, People’s Republic of China

Aim: To identify the craniofacial characteristics that contribute to long-term stability of protraction facemask treatment of Class IIImalocclusion. Methods: Fifty subjects who met the following criteria were recruited: subjects with an anterior crossbite and ‘Wits’ appraisal < -3.5 mm; subjects who had been successfully treated with a protraction facemask (at the end of active orthopaedic treatmentthe overjet was overcorrected by more than 4 mm); the facemask treatment was started at either CS1 or CS2 and the subjectswere followed until CS4; no subject had a congenital craniofacial deformity. Based on the occlusal status at CS4, three groupswere identified: Stable group (SG), Unstable group (USG) and a Failed group (FG). One-way analysis of variance andScheffe’s post-hoc multiple comparisons were used to analyse the differences between the groups. Stepwise discriminant analysis was used to identify the craniofacial characteristics able to predict the stability of protraction facemask treatment.Results: There were no statistically significant differences between USG and FG. The N-S-Ar was significantly larger and Co-Gn, Wits and LAFH significantly smaller in the SG group as compared with the USG and FG groups. The critical scorebetween SG and USG was 0.368 and between USG and FG it was -0.981. Individuals with scores higher than 0.368showed relatively stable occlusions at CS4, whereas anterior crossbites returned in individuals with scores less than -0.981 at CS4. The overall percentage of correctly classified cases was 74 per cent, with 90.0 per cent in SG and 73.3 per cent in FG. Conclusions: A severe maxillo-mandibular discrepancy, an increased vertical dimension and a prognathic mandible wereunfavourable factors for long-term stability following early treatment of severe Class III subjects with protraction facemasks.(Aust Orthod J 2010; 26: 171–177)

Received for publication: May 2010Accepted: August 2010

Yan Gu: [email protected]

GU


study was based on 50 subjects who had orthopaedictreatment prior to the adolescent growth spurt.

Materials and methodsSampleFifty subjects (28 females, Mean age: 9.3 ± 1.7 years;22 males, Mean age 9.3 ± 1.4 years) who met the following criteria were recruited:

1. The subjects had an anterior crossbite with a ‘Wits’ appraisal less than -3.5 mm and no functionalshift.

2. The negative overjet was overcorrected with a protraction facemask and more than 4 mm of overjetwas present at the end of orthopaedic treatment(Figure 1).

3. Facemask treatment was started at cervical ver-tebral maturation stage CS1 or CS2 and, on average,lasted 12 months. All subjects were followed untilCS4.16

4. Subjects with congenital craniofacial deformitieswere excluded.

At CV4 the subjects were classified into the followinggroups:

1. Stable group (SG): 20 subjects (11 females, Meanage: 9.2 ± 2.1 years; 9 males, Mean age: 9.5 ± 1.3years) who had ≥ 2 mm of overjet and overbite.

2. Unstable group (USG): 15 subjects (8 females,Mean age: 9.4 ± 1.1 years; 7 males, Mean age: 9.4 ± 1.9years) with an overjet and overbite between 0 and 2 mm.

3. Failed Group (FG): 15 subjects (9 females, Meanage: 9.4 ± 1.9 years; 6 males, Mean age: 9.0 ± 1.6years) with an anterior crossbite i.e. overjet ≤ 0 mm.

Cephalometric analysis The cephalometric variables were measured on lateralcephalometric radiographs taken at the start of treat-ment (i.e. CV1 or CV2) by one investigator and thenverified by another investigator (Table I). Skeletalmaturation was assessed by examiners experienced inthe CVM method of Baccetti and coworkers.16 Anydisagreements between the two investigators wereresolved to the satisfaction of both investigators.

Statistical analysisAll statistical analysis was performed with SPSS 14.0(SPSS Inc., Chicago, IL, USA). Because of the smallnumber of subjects available, the data from thefemale and male subjects were pooled. One-wayanalysis of variance and Scheffe’s post-hoc multiplecomparisons were performed to compare the groups.Stepwise discriminant analysis was performed toidentify the cephalometric variables able to predictthe stability of protraction facemask treatment ofClass III malocclusion.

(a) (b)

Figure 1. (a) A 10 year-old girl with a protraction facemask. (b) The upper appliance, showing the protraction hooks.

Method errorThirty randomly chosen lateral cephalometric radio-graphs were digitised and remeasured two weeks apartand Dahlberg’s method errors calculated.17 The com-bined error did not exceed 0.3 mm for the linear variables and 0.5 degree for the angular variables.

Results

The cranial base angle (N-S-Ar) was significantlylarger in the SG group (Mean: 124.7 degrees) as com-pared with the USG (Mean: 119.0 degrees) and FG(Mean: 120.3 degrees) groups. There were no statisti-cally significant differences between the FG and USGgroups (Table I).

There were no significant differences in maxillaryposition, as evaluated by the perpendicular distancefrom A point to the perpendicular to Frankfort hori-zontal through N (A-NFH) and the mandibularcondyle to A point distance (Co-A). In the mandible,the gonial angle (Go angle) was significantly larger inFG than that in SG (Table I). Mandibular length(Co-Gn) was significantly larger in the USG and FGas compared with SG. The mean values for SG, USGand FG were 108.3 mm, 114.0 mm and 114.3 mm,respectively. However, the mean values of Ar-Go andGo-Me were similar among the three groups (Table I).

The maxillo-mandibular discrepancy in the SG was significantly smaller (-7.8 mm) than the

STABILITY OF FACEMASK TREATMENT


Table I. Comparison of the cephalometric variables.

Measurements SG USG FG p* p p p(N = 20) (N = 15) (N = 15) SG vs USG SG vs FG USG vs FG

CraniofacialN-S-Ar 124.7 ± 5.1 119.0 ± 4.1 120.3 ± 3.9 0.001 0.002 0.014 0.809

MaxillaA-NFH -4.5 ± 2.3 -3.3 ± 1.8 -5.2 ± 2.4 0.057 0.261 0.648 0.062Co-A 80.2 ± 4.6 80.6 ± 4.6 81.7 ± 3.6 0.619 0.973 0.631 0.794

MandibularPg-NFH -5.8 ± 6.7 -2.6 ± 4.4 -7.1 ± 6.2 0.111 0.290 0.829 0.130Ar-Go 46.9 ± 5.6 50.4 ± 5.5 48.5 ± 4.1 0.161 0.421 0.933 0.674Go-Me 63.8 ± 4.4 66.6 ± 4.9 67.4 ± 6.6 0.125 0.325 0.163 0.925Co-Gn 108.3 ± 6.5 114.0 ± 6.4 114.3 ± 5.7 0.010 0.040 0.028 0.991Go angle 125.1 ± 5.4 128.9 ± 5.2 130.5 ± 5.6 0.015 0.129 0.021 0.743

Maxilla-mandibular relationshipWits -7.8 ± 2.5 -11.6 ± 3.2 -11.9 ± 4.1 0.001 0.007 0.003 0.959

VerticalLAFH 60.0 ± 3.4 63.8 ± 4.1 66.5 ± 2.6 0.000 0.009 0.000 0.106S-Go 75.5 ± 5.9 76.8 ± 6.3 75.5 ± 3.9 0.794 0.796 1.000 0.806FH-MP 26.9 ± 5.8 29.3 ± 4.9 31.4 ± 5.8 0.066 0.443 0.069 0.596

DentalU1-SN 104.2 ± 9.2 106.8 ± 12.7 105.3 ± 6.4 0.749 0.749 0.949 0.919L1-FH 63.2 ± 8.4 64.8 ± 8.4 63.9 ± 7.0 0.434 0.466 0.982 0.617

Soft tissueUL E Line -1.6 ± 2.4 -1.1 ± 2.0 -0.4 ± 2.0 0.262 0.791 0.262 0.663LL E Line 1.9 ± 2.9 3.0 ± 2.6 3.5 ± 3.3 0.238 0.505 0.271 0.911Nasolabial angle 103.0 ± 12.9 102.4 ± 10.9 110.6 ± 10.3 0.104 0.990 0.174 0.171

* ANOVASignificant values in bold (p < 0.05)

GU


maxillo-mandibular relationships in both the USG(-11.6 mm) and FG (-11.9 mm) groups (Table I).

The mean lower anterior facial height (LAFH) in SG,USG and FG were 60.0 mm, 63.8 mm and 66.5 mm,respectively. Significant differences were noted whenSG was compared with USG and the FG (Table I).There were no significant differences in the Frankfortmandibular plane angle (FH-MP) between thegroups.

There were no statistically significant group differ-ences in the inclinations of the incisors (U1-SN, L1-FH) or the soft tissue measurements (UL E line,LL E Line, Nasolabial angle).

Discriminant analysis Stepwise analysis was performed to generate threevariables: Cranial base angle (N-S-Ar), Wits andlower anterior facial height (LAFH). Unstandardisedcanonical discriminant function coefficients of the selected variables, along with a constant, led tothe following equation: Individual Score = 0.141 x (N-S-Ar) + 0.151 x (Wits) - 0.218 (LAFH) - 1.859(Table II). The critical score between the SG andUSG was 0.368 and the critical score between USGand FG was -0.981. The results suggest if a patient’sscore is higher than 0.368, early treatment with a protraction facemask would result in a relatively stable occlusion at the cervical vertebral maturationstage CV4. On the other hand, if an individual’s scoreis less than -0.981, the incisors are likely to relapseinto a crossbite by the end of adolescent growth spurt(CV4).

In the present study, the percentage of correctly clas-sified cases based on the above equation was 74 percent, with 90.0 per cent in the Stable Group and 73.3per cent in the Failed Group (Table III).

Discussion

Previous studies have reported that Class III mal-occlusions become more pronounced with growth.18

Therefore, orthopaedic treatment of skeletal Class IIImalocclusions in either the mixed or the deciduousdentition has received increasing attention. Treatmenttiming is, however, complicated due to the variabilityin craniofacial growth and the different responses tothis form of treatment. Confidence in early treatmentof these difficult malocclusions has been shaken bymalocclusions that, although successfully corrected inchildhood, relapsed in adolescence. Discriminantanalysis had been used in previous studies to pre-dict the outcomes to different forms of Class III treatment.19–26

Some previous studies have graded the treatment out-comes into two groups: a successfully treated groupand a failed or relapse group. In our experience a two-point method does not include all responses to earlyorthopaedic treatment. We found a borderline groupof cases with close to zero overbite and overjet thatwere not covered by a simple two-point scheme, sowe graded the occlusal outcomes at CV4 into Stable,Unstable and Failed groups. We also decided to usecervical vertebral maturation to describe the develop-mental status of our subjects because chronologicalage is associated with wide variation in the timing of

Table II. Discriminant analysis.

Predictive Standardised canonical Unstandardised canonical variables discriminant function discriminant function

coefficients coefficients

N-S-Ar 0.633 0.141Wits 0.494 0.151LAFH -0.753 -0.218Constant -1.859

Individual score = 0.141 x (N-S-Ar) + 0.151 x (Wits) - 0.218 (LAFH) - 1.859Group centroids: SG = 1.471; USG = -0.735; FG = -1.227

Table III. Group classification based on the discriminant analysis.

Group Predicted group membership

SG USG FG Total

Original count 1 18 2 0 202 2 8 5 153 0 4 11 15Per cent 1 90.0 10.0 0.0 100.02 13.3 53.3 33.3 100.03 0 26.7 73.3 100.0

74 per cent of the original cases were correctly classified

spurts in facial growth. Cervical vertebral maturation,on the other hand, is regarded as an acceptable indi-cator of skeletal maturity and the adolescent growthspurt.16,27–28

A protraction facemask has become an acceptedmethod of early orthopaedic treatment of skeletalClass III malocclusions because the majority of thesemalocclusions have a maxillary skeletal retrusion.14–15

However, as treatment with a facemask usually ceasesin the mixed dentition and further facial growth willoccur, these subjects should be followed to determineif additional orthodontic and/or surgical treatment isneeded. The stability of protraction facemask treat-ment depends, to a large extent, on the magnitudeand direction of late growth in the face. Previous longitudinal studies have demonstrated that the adoles-cent peak in mandibular growth in Class III subjectsoccurs between cervical vertebral maturation stages 3and 4 (CS3 to CS4). Between the late maturationstages of CS4 and CS6, increases in mandibularlength in females and males with Class III mal-occlusions were two to three times more than in sub-jects with normal occlusion. Furthermore, increasesin the vertical dimension become apparent at latematuration stages.29 In the present study, an anteriorcrossbite at follow-up did not automatically meanthat surgical intervention was required: some of thesepatients were treated with additional orthodontictreatment.

We used skeletal, dental and soft tissue measurementsthat may influence the outcome of treatment. Thefirst variable extracted by the discriminant analysiswas the cranial base angle (N-S-Ar). We found thatan acute N-S-Ar angle was associated with a prog-nathic mandible and was a good indicator that protraction facemask treatment was unlikely to besuccessful in the long-term. Others have reported thatthe cranial base angle becomes more acute in growingClass III subjects and, as a result, a prognathic profiledevelops with age.13,30–33

It is interesting to note that neither maxillary positionnor maxillary size significantly influenced the long-term treatment outcome with a protraction facemask.Some investigators have reported that the mandiblein skeletal Class III malocclusions is larger, but similarin shape, to an average-size mandible.34–35 Otherinvestigators have reported that although mandibularlength was increased in Class III malocclusions, anobtuse gonial angle was the major contributor to the

prognathism.9–11,13,36 Our findings are in agreementwith this latter view: we found small, but statisticallysignificant, differences in the gonial angle and thelength of the mandibular body (Co-Gn) between SGand FG. In the present study, no parameters describ-ing the position and size of the mandible were identified in the discriminant model. Although ourfindings indicated that mandibular shape (Co-Gn,Go angle) were important factors in occlusal stability,the discriminant analysis disclosed that the maxillo-mandibular relationship, as assessed by the Witsappraisal, was a more important factor for long-termstability of facemask treatment.

In agreement with previous studies, we confirmedthat increases in lower anterior face height during andfollowing adolescence are likely to lead tounfavourable occlusal changes following facemasktreatment.9–11,13,29,37 The mean lower anterior facialheight in the FG was significantly larger than thelower anterior face height in the SG.

The predictive model developed in the present studyprimarily identifies the good responders to early treat-ment with a protraction facemask, but it does not dis-tinguish between surgical and non-surgical patients.In the Failed and Unstable groups alternative ortho-dontic therapies should be considered. Class III mal-occlusion is a heterogeneous and complex anomalywith a distinct craniofacial pattern, established earlyin development. It often becomes more severe withage, leading to a marked skeletal sagittal imbalance.Due to the fact that some Class III malocclusionsdeteriorate over time, there is a need to identifypatients who would benefit from early treatment ofthe discrepancy. Although this study indentified somecephalometric measurements that can be used to pre-dict the outcome of facemask treatment, the modelwould be improved with a larger sample. This sug-gests that a multicentre study and the addition oftransverse parameters, which are often features ofmaxillary hypoplasia, may improve the predictivepower of the discriminant model.

Conclusions

A severe maxillo-mandibular discrepancy, anincreased vertical dimension and a prognathicmandible were unfavourable factors for long-termstability following early treatment of severe Class IIIsubjects with protraction facemasks.



The ability to predict the outcome of facemask treat-ment at the mixed dentition stage is an importantadvance for orthodontists.


Dr Yan GuDepartment of OrthodonticsPeking UniversitySchool and Hospital of StomatologyNo. 22 ZhongGuanCun NandajieHaiDian District, Beijing 100081People’s Republic of ChinaEmail: [email protected]

References1. Fränkel R. Maxillary retrusion in Class III and treatment

with the function corrector III. Trans Eur Orthod Soc 1970:249–59.

2. Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgeno-cephalometric study of skeletal changes during and afterchin cup treatment. Am J Orthod 1984;85:341–50.

3. Macdonald KE, Kapust AJ, Turley PK. Cephalometricchanges after correction of Class III malocclusion with max-illary expansion/facemask therapy. Am J Orthod DentofacialOrthop 1999;116:13–24.

4. Campbell PM. The dilemma of Class III treatment. Early orlate? Angle Orthod 1983;53:175–91.

5. Joondeph DR. Early orthodontic treatment. Am J OrthodDentofacial Orthop 1993;104:199–200.

6. Deguchi T, Kuroda T, Minoshima Y, Graber TM.Craniofacial features of patients with Class III abnormali-ties: growth-related changes and effects of short-term andlong-term chincup therapy. Am J Orthod DentofacialOrthop 2002;121:84–92.

7. Tollaro I, Baccetti T, Franchi L. Mandibular skeletal changesinduced by early functional treatment of Class III malocclu-sion: a superimposition study. Am J Orthod DentofacialOrthop 1995;108:525–32.

8. Sugawara J, Asano T, Endo N, Mitani H. Long-term effectsof chincap therapy on skeletal profile in mandibular prog-nathism. Am J Orthod Dentofacial Orthop 1990;98:127–33.

9. Jacobson A, Evans WG, Preston CB, Sadowsky PL.Mandibular prognathism. Am J Orthod 1974;66:140–71.

10. Guyer EC, Ellis E, McNamara JA Jr, Behrents RG.Components of Class III malocclusion in juveniles and ado-lescents. Angle Orthod 1986;56:7–30.

11. Tollaro I, Baccetti T, Bassarelli V, Franchi L. Class III mal-occlusion in the deciduous dentition: a morphological andcorrelation study. Eur J Orthod 1994;16:401–8.

12. Williams S, Andersen C. The morphology of the potentialClass III skeletal pattern in the growing child. Am J Orthod1986;89:302–11.

13. Battagel JM. The aetiological factors in Class III mal-occlusion. Eur J Orthod 1993;15:347–70.

14. Ngan P, Hagg U, Yiu C, Wei H. Treatment response andlong-term dentofacial adaptations to maxillary expansionand protraction. Semin Orthod 1997;3:255–64.

15. Westwood PV, McNamara JA, Baccetti T, Franchi L, SarverDM. Long-term effects of Class III treatment with rapidmaxillary expansion and facemask therapy followed by fixedappliances. Am J Orthod Dentofacial Orthop 2003;123:306–20.

16. Baccetti T, Franchi L, McNamara JA. The cervical vertebralmaturation (CVM) method for the assessment of optimaltreatment timing in dentofacial orthopedics. Semin Orthod2005;11:119–29.

17. Dahlberg G. Statistical methods for medical and biologicalstudents. London: Allen and Unwin, 1940;122–32.

18. Mitani H, Sato K, Sugawara J. Growth of mandibular prog-nathism after pubertal growth peak. Am J OrthodDentofacial Orthop 1993;104:330–36.

19. Battagel JM. Predictors of relapse in orthodontically treatedClass III malocclusions. Br J Orthod 1994;21:1–13.

20. Franchi L, Baccetti T, Tollaro I. Predictive variables for theoutcome of early functional treatment of Class III malocclu-sion. Am J Orthod Dentofacial Orthop 1997;112:80–6.

21. Tahmina K, Tanaka E, Tanne K. Craniofacial morphology inorthodontically treated patients of Class III malocclusionwith stable and unstable treatment outcomes. Am J OrthodDentofacial Orthop 2000;117:681–90.

22. Moon YM, Ahn SJ, Chang YL. Cephalometric predictors oflong-term stability in the early treatment of Class III mal-occlusion. Angle Orthod 2005;75:747–53.

23. Stellzig-Eisenhauer A, Lux CJ, Schuster G. Treatment decision in adult patients with Class III malocclusion:Orthodontic therapy or orthognathic surgery? Am J OrthodDentofacial Orthop 2002;122:27–38.

24. Baccetti T, Franchi L, McNamara JA. Cephalometric variables predicting the long-term success or failure of combined rapid maxillary expansion and facial mask therapy. Am J Orthod Dentofacial Orthop 2004;126:16–22.

25. Tahmina K, Tanaka E, Tanne K. Craniofacial morphology inorthodontically treated patients of Class III malocclusionwith stable and unstable treatment outcomes. Am J OrthodDentofacial Orthop 2000;117:681–90.

26. Ghiz MA, Ngan P, Gunel E. Cephalometric variables to pre-dict future success of early orthopedic Class III treatment.Am J Orthod Dentofacial Orthop 2005;127:301–6.

27. Flores-Mir C, Burgess CA, Champney M, Jensen RJ, PitcherMR, Major PW. Correlation of skeletal maturation stagesdetermined by cervical vertebrae and hand-wrist evaluations.Angle Orthod 2006;76:1–5.

28. Gu Y, McNamara JA. Mandibular growth changes and cervi-cal vertebral maturation – a cephalometric implant study.Angle Orthod 2007;77:947–52.

29. Baccetti T, Reyes BC, McNamara JA. Craniofacial changesin Class III malocclusion as related to skeletal and dentalmaturation. Am J Orthod Dentofacial Orthop 2007;132:171.e1–171.e12.

30. Ellis E, McNamara JA, Jr. Components of adult Class IIImalocclusion. J Oral Maxillofac Surg 1984;42:295–305.

31. Björk A. Some biological aspects of prognathism and occlu-sion of teeth. Acta Odontol Scand 1950;9:1–40.

32. Rakosi T. The significance of roentgenographic cephalomet-rics in the diagnosis and treatment of Class III malocclu-sions. Trans Eur Orthod Soc 1970:155–70.

33. Baccetti T, Antonini A, Franchi L, Tonti M, Tollaro I.Glenoid fossa position in different facial types: a cephalo-metric study. Br J Orthod 1997;24:55–9.

GU


34. Stapf W. A cephalometric roentgenographic appraisal of thefacial pattern in Class III malocclusions. Angle Orthod1948;18:20–3.

35. Smith A, Chambers F. Mandibular prognathism corrected bynewly devised ostectomy of the ramus. Am J Dent Assoc1962;64:328–44.

36. Chang HP, Kinoshita Z, Kawamoto T. Craniofacial patternof Class III deciduous dentition. Angle Orthod1992;62:139–44.

37. Miyajima K, McNamara JA, Jr., Sana M, Murata S. Iizuka T.An estimation of craniofacial growth in the untreated ClassIII female with anterior crossbite. Am J Orthod DentofacOrthop 1997;112:425–34.



Introduction

Transverse constriction of the maxillae with anaccompanying posterior crossbite is frequently treated by rapid maxillary expansion (RME).1 Theprevalence of a posterior crossbite ranges from 2.7 to23.3 per cent depending on the population group,1–5

but not all posterior crossbites are accompanied by anarrow upper facial skeleton and deep palatal vault.6Rapid maxillary expansion separates the maxillae overa few days and the expanded midpalatal suture even-tually fills with new bone. This procedure increasesthe widths of the maxillary arch and the upper facialskeleton.7

Rapid maxillary separation is usually carried out withan appliance attached to the maxillary first molarsand premolars or deciduous molars, and activated bya screw.7,9 The force produced by the RME appliance

is applied to the teeth, which act as ‘handles’ separat-ing the maxillae and ‘bending’ the alveolar processesoutwards before the anchor teeth have time to movethrough the alveolar bone.8 While significant relapsemay be found in cases treated by conventional maxil-lary expansion appliances, RME is claimed to bemore stable.7,10,11 It has also been claimed that slowseparation of the maxillae produces less tissue resist-ance in the nasomaxillary complex and a more stableresult.8,12 Iseri and Ozsoy separated the maxillae overa few days and then used ‘slow’ expansion until ade-quate dental expansion had been obtained.13 Theycalled this method of rapid expansion followed byslow expansion ‘semi-rapid’ expansion. They reportedthat this simple method of varying the activation rateof the appliance resulted in significant skeletal anddental expansion in older adolescents and adults, andsatisfactory stability in the long-term.13


Effects of rapid-slow maxillary expansion on thedentofacial structures

Nihat Kilic* and Hüsamettin Oktay†

Department of Orthodontics, Faculty of Dentistry, Atatürk University, Erzurum, Turkey* and Department of Orthodontics, Faculty ofDentistry, Istanbul Medipol University, Istanbul, Turkey†

Background: To date, no study has determined if rapid followed by slow maxillary expansion (also termed ‘semi-rapid’ expansion) has the same effects on the dentofacial skeleton as rapid maxillary expansion.Objective: To determine the vertical and sagittal changes in the facial skeleton during and following rapid then slow maxillaryexpansion (R-SME).Methods: Bonded maxillary expansion appliances were used to separate the maxillae over six days by activating the midlinescrews twice a day. The screws were then activated three times a week until sufficient expansion was obtained (Mean: 3.4months) and used as retainers for six months. Cephalometric measurements at the start of expansion (T1), end of expansion (T2)and end of retention (T3) were compared with paired t - tests. Pearson correlation coefficients were used to determine the associations between the expansion (dental and skeletal) and the cephalometric changes. Results: The maxillae moved forward a small, but statistically significant, extent during expansion. The upper molars were extruded and the mandible ‘rotated’ downward and backward. Although the vertical height of the facial skeleton (SN/GoMe,S-Go, N-Me, ANS-Me) increased significantly during expansion, the changes were small and highly variable. Some dimensions (SN/GoMe) relapsed during retention, while others (S-Go, N-Me) increased.Conclusions: Rapid then slow maxillary expansion caused a small, but statistically significant, forward movement of the upperfacial skeleton, a small downward and backward rotation of the mandible and a small increase in face height. The changeswere similar to those found during rapid maxillary expansion.(Aust Orthod J 2010; 178–183)

Received for publication: March 2010Accepted: August 2010

Nihat Kilic: [email protected] Oktay: [email protected]

RAPID-SLOW MAXILLARY EXPANSION


Conventional banded RME appliances are widelyused, and lateral cephalometric studies indicate thatduring expansion the maxillae move anteriorly, themaxillary posterior teeth move downward and the mandible rotates downward and backward. Thesechanges are usually accompanied by an increase in theheight of the face, an increase in the overjet andreduced overbite.7,10,11,14

In this preliminary study we aim to determine thesagittal and vertical changes in the facial skeleton fol-lowing rapid-slow expansion (R-SME). The under-lying hypothesis is that a short period of rapid expan-sion followed by slow expansion will result in similarsagittal and vertical skeletal changes as rapid maxillaryexpansion.


Lateral cephalometric radiographs of 20 subjects (15 females, 5 males), treated with bonded maxillaryexpansion appliances in the Department of Ortho-dontics, Faculty of Dentistry, Atatürk University,were used in this study. All subjects had a severe max-illary arch deficiency, a bilateral posterior crossbiteand a deep palatal vault. No subject had previousorthodontic treatment. The subjects had a mean ageof 13.44 ± 0.98 years at the start of the study.Informed consent was obtained from the parents ofall subjects.

The acrylic bonded expansion appliance and the acti-vation schedule used in this study were identical to

those used by Iseri and Ozsoy (Figure 1).13 In brief,the appliance was a tooth- and tissue-born rigid,acrylic appliance with posterior bite planes, bondedto the upper posterior teeth. The appliances were acti-vated twice a day for 5–7 days, i.e. one quarter turnin the morning and a quarter turn in the evening,until the midpalatal suture had opened. Each quarterturn of the screw produced 0.2 mm expansion. Whenthe midpalatal suture had opened (this was confirmedwith an occlusal radiograph), the appliance wasdebonded and used as a removable expansion appli-ance. The appliance was then activated three times aweek (i.e. 0.6 mm per week) until adequate expan-sion was achieved. It was then used as a retainer. Themean period of expansion was 3.41 ± 0.81 monthsand the mean length of retention was 6.02 ± 0.17months. The maxillary intermolar distance was meas-ured on stone casts taken before expansion (T1), afterexpansion (T2) and after retention (T3).

Lateral and posteroanterior cephalometric radio-graphs were taken with a Siemens Nanodor 2 ceph-alostat (Siemens AG, Munich, Germany). During theexposure the subjects adopted a habitual, unstrainedbody posture with the teeth in the intercuspal posi-tion and the lips at rest. The cephalometric radio-graphs were taken before expansion (T1), after 3.41 ±0.81 months expansion (T2) and after 6.02 ± 0.17months retention (T3). The radiographs werescanned at 144 dpi with an Epson Expression 1860Pro scanner (Seiko Epson Corp., Nagano-Ken, Japan)and the parameters shown in Figure 2 measured with

Figure 1. The bonded acrylic R-SME appliance.

Quick Ceph 2000 (Quick Ceph Systems Incor-porated, San Diego, CA, USA). The basal maxillarywidth, the distance between right and left maxillarepoints (the points located at the depths of the con-cavities on the lateral maxillary contours, at the junc-tions of the maxillae and the zygomatic buttresses)was measured on the T1, T2 and T3 posteroanteriorcephalometric films.

Statistical methodsFifteen radiographs were randomly selected andremeasured two weeks later by the same investigator.Intraclass correlation coefficients were calculated toassess the reliability of the method.15 The T2-T1, T3-T1 and T3-T2 differences were compared with pairedt-tests and associations between the amounts ofexpansion (dental and skeletal) and the vertical andsagittal changes were determined with Pearson’s cor-relation coefficients. All statistical analyses were per-formed using the SPSS software package (SPSS forWindows 98, version 10.0, SPSS Incorporated,Chicago, IL, USA).

Results

The coefficients of reliability for the cephalometricmeasurements ranged from .994 (N-Me) to .932

(PP/SN). We concluded that the method of measure-ment met the requirements of the study.

The mean maxillary dental expansion was 7.53 ± 1.47mm and mean skeletal expansion was 2.80 ± 1.06mm. The cephalometric measurements at T1, T2 andT3 are given in Table I and comparisons of the T2-T1, T3-T1 and T3-T2 measurements in Table II.Statistically significant changes were observed for allmeasurements except OP/SN and U1-SN angles aftermaxillary expansion. The SNB, PP/SN, interincisalangles and overbite decreased significantly duringmaxillary expansion (T2-T1), and the remainingmeasurements increased significantly during thisperiod. During the retention period (T3-T2), SNA,ANB, SN/GoMe and overjet decreased significantly,whereas SNB, S-Go, and L1-GoMe and overbiteincreased significantly. There were no statistically significant changes T3-T2 in the remaining measurements.

According to the overall changes (T3-T1), the maxil-lae moved forward (SNA), the mandible rotateddownward and backward (SN-GoMe, SNB), the vertical dimensions of the face (N-Me, ANS-Me) andthe overjet increased, the overbite decreased, thepalatal plane rotated counterclockwise (PP/SN), thelower incisors protruded (L1-GoMe) and distance ofthe maxillary first molar from the palatal plane (Ms-PP) increased significantly.

No significant correlations were found between the amounts of expansion (maxillary dental and skel-etal expansion) and either the sagittal or the verticalchanges. The correlation coefficients ranged from -.325 to .301.

Discussion

We aimed to determine the vertical and sagittalchanges in the facial skeleton during and following R-SME. We found the maxillae moved forward asmall, but statistically significant, extent duringexpansion and the mandible rotated downward andbackward. Although the vertical height of the facialskeleton increased significantly during expansion, thechanges were small and variable, and may not be clin-ically significant. Some of the height dimensionsrelapsed during retention, while others increased,possibly the result of continued vertical growth in thedentofacial skeleton. The sagittal and vertical changesfollowing R-SME were similar to those following RME.

KILIC AND OKTAY


Figure 2. The measurements used in this study.



The SNA angle increased approximately 1.3 degreesafter maxillary expansion and relapsed 0.22 degreeduring the retention period: the net change was 1.06degree. The increase in the SNA angle indicates thatthe maxillae moved forward during R-SME. Themajority view is that RME produces significant for-ward movement of the maxillae,10,14,16–20 althoughsome researchers have reported less forward move-ment after RME21 and R-SME.22 Our finding thatSNA remained unchanged during retention is similarto the findings reported by others who used rigidacrylic bonded expansion appliances and either slowexpansion or rapid followed by slow expansion.12,13

According to these authors, there is less tissue resist-ance in the nasomaxillary complex during R-SME,anteroposterior movement of maxillae is controlledand the results are relatively stable.

The SNB angle decreased 1 degree after R-SME, butapproximately 0.5 degree returned during the retention period, resulting in a net decrease of only0.5 degree.7,20,23,24 When this reduction and the

increases in the ANB angle, SN/GoMe, N-Me andANS-Me are considered, it appears the mandible had moved downward and backward after maxillaryexpansion.7,10,16,17,20,24–28 The changes in mandibularposition were small and may not be permanent.

The vertical increases in the facial skeleton (e.g. N-Me and ANS-Me) and backward rotation of themandible also resulted in a small, but statistically sig-nificant increase in the overjet and decrease in theoverbite: confirming what others have observed at theend of maxillary expansion.4,7,10,16,17–19,21,28,29 Oursubjects had an anterior open bite at the end ofexpansion. During retention, however, the overjetreduced to 4.48 mm (from 4.98 mm) and the over-bite increased to an edge-to-edge occlusion. Duringexpansion we observed significant increases in thepositions of the maxillary (Ms-PP) and mandibularmolars (Mi-GoMe), confirming Ozsoy’s observationof similar changes after R-SME in older adolescentsand adults.30 Buccal tipping of the maxillary teethduring expansion and contact with the opposing

Table 1. The cephalometric measurements before expansion (T1), after expansion (T2) and after retention (T3).

T1 T2 T3


Skeletal measurementsSNA 78.09 4.01 79.37 4.38 79.15 4.28SNB 74.63 3.99 73.68 4.02 74.16 4.43ANB 3.46 2.53 5.67 2.50 5.00 2.52SN/GoMe 39.93 6.61 41.08 6.71 40.59 7.00OP/SN 19.95 5.06 20.10 5.02 19.74 5.05PP/SN 9.26 3.16 8.54 2.53 8.52 3.16S-Go 75.46 5.23 76.31 5.34 77.00 4.72N-Me 123.35 5.54 125.88 5.73 126.27 5.82ANS-Me 72.58 5.02 75.11 5.10 75.09 4.76

Dental measurementsMs-PP 24.76 2.04 25.37 2.26 25.46 2.22Mi-GoMe 31.82 1.84 32.21 1.81 32.08 1.97U1-SN 100.98 7.31 101.56 6.82 101.42 7.06L1- GoMe 89.79 5.46 90.18 5.57 90.49 5.62Interincisal 129.31 7.97 127.20 8.07 127.25 7.79Overjet 3.85 2.52 4.98 2.53 4.48 2.75Overbite 0.93 1.39 -0.69 1.73 0.02 1.50

Soft tissue measurementsLs-E Line -3.68 2.89 -3.14 3.45 -3.20 3.44Li-E Line -1.59 3.64 -1.04 4.09 -1.56 3.95

teeth is the most likely reason for the increases in thevertical measurements during R-SME.26

There were no significant changes in the inclinationsof the upper incisors during expansion or duringretention, however there were small but significantincreases in the inclinations of the lower incisors tothe mandibular plane. Similar changes were reported byOzsoy after R-SME.30 We attribute the changes in thelower incisors to the development of an anterior openbite and a lower tongue position after expansion.18

We used adolescents for this study because this is theusual age group for orthodontic treatment and wewanted the permanent molars and premolars to befully erupted. We also used bonded expansion appli-ances with occlusal coverage because some authoritiesconsider that bonded appliances may have a greaterorthopaedic effect and less tipping of the anchor teeththan conventional RME appliances.

Conclusions

R-SME caused a small, but statistically significant,forward movement of the upper facial skeleton, asmall downward and backward rotation of mandibleand a small increase in face height.

The changes were highly variable and no significantassociations were found between the amount ofexpansion and the sagittal and vertical changes.

R-SME produced similar dentofacial changes to thosefound during and following conventional RME.


Dr Nihat KilicAtatürk ÜniversitesiDis Hekimligi FakültesiOrtodonti Anabilim Dalı 25240 Erzurum

KILIC AND OKTAY


Table II. Comparison of the cephalometric measurements.

T2-T1 T3-T1 T3-T2 p

Mean SD Mean SD Mean SDdifference difference difference difference difference difference T2-T1 T3-T1 T3-T2

Skeletal measurementsSNA 1.28 0.82 1.06 0.55 -0.22 0.35 0.000 0.000 0.010SNB -0.95 0.91 -0.47 0.87 0.48 0.80 0.000 0.027 0.015ANB 2.21 0.99 1.54 0.75 -0.68 0.81 0.000 0.000 0.001SN/GoMe 1.16 1.25 0.66 1.24 -0.49 0.99 0.001 0.027 0.040OP/SN 0.15 1.53 -0.21 1.58 -0.36 1.20 0.645 0.559 0.197PP/SN -0.72 1.37 -0.74 1.38 -0.02 1.20 0.029 0.027 0.956S-Go 0.85 1.28 1.55 1.73 0.70 1.29 0.008 0.001 0.026N-Me 2.53 1.48 2.92 1.93 0.39 1.76 0.000 0.000 0.334ANS-Me 2.53 1.70 2.51 1.75 -0.02 1.17 0.000 0.000 0.940

Dental measurementsMs-PP 0.61 0.84 0.70 0.85 0.09 0.72 0.004 0.002 0.585Mi-GoMe 0.39 0.74 0.26 0.99 -0.13 1.11 0.030 0.254 0.608U1-SN 0.58 2.20 0.44 2.02 -0.14 0.83 0.254 0.336 0.476L1- GoMe 0.39 0.43 0.69 0.48 0.31 0.37 0.001 0.000 0.002Interincisal -2.11 2.45 -2.06 2.66 0.05 1.44 0.001 0.003 0.878Overjet 1.13 1.25 0.64 1.08 -0.50 0.84 0.001 0.017 0.016Overbite -1.61 1.15 -0.91 0.80 0.70 0.87 0.000 0.000 0.002

Soft tissue measurementsLs-E Line 0.54 1.18 0.48 1.23 -0.06 0.77 0.049 0.099 0.711Li-E Line 0.55 1.16 0.03 1.72 -0.53 1.15 0.047 0.949 0.054




TurkeyEmail: [email protected]: +90.442.3411807 Fax: +90.442.2360945 - 2312270

References1. McNamara JA. Maxillary transverse deficiency. Am J Orthod

Dentofacial Orthop 2000;117:567–70.2. Thilander B, Pena L, Infante C, Parada SS, de Mayorga C.

Prevalence of malocclusion and orthodontic treatment needin children and adolescents in Bogotá, Colombia. An epi-demiological study related to different stages of dentaldevelopment. Eur J Orthod 2001;23:153–67.

3. Kurol J, Berglund L. Longitudinal study and cost-benefitanalysis of the effect of early treatment of posterior cross-bites in the primary dentition. Eur J Orthod 1992;14:173–9.

4. Sandikcioglu M, Hazar S. Skeletal and dental changes aftermaxillary expansion in the mixed dentition. Am J OrthodDentofacial Orthop 1997;111:321–7.

5. Thilander B, Lennartsson B. Study of children with uni-lateral posterior crossbite, treated and untreated, in thedeciduous dentition-occlusal and skeletal characteristics ofsignificance in predicting the long-term outcome. J OrofacOrthop 2002;63:371–83.

6. Allen D, Rebellato J, Sheats R, Ceron AM. Skeletal and dental contributions to posterior crossbites. Angle Orthod2003;73:515–24.

7. Bishara SE, Staley RN. Maxillary expansion: clinical impli-cations. Am J Orthod Dentofacial Orthop 1987;91:3–14.

8. Memikoglu TU, Íseri H. Effects of a bonded rapid maxillaryexpansion appliance during orthodontic treatment. AngleOrthod 1999;69:251–6.

9. Kilic N, Oktay H. Effects of rapid maxillary expansion onnasal breathing and some naso-respiratory and breathingproblems in growing children: a literature review. Int JPediatr Otorhinolaryngol 2008;72:1595–601.

10. Velazquez P, Benito E, Bravo LA. Rapid maxillary expansion.A study of the long-term effects. Am J Orthod DentofacialOrthop 1996;109:361–7.

11. Gurel HG, Memili B, Erkan M, Sukurica Y. Long-termeffects of rapid maxillary expansion followed by fixed appliances. Angle Orthod 2010;80:5–9.

12. Mew JR. Semi-rapid maxillary expansion. Br Dent J 1977;143:301–6.

13. Iseri H, Özsoy S. Semirapid maxillary expansion – a study oflong-term transverse effects in older adolescents and adults.Angle Orthod 2004;74:71–8.

14. Oliveira NL, Da Silveira AC, Kusnoto B, Viana G. Three-dimensional assessment of morphologic changes of the maxilla: a comparison of 2 kinds of palatal expanders. Am JOrthod Dentofacial Orthop 2004;126:354–62.

15. Houston WJ. The analysis of errors in orthodontic measure-ments. Am J Orthod 1983;83:382–90.

16. Haas AJ. Rapid expansion of the maxillary dental arch andnasal cavity by opening the midpalatal suture. Angle Orthod1961; 31:73–90.

17. Akkaya S, Lorenzon S, Ücem TT. A comparison of sagittaland vertical effects between bonded rapid and slow maxillaryexpansion procedures. Eur J Orthod 1999;21:175–80.

18. Erverdi N, Sabri A, Kucukkeles N. Cephalometric evalua-tion of Haas and Hyrax rapid maxillary appliances in thetreatment of the skeletal maxillary transverse deficiency. JMarmara Univ Dent Fac 1993;1:361–6.

19. Taspinar F. The computerized tomographic and cephalo-metric evaluation of the changes resulted from rapid maxil-lary expansion. (Dissertation). Ataturk University, HealthSciences Institute, Department of Orthodontics, Erzurum,2002.

20. Kılıc N. Investigation of the changes at dentofacial struc-tures and tonus of masticatory muscles induced by semirapid and rapid maxillary expansion (Dissertation). AtaturkUniversity, Health Sciences Institute, Department ofOrthodontics, Erzurum, 2005.

21. Chung CH, Font B. Skeletal and dental changes in the sagit-tal, vertical, and transverse dimensions after rapid palatalexpansion. Am J Orthod Dentofacial Orthop 2004;126:569–75.

22. Ramoglu SI, Sari Z. Maxillary expansion in the mixed dentition: rapid or semi-rapid? Eur J Orthod 2010;32:11–18.

23. McNamara JA, Brudon WL. Orthodontic and orthopedictreatment in the mixed dentition. Ann Arbor: NeedhamPress Inc., 1996:131–69.

24. Sari Z, Uysal T, Usumez S, Basciftci FA. Rapid maxillaryexpansion. Is it better in the mixed or in the permanent dentition? Angle Orthod 2003;73:654–61.

25. Kilic N, Kiki A, Oktay H, Erdem A. Effects of rapid maxil-lary expansion on Holdaway soft tissue measurements. Eur JOrthod 2008;30:239–43.

26. Kilic N, Kiki A, Oktay H. A comparison of dentoalveolarinclination treated by two palatal expanders. Eur J Orthod2008;30:67–72.

27. Oktay H, Kilic N. Evaluation of the inclination in posteriordentoalveolar structures after rapid maxillary expansion: anew method. Dentomaxillofac Radiol 2007;36:356–9.

28. Mossaz-Joelson K, Mossaz CF. Slow maxillary expansion: acomparison between banded and bonded appliances. Eur JOrthod 1989;11:67–76.

29. Haas AJ. Palatal expansion: just beginning to dentofacialorthopedics. Am J Orthod 1970;57:219–55.

30. Özsoy FS. Evaluation of the effects of semirapid maxillaryexpansion on dentofacial structures. (Dissertation). AnkaraUniversity, Health Sciences Institute, Department ofOrthodontics, Ankara, 2001.

Introduction

The practice of bonding attachments to molars hasnot been widely accepted because it is believed thatbonded buccal tubes have inadequate bondstrengths.1,2 The failure rate of bonded buccal tubeshas been reported to be as high as 21 per cent.3 Thebond strength of buccal tubes can be improved byincreasing the etch time to 30 seconds,4 use of foilmesh bonding pads,5,6 sand blasting the attachments7

and using different resin adhesives.8 According to oneauthority, bond strength is influenced by the size anddesign of the bonding pad, but others consider thatshear bond strength is independent of the surfaceareas of bonding pads between 6.82 and 12.32mm2.9,10 The limitations in previous studies are theuse of bovine teeth, use of premolars rather thanmolars, use of attachments with different surfaceareas and different types of bonding pad.

Our aims were to compare the in-vitro shear bondstrengths of different buccal tubes bonded to humanmolars, and to determine the sites of failure using themodified adhesive remnant index (ARI).


Eighty lower right first molar teeth were collected,sterilised with 0.5 per cent chloramine for one weekand stored in distilled water for 24 hours. The buccalsurfaces of all teeth were sound. The teeth were randomly assigned to four groups and mounted inacrylic resin blocks to facilitate debonding in a uni-versal testing machine. Lower right MBT prescrip-tion buccal tubes from the following sources wereused: A (American Orthodontics, Sheboygan, WI,USA); B (Small base; 3M Unitek, Monrovia, CA,USA); C (Large base; 3M Unitek, Monrovia, CA,USA); D (Hangzhou Dentop, Zhejiang, Hangzhou,China).

The buccal surface of each tooth was polished withfluoride-free pumice powder for 20 seconds, sprayedwith water and dried with a blast of air. The buccalsurfaces were then etched for 30 seconds with 35 percent phosphoric acid gel (Transbond XT etchant gel,3M Unitek, Monrovia, CA, USA), rinsed for 30 seconds with distilled water and dried with air for 20 seconds. A thin layer of Transbond XT primer


Shear bond strengths of buccal tubes

Kathiravan Purmal and Prema SukumaranDental Faculty, University Malaya, Kuala Lumpur, Malaysia

Aims: To investigate the shear bond strengths of buccal tubes and to determine the sites of failure.Method: Four orthodontic buccal tubes were selected: A, American Orthodontics; B, 3M Unitek - small base; C, 3M Unitek -large base; D, Hangzhou Dentop. Twenty buccal tubes from each group were bonded to the buccal surfaces of lower right firstmolars with the same light-cured composite resin. The buccal tubes were debonded with a universal testing machine and thedata analysed. The amount of adhesive remaining on the teeth after debonding was classified with the modified adhesive remnant index (ARI).Results: The groups ranked from the highest to lowest bond strength (MPa) were: B, A, D and C. The bond strengths of the buccal tubes, except Groups A and B, were significantly different (p < 0.05). The majority of the buccal tubes (63 per cent)had modified ARI scores of 1 and 2 and 25 per cent of the tubes had scores of 4 and 5. After debonding, no adhesiveremained on 40 per cent of the teeth in Groups B and D.Conclusions: The shear bond strengths of the buccal tubes fell below the value considered to be clinically acceptable. Therewere no differences between the shear bond strengths of the buccal tubes with photoetched and microetched bases. The buccal tubes with the largest base failed prematurely, possibly because the unsupported bonding pad flexed during debonding. (Aust Orthod J 2010; 26: 184–188)

Received for publication: March 2009Accepted: September 2010

Kathiravan Purmal: [email protected] Prema Sukumaran: [email protected]

SHEAR BOND STRENGTHS OF BUCCAL TUBES


(3M Unitek, Monrovia, CA, USA) was then brushedon the etched surface. Transbond XT light-curedcomposite resin (3M Unitek, Monrovia, CA, USA)was placed on the bonding pad and the attachmentpressed on the buccal surface by an experiencedorthodontist. Surplus resin was removed with a sharp,dental instrument. The resin was cured with anOptilux 400 curing light (Demetron Research Corp,Danbury, CT, USA) at 400 MW/cm2 by placing thelight 10 mm from the mesial (20 seconds) and distaledges (20 seconds) of each bonding pad. The sampleswere stored in distilled water at 37 ºC for 24 hoursbefore debonding.

Each specimen was mounted in a ShimadzuUniversal Testing Machine (Shimadzu Corporation,Kyoto, Japan) so that the middle of the buccal surfacewas parallel to the long axis of the blade used todebond the tubes (Figure 1). The universal testingmachine had a load cell of 1 kg and crosshead speedof 1 mm/min. The shear load was applied on theocclusal side of the buccal tube, as close as possible tothe base. The force required to debond a buccal tubewas recorded in newtons (N) and converted to forceper unit area (MPa), by dividing the force by the surface area of the base. The latter was measured bytracing the base on graph paper and counting thenumber of squares enclosed by the outline (Table I).

To determine the sites of failure, the teeth and buccaltubes were examined at x10 magnification (LeicaImage Analyzer, Houston, TX, USA) and the amountof adhesive on the tooth surface was scored with themodified adhesive remnant index (ARI): 1, all of theadhesive remained on the enamel with an impression

of the base of the buccal tube; 2, more than 90 percent of the adhesive remained on the tooth surface; 3,less than 90 per cent but more than 10 per cent of theadhesive remained on the tooth surface; 4, less than10 per cent of the adhesive remained on the toothsurface; 5, no adhesive remained on the tooth surface.11,12

Statistical analysisOne-way analysis of variance (ANOVA) was used tocompare the shear bond strengths of the buccal tubes.Tukey HSD post-hoc tests were employed to analysethe shear bond strength data. The distributions ofresidual adhesive (ARI) were compared using the chi-squared test. A significance level of 0.05 was used forall tests.

Results

The 3M Unitek small base buccal tubes were slightlymore than half the area of the large base 3M Unitekbuccal tubes and 80 per cent of the area of theHangzhou Dentop tubes. The mean base area of theHangzhou Dentop tubes was approximately 85 percent of the mean base area of the AmericanOrthodontics tubes (Table I).

The highest mean shear bond strength was observedin Group B (4.32 ± 0.73 MPa) and the lowest meanbond strength in Group C (1.71 ± 0.60 MPa) (TableI). The mean shear bond strengths of the tubes weresignificantly different, except for the tubes in GroupsA and B (Table II). The largest mean difference of2.61 MPa occurred between the Group B and GroupC buccal tubes.

Table I. Base sizes and shear bond strengths of the buccal tubes.

Group N Mean size Mean SBS ± SD 95 per cent(mm2) (MPa)* CI

A 20 26.50 3.88 ± 0.34 3.73, 4.04B 20 18.20 4.32 ± 0.73 3.98, 4.66C 20 32.60 1.71 ± 0.60 1.43, 1.99D 20 22.70 3.34 ± 0.66 3.03, 3.65

A: American Orthodontics, 80 gauge photoetched foil mesh baseB: 3M Unitek (small base), 80 gauge microetched foil mesh baseC: 3M Unitek (large base), 80 gauge microetched foil mesh baseD: Hangzhou Dentop, 80 gauge microetched foil mesh base* One-way ANOVA, p = 0.00

Figure 1. A specimen ready for debonding.

PURMAL AND SUKUMARAN


The distributions of ARI scores are given in Table IIIand were significantly different (p < 0.05). In GroupsA and C most of the resin remained on the surfacesof the teeth, whereas in Groups B and D there was noadhesive on 40 per cent of the teeth. The ARI scoresin Group D were variable: all of the resin remainedon 10 per cent of the teeth, a further 10 per cent ofthe teeth retained 90 per cent of the resin, and 30 percent of the teeth retained between 90 and 10 per centof the resin (Table III).

Discussion

We compared the shear bond strengths of four differ-ent buccal tubes under standardised in-vitro con-ditions and found that the buccal tubes with the

largest bonding pads had the lowest bond strengths.The buccal tubes with the smallest pad area had thehighest bond strength, but it fell below the value con-sidered to be clinically acceptable. The ARI scores forbuccal tubes with the smallest bonding pad weremore-or-less evenly distributed between the extremescores, whereas most of the adhesive remained on theteeth when the buccal tubes with the largest bondingpads (Groups A and C) were debonded. The buccaltubes we tested had different base areas and differenttypes of retentive meshes, but we considered them asingle independent variable in our analysis.

Several investigators have proposed that increasingthe surface area of the bonding pad increases the loadcarrying capacity of an attachment and, presumably,results in a higher shear bond strength.9,13 However,MacColl et al.10 reported that shear bond strengthwas independent of the surface area of bonding padsabove 6.82 mm2. We found the smallest attachmentshad the highest bond strength, and postulate that themultilayer bases of the largest buccal tubes were notuniformly rigid. In our view, if the periphery of thebonding pad is not supported by the actual attach-ment it would be somewhat ‘flexible’ and relativelyeasily deformed by a shear force (Figure 2). On theother hand, when the buccal tube covered the bond-ing pad the tube-pad combination was more rigidand, therefore, less likely to fail (Figure 3).14

Table II. Comparisons of the shear bond strengths.

Shear bond strength (MPa)

Group, Manufacturer Comparison Mean difference p*

A, American Orthodontics B, 3M Unitek, small base -0.44 0.11C, 3M Unitek, large base 2.18 0.00D, Hangzhou 0.54 0.03

B, 3M Unitek, small base A, American Orthodontics 0.44 0.11C, 3M Unitek, large base 2.61 0.00D, Hangzhou 0.98 0.00

C, 3M Unitek, large base A, American Orthodontics -2.18 0.00B, 3M Unitek, small base -2.61 0.00D, Hangzhou -1.63 0.00

D, Hangzhou A, American Orthodontics -0.54 0.03B, 3M Unitek, small base -0.98 0.00C, 3M Unitek, large base -1.63 0.00

* Tukey HSD, significant differences in bold

Table III. Comparisons of the modified ARI scores.

ARI Group count (Per cent)

A B C D Total

1 12 (60) 6 (30) 14 (70) 2 (10) 34 (43) 2 4 (20) 4 (20) 6 (30) 2 (10) 16 (20)3 2 (10) 2 (10) 0 (0) 6 (30) 10 (13)4 2 (10) 0 (0) 0 (0) 2 (10) 4 (5)5 0 (0) 8 (40) 0 (0) 8 (40) 16 (20)

Total 20 (100) 20 (100) 20 (100) 20 (100) 80 (100)

Chi-squared test, p < 0.05

SHEAR BOND STRENGTHS OF BUCCAL TUBES


Other factors that may have influenced our findingsare the closeness of fit of the bonding pads, the extentof polymerisation and the effect of immersion inwater before testing.15 A buccal tube with a large basearea is likely to be less well-adapted to the surface ofthe tooth, leading to an uneven and, in parts, thicklayer of adhesive.14 The latter may include smallinclusions of air and is more likely to develop cracksas the concentration of stress increases proportionallywith the thickness of the resin layer.16

Maximum conversion of monomer to polymer is nec-essary for composite resin to achieve optimal physicalproperties.17 Complete polymerisation of the resinbeneath a buccal tube relies on the polymerising lightreaching all parts of the resin. Recent studies havereported that there was no significant difference inthe shear bond strengths when the tip of the curinglight was positioned between 1 and 10 mm from thebases of the brackets.18,19 We followed the manu-facturers’ directions and placed the light 10 mm from the mesial and distal edges of the metal bond-ing pads, but it is possible that resin in the most inaccessible parts of the mesh base was not completelypolymerised.20,21

The storage media used may have influenced thebond strength. We sterilised the teeth before usingthem in a 0.5 per cent solution of chloramine, whichaccording to Jaffer and coworkers15 should not affectthe shear bond strengths. After bonding, however, wesimulated the oral environment by storing the teethin water, which may have contributed to a loss ofbond strength.22

The Group B buccal tubes may have had the highestbond strength and smallest base area, but in 60 percent of the teeth much of the resin still remainedattached to the teeth. The area of unsupported base isgreater in Groups A and C (26.50 mm2 and 32.60

mm2, respectively) and most of the resin remainedattached to the teeth in these groups, strengtheningour belief that the peripheries of the buccal tubesflexed when subjected to the shear force and contributed to early failure.

Conclusions

Within the limitations of this study the conclusions are:

1. None of the buccal tubes had sufficient shear bondstrength for clinical use.

2. Increasing the area of the base did not increase theshear bond strength. The area of unsupported base may flex when subjected to a shear force andcontribute to early failure.

3. There were no differences in bond strengthbetween photoetched or microetched bases.

4. The buccal tubes in Groups B and D had the high-est bond strengths and more tubes failed at the tooth-resin interface.

Acknowledgment

We thank The University of Malaya for providing thefinancial support for this study (Grant No:FS253/2008A).


Dr Kathiravan PurmalDepartment of General Dental Practice and Oral andMaxillofacial ImagingDental FacultyUniversity Malaya50603 Kuala LumpurMalaysiaTel: +603 7967 4555Fax: +603 7967 4575Email: [email protected]

Figure 2. A multilayer buccal tube with a large base (Group C), showingthe unsupported flange.

Figure 3. A buccal tube with a small base (Group B). The attachmentextends almost to the edge of the bonding pad.

Layer 1

Layer 2

Layer 3

PURMAL AND SUKUMARAN


References1. Knoll M, Gwinnett AJ, Wolff MS. Shear strength of brackets

bonded to anterior and posterior teeth. Am J Orthod 1986;89:476–9.

2. Banks P, Macfarlane TV. Bonded versus banded first molarattachments: a randomized controlled clinical trial. JOrthod 2007;34:128–36; discussion 111–12.

3. Millett DT, Hallgren A, Fornell AC, Robertson M. Bondedmolar tubes: a retrospective evaluation of clinical perform-ance. Am J Orthod Dentofacial Orthop 1999;115:667–74.

4. Johnston CD, Burden DJ, Hussey DL, Mitchell CA.Bonding to molars – the effect of etch time (an in vitrostudy). Eur J Orthod 1998;20:195–9.

5. Maijer R, Smith DC. Variables influencing the bondstrength of metal orthodontic bracket bases. Am J Orthod1981;79:20–34.

6. Regan D, van Noort R. Bond strengths of two integralbracket-base combinations: an in vitro comparison with foil-mesh. Eur J Orthod 1989;11:144–53.

7. Johnston CD, McSherry PF. The effects of sandblasting onthe bond strength of molar attachments: an in vitro study.Eur J Orthod 1999;21:311–17.

8. Millett DT, Letters S, Roger E, Cummings A, Love J.Bonded molar tubes: an in vitro evaluation. Angle Orthod2001;71:380–5.

9. Wang WN, Li CH, Chou TH, Wang DD, Lin LH, Lin CT.Bond strength of various bracket base designs. Am J OrthodDentofacial Orthop 2004;125:65–70.

10. MacColl GA, Rossouw PE, Titley KC, Yamin C. The rela-tionship between bond strength and orthodontic bracketbase surface area with conventional and microetched foil-mesh bases. Am J Orthod Dentofacial Orthop 1998;113:276–81.

11. Artun J, Bergland S. Clinical trials with crystal growth con-ditioning as an alternative to acid-etch pretreatment. Am JOrthod 1984;85:333–40.

12. Bishara SE, VonWald L, Olsen ME, Laffoon JF. Effect oftime on the shear bond strength of glass ionomer and com-posite orthodontic adhesives. Am J Orthod DentofacialOrthop 1999;116:616–20.

13. Cozza P, Martucci L, Toffol LD, Penco SI. Shear bondstrength of metal brackets on enamel. Angle Orthod 2006;76:851–6.

14. Matasa CG, Eng C, Sci T. Buccal tube’s bond strength: acomparison reveals unexpected differences. Orthod MatInsider 2009;21:1–8.

15. Jaffer S, Oesterle LJ, Newman SM. Storage media effect onbond strength of orthodontic brackets. Am J OrthodDentofacial Orthop 2009;136:83–6.

16. Patrick RL, Minford JD. Treatise on Adhesion andAdhesives. In: Raton B, ed. CRC Press, 1991:337–8.

17. Ruyter IE, Oysaed H. Conversion in different depths ofultraviolet and visible light activated composite materials.Acta Odontol Scand 1982;40:179–92.

18. Gronberg K, Rossouw PE, Miller BH, Buschang P. Distanceand time effect on shear bond strength of brackets curedwith a second-generation light-emitting diode unit. AngleOrthod 2006;76:682–8.

19. Bennett AW, Watts DC. Performance of two blue light-emit-ting-diode dental light curing units with distance and irra-diation-time. Dent Mater 2004;20:72–9.

20. Oesterle LJ, Messersmith ML, Devine SM, Ness CF. Lightand setting times of visible-light-cured orthodontic adhesives.J Clin Orthod 1995;29:31–6.

21. Oesterle LJ, Shellhart WC, Belanger GK. Effect of tackingtime on bond strength of light-cured adhesives. J ClinOrthod 1997;31:449–53.

22. Murray SD, Hobson RS. Comparison of in vivo and in vitroshear bond strength. Am J Orthod Dentofacial Orthop2003;123:2–9.

Introduction

Movement of the mandible has been investigated anddocumented for over a century,1 and as technologyadvanced, so has our ability to accurately capturemandibular motion in three planes of space. Of late,magnetic and opto-electric camera systems have beenemployed to track human movement, including thetranslation and rotation of the mandible in the threeplanes of space.2–6 In dentistry, kinematic studieshave been used to investigate normal jaw physiologyand function,7–10 and the changes associated withtemporomandibular dysfunction11,12 and orthog-nathic surgery.13–15 To our knowledge no studies have examined condylar motion in patients usingfunctional appliances.

Functional appliances, including the design popu-larised by William Clark,16 are used to treat Class IImalocclusions characterised by mandibular retrog-nathia. The dentoalveolar effects of functional

appliances are well-documented,17 but there is lesscertainty of their effects on the condyle and the artic-ulating surface. Primate studies have indicated thatthere is some remodelling of the condylar heads in aposterior direction and that the glenoid fossae areremodelled by a combination of bone deposition pos-teriorly and resorption anteriorly.18,19 Furthermore,there is evidence to suggest that the retrodiscal tissuebecomes increasingly vascularised during prolongedmandibular advancement,20 indicating an inflamma-tory response in that region. Whilst these changeshave not been confirmed in human subjects, we pos-tulate that local adaptations within the humancondylar joint during anterior posturing of themandible may produce functional changes inmandibular kinematics.

The aim of this study was to describe the mandibularmotion in an individual undergoing growth modifi-cation orthodontic treatment using a Clark twinblock appliance.


The effect of a Clark twin block on mandibularmotion: a case report

Catherine O’Shea,* Andrew Quick,† Gillian Johnson,+ Allan Carman+ and PeterHerbison±

Royal Children’s Hospital, Brisbane, Queensland, Australia;* Schools of Dentistry,† Physiotherapy+ and Medicine,± University of Otago,Dunedin, New Zealand

Aims: To investigate mandibular motion in six degrees of freedom before, during and after twin block treatment in one individual.Methods: The appliance was worn for eight months, and motion recordings, using a 12-camera opto-electric system, were captured prior to placement of a twin block appliance and 2, 4, 14 and 52 weeks after insertion.Results: The wide variations in mandibular motion that accompany twin block wear disappeared post-treatment, except for anincrease in anteroposterior movement of the mandible.Conclusion: Twin block therapy appears to affect mandibular motion temporarily.(Aust Orthod J 2010; 26: 189–194)

Received for publication: February 2010Accepted: May 2010

Catherine O’Shea: [email protected] Quick: [email protected] Johnson: [email protected] Carman: [email protected] Herbison: [email protected]

O’SHEA ET AL


MethodsAn 11 year-old male subject with a Class II division 1malocclusion and a retrusive mandible was referred tothe Orthodontic Clinic, University of Otago. TheANB angle was 10 degrees and the Wits value was +9 mm. The pretreatment intra-oral photographs ofthe subject are shown in Figure 1. The study wasapproved by the University of Otago Human EthicsCommittee and informed consent was obtained forthe mandibular motion study.

The proposed intervention consisted of two phases: atwin block appliance followed by fixed appliances.The twin block appliance, which incorporated anupper labial bow to retract the upper incisors, wasrelieved to allow exfoliation of the remaining decid-uous canines and molars and eruption of the permanent molars. The method of capturingmandibular motion was similar to that described pre-viously.12 Briefly, a vacuum-formed occlusal splintwas fabricated to fit the subject’s lower dentition, towhich was attached a wire frame that supported sevenreflective markers: three anterior and two on eachside. A new splint was manufactured for each record-ing to accommodate teeth that may have moved inthe interim.

Six cranial reference markers were attached to a tightfitting latex swim cap worn by the subject and twomarkers were placed over the condylar heads, deter-mined by palpation (Figure 2). Motion was capturedusing a 12 camera infra-red Motion Analysis System(Motion Analysis Corporation, Santa Rosa, CA,USA) at a sampling rate of 60 Hz and supported byEvaRT 4.0 software (Motion Analysis Corporation).

Recordings of condylar motion were made prior totwin block therapy, after 2, 4 and 14 weeks treatment,

and 12 months from the start of treatment. The sub-ject was instructed to wear the twin block appliancefull-time, although compliance was not monitored.He was treated for 8 months and during this time theoverjet reduced from 11 mm to 3 mm (Figure 3). Atthe end of this phase of treatment a modified Hawleyretainer with a lower anterior bite plane was fitted.The subject declined the second phase of fixed appliance treatment.

At each recording, the subject was orientated in a nat-ural head position and the static position (with theteeth in maximum intercuspation) recorded for 6 seconds. He was then asked to perform a comfortableopen and closing movement of his mouth within a 6-second time frame and this was repeated six times ateach recording. A custom-written programme was thenused to identify the opening and closing parts of eachrecording and each cycle was normalised to 100 points.

During the 6-second static recording the mandibular(MP) and cranial (CP) axes were located while thejaw was closed (Figure 4). The origin of the mandibu-lar axes (MP) was located at the midpoints of markersoverlying the right and left condyles. An orthogonalaxes system was then constructed with the Z-axispassing through MP and the midpoint of the jawdevice, and the X-axis passing through the left andright condylar markers. The Y-axis was perpendicularto the X- and Z-axes. Similarly, the origins of the cranial axes (CP) were located at the midpoints of theleft and right temporal markers. A second orthogonalaxes system was then constructed with Z-axis passingthrough CP and the frontal head marker, and the X-axis passing through the left and right temporalmarkers. The local coordinates of all mandibular andcranial markers were then calculated with respect to

Figure 1. Pretreatment intra-oral photographs.

Figure 2. A model showing the arrangement ofreflective markers attached to the cranial cap, thelateral pole of the right condyle and the splint.

each axes system. During the movement trials, themandibular and cranial axes were reconstructed fromlocal and global coordinates of the correspondingmarkers using a least squares fitting procedure. Therelative rotation and translation between the MP andthe CP were calculated in degrees and millimetresrespectively along three axes: X, left-right; Y, vertical;Z, anteroposterior (Figure 5).

The error of detection of an individual reflectivemarker by the camera under dynamic conditions wasless than 0.4 mm, which is considered insignificantwith respect to the total movement recorded by thetwo points. The error in rotation within and betweenthe recording sessions had previously been calculatedby Johnson et al. as less than 1 degree.12

Statistical analysis A one-way analysis of variance (ANOVA) was used tocompare the mean differences in the dependent vari-ables of mean maximum rotation (degrees) and meanmaximum translation (mm) between the pretreat-ment and the four post-insertion recordings (the lastbeing the post-treatment 12-month recording).

Results The results were based on the means of six repeatmeasures during each recording session with theexception of the 4-week and 12-month recordings,where on both occasions the results of one of the sixmeasures was discarded due to technical difficulties.The mean rotation data about each of the three axesand the mean translation data for the pretreatmentand final (12-month) recordings are shown in Figure 6.

Statistically significant differences were foundbetween the mean maximum rotation pretreatmentand the 2-week, 14-week and 12-month recordingsin the X-axis, between the mean maximum rotationpretreatment and the 4-week, 14-week and 12-month recordings in the Y-axis, and between themean maximum rotation pretreatment and the 2-week, 4-week, 14-week and 12-month in the Z-axis(Table I).

Significant differences were also found between themean maximum translation pretreatment and the 2-week, 14-week and 12-month recordings in the X-axis, between the mean maximum rotation pretreat-ment and the post-insertion recordings in the Y-axis

TWIN BLOCK THERAPY AND MANDIBULAR MOTION


Figure 3. Intra-oral photographs after 8 months treatment.

Figure 4. The cranial global axes (CP) andmandibular global axes (MP) are calculated fromthe cranial and mandibular markers, respectively.

Table I. Mean differences (95% CI) between the mean maximum rotation pretreatment and the four post-insertion recordings in the X, Y and Z axes.

Rotation Post-insertion Post-insertion Post-insertion Post-insertion(degrees) 2 weeks 4 weeks 14 weeks 12 months

Mean (95% CI) Mean (95% CI) Mean (95% CI) Mean (95% CI)

X 3.60 (0.92, 6.28)* 1.46 (-1.33, 4.27)** 8.09 (5.42, 10.77)** 8.08 (5.26, 10.87)**Y 0.17 (-0.64, 0.417)* -5.05 (-5.30, 4.79)** -5.16 (-5.40, 4.92)** -2.16 (-2.41, 1.91)**Z -0.65 (-1.19, -0.09)* 4.07 (3.49, 4.65)** 1.70 (0.59, 1.75) ** -0.84 (-1.23, -.045)**

ANOVA, * p < 0.05, ** p < 0.01

O’SHEA ET AL


at 2-weeks, 4-weeks and 12-months, and between themean maximum pretreatment translation and allpost-insertion values (Table II).

Discussion

Although not specifically assessed using a clinical out-come measure such as the PAR Index,21 there was anoverall improvement in the occlusion at the end ofphase one treatment, which suggests that compliancewas adequate (Figures 1 and 3).

The kinematic model used in this study reducesmandibular motion to a single ‘condyle equivalent’, apoint situated midway between the lateral poles ofthe right and left condyles, referred to as MP. Thekinematics of this point were tracked relative to a static reference point, midway between the stable cranial markers (CP). The system can accurately trackrelative movement between these points with sixdegrees of freedom, but it is unable to locate the start-ing position of MP relative to anatomical cranialstructures. The assumption made in previous kine-matic studies is that condylar movement begins at the

resting position when teeth are in contact, which canapproximate, but not necessarily coincide with centric relation. Centric relation has been looselydefined as the position when the condyles are in theirmost anterosuperior positions against the slopes ofthe articular eminences.22 The method of determin-ing condylar position by palpation has been criticisedin the past because it is subjective, and has a locationerror that can vary up to 5 mm.23 We attempted tolimit errors in location by using the same operator tolocate the points in one subject. It has also beenshown that the overall pattern of jaw movement is thesame despite variations in location of the condyles,although some differences in the shape of the path ofjaw motion can be expected.24 In our study, the useof a single representative point, located between thecondyles, further reduced any error due to inaccuratemarker placement over a condyle.

In patients undergoing twin block therapy, thecondyles may not necessarily be in centric relation asthe mandible is encouraged to posture anteriorly.Figure 7 shows the approximate tracking of point MPover the five recordings in the anteroposterior andsuperior-inferior planes, relative to the automatic origin generated at each recording and with approxi-mate envelopes of error. Minimal variation inmandibular opening occurred at the pretreatmentand 2-week recordings, although a slightly greateropening was observed after two weeks of appliancewear. The 4-week recording was statistically differentfrom the two initial recordings: MP was positionedmore posteriorly and inferiorly than initially.

A possible explanation for this difference is that thecondyle started from a more anterior position as aresult of posturing, and in order to achieve opening,the condyles had to move in a posterior direction relative to CP. Mandibular motion in both planes wasvery variable, as indicated by the large standard deviations. Furthermore, absolute opening was

Table II. Mean differences (95% CI) between the mean maximum translation pretreatment and the four post-insertion in the X, Y and Z axes.

Translation Post-insertion Post-insertion Post-insertion Post-insertion(mm) 2 weeks 4 weeks 14 weeks 12 months

X 1.06 (0.61, 1.51)** -0.39 (-0.86, 0.08)** 1.10 (0.63, 1.58)** -0.88 (-1.35, -0.40)**Y -5.11 (-6.98, 3.24)** -8.40 (-10.36, -0.17)** -2.12 (-4.08, 1.06)** -0.88 (-2.84, 1.06)**Z 2.09 (0.98, 3.20)** -8.78 (-9.94, 7.62)** 6.42 (5.26, 7.58)** 6.52 (5.36, 7.68)**

ANOVA, * p < 0.05, ** p < 0.01

Figure 5. The axes and planes of mandibular movement. In this model thecentre of the mandible is the midpoint of the condylar markers.

approximately double the initial value, although thismay be partly due to a training effect, despite meas-ures taken to minimise this. The 14-week recordingsindicated that MP moved anterior-inferiorly,although this was also accompanied by large varia-bility in jaw kinematics in both the A-P and the superior-inferior planes. The final recording at theend of treatment (12 months) shows that mandibularmotion became more consistent in the vertical plane,with average opening values similar to those obtainedat the first recording. Point MP translated anteriorlyapproximately two and a half times more than in theinitial recording, with more variation in the horizontalplane. Table I indicates significant rotation within themandible between the initial and final recordings(approximately 8 degrees), but this may not have clinical significance. The results indicate thatmandibular opening and closing during twin blocktherapy undergo a phase of dramatic fluctuation,accompanied by forward posturing, but these returnto a more consistent motion post-treatment that

TWIN BLOCK THERAPY AND MANDIBULAR MOTION


Figure 6. Graphs depicting the mean rotation (A) and translation (B) (dashed lines, ± 95% CI) in the X, Y and Z planes. Each line is based on six repetitive trialsfrom the pretreatment and post-treatment sessions.

Figure 7. Trajectories of MP in the anterior-posterior and superior-inferiorplanes at the initial and four post-insertion recordings, together with the stan-dard deviation envelopes (not to scale).

4 weeks

14 weeksPre-

treatment

2 weeks

12 months

-7 -6 -5 -4 -3 -2 -1 1 2 3 4 5 6 7 8 9 10 11 12 13 14

-1

-2

-3

-4

-5

-6

-7

-8

-9

-10

-11

-12

-13

-14

-15

-16

-17

-18

-19

-20

-21

-22

-23

-24

Per cent of movement Per cent of movement

Per cent of movement Per cent of movement Per cent of movement

Per cent of movement

largely resembles the pretreatment pattern, except fora greater anteroposterior movement.

Conclusions

During treatment the twin block appliance changedmandibular function from the usual anterior move-ment on opening to a distal movement of themandible. Mandibular movement during therapy wasvery variable, but these changes largely disappearedafter removal of the appliance: the condylar tra-jectories tended to return to the pretreatment curves.

Acknowledgment

Funding for this study was supported by the NewZealand Association of Orthodontists.


Dr Andrew QuickSchool of DentistryUniversity of OtagoPO Box 647DunedinNew ZealandTel: +64 3 479 7480Fax: +64 3 479 7070Email: [email protected]

References1. Luce CE. The movements of the lower jaw. Boston M Surg J

1889;121:8–11.2. Mongini F, Tempia-Valenta G. A graphic and statistical

analysis of the chewing movements in function and dys-function. J Craniomandibular Pract 1984;2:125–34.

3. Mesqui F, Palla S. Real-time non-invasive recording and dis-play of functional jaw movements. J Oral Rehabil 1985;12:541–2.

4. Proeschel P. An extensive classification of chewing patternsin the frontal plane. Cranio 1987;5:55–63.

5. Airoldi R, Gallo LM, Palla S. Precision of the jaw trackingsystem JAWS-3D. J Orofac Pain 1994;8:155–64.

6. Naeije M, Van der Weijden JJ, Megens CC. OKAS –3D: anopto-electric jaw movement analysis system with six degreesof freedom. Med Biol Eng Comput 1995;33:683–8.

7. Zafar H, Nordh E, Eriksson PO. Temporal coordinationbetween mandibular and head-neck movements during jawopening-closing tasks in man. Arch Oral Biol 2000:45;675–82.

8. Gallo LM, Fushima K, Palla S. Mandibular helical axis path-ways during mastication. J Dent Res 2000:79;1566–72.

9. Lewis RP, Buschang PH, Throckmorton GS. Sex differencesin mandibular movements during opening and closing. Am JOrthod Dentofacial Orthop 2001:120;294–303.

10. Proeschel PA. Chewing patterns in subjects with normalocclusion and with malocclusions. Semin Orthod2006:12;138–49.

11. Miyawaki S, Tanimoto Y, Inoue M, Sugawara Y, Fujiki T,Takano-Yamamoto T. Condylar motion in patients withreduced anterior disk displacement. J Dent Res 2001:80;1430–5.

12. Johnson GM, Coe H, Wirawan R, Wong L, Lee C,MacFadyen E. Objective discrimination between man-dibular open/close excursion patterns: a clinical case report.Cranio 2007:25;218–24.

13. Athanasiou AE. Electrognathographic patterns of mandibu-lar motion after bilateral vertical ramus setback osteotomy.Int J Adult Orthodon Orthognath Surg 1992:7;23–9.

14. Ehmer U, Broll P. Mandibular border movements and mas-ticatory patterns before and after orthognathic surgery. Int JAdult Orthodon Orthognath Surg 1992:7;153–9.

15. Throckmorton GS, Ellis E. Recovery of mandibular motionafter closed and open treatment of unilateral mandibularcondylar process fractures. Int J Oral Maxillofac Surg 2000:29;421–7.

16. Clark WJ. Twin block functional therapy. 1995. Mosby-Wolfe, Turin, Italy.

17. Dermaut LR, Aelbers CMF. Orthopedics in orthodontics:fiction or reality. A review of the literature – Part II. Am JOrthod Dentofacial Orthop 1996:110;667–71.

18. Adams CD, Meikle MC, Norwick KW, Turpin DL.Dentofacial remodelling produced by intermaxillary forcesin Macaca mulatta. Arch Oral Biol 1972:17;1519–35.

19. McNamara JA, Carlson DS. Quantitative analysis of tem-poromandibular joint adaptations to protrusive function.Am J Orthod 1979:76;593–611.

20. Woodside DG, Metaxas A, Altuna G. The influence of func-tional appliance therapy on glenoid fossa remodelling. Am JOrthod Dentofacial Orthop 1987:92;181–98.

21. Richmond S, Shaw WC, O’Brien KD, Buchanan IB, JonesR, Stephens CD et al. The development of the PAR index(Peer Assessment Rating): reliability and validity. Eur JOrthod 1992:14;125–39.

22. Rinchuse DJ, Kandasamy S. Centric relation: a historicaland contemporary orthodontic perspective. J Am DentAssoc 2006;137:494–501.

23. Zwinjenburg A, Megens CC, Naeije M. Influence of choiceof reference point on the condylar movement paths duringmandibular movements. J Oral Rehab 1996:23;832–7.

24. Ostry DJ, Munhall KG. Control of jaw orientation and posi-tion in mastication and speech. J Neurophysiol 1994:71;1528–45.

O’SHEA ET AL


Introduction

The failure of a tooth to emerge into the dental archis usually due to crowding or the presence of anobstruction, such as another tooth, in the path oferuption.1,2 Occasionally, an unerupted toothmigrates to the opposite side of the arch. This isreferred to as ‘transmigration’.4

Transmigration usually involves a lower tooth, such asa lateral incisor, a second premolar or a canine, andon rare occasions the upper canines.3,5,6 Migratedcanines typically remain impacted.7,8 Occasionally,they may erupt ectopically in the midline or on theopposite side of the arch.9–11 In some cases, canineshave erupted next to the contralateral canine, in amirror image fashion.12 The first sign that a canine istransmigrating may be failure of a lower permanentcanine to erupt, or retention of a lower primarycanine.7,13 Absence of a developing permanent lowercanine under a deciduous canine is associated withslow resorption of the root of the deciduous canine.14

Tooth migration in the mandible is unlikely to bedetected during a routine clinical examination. It israrely discovered on a routine periapical radiographicexamination because the tooth is generally impactedunder the apices of the permanent teeth, and liesadjacent to the mandibular border. Therefore, when apermanent tooth is ‘missing’ a panoramic radio-graph should be taken. The female to male ratio oftransmigrated teeth is 1.6:1.15

The treatment options for a transmigrated lowercanine are: surgical removal of the impacted canineand retention of the deciduous canine for as long aspossible; transplantation; surgical exposure, forcederuption and orthodontic alignment; and extractionfollowed by prosthetic replacement.16 Surgical extrac-tion is the most favoured form of treatment, espec-ially when the lower arch is crowded and space isneeded to align the lower teeth.16,17 If the lower incisors are in a normal position and there is suffi-cient space in the arch for the transmigrated canine,transplantation may be undertaken.18 Surgical


Orthodontic treatment of a transmigratedmandibular canine: a case report

Göksu Trakyalı,* S‚ule Kavaloglu Çıldır† and Nüket Sandallı†

Departments of Orthodontics* and Pedodontics,† Faculty of Dentistry, Yeditepe University, Istanbul, Turkey

Background: Intraosseous migration of a lower canine across the midline is a rare dental anomaly. The treatment optionsinclude: forced eruption of the unerupted tooth using orthodontic traction, autotransplantation, extraction followed by prostheticreplacement.Aim: To report the management of a transmigrated lower right canine. Method: The treatment involved surgical, orthodontic and cosmetic dental treatment. No permanent teeth were extracted.Results: The transmigrated canine was placed between the left central and lateral incisors and the crown recontoured to simulate a lateral incisor. An acceptable aesthetic and functional outcome was gained.Conclusion: Transmigration is a rare dental condition that can be treated successfully with a collaborative effort from severaldental disciplines.(Aust Orthod J 2010; 26: 195–200)

Received for publication: December 2009Accepted: May 2010

Göksu Trakyalı: [email protected]‚ule Kavaloglu Çıldır: [email protected]üket Sandallı: [email protected]

TRAKYALI ET AL


exposure, combined with orthodontic alignment, canbe performed for labially impacted transmigratedcanines. When the crown of a transmigrated caninehas migrated past the contralateral incisors or if theapex of the transmigrated canine has migrated pastthe apex of the ipsilateral lateral incisor, it is usuallyimpossible to move the unerupted tooth into its correct place in the arch.

The purpose of this article is to report multidiscipli-nary treatment of a transmigrated lower right canine.The tooth was positioned between the roots of the left central and lateral incisors and the crownrecontoured to simulate a lateral incisor.

Case reportPretreatment evaluationAn 11 year-old girl was referred to the OrthodonticDepartment at Yeditepe University with an impacted,

lower right canine and retained lower right deciduouscanine. She was in good health and had no history ofdental trauma. The intra-oral examination revealedAngle Class II molar and canine relationships, anoverbite of 2 mm, an overjet of 5 mm, no upper orlower arch crowding and the lower left permanentcanine was rotated mesio-lingually (Figure 1).

Analysis of the pretreatment lateral cephalometricradiograph revealed normal vertical values and askeletal Class II relationship (Figure 2, Table I).Radiographic examination also revealed that thelower right canine was positioned vertically with thetip of the crown labial to the roots of the lower leftcentral and lateral incisors (Figure 2). There were carious lesions in the occlusal surfaces of upper rightfirst molar and lower left first molar.

Treatment planThe treatment plan called for extraction of the lowerright deciduous canine and closure of the extractionspace by moving the right lateral incisor and the bothcentral incisors to the right side. Surgical exposureand forced eruption of the unerupted right caninewere planned in order to place the transmigratedcanine between the contralateral central and lateralincisors. A Jasper Jumper appliance was used to estab-lish bilateral Class I molar relationships and to correctthe overbite and overjet.

Treatment progressBefore active orthodontic treatment, the paedodon-tist responsible for the patient’s dental care restoredboth carious teeth. The treatment objectives andalternatives were explained to the patient and her parents and informed consent was obtained.

(a) (b)

Figure 1. (a) Frontal view before orthodontic treatment. (b) Lower occlusal view before orthodontic treatment.

Table I. Pre- and post-treatment cephalometric measurements.

Cephalometric variables Before treatment After treatment

U1/L1 (degrees) 144.0 126.0U1/NA (degrees) 23.0 19.0L1/NB (degrees) 35.0 29.0SNA (degrees) 75.5 76.5SNB (degrees) 70.5 72.5ANB (degrees) 5.0 4.0Maxillary depth (degrees) 86.0 87.0GoMeSN (degrees) 35.0 31.0Saddle angle (degrees) 136.0 137.0FMA (degrees) 28.0 21.0SN/OccP (degrees) 20.0 15.0Jaraback (ratio) 65.7 72.0ANSMe/NMe (ratio) 58.0 58.4

TRANSMIGRATED MANDIBULAR CANINE


Upper and lower 0.022 inch metal Roth bracketswere bonded to the teeth in both arches (VictorySeries, 3M Unitek, Monrovia, CA, USA) and thelower right deciduous canine was extracted. Theupper arch was aligned and the lower arch levelled.The rotated left canine was corrected with a 0.016inch and 0.016 x 0.016 inch NiTi archwires. A 0.016x 0.016 inch stainless steel archwire was used to movethe lower incisors towards the right side (Figure 3).Five months later, an open coil spring was used to create space between the left central and lateral incisors for the transmigrated canine.

After four months treatment, the transmigrated lowerright canine was surgically exposed and a bracketbonded to the crown. At the next appointment traction was applied to the transmigrated canine with

a 0.016 inch NiTi segmental wire between the leftcentral and lateral incisors. The main archwire was a0.016 x 0.016 inch stainless steel wire with an offsetbetween the left central and lateral incisors (Figure 3).After forced eruption of the transmigrated canine,which took 5 months, a Jasper Jumper fixed func-tional appliance and upper and lower 0.017 x 0.025inch stainless steel archwires were used to correct theClass II malocclusion. The Jasper Jumper appliancewas activated once a month for 4 months. Finishingarchwires were used to torque teeth in both archesand were left in place for 4 months.

The fixed appliances were removed after 2 years and5 months of active orthodontic treatment. The tipand labial surface of the transmigrated right caninewere reshaped to simulate a lateral incisor. The lower

(a) (b)

Figure 2. (a) Pretreatment lateral cephalometric radiograph. (b) Pretreatement panoramic radiograph.

(a) (b)

Figure 3. (a) The 0.016 x 0.016 inch stainless steel archwire used to correct the lower midline. (b) Forced eruption of the transmigrated canine with the sectionalarchwire.

TRAKYALI ET AL


arch was retained with a 0.0175 inch sectional wirebonded to the lingual surfaces of the lower incisorsand canines.

Treatment results

During treatment, the upper (U1/NA) and lowerincisors (L1/NB) were proclined 4 degrees and 6 degrees, respectively. As a result, the interincisalangle (U1/L1) decreased from 144 degrees to 126degrees (Figure 4, Table I). The post-treatmentpanoramic radiograph revealed resorption of the dis-tal root of the lower right first permanent molar, pos-sibly due to the asymmetric Class I forces used tomove the incisors to the right side (Figure 5). Thelower right molar was root-filled by her paedodon-tist. Currently, the patient is recalled for retentionchecks.

Multidisciplinary treatment involving surgical expo-sure and orthodontic traction of the transmigratedcanine, alignment and correction of the Class II mal-occlusion and cosmetic reshaping of the canine tosimulate a lateral incisor, provided this patient withan acceptable aesthetic and functional result.

Discussion

Developing teeth move within the jaws before emerg-ing into the mouth. It is not known why a tooth devi-ates from its normal path of eruption and erupts in anabnormal position. The lower canines are the mostlikely teeth to migrate to the opposite side.5,7,19 Theangle between the long axis of an unerupted canineand the midsagittal plane indicates whether a canineis ‘displaced’ (between 25 and 30 degrees) or likely tomigrate across the midline (30 and 95 degrees).18

(a) (b)

Figure 4. (a) Frontal view after orthodontic treatment. (b) Lower occlusal view after orthodontic treatment.

(a) (b)

Figure 5. (a) Post-treatment lateral cephalometric radiograph. (b) Post-treatment panoramic radiograph.

According to Joshi, when the angle between the mid-sagittal plane and the dental axis exceeds 50 degrees,transmigration is predictable; if the angle fallsbetween 30 and 50 degrees transmigration may develop, and if the angle if less than 30 degrees trans-migration is unlikely to occur.14 In our patient theangle between the impacted canine and the mid-sagittal plane was about 80 degrees and the tooth hadmigrated across the mandibular midline.If a migrating tooth can be diagnosed early, it may bepossible to surgically expose the tooth and move itinto the arch. We elected to treat our patient with acombination of surgery and orthodontic treatment.Alternative treatment options are to transplant thetooth to a space in the arch, extract the uneruptedtooth and use the deciduous canine as a replacementfor the permanent canine or leave the transmigratedcanine in situ.16,18 Some clinicians prefer to trans-plant teeth with immature roots, so only a short period of time is available for the tooth to be detect-ed and transplanted. Furthermore, it may be difficultto remove the impacted tooth intact and avoid damage to the root and/or adjacent teeth: situationsthat reduce the likelihood of a successful long-termoutcome. In our case, the root of the lower canine wascompletely formed and the tooth was accessible. Ourpatient had a deep overbite, upright incisors and minimal crowding and did not require the extractionof any permanent teeth. The second and most com-mon option would have been to extract the trans-migrated canine. This option is generally favouredwhen the arch is crowded and a tooth needs to beextracted as part of the orthodontic treatment.16,17

Wertz noted that surgical repositioning of an impacted tooth can be attempted before the tooth is extracted.20 A third option would be to leave thetransmigrated canine in situ, but this approach canlead to long-term complications. Impacted teeth havethe potential to become ankylosed, making futuresurgical removal difficult, and they can continue toerupt, leading to resorption of overlying roots and, ifthey erupt, crowding. The deciduous canine couldhave been left in position and the appearance of thecrown enhanced with composite resin. In our case thetransmigrated canine could have been extracted, theextraction space closed and the occlusion adjustedwith the aid of temporary anchorage devices. Werejected the latter treatment plan because treatmentwould have taken longer and required an additionalsurgical procedure.

There were some disadvantages to our treatment.Firstly, the incisors were proclined between 4 and 6degrees, due to the Jasper Jumper appliance.Secondly, we detected a slight colour difference in thelower left canine after the cosmetic reshaping pro-cedures and, thirdly, the transmigrated canine had aslightly longer clinical crown than the adjacent lateral incisor. The latter was not considered a greataesthetic disadvantage. Finally, there was no contactbetween the right lower lateral incisor and upper rightcanine during lateral excursions of the mandible. Thiswas not considered to be a problem.

Summary

Transmigration of a mandibular canine is a rare event.Early diagnosis of an impacted tooth likely to migrateacross the midline allows the orthodontist to presentmultiple treatment options to the patient and his/herfamily. Surgical exposure and forced eruption of thetransmigrated canine, combined with non-extractionorthodontic treatment and good patient cooperationcan give an acceptable orthodontic result.


Dr Göksu TrakyalıYeditepe ÜniversitesiDis‚hekimligi FakültesiOrtodonti Anabilim Dalı Barbaros BulvarıS‚akir Kesebir Sokak, No: 26,Balmumcu-Bes‚iktas‚, 34349IstanbulTurkeyTel: +90 212 347 71 37Email: [email protected]

References1. Daskalogiannakis J. Glossary of Orthodontic Terms, ed 1.

Berlin, Germany: Quintessence 2000:2142.2. Bishara SE. Impacted maxillary canines: a review. Am J

Orthod Dentofacial Orthop 1992;101:159–71.3. Shapira Y, Kuftinec MM. Intrabony migration of impacted

teeth. Angle Orthod 2003;73:738–43. 4. Ando S, Aizawa K, Nakashima T, Sanka Y, Shimbo K,

Kiyokawa K. Transmigration process of the impactedmandibular cuspid. J Nihon Univ Sch Dent 1964;6:66–71.

5. Aydin U, Yilmaz HH. Transmigration of impacted canines.Dentomaxillofac Radiol 2003;32:198–200.

6. Shapira Y, Kuftinec MM. Unusual intraosseous trans-migration of a palatally impacted canine. Am J OrthodDentofacial Orthop 2005;127:360–3.

7. Javid B. Transmigration of impacted mandibular cuspids. IntJ Oral Surg 1985;14:547–9.

TRANSMIGRATED MANDIBULAR CANINE


TRAKYALI ET AL


8. Miranti R, Levbarg M. Extraction of a horizontally trans-migrated impacted mandibular canine: report of case. J AmDent Assoc 1974;88:607–10.

9. Brezniak N, Ben-Yehuda A, Shapira Y. Unusual mandibularcanine transposition: a case report. Am J OrthodDentofacial Orthop 1993;104:91–4.

10. Kaufman AY, Buchner A, Gan R, Hashomer T.Transmigration of mandibular canine. Report of a case. OralSurg Oral Med Oral Pathol 1967;23:648–50.

11. Pratt RJ. Migration of canine across the mandibular mid-line. Br Dent J 1969;126:463–4.

12. Batra P, Duggal R, Parkash H. Canine ectopia: report of twocases. J Indian Soc Pedod Prev Dent 2003;21:113–16.

13. Tarsitano JJ, Wooten JW, Burditt JT. Transmigration ofnonerupted mandibular canines: report of cases. J Am DentAssoc 1971;82:1395–7.

14. Joshi MR. Transmigrant mandibular canines: a record of 28cases and a retrospective review of literature. Angle Orthod2001;71:12–22.

15. Peck S. On the phenomenon of intraosseous migration ofnonerupting teeth. Am J Orthod Dentofacial Orthop 1998;113:515–17.

16. Camilleri S, Scerri E. Transmigration of mandibularcanines-a review of the 21literature and a report of fivecases. Angle Orthod 2003;73:753–62.

17. Thoma KH. Oral Surgery, ed 2. St Louis: Mosby,1952:62–3.18. Howard RD. The anomalous mandibular canine. Br J

Orthod 1976;3:117–21.19. Mupparapu M. Patterns of intra-osseous transmigration and

ectopic eruption of mandibular canines: review of literatureand report of nine additional cases. Dentomaxillofac Radiol2002;31:355–60.

20. Wertz RA. Treatment of transmigrated mandibular canines.Am J Orthod Dentofacial Orthop 1994;106:419–27.

Introduction

Mandibular deviation is the deviation of themandible as it moves from a postural position intothe intercuspal position. It may be due to inter-mediate or initial tooth contacts deflecting themandible and it may be associated with a facialasymmetry, which may worsen if the cause of thedeviation is left untreated. Congenital anomalies andenvironmental factors, such as condylar fracture, maylead to the development of facial asymmetry.1,2 Othercauses are believed to be: internal derangements inthe temporomandibular joint,3 rheumatoid arthritis,4osteoarthritis,4–6 condylar hyperplasia or hypoplasia,7,8

temporomandibular ankylosis,9 tumours in the tem-poromandibular region10 and lateral crossbite.11

Untreated fractures of the mandible can display vary-ing degrees of facial asymmetry.2 There have been several long-term studies of children with fracturedmandibular condyles, and the consensus is that manyfractured condyles are undiagnosed and regeneratespontaneously.12–14

Children with a mandibular deviation due to prema-ture tooth contacts should be treated as soon as convenient to avoid the development of a skeletal

asymmetry. Often orthodontic treatment to eliminatethe crossbite is all that is required. We report treat-ment of a child with anterior and unilateral posteriorcrossbites, a mandibular deviation to the left side dur-ing closure of the jaws and a marked facial asymmetry.

Case reportDiagnosisA 13.5 year-old girl with a unilateral posterior cross-bite and noticeable facial asymmetry was referred to aprivate practice office for orthodontic treatment. Herparents gave no history of head injury or significantmedical problems. At the time of examination shehad a full permanent dentition, except for the thirdmolars.

The extra-oral examination revealed that she had anobvious suborbital hypoplasia of the left side of herface (Figure 1). The mandible was displaced to theleft side and the lower dental midline was displaced 6 mm to the left of the facial and upper dental mid-lines. During closure of the jaws into occlusion, initial contacts occurred between the upper right pre-molars and first molar and the opposing teeth. Thebuccal surface of the lower right first molar had wear


Non-surgical treatment of mandibular deviation: a case report

Abdolreza Jamilian* and Rahman Showkatbakhsh†

Department of Orthodontics, School of Dentistry, Islamic Azad University* and Shahid Beheshti University of Medical Sciences,† Tehran, Iran

Background: Mandibular deviation due to premature contact of teeth in crossbite may be associated with facial asymmetry.Aim: To describe the non-surgical treatment of mandibular deviation associated with a marked facial asymmetry.Methods: A 13.5 year-old girl presented with a unilateral posterior crossbite, noticeable facial asymmetry, anterior crossbiteand displacement of the mandible on closure. She had no history of head injury or significant medical problems and her parents rejected surgical correction. A removable appliance was used to correct the crossbite followed by fixed appliances tocomplete treatment.Results: Treatment resulted in a marked improvement in facial symmetry and elimination of the mandibular displacement.Conclusions: Early correction of a functional deviation associated with a unilateral facial asymmetry may avoid the need for surgery.(Aust Orthod J 2010; 26: 201–205)

Received for publication: April 2010Accepted: June 2010

Abdolreza Jamilian: [email protected] Showkatbakhsh: [email protected]

JAMILIAN AND SHOWKATBAKHSH


facets from contact with the palatal surface of theupper first molar. In the intercuspal position theupper right first and second premolars and the firstmolar were in buccal crossbite and the upper left central incisor, lateral incisor and canine were inpalatal crossbite. On the right side the canine andmolar relationships were Class III, but on the left sidethe molar relationship was Class I and the canine relationship was Class II (Figure 1). There was no evidence suggesting a fractured mandibular condyleand the patient and her parents could not recall anaccident likely to result in a condylar fracture.

The pretreatment radiographs are shown in Figure 2.The posteroanterior cephalometric radiographshowed a conspicuous left side suborbital hypoplasia.The lateral cephalometric radiograph showed a skele-tal Class III relationship and proclined upper andlower incisors (Table I).

Treatment objectives and alternativesThe treatment objectives were to eliminate the ante-rior and posterior crossbites and achieve a normalbuccal occlusion with an ideal overbite and overjet.The treatment plan accepted by the patient and herparents was to extract the upper and lower right second premolars, correct the anterior crossbite witha removable appliance with a posterior bite plane, andthen correct the unilateral posterior crossbite, alignthe teeth and close any residual extraction spaces witha fixed appliance. It was estimated that treatmentwould take 3 years. Alternative treatment plans usingrapid maxillary expansion and miniscrews wererejected. The possibility of future surgery to correctthe skeletal asymmetry was discussed with thepatient’s parents and rejected by them.

Treatment progressThe anterior crossbite was corrected with a removableappliance with a screw behind the upper left incisors

(a) (b) (c)

Figure 1. Pretreatment facial and intra-oral photographs. (a) Frontal view. (b) Frontal view with smile. (c) Intra-oral.

Table I. Cephalometric analysis.

Pretreatment Post-treatment

SNA (degrees) 81.1 78.7SNB (degrees) 79.8 77.6ANB (degrees) 1.3 1.1U1 to MxPl (degrees) 122.0 128.0L1 to MnP1 (degrees) 102.0 101.0Intercisal angle (degrees) 119.0 118.0MMPA (degrees) 11.0 10.0Facial proportion (per cent) 67.0 69.0L1 to A-Pog line (mm) 3.2 2.4SN to MxP1 (degrees) 16.0 15.0

and canine and a posterior bite plane to disoccludethe teeth in crossbite. This appliance was retainedwith Adams’ clasps on the first molars and the firstpremolars and C-clasps on the upper canines andcentral incisors. The patient was instructed to wearthe appliance full-time except for eating, contactsports and toothbrushing. The appliance correctedthe anterior crossbite and was used for 6 months.

A standard 0.018 inch edgewise appliance was thenplaced (American Orthodontics, Sheboygan, WI,USA) and the teeth levelled and aligned with a 0.012inch stainless steel wire and then a 0.016 inch stain-less steel wire. The remaining extraction spaces wereclosed with stainless steel 0.016 inch round archwires.Three intermaxillary elastics were used for 16 monthsto correct the posterior crossbite, mandibular

NON-SURGICAL TREATMENT OF MANDIBULAR DEVIATION


(a) (b) (c)

Figure 3. Post-treatment photographs. (a) Frontal view. (b) Frontal view with smile. (c) Intra-oral.

(a) (b) (c)

Figure 2. Pretreatment radiographs. (a) Panoramic radiograph. (b) Posteroanterior radiograph. (c) Lateral cephalometric radiograph.

JAMILIAN AND SHOWKATBAKHSH


deviation and the midlines: one diagonal elastic fromthe upper right canine to the lower left canine; onecross elastic from the buccal surface of the upper rightfirst molar band to the lingual surface of the lowerright first molar band; one cross elastic from the lin-gual surface of the upper left first molar band to the buccal surface of the lower left first molar band.

Following correction of the mandibular midline, aClass III elastic was used to correct the right molarand the canine relationships. After a good occlusalrelationship was obtained, detailing and finishing

procedures were undertaken. The appliance wasremoved after 3 years and 4 months treatment and anupper Hawley retainer placed.

Treatment resultsThe extra-oral photographs show the patient has animproved facial profile and less marked facial asym-metry (Figure 3). The intra-oral photograph showsthat the crossbites have been eliminated, the midlinesare coincident and a normal occlusal relationship hasbeen established. No root resorption was found onthe post-treatment panoramic radiograph (Figure 4).At the end of treatment the upper and lower incisorswere proclined (Figure 5, Table I).

Discussion

When our patient presented we were concernedabout the obvious facial asymmetry and our firstthoughts were that the asymmetry would eventuallyneed surgical correction. The patient and her parentsrejected a surgical solution, which led us to propose amore conservative line of treatment. We set out tocorrect the crossbites and midline discrepancy using aremovable appliance followed by a fixed appliance.The treatment took longer than we anticipatedbecause we asked the patient to remove the removable

(a) (b) (c)

Figure 4. Post-treatment radiographs. (a) Panoramic radiograph. (b) Posteroanterior radiograph. (c) Lateral cephalometric radiograph.

Figure 5. Pre- and post-treatment tracings superimposed on S-N, at sella.

appliance during eating and for some sporting activ-ities, and it may have been left out of the mouth forlonger periods than desirable. Furthermore, becausewe did not use a bite plane with the fixed applianceocclusal interferences slowed correction of the posterior crossbite.

After correction of the anterior crossbite the upperand lower right second premolars were extracted toenable the lower midline to be corrected and to estab-lish Class I canine and molar relationships. At thisstage a full fixed appliance with continuous archwireswas placed and the removable appliance with the biteplane discontinued. On reflection, an upper remov-able appliance with posterior bite planes and fly-overclasps and waxed out over the upper right premolarand molars may have allowed the treatment to pro-ceed more quickly because it would have preventedocclusal interferences from the right premolar andmolar. Further correction and better interdigitationwere achieved by the fixed appliances with the help ofthe diagonal and cross elastics. The mandibular deviation and midlines were corrected and normaloverbite and overjet were achieved. The dental andfacial aesthetics were improved to a great extent.

Facial asymmetry is a difficult deformity to correct.Orthognathic surgery along with orthodontics is thefirst treatment plan for severe mandibular deviation,especially in non-growing patients. It has also beenreported that facial asymmetries in children are frequently due to undiagnosed fractured condylesand that the majority of the condyles regeneratespontaneously.12

Asymmetries can be classified according to the struc-tures involved into dental, skeletal and functional.Dental asymmetries can be due to local factors suchas early loss of deciduous teeth or thumb sucking.Skeletal asymmetries may involve the maxilla,mandible or both bones. Functional asymmetriesarise when a malposed tooth deflects the mandibleduring closure into occlusion or by a constrictedupper arch.2

Conclusion

A patient with mandibular deviation and markedfacial asymmetry was successfully treated non-surgically. Early treatment of crossbites with an assoc-iated facial asymmetry may reduce the facial asymmetry.


Associate Professor Abdolreza JamilianNo. 2713 Jam Tower Next to Jame JamVali Asr StTehran 1966843133IranTel: 0098 21 2201 1892Fax: 0098 21 2202 2215Email: [email protected]

References 1. Proffit WR, White RP. Surgical-orthodontic Treatment. St

Louis, Mosby Year Book; 1991:24–70. 2. Bishara SE, Burkey PS, Kharouf JG. Dental and facial

asymmetries: a review. Angle Orthod 1994;64:89–98.3. Trpkova B, Major P, Nebbe B, Prasad N. Craniofacial asym-

metry and temporomandibular joint internal derangementin female adolescents: a posteroanterior cephalometricstudy. Angle Orthod 2000;70:81–8.

4. Gynther GW, Tronje G, Holmlund AB. Radiographicchanges in the temporomandibular joint in patients withgeneralized osteoarthritis and rheumatoid arthritis. OralSurg Oral Med Oral Pathol Oral Radiol Endod 1996;81:613–18.

5. Dibbets JM, Carlson DS. Implications of temporomandibu-lar disorders for facial growth and orthodontic treatment.Semin Orthod 1995;1:258–72.

6. Kjellberg H. Craniofacial growth in juvenile chronic arthritis.Acta Odontol Scand 1998;56:360–5.

7. Westesson PL, Tallents RH, Katzberg RW, Guay JA.Radiographic assessment of asymmetry of the mandible.AJNR Am J Neuroradiol 1994;15:991–9.

8. Tallents RH, Guay JA, Katzberg RW, Murphy W, Proskin H.Angular and linear comparisons with unilateral mandibularasymmetry. J Craniomandib Disord 1991;5:135–42.

9. Subtelny JD. The degenerative, regenerative mandibularcondyle: facial asymmetry. J Craniofac Genet Dev BiolSuppl 1985;1:227–37.

10. Hall HD. Facial asymmetry. In: Bell WH, editor. Surgicalcorrection of dentofacial deformities: new concepts.Philadelphia: WB Saunders; 1985:153–68.

11. Pirttiniemi PM. Associations of mandibular and facial asym-metries: a review. Am J Orthod Dentofacial Orthop1994;106:191–200.

12. Harkness EM, Thorburn DN. Hemifacial microsomia labelquestioned. Angle Orthod 1990; 60:5–6 (Letter).

13. MacGregor AB, Fordyce GL. The treatment of fractures ofthe neck of the mandibular condyle. Br Dent J1957:102:351–7.

14. Proffit WR, Vig KW, Turvey TA. Early fracture of themandibular condyles: frequently an unsuspected cause ofgrowth disturbances. Am J Orthod 1980:78:1–24.

NON-SURGICAL TREATMENT OF MANDIBULAR DEVIATION




Editorial

This issue is one of the largest so far and covers a widerange of topics from bonding (and debonding) to lip– tooth relationships during smiling and speech toforces and moments with reverse curve NiTi arch-wires. It opens with a randomised clinical trial of theutility of custom bases for indirect bonding by PeterMiles. Peter’s interesting study has important infor-mation for the increasing number of clinicians whouse indirect bonding.

Exogenous opioids reduce macroscopic tooth move-ment in rats, according to Drs Akhoundi, Dehpour,Rashidpour, Alaeddini, Kharazifard and Noroozi.They suggest that opiate-based analgesics, which arereadily available and may be used by patients for painrelief, may do the same in humans.

Chromatic adhesives are an attractive propositionbecause they aid flash clean-up. June Lee, GeorgeGeorgiou and Steven Jones report there were no dif-ferences in the unfatigued and fatigued bond strengthsof chromatic and light-cured adhesives, but urge caution before their results are confirmed by clinicaltests.

The intrusive forces exerted on the upper incisors byNiTi reverse curve archwires are very high regardlessof the type of bracket, according to Drs Sifakakis,Pandis, Makou, Eliades and Bourauel. Lighter arch-wires may be more effective than the NiTi archwirethey used and, presumably, result in less tissue damage.

Debonding ceramic brackets can be a stressful pro-cedure, particularly if ceramic remnants are leftbehind or the enamel fractures. Drs Lemke, Xu,Hagan, Armbruster and Ballard compared the bondstrengths and modes of failure of ceramic and metalbrackets and their findings will be of interest to clinicians using ceramic brackets.

Drs Ghoneima, Abdel-Fattah, Eraso, Fardo, Kula andHartsfield used CT imaging to investigate the skeletaland dental changes during rapid maxillary expansion.They consider 3-D volumetric reconstruction gives a better evaluation of treatment outcomes than traditional radiographic methods.

In their study of glass ionomer cements, DrsDastjerdie, Zarnegar, Behnaz and Seifi tell us that thecements contributed little to band retention, and

imply that well-adapted bands are the key to goodretention.

Many orthodontists (and professional associations)use the word ‘smile’ in their literature. RoozbehRashed and Farzin Heravi look at the impact of various types of malocclusion on lip – tooth relation-ships during smiling and speech. They suggest thatdynamic records during smiling and speech should bepart of our diagnosis and treatment planning and havedesigned a software programme to facilitate these.

Many clinicians will agree that extraction of lower second premolars provides more space for uneruptedthird molars than extraction of the first premolars, butis it sufficient to allow the lower third molars to eruptinto the arch? Drs Celikoglu, Kamak, Akkas andOktay give us data of the actual space gained and theextent of third molar uprighting following either premolar extractions or nonextraction treatment.

Drs Ebin, Zam and Othman tell us Malay childrenwith repaired unilateral cleft lip and palate have normalmandibles, but retrusive maxillae. They postulate thatpressure from the repaired lip may be responsible forthe retrusive maxillae and retroclined incisors.

In this latest investigation of facemask therapy, Dr Guidentifies the craniofacial features contributing tolong-term stability of this type of treatment. Dr Gualso calls for a multicentre study to improve the predictive power of the discriminant model.

A few days of rapid maxillary expansion followed by aperiod of slow opening has the same effects on thefacial skeleton as rapid maxillary expansion alone,according to Drs Kilic and Oktay. The sagittal andvertical changes were small and variable and may notbe clinically significant, according to Nihat Kilic andHüssamettin Oktay.

Somewhat surprisingly, buccal tubes with large bond-ing pads had lower shear bond strengths than tubeswith small bonding pads. Drs Purmal and Sukumaranthink the periphery of the large pads may have ‘flexed’during debonding, leading to early dislodgement. Ifthey are correct, a design change should improve theretention of bonded buccal tubes.

The Clark twin block is the appliance of choice for many Class II division 1 malocclusions. Catherine

Effective orthodontics

28001_aoj_ortho_jnl_26.2_dec 15:06:24 10-11-08 Yellow Magenta Cyan Black Sect 8 Back


O’Shea, Andrew Quick, Gillian Johnson, AllanCarman and Peter Herbison combine to analysemandibular motion in this case report, and tell us that appliance-induced changes in condylar trajectories may be temporary.

In this case report Drs Trakyalı, Çıldır and Sandallıdescribe their treatment of a lower transmigratedcanine. They used a combination of forced eruption andorthodontic treatment and obtained an excellent result.

Drs Jamilian and Showkatbakhsh describe their non-surgical treatment of a young girl with mandibulardeviation. The case was beautifully treated andAbdolreza Jamilian and Rahman Showkatbakhshpoint out the advantage of combining a bite planewith the fixed appliances.

Associate Professor Craig Dreyer will take over edi-torship of the Journal in January 2011. Craig is a sen-ior staff member in orthodontics, the Assistant Deanof Clinical Services at the University of Adelaide andhas been acting-Dean on several occasions. He hasbeen Chairman of the Appeals Committee of theAustralian Society of Orthodontists for many years,which speaks highly of the Society’s confidence in hisfairness and dedication. Many of you know himthrough his excellent reviews for the Recent publica-tion section of the Journal, his publications on tissuereactions and excellent chapters in recent orthodontictextbooks. He is an experienced editor having super-vised many theses from honours to doctorate level.A/Prof Dreyer has been invited to speak at many uni-versities and conferences: most recently as a keynotespeaker at the World Federation of Orthodontists’Conference in Sydney. He has also used his skills andextensive knowledge of orthodontics to teach post-graduate students at Khon Kaen University, to reviewarticles for numerous journals, to provide curriculumadvice for the Batchelor of Oral Health programme atthe University of Adelaide and coordinate the Fourthyear undergraduate programme at the Univers-ity. As external examiners our paths have crossed and the postgraduate students he examined spokehighly of his knowledge and fairness. I am con-fident you will find him an excellent editor for theJournal.

Finally, I would like to thank those who have con-tributed to the Journal and supported me during myterm as editor.

Michael Harkness

Retirement of Michael HarknessAimee deCathelineau, as current senior editor of theJournal of Cell Biology, recently said, ‘. . . when youread 100 papers you find out what a journal is reallyabout . . .’. When you read 100 papers from the Aus-tralian Orthodontic Journal, you gain the impressionthat the Journal is about, well, orthodontics. WhatAimee deCathelineau has inferred is that an editorhas a crucial role in determining the nature of a journaland the emphasis and the direction that editorial con-tent and manuscripts should take. Writing in Nature,Kendall Powell1 described an editor’s role as the ‘Gate-keeper’s burden’, as submitted papers are chaperonedthrough the peer-review and editorial processes and,ultimately, in deciding whether a paper is published.

Over almost a decade, Michael Harkness has been theshepherd of our Journal and the overseer of its devel-opment. A glance at the last issue published in May2010 reveals the extent of his contribution. In it thereare articles on growth and development, orthodonticmaterials, therapy, treatment planning, prevention andmore. The direction that the Journal has taken has beentopical, relevant and of intense interest to the readership.

The responsibilities of liaising with authors, chasingreferees and the editing of manuscripts can seem anever-ending task. Like his predecessors, Michael hasdedicated considerable time, untiring effort andremarkable expertise to the publication of a journalthat is increasing in its academic value and its popul-arity. His strong and broadly-based foundation in science has been applied to the Journal’s content. Hiscreative and imaginative view of orthodontics and itsfuture prospects has enabled the Journal to growunder his leadership, whilst maintaining a historicalperspective of the profession. The Journal’s readershiphas basked in an intellectual atmosphere sustained byMichael’s honesty and integrity in all aspects of theediting and publishing process.

Upon his retirement as editor, Michael Harknessleaves a legacy of service and dedication to the Journalfor which the Australian Society of Orthodontists isproud and thankful. Its continued success has beenbecause of his devotion. The Society wishes Michaela happy and long ‘retirement’, doing the things thathe, heretofore, has been unable to do. Best wishes andthank you from a grateful Society.

Craig Dreyer, on behalf of the Journal readership

Reference1. Powell K. Gatekeepers burden, Nature 2010;464:800–1.


EDITORIAL

207




Letter

Optimal force

Sir,

I read with interest the article, ‘The dimensions of theroots of the human permanent dentition as a guide tothe selection of optimal orthodontic forces’ by Dr Brian Lee in the May 2010 issue of the Journal.This thought-provoking and challenging article pro-vided data on the dimensions of roots of teeth, whichallowed us to estimate the optimal forces for ortho-dontic tooth movement. This is a significant contri-bution for orthodontists seeking a more objectivemethod of assessing the force requirements to moveteeth. He also demonstrated that the product of rootlength and width gives a better estimate of root areathan length alone. Current technology, such as three-dimensional imaging, may allow the dimensions of the roots of individual teeth to be measured accur-ately and more conveniently than the manual methods used by Dr Lee.

The next technological step will be to design andmanufacture stress-breaking brackets. To a limitedextent these are available in active self-ligating brackets where the self-ligating latch exerts a force onthe archwire. Other stress-breaking designs have beenproposed, but alas none are widely available. When

the force is greater than optimal, a stress-breakingbracket is able to reduce the applied force acting viathe bracket slot.1 If the manufacturers of brackets canmake the intricately designed self-ligating bracketswith ever more complex mechanisms, surely a cali-brated stress-breaking bracket is not beyond theircapabilities?

An assessment of the optimal forces required to movethe teeth and use of a stress-breaking bracket shouldresult in less tissue damage during orthodontic toothmovement, more patient comfort, more rapid toothmovement and less chair-side time. The challenge isfor the profession and manufacturers to explore thesepossibilities and produce a truly stress-breaking bracket.

Felix GoldschmiedPO Box 187 Kings MeadowsTasmania 7249 Australia Email address: [email protected]

Reference 1. Goldschmied F. A new bracket system. Part I. Aust Orthod J

2001;17:1-7.

Letters and brief communications are welcomed and need not concern what has been published in the Australian Orthodontic Journal. We will printexperimental, clinical and philosophical observations, reports of work in progress, educational notes and travel reports relevant to orthodontics. We reserve the right to edit all Letters to meet our requirements of space and format. All financial interests relevant to the content of a Letter must be disclosed. The views expressed in Letters represent the personal opinions of individual writers and not those of the Australian Society of OrthodontictsInc., the Editor, or BPA Print Group Pty Ltd.

28

00

1_

ao

j_o

rth

o_

jnl_

26

.2_

de

c 1

5:0

6:2

4 1

0-1

1-0

8 Y

ello

wM

ag

en

taC

ya

nB

lack

S

ect 8

Fro

nt

28001_aoj_ortho_jnl_26.2_dec 15:06:24 10-11-08 YellowMagentaCyanBlack Sect 8 Front



Head and Neck Anatomy for Dental Medicine

Edited by Eric W Barker. Based on thework of Michael Schuenke, Erik Schulteand Udo Schumacher Publisher: Thieme 2010(www.thieme.com)ISBN: 978 1 604 06209 0Price: USD $64.95

This is an impressively illustrated atlas with colour-coded tabs for easy referencing to the different chapters. The 14 chapters are recommended as an‘efficient study tool’, not only for students, but also for a broader practitioner-based audience.

The important facts and figures are tabulated into sev-eral aspects, such as embryonic origins and ossificationtimelines. The information in the tables is referencedin the number/codes to the illustrations, which shouldenhance understanding.

The excellent artwork and colour-coded illustrationsare based on large diagrams that correspond to simu-lated dissections. The emphasis is on transverse andlateral views and the illustrations show the overlyinglayers peeled away. Embryonic development and neuroanatomy are comprehensively covered, and anexceptionally clear illustration of the biomechanics ofthe temporomandibular joint is provided.

The clinical relevance of features important to future applications, such as LeFort I - III fractures, isgiven. These are particularly useful for under-graduate students. In addition, embryological anom-alies have been clearly depicted and in-depth detailsprovided.

With special reference to oral cavity, the landmarks ofvarious soft and hard tissue components on ortho-pantomograms are provided. These establish ‘spirallearning’ as the students can revisit these as they movethrough the clinical years of their courses.

The final interesting chapter on sectional anatomycorrelates the diagrams to MRI images (MagneticResonance Imaging), which clarify and enhanceunderstanding of the complex relationships betweendifferent structures. An understanding of this infor-mation is of paramount importance for 21st centuryimaging.

Overall, the book has many excellent illustrations,particularly for visual learners, that should enhancethe retention of information. A criticism would be thelack of detailed text accompanying the illustrationsand legends. It is essentially an atlas that attempts tohighlight some clinical associations. The book allowsone-off registration for the internet/interactive teach-ing tools, however the registration process is throughWinkingSkull.com and this could prove to be atedious process.

Shazia Naser-ud-Din

Bruxism: Theory and Practice

Author: Daniel A. PaesaniPublisher: Quintessence 2010(www.quintpub.com)ISBN: 978 1 85097 191 7Price: USD $248.00

Bruxism is a complex phenomenon that has bothintrigued and mystified the dental profession formany years. The aetiology has been the subject ofdebate with some believing that it is a centrally drivenprocess, while others believe that it is peripherally gen-erated activity that is mediated by tooth contacts.Dentists appear to believe that all patients brux for acertain period each night and that over a certainthreshold this activity, rather than being a normalhabit, becomes a pathological process that can lead to

Book reviews

28

00

1_

ao

j_o

rtho

_jn

l_2

6.2

_d

ec

15

:06

:24

10

-11

-08

Ye

llow

Ma

ge

nta

Cya

nB

lack

Se

ct 8

Fro

nt

28001_aoj_ortho_jnl_26.2_dec 15:06:24 10-11-08 Yellow Magenta Cyan Black Sect 8 Front


BOOK REVIEWS


significant tooth wear. Dental treatments vary frompreventative measures through to occlusal adjustmentwith adjunctive appliances.

This text is an evidence-based volume providingcomprehensive information and a thorough overviewof bruxism. There are 25 chapters divided into threesections, written by multiple contributors fromaround the world. The text is edited by Dr DanielPaesani who has been the Professor of Stomatog-nathic Physiology in the School of Dentistry,Universidad del Salvador/AOA, Buenos Aires,Argentina for 12 years. It is clearly written, has excel-lent photographs and a detailed review of the liter-ature. According to Dr Paesani, the premise was thatthe information should be based on scientific evidence, thus removing ambiguity from the subjectand providing a sound basis for clinical practice.

The volume is divided into three sections: the firstcomprises eight chapters and provides an overview ofbruxism, the second comprises nine chapters anddeals with the effects of bruxism on the masticatorysystem and the final (third) section comprises eight chapters describing clinical approaches to thetreatment of bruxism.

Part 1 introduces the reader to bruxism and has chap-ters that provide guidelines for diagnosis, sleep phys-iology, the main aetiological theories, influence ofperipheral sensory factors and emotional factors,movement disorders and bruxism in children.Chapter 1 introduces us to bruxism and contains anexcellent summary of the prevalence of bruxism bycollating studies and presenting the results in tables.Chapter 2 deals with the diagnosis of bruxism andChapter 3 discusses sleep physiology and bruxism.The latter details the different phases of sleep andsleep architecture. Chapter 4 is an excellent summaryof the aetiology of bruxism. It reviews the literatureon the aetiology of bruxism and tries to establish themost important aetiological factors that are impli-cated in the phenomenon. Establishing these factorsis thought to be clinically important as they ultimatelymay determine the treatment that is undertaken bythe clinician. Chapters 5 and 6 deal with peripheralsensory factors and emotional factors in the aetiologyof bruxism. These are particularly interesting chaptersbecause they provide insights into how occlusal inter-ferences are thought to provide a neuromuscularstimulus capable of triggering bruxism. Currently,most authors lean towards a central aetiology;

however, the theory of peripheral influences has notbeen abandoned. Chapter 7 gives an overview ofmovement disorders and how they impact on den-tistry. Chapter 8 will be of interest to orthodontists,as it gives an excellent summary of bruxism in chil-dren. Despite bruxism being common in children,the literature is not extensive enough to provide afirm basis for evidence-based clinical practice.Interestingly, this chapter cites a study that shows thatocclusal splints are not useful in reducing the symp-toms of bruxism in children.

Part 2 provides a detailed analysis of the effect ofbruxism on the components of the masticatory sys-tem. Chapters 9, 10 and 11 describe tooth wear, den-tal erosion and reflux as a cause of dental erosion, respectively. Tooth wear is commonly encountered indental practice and orthodontists are often asked tocomment on the relationship between bruxism, mal-occlusion and tooth wear. Importantly, tooth wear isnot exclusively caused by bruxism and may have several different aetiologies. This chapter providesdetailed descriptions on tooth wear patterns and iswell supplemented by excellent clinical photographs.The chapters on erosion are very detailed and clearlydescribe various aetiologies. Chapter 11 is solelydevoted to discussion of gastroesophageal reflux as acause of dental erosion. Chapter 12 discusses contro-versies on the effect of bruxism. This chapterdescribes some of the controversies and reviews theliterature relating to them. It starts by discussing theeffect of bruxism on progressive dental crowding.Periodontists have dealt with the effect of bruxism onthe disruption of the dental occlusion and do notagree whether bruxism should be considered as acause of pathologic tooth migration. Other areas dis-cussed are the effects of bruxism on the soft tissuesand bone. Chapter 13 deals with the effect of brux-ism on teeth and its relationship with endodontics.Chapter 14 discusses the influence of trauma fromthe occlusion on the periodontium. The relationshipbetween occlusal force and periodontal disease is con-troversial. This chapter comprehensively reviews theliterature and concludes that occlusal trauma per sewill not lead to periodontal disease. Chapter 15describes the effects of bruxism on muscles. Chapter16 explores TMJ dysfunction and bruxism. It detailsTMD and has an extensive literature review. It hasbeen suggested that there is a causal relationshipbetween TMD, bruxism and stress, though more dataneeds to be collected to support this theory. The final




BOOK REVIEWS

211

chapter in this section discusses craniofacial pain andbruxism. Although there is a potential relationship, ittends to be ‘non linear’ and it is suggested that craniofacial pain and bruxism should be treated asseparate problems in patients.

Part 3 provides chapters dealing with clinicalapproaches to the treatment of bruxism. Chapter 18provides a description of pharmacological effects ofdrugs (both central-action and peripheral-action) onbruxism. Chapter 19 will be of significant interest tothe dental clinician as it discusses the criteria forselection of dental materials, analyses of wear mecha-nisms and relates both to the bruxing patient. Thereis a discussion of posterior composite resin restora-tions, which is particularly relevant in this aestheticera of restorative dentistry. Regardless of the restora-tive material used, all show increased wear in thebruxing patient. Chapter 20 outlines evidence relatedto the treatment of bruxism. It describes treatmentsincluding occlusal splints, mandibular anterior repo-sitioning appliances and behaviour modificationtreatments. Chapters 21 to 23 deal with oral restora-tion and its relationship to bruxism. Chapter 21 is anintroduction to complex oral restoration anddescribes centric relation, RP, rotation of themandible and the anterior bite plane method.Chapter 22 focuses on restoration of the worn denti-tion. It outlines general management and rehabilita-tive strategies. Rehabilitative techniques are describedand are well supported with excellent clinical photo-graphs. Chapter 23 deals with the effect of bruxismon implant restorations. Implants are an importantpart of restorative dentistry and it is important toexplore the relationship between bruxism andimplants. Although the literature generally considersbruxism to be a contraindication for dental implanttreatment, there is no clear evidence that implant fail-ure is caused by bruxism. Chapter 24 examines theuse of botulinum toxin in the treatment of bruxism.The last chapter describes the clinical treatment ofbruxism. It includes a discussion on canine guidance,bruxism splints and treatments with botulinumtoxin. Different types of splints are described anddetail is provided on the fabrication of the splints.Excellent photographs supplement the text.

In summary, this book provides comprehensive infor-mation on bruxism. It is clearly written and relativelyeasy to read. I found it provides a good balancebetween being concise and providing detail in the

various topics related to bruxism. The literature hasbeen reviewed in detail and each chapter is well refer-enced. This text serves both as an academic referenceand a clinical guide in the treatment of bruxism, andshould have a place in the libraries of all dental clini-cians and orthodontists.

Andrew Barry

Microimplants in Orthodontics

Authors: Jae-Hyun Sung, Hee-Moon Kyung,Hyo Sang Park, Seong-Min Bae and Oh-Won KwonPublisher: Dentos Australia Pty Ltd (Email: [email protected])ISBN: 89 956605-0-3-93510Price: AUD $200

This hardcover book, published by Dentos, is a full-colour volume written by several South Korean pioneers and leaders in the field of microimplanttechnology as well as Professor James McNamarafrom Ann Arbor. Well-illustrated and laid out, thebook is divided into seven chapters.

The first summarises the history of skeletal anchoragein orthodontics, commencing with the early work ofBrånemark and colleagues in osseo-integration in the1970s, through to the more recent studies of thisdecade. Several illustrations are a little unclear, butthis quality may be due to their reproduction fromoriginal publications. A comprehensive reference listis cited at the end of each chapter.

The second chapter deals with guidelines, includingillustrations, for implant size and site selection.Anatomical areas in both the mandible and maxillaare discussed with respect to proposed orthodonticmovements, surgical considerations and suggestedmicroimplant size.

A short third chapter outlines the development ofnew smaller orthodontic microimplants and theirclinical applications. These fixtures (Absoanchor,Dentos Inc.), designed by one of the authors, canthus be placed in any area of the mouth, includingthe interradicular areas. Various designs, selectedaccording to site and function, are illustrated together with recommended elastomers.

Surgical procedures for implant insertion andremoval are comprehensively described in Chapter 4.



BOOK REVIEWS


These include the surgical armamentarium, operativeprocedures, pitfalls and the timing of force applica-tion. This section is comprehensively illustrated with high quality photographs and diagrammatic representations of clinical procedures.

Chapter 5 describes and illustrates biomechanicalconsiderations in anchorage, and addresses tech-niques for control in all dimensions ranging frommolar intrusion in open bite cases to achieving uni-lateral maxillary constriction with an implant at themidpalatal suture.

Clinical case reports are presented in the followingand largest chapter. The authors aim to demonstratea wide variety of applications for microimplantanchorage, and commence with a classification oftheir cases, ranging from skeletal malocclusions tominor tooth movement. Extensive clinical photo-graphs and pre- and post-treatment superimpositionsare included with each case. Other interesting usesinclude placement for intra- or intermaxillary elastics(also following orthognathic surgery for fixation) andpotential anchor units for fixed functional appliances.

The concluding chapter evaluates success and failurerates of implants, referring to recent published studies.

This reference guide provides a clear and well-illus-trated overview of microimplant usage for orthodon-tic anchorage based on directional force mechanics,and would be a valuable addition to the library of anyorthodontist or oral and maxillofacial surgeon withan interest in implant technology as an adjunct toroutine orthodontic protocols.

Denise Lawry

Change Your Smile. Fourth Edition

Author: Ronald E. GoldsteinPublisher: Quintessence 2009(www.quintpub.com)ISBN: 978 0 86715 466 5Price: USD $29.50

This is a comprehensive book about cosmetic den-tistry for patients, and for dentists to show patientswhat can be done to correct common dental aesthetic problems, in order to improve their smilesand enhance their facial appearance. It is written inlayman’s language and is full of ‘before’ and ‘after’photographs and diagrams to illustrate to patients

what can be achieved with the latest techniques incosmetic dentistry. The book also attempts to listsome of the limitations of cosmetic dentistry.

Chapter 1 begins with a list of questions to beanswered by the patient, to see if the patient reallyneeds and wants to change their smile. It reminds thepatient that their smile does not only consist of thesix front teeth, but all the teeth and gum tissue thatshow when the patient is speaking or in the maxi-mum smiling position. He also advises patients tolook at their facial proportions. The Smile Analysis,which is another list of questions, points out the dif-ferent dental problems that can affect the smile. Thisanalysis asks the patient to look at the size, shapes andpositions of his or her teeth and the condition of thegums, the patient’s facial appearance and lip positionswhen smiling. There are lots of photos illustrating theproblems listed. This chapter also tells the patienthow to select a good cosmetic dentist. The authoradvises that it is very important to have good com-munications with the dentist, stating exactly what thepatients’ concerns are and to discuss the treatmentoptions and their costs before making a final decision.The next nine chapters are about the actualproblems and detailed treatment options:

Chapter 2, Staining and discolouration of teeth;Chapter 3, Decay and old fillings; Chapter 4,Fractured teeth; Chapter 5, Spaces between teeth;Chapter 6, Missing and lost teeth; Chapter 7,Crooked teeth; Chapter 8, Bite problems; Chapter 9,How your smile can make you look younger andChapter 10, How the gums affect the overall appear-ance of your smile. The types of treatment recom-mended are cosmetic contouring, bonding, porcelainveneers, crowns, orthodontics, fixed and removablebridges, implants and dentures. At the end of eachchapter there is a table summarising the treatmentsolutions, treatment time, maintenance needed, costs,advantages, disadvantages and treatment longevity.

In Chapter 6, on the treatment of missing teeth, theauthor recommends the use of a fixed bridge, remov-able bridge, complete denture or implants as treatmentoptions, but orthodontics is not listed as a treatmentoption. Chapter 10 tells the patients everything theyneed to know about keeping their gums healthy and,hence, improving their smile. The author explainswhat healthy gums look like and the causes of gumdisease, and how to prevent it or treat it. He also gives a few solutions on how to mask bone loss

28

00

1_

ao

j_o

rtho

_jn

l_2

6.2

_d

ec

15

:06

:24

10

-11

-08

Ye

llow

Ma

ge

nta

Cya

nB

lack

Se

ct 8

Fro

nt




BOOK REVIEWS

213

and gingival recession and how to treat a ‘gummysmile’.

Chapter 11 is about making changes to the patient’sfacial features to make them look better. The first halfof this chapter is written by a maxillofacial surgeon,Dr Louis S. Belinfante and the second half is by twoplastic surgeons Drs Farzad Nahai and Foad Nahai.Dr Belinfante explains in simple terms what orthog-nathic surgery involves, the costs, and what orthog-nathic surgery can correct. He emphasises that goodcommunication between surgeon and patient is nec-essary for success. He also gives advice on how toselect a good maxillofacial surgeon. There are ‘before’and ‘after’ photos of pre- and post-orthognathic sur-gery. Unfortunately, the photograph on page 177 isupside down. He finishes with a table summarisingtreatment options, risks and costs.

The plastic surgeons warn patients that cosmetic sur-gery should be carried out for the ‘right’ reasons, andlist questions to determine if a patient is a candidatefor plastic surgery. They give advice on how to selectan appropriate surgeon and show the patient whattype of things can be achieved with plastic surgeryand/or minimally invasive procedures, such as Botoxand facial fillers. They also give a summary table atthe end. The last chapter, ‘Finishing touches’, givesadvice on health, skin and lip care, diet, beauty andhairstyle.

The book ends with an appendix. This is a quick lookat the major cosmetic dentistry techniques presentedin the book and how they are carried out. It gives thepatient a description of what is to be done to theirteeth. The procedures covered are bonding, crowns,veneers, bridges, implants and orthodontics. Again,

dontics mentions braces (metal and tooth-coloured),but advises the patient to ask about Invisalign, lingualbraces and spring aligners. He lists the disadvantagesof lingual braces and the spring aligners, but doesn’t give any disadvantages of Invisalign for ortho-dontic treatment. Throughout the book the authorrecommends Invisalign for orthodontic treatment.

Overall, the book is a bit repetitive, but it is compre-hensive. It is a useful book for cosmetic dentists tohave in their surgeries or waiting rooms to showpatients what cosmetic dentistry can do to changetheir appearances. The photographs and illustrationsmake it easier for the dentist to explain their treat-ment procedures to the patient. Some of the solutions

suggested do not correct the problem but mask itnicely, hence patients may be tempted to select acompromise or easy solution.

Kit Chan

Dental Implants: The Art and Science

Authors: Charles A. Babbush, Jack A.Hahn, Jack T. Krauser and Joel L. RosenlichtPublisher: Elsevier Australia 2010(http://shop.elsevier.com.au)ISBN: 9781416053415Online price: AUD $283.50

This is a review of the second edition of this book,which aims to provide a comprehensive review of theprinciples and concepts in the constantly changingfield of implant dentistry. The book outlines the basicconcepts in implant dentistry, but has a very NorthAmerican focus in its discussion of fee structures,practice set-up and demand for treatment.Furthermore, there is a distinct bias towards theimplants and treatment modalities proposed byNobelbiocare.

The initial chapters focus on diagnosis and treatmentplanning of the implant patient. This seems to belargely surgically driven and there is limited discus-sion of the prosthetic treatment planning involved inthese cases. The latter half of the book focuses on sur-gical anatomy, soft and hard tissue grafting proce-dures, nerve repositioning and immediate loading ofimplants in single tooth and full arch rehabilitations.Again, there is a very limited discussion about theprosthetic aspects of the management of treatment.There is a discussion limited to two pages about theplacement of implants in young patients and this isfollowed by several case studies. There is no discus-sion at all about the use of implants as orthodonticanchorage.

Of interest is that three of the four authors are max-illofacial surgeons. As such I suspect that this hasinfluenced the overall direction and tone of this bookas it has a strong surgical bias. Where I find the bookfurther lacking is in discussions of implant soft tissueaesthetics, long-term maintenance and the success ofthese modalities of treatment.

this section is well-illustrated. The section on ortho-

28

00

1_

ao

j_o

rtho

_jn

l_2

6.2

_d

ec

15

:06

:24

10

-11

-08

Ye

llow

Ma

ge

nta

Cya

nB

lack

Se

ct 9

Fro

nt



I must conclude that this book may prove interestingto readers who seek greater knowledge in some of themore advanced and controversial surgical implanttechniques. However, the book as a whole is disjoint-ed, and does not inform individuals who have a lim-ited knowledge of implant dentistry; they wouldprobably be better to look elsewhere to attain a morecomprehensive discussion of the topic.

Eric Tan

Implant Dentistry: A Practical Approach.Second Edition

Author: Arun K. Garg Publisher: Mosby Elselvier 2010(http://shop.elsevier.com.au)ISBN: 9780323055666Online price: AUD $160.20

This second edition is well set out and illustrated.Professor Garg has presented a fairly concise, well-documented and an easy-to-read contemporary text.This is a comprehensive text with 19 chapters andfour appendices.

It begins with a chapter on the historical developmentof dental implants, which is well compiled and ishelpful in understanding the history of implants andhow implant design has changed with time and our knowledge of biology. This gives an excellent his-tory of the development of implants from bone totitanium and the evolution of endosteal andperiosteal dental implant designs.

Professor Garg then moves on to the armamentariumrequired for implant dentistry. He includes the use ofan implant guiding system to assist with implant totooth and inter-implant spacing during surgicalplacement. This chapter is a good reference for thebasic and extended use of surgical instruments.

His discussion of medical history and anatomic con-siderations for implant dentistry are practical. Oftenanatomic considerations are not practically related toimplant dentistry, but this chapter is well-written andillustrated and is a useful review of the vital structuresand landmarks that the implantologist needs to graspfor surgical practice.

One of the highlight chapters is on surgical templatesin implant dentistry. The transfer of our proposedtreatment from diagnostic wax-up to imaging andthen to surgery is critical. This chapter takes usthrough the manufacture of simple single tooth templates, to fully edentulous situations. He also discusses the various com-puterised template systemsavailable and their applications. The chapters on sterilisation, disinfection and asepsis;medical history; generalised surgical techniques andwound healing; and suturing techniques provide ade-quate information, but could go into more detail asthese are all vitally important to the practical aspectsof surgery.The chapter on anterior single tooth implants pres-ents a classification of immediate extraction andimmediate placement, but does not present a solidi-fied philosophy of technique. Articles and techniquesfrom the literature are presented, when clear clinicaltechniques and guidelines would be useful. Thedescription of implant properties desirable does notyet include the technique of laser etching of theimplant surface for soft and hard tissue attachment.The highlight of this book is his chapter on bonebiology, osseointegration and bone grafting.Understanding bone biology and physiology enablesthe implant clinician to adequately engineer treat-ment plans with an understanding of the effect offorce on the proposed prosthesis. The author has con-cisely summarised the salient points of this expandingfield of knowledge. The chapters on considerations for implants in thegeriatric patient, peri-implantitis and guidelines forhandling complications associated with implant pro-cedures are useful short summaries on these aspects ofimplant dentistry. The final third of the book contains a glossary ofimplant terminology and appendices on Americanitem number use, consent forms, surgical trays, a use-ful appendix on post-operative instructions anddietary menus for patients of implant surgery. In thisfinal appendix, he includes a suggested lifestylechange for patients that may not be well received bythe Australian patient psyche. A useful inclusionwould be a chapter on the surgical placement and useof implants and mini-implants in orthodontics.In summary, this is a useful addition to the implantologist’s library.Dan Brener

BOOK REVIEWS




Orthodontic and Dentofacial OrthopedicTreatment

Authors: Thomas Rakosi and Thomas GraberPublisher: Thieme 2010Distributor: Elsevier Australia(http://shop.elsevier.com.au)ISBN: 978313127761 9Online price: AUD $278.10

This book adds to the burgeoning collection of com-pilation texts that are now available for the ortho-dontic and dental professions. It is meant to be atreatment book and a companion volume toOrthodontic Diagnosis, which was first published in1993. Edited by Drs Thomas Graber and ThomasRakosi it has 14 contributors who are well-knownacademics and clinicians from around the world.Unfortunately, Dr Graber was unable to see the com-pleted work and the book is dedicated to his memory.

There are 16 chapters, each of which is very well illus-trated and generally read well. Each chapter is well-referenced, but a few need to give more currentreferences. The reviewer acknowledges that there is alag period between the writing of a textbook and itspublication, and it is often difficult to cite contem-porary references. Three chapters have no referencesmore current than 2000 and five no more recent than2001.

The first few chapters introduce the reader to thera-peutic diagnosis, preventive orthodontics and earlytreatment; interceptive guidance of the occlusion,including serial extraction followed by mechanother-apy. The next three chapters consider functional

appliances. The first discusses the principles, scopeand limitations of functionals, together with a discus-sion of the activator and the bionator. The secondchapter (written by Dr Clark) is about his twin blockappliance and the third chapter explores the use ofrare-earth magnets to help in mandibular propulsion.There follows chapters on early maxillary expansionand inter-arch compression springs, which introducethe reader to a number of systems including theHerbst, Jasper jumper, Forsus and Twin Force.

The next section of the book is related more to fixedappliance systems and has chapters exploring anchor-age control, segmented arch mechanics, theAlexander discipline, implants and orthodontics, andtreatment with the Invisalign system. A comprehen-sive chapter on tooth stripping by Zachrisson follows,and the book concludes with chapters on active reten-tion procedures and treatment planning formandibular distraction osteogenesis respectively.

As a treatment manual it does well, but could havebeen so much more. In the preface the editors com-ment that for this new treatment textbook they havechosen orthodontic topics that they consider to bethe ‘most important for rendering the highest level ofservice, in the safest, most practice-efficient way’. Abig call. You cannot please everyone, but perhapssome chapters on the straight-wire appliance which isarguably the most commonly practiced technique inthe world at the current time in one guise or another,self-ligating bracket systems, aesthetic bracket systems,lingual orthodontics and orthognathic surgery wouldadd that little bit more depth to make it the definitivetext it deserves to be. It would sit well as a referenceguide in dental libraries and for postgraduate students, but will have limited appeal to the moreexperienced orthodontist.

Andrew Toms


BOOK REVIEWS

215




Effectiveness of a lower lingual arch as aspace holding device

A.I. Owais, M.E. Rousan, S.A. Badran and E.S. Abu Alhaija

The early loss of primary teeth has the potential tocreate an arch length discrepancy leading to crowdingor tooth impaction. The greatest space loss has beenattributed to mesial movement of the first permanentmolars, and a lower lingual arch has been accepted asa standard component of preventive orthodontic spacemaintenance. Despite widespread use, little is knownregarding the efficiency of the lingual arch and itseffect on the dimensions of the mandibular arch. Thisstudy therefore examined the effectiveness of the lingual arch and compared two different wire gauges.The authors identified 67 subjects from an ortho-dontic centre into which 44 lingual arches were placedand monitored. Selected subjects who were in themixed dentition, possessed a Class I or mild Class IImalocclusion, a normal or slightly increased overbiteand had primary second molars earmarked for extrac-tion. Subjects were randomly divided into two groups,which either had an arch made from 0.9 mm or 1.25mm wire. A group of 23 patients who received notreatment served as controls. Arch assessments weremade from pretreatment cephalograms, dental panto-grams and study casts taken and retaken at six monthsand at the end of treatment.In both treatment groups, the lower incisors proclinedand moved forward, and space loss in the area of theextracted primary second molar occurred. While archlength preservation occurred, it was at the expense oflower incisor proclination and the loss of primarymolar extraction space. The lingual arch made from0.9 mm wire was found to be superior for arch lengthpreservation. The preference for the smaller gauge wirewas determined by the fewer breakages and clinicalproblems compared with the more rigid 1.25 mm wire.

European Journal of Orthodonticsdoi:10.1093/ejo/cjq022

Longitudinal changes in microbiology andclinical periodontal parameters after removalof fixed orthodontic appliances

J. van Gastel, M. Quirynen, W. Teughels, W. Coucke andC. Carels

It is well known that the placement of orthodonticbands and brackets influences plaque accumulationand growth. In addition, there are significant differ-ences in biofilm formation and periodontal reactionbetween different bracket types and between bondedand control teeth. The aim of this longitudinal studywas to monitor patients’ microbiological and clinicalparameters from bracket placement up to 3 monthspost-treatment.Twenty-four patients (10 males and 14 females, aged14.6 ± 1.0 years) were investigated for the micro-biology of sub- and supra-gingival flora, periodontalprobing depth, bleeding on probing and gingivalcrevicular fluid flow, and assessed upon the placementof orthodontic appliances, upon their removal andthree months post-treatment. All patients receivedstandardised oral hygiene instructions and wereselected to be free of extensive dental work and perio-dontal disease, to be non-smokers and not takingantibiotics.The statistically evaluated results demonstrated thatsub- and supra-gingival colony-forming unit ratio ofaerobic to anaerobic bacteria decreased significantlyfrom the time appliances were placed until theirremoval. Microbial levels did not recover in the threemonths after treatment, which meant a sustainedincrease in the levels of anaerobes.Clinical parameters for periodontal probing depth,bleeding on probing and gingival crevicular fluidshowed significant increases while appliances were inplace, but decreased following debanding/debondingto still remain higher than original levels. The authorsconcluded that fixed appliances altered microbial andperiodontal parameters, which did not recover to pre-treatment levels over the examination period. It was

Recentpublications

Abstracts of recently published papers reviewed by the Assistant Editor, Craig Dreyer

28

00

1_

ao

j_o

rtho

_jn

l_2

6.2

_d

ec

15

:06

:24

10

-11

-08

Ye

llow

Ma

ge

nta

Cya

nB

lack

Se

ct 9

Fro

nt




RECENT PUBLICATIONS

217

suggested that the prospect of any required perio-dontal treatment best be left until at least threemonths after orthodontic therapy.

European Journal of Orthodonticsdoi:10.1093/ejo/cjq032

Relationship between initial crowding andinterproximal force during retention phase

K. Okazaki

Long-term stability of tooth alignment has beenstated as an aim of orthodontic treatment, but oftenthere is disappointment in the poor patient response.It has been shown that most of the treatment collapseoccurs in the two years after the cessation of reten-tion, and that contact point displacement was relatedto the level of interproximal force in treated anduntreated cases. The present study chose to examinethe change in interproximal force (IPF) betweenlower anterior teeth during the retention phase, itsrelationship between the irregularity index beforeorthodontic treatment, and the total IPF. In addition,the effects of erupting third molars on the total IPFwere recorded.Forty patients who underwent orthodontic treatmentwith premolar extractions in the Department ofOrthodontics of Nihon University Dental Hospitalwere selected after applying the following criteria.Cases in which the overbite fell in the range of 0.5 to4.0 mm, an overjet of 1.0 - 4.0 mm or crowding of0.5 - 10.0 mm in the lower anterior teeth, were chosen. Following fixed appliance treatment, cor-rected incisors were retained by a wrap-aroundretainer without any interproximal reduction of toothsubstance. Interproximal force was measured by theplacement of a 30 mm-thick titanium strip betweenthe mandibular anterior teeth and with the patientseated upright, the strip was withdrawn using a digital force gauge at 10 mm/sec. Five anterior con-tact points were measured, each three times, and val-ues averaged and then added. This sum produced atotal IPF for each patient and the procedure was performed at each visit until 18 months after activetreatment.The IPF effects of third molars were assessed by com-parison of patients with impacted third molars andtheir relationship with second molars as determinedby panoramic radiology. One-way analysis of vari-ance and intergroup comparisons were statisticallydetermined.

The total interproximal force increased during theretention phase study period. There was a positivecorrelation between the pretreatment irregularityindex and the total IPF. The effects of the thirdmolars were not statistically significant. The authorssuggested that the total increase in IPF may be anindication of relapse in mandibular anterior crowd-ing. Although other relapse factors need consideration,it was suggested that clinicians pay special attentionto the relapse potential of increasing IPF, particularlyif severe irregularity existed prior to treatment.

Journal of Oral Science 2010; 52: 197-201

Adult orthodontics — who’s doing what?

M.K. Cedro, D.R. Moles and S.J. Hodges

A United Kingdom Adult Dental Health Survey in1998 indicated that 27 per cent of adults were dis-satisfied with the appearance of their teeth. A morerecent British Dental Health Foundation Surveyrevealed that one in two adults approaching middle-age would consider having dental treatment purely toimprove their smile. In addition, adults in the 36 to45 year age group were much more likely to considercosmetic treatment to improve the appearance oftheir dentition. While it has been revealed that adultsin the 18 to 30 age group make up approximately 17per cent of the average orthodontist’s workload, theaim of this study was to assess the factors and estimatethe number of adults currently being treated by specialist orthodontists in the UK, within the NHSand privately. After a small pilot study, three postings of a question-naire yielded 724 usable responses, out of a total of1034 sent to registrants on the General Dental Coun-cil’s Specialist List in Orthodontics, on 1 September2007. The final response rate was 70 per cent.Respondents had worked as orthodontists for a meanof 15.7 years, although there was a wide distributionranging from six months to 51 years. The main workplace for the majority of respondentswas specialist orthodontic practice (62.3 per cent),followed by the hospital service (29.2 per cent). Aminority worked in university (academic) posts (1.8per cent). The most commonly reported adult agegroups treated were 26 - 35 years (73.9 per cent ofrespondents) and 36 - 45 years (64.6 per cent ofrespondents). The age group least frequently treatedwere those aged 55 years and older (16.9 per cent ofrespondents).

28

00

1_

ao

j_o

rth

o_

jnl_

26

.2_

de

c 1

5:0

6:2

4 1

0-1

1-0

8 Y

ello

wM

ag

en

taC

ya

nB

lack

S

ect 9

Fro

nt



RECENT PUBLICATIONS


Slightly more than half (55.1 per cent) indicated thatthe majority of their NHS adult patients werereferred by general dental practitioners and 61.3 percent stated that general dental practitioners were theirmain source of private patient referrals. In addition, asubstantial proportion of orthodontists stated thatthe majority of their private adult patients were self-referred (25.7 per cent of respondents). The mean percentage of adults undergoing ortho-dontic-only treatment was 72.5 per cent and adjunctive multidisciplinary treatment was 22.8 percent. The most common appliance type used was thepre-adjusted edgewise appliance followed by self-ligating systems. Concerns regarding the appearanceof the appliances were cited as the most commoncomplicating factor expressed by the adult patients.In the previous financial year, the total number ofadult cases started by all questionnaire respondentswithin the NHS was 14,099 and privately was18,511. While it has been reported that the numberof adult orthodontic patients is increasing, no previ-ous data from specialist orthodontic providers areavailable by which to compare these results. There-fore, the authors suggest that this information be viewed as a baseline for comparison with futurestudies.

Journal of Orthodontics 2010; 37: 107–117

Periodontal regeneration with or withoutlimited orthodontics for the treatment of 2- or 3- walled infrabony defects

S. Ogihara and H-L. Wang

Past studies on forced eruption of teeth in a healthyperiodontium have generally indicated a beneficialeffect on alveolar bone levels. Unhealthy periodon-tium has been treated and subjected to the applica-tion of enamel matrix derivative (EMD) or the use ofdemineralised freeze-dried bone allograft (DFDBA)in order to recover lost bone. The results have beenequivocal. The authors of this study therefore aimedto compare the clinical efficacy of limited orthodon-tics combined with EMD/DFDBA in the treatmentof 2- or 3-walled infrabony pockets.A randomised, parallel clinical trial was undertaken ina private periodontal practice over a 4-year period.The treatment duration was one year with a one-yearfollow-up. Forty-seven patients (Mean age: 53.0 ±10.7 years) were randomly allocated into two inter-

vention groups, both of which were treated withEMD/DFDBA, but only one group of 24 patientsreceived orthodontic care. Patients had either a 2- or3-walled infrabony defect of at least 6 mm, which wasmanaged with EMD and DFDBA for four weeksprior to the application of an orthodontic extrusiveforce. Probing depth and the clinical attachment levelwere recorded prior to treatment and again at oneyear. The primary outcome measure was an absolutechange in probing depth and attachment level. A sec-ondary outcome was an absolute change in openprobing attachment level gain and percentage defectresolution from the commencement of surgical treat-ment to re-entry surgery six months later. Resultsindicated that both groups showed a significantimprovement following treatment. The group thatreceived the orthodontic extrusion had statisticallysignificant probing attachment level gain related to 2-wall defects. The authors concluded that both treat-ments were effective in managing all infrabonydefects, but limited orthodontics provided an addi-tional benefit in 2-wall defects. The authors contendthat the results should be viewed with a degree of caution because of inherent limitations of the study,but at least the work highlighted that there are otherbenefits of orthodontic care apart from the expectedaesthetic improvement.

Journal of Periodontologydoi: 10.1902/jop.2010.100127

Orthodontic extrusion of the lower thirdmolar with an orthodontic mini-implant

W. Park, J-S. Park, Y-M. Kim, H-S. Yu and K-D. Kim

Lower third molar extraction is one of the most com-mon surgical procedures in oral and maxillofacial surgery. Damage to the inferior alveolar nerve andsubsequent neurological changes are the most seriouscomplications associated with third molar removal.The introduction of cone beam computed tomo-graphy has allowed the 3-D visualisation of thirdmolars and their relationship with the inferior alveo-lar nerve, but has not entirely removed the risk ofnerve damage due to surgery.Two techniques have been introduced to minimisethe risk of post-third molar extraction paraesthesia.Coronectomy has been advocated but remains controversial while extraction of the third molar fol-lowing orthodontic extrusion occurs only rarely.However, the advent of the miniscrew has provided




RECENT PUBLICATIONS

219

anchorage possibilities in regional orthodontic treat-ment and the use of simple orthodontic appliances. The authors describe two cases in which orthodonticextrusion of an impacted third molar was undertakenbecause of its close approximation to the inferior alveolar nerve. In both cases, miniscrews were placedin the lower premolar region and segmental appliances attached to the buccal teeth. An elevatingarchwire was inserted back to the third molar whilevertical anchorage was reinforced by the attachmentof the premolars to the mini-screw. Six and nine months after the commencement ofextrusion, the third molars were uneventfullyextracted and the inferior alveolar nerve left intact.While the complications with this approach werereportedly minimal, the foreseen difficulty is thebonding of an attachment to the third molar.

Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology andEndodontics

doi:10.1016/j.tripleo.2010.04.031

Orthodontic therapy and gingival recession:a systematic review

I. Joss-Vassalli, G. Grebenstein, N. Topouzelis, A. Sculean and C. Katsaros

Long-term epidemiological studies have indicatedthat despite a reasonable level of oral hygiene, gingi-val recession is found in 60 per cent of the youngerpopulation (≤ 20 years) and more than 90 per cent ofthose older. The occurrence of recession has beenfound to be much higher in a population who exper-ience no dental care. The reasons for gingival recession have been associated with mechanical, periodontal or to inflammatory disease. This studytherefore aimed to assess the effects of orthodontictreatment on the occurrence of gingival recession bya systematic review the gingival effects of incisor inclination change.The study comprised a literature search undertakenby two of the authors who accessed the PubMed,EMBASE Excerpta Medica and CENTRAL of theCochrane Library databases. Appropriate MeSHsearches were conducted using the terms ‘gingivalrecession’, ‘orthodontics’, ‘gingival disease’ and arti-cles in any language were considered. The inclusioncriteria were human or animal studies, controlled orrandomised clinical trials and the occurrence of gingival recession associated with anterior teeth.Exclusion criteria identified medically compromised

patients, studies of injured or traumatised anteriorteeth and studies in which periodontal disease wasevident.Of the 1925 articles initially identified, only 17 werefinally included. Eleven articles were retrospectiveclinical studies in humans, while six were animalstudies.The authors’ results and conclusions indicated thatthere were no high-quality animal or clinical studieson gingival recession. The major reason for the lowlevel of evidence in the animal as well as in the humanstudies was the lack of diagnostic reliability tests. Ani-mal studies tended to suggest more gingival recessionin displaced incisors than in control teeth. Clinicalstudies showed that more proclined teeth comparedwith less proclined teeth or untreated teeth, andmovement of the incisors out of the osseous envelopeof the alveolar process, may be associated with ahigher tendency for developing gingival recession.Because of the low level of evidence of the includedstudies, the authors suggest that the results be consid-ered with caution. In addition, the amount of reces-sion found in studies with statistically significant differences between proclined and upright incisors issmall and the clinical consequence questionable.It was suggested that further prospective, randomisedclinical studies, including clinical examination of oralhygiene and the gingival condition before, duringand after treatment, were needed to clarify the effectof orthodontic changed incisor inclination and theoccurrence of gingival recession.

Orthodontics and Craniofacial Research2010; 13: 127-141



Australian Orthodontic Journal Volume 26 No. 2 November 2010-220

In appreciationReviewers for the Australian Orthodontic Journal

Rola Al Habashneh, Irbid, JordanKazem Al Nimri, Irbid, JordanMichael Anderson, Ashgrove, QPaul Armbruster, Louisiana, United States of AmericaJohn Armitage, Melbourne, VicDavid Armstrong, Coffs Harbour, NSWStephen Atkin, Redcliffe, QSaeed Banabilh, Kelatan, MalaysiaMatthew Barker, Wellington, New ZealandDerek Barwood, Auckland, New ZealandDonna Batchelor, Christchurch, New ZealandPhillip Benson, Sheffield, United KingdomEduardo Bernabe, London, United KingdomJim Bokas, Burwood, VicPierre Bourdiol, Clermont-Ferrand, FranceGuy Burnett, Adelaide, SABarbara Carach, North Ringwood, VicLuke Chapman, Louisiana, United States of AmericaTony Collett, Ferntree Gully, VicJohn Coolican, Chatswood, NSWAngela Coombe, Pymble, NSWAmy Counts, Florida, United States of AmericaMichael Courtney, Palmerston North, New ZealandMarguerite Crooks, Christchurch, New ZealandPaul Crowther, Christchurch, New ZealandAli Darendeliler, Sydney, NSWSaxton Dearing, Napier, New ZealandCraig Dreyer, Adelaide, SABernadette Drummond, Dunedin, New ZealandPeter Dysart, Dunedin, New ZealandCarlos Flores-Mir, Alberta, CanadaMatthew Foo, Pymble, NSWPeter Fowler, Christchurch, New ZealandElissa Freer, Mt Ommaney, QTerry Freer, Bardon, QJohn Fricker, Manuka, ACTShane Fryer, Wollongong, NSWGeorge Georgiou, London, United KingdomAllahyar Geramy, Tehran, IranPeter Gilbert, Dunedin, New ZealandKeith Godfrey, Sutherland, NSWUrban Hägg, Hong Kong, People’s Republic of ChinaFiona Hall, Mount Lawley, WAWinifred Harding, Dunedin, New ZealandJames Hartsfield, Kentucky, United States of AmericaJames Hawkins, Sydney, NSW

David Healey, Dunedin, New ZealandFarzin Heravi, Mashhad, IranJunichiro Iida, Sapporo, JapanHideki Ioi, Fukouka, JapanBrooke Jolly, New Plymouth, New ZealandViral Kachiwala, Muscat, OmanBrett Kerr, Ashgrove, QElias Kontogiorgos, Texas, United States of AmericaBudi Kusnoto, Chicago, United States of AmericaEden Lau, Lower Mitcham, SAIgor Lavrin, Melbourne, VicGavin Lenz, Brisbane, QKerry Lester, Woollahra, NSWPei-Ti Lin, Parkville, VicEric Liou, Taipei, TaiwanLombardo Luca, Ferrera, ItalyErin Mahoney, Sydney, NSW Sameh Malek, Burwood, NSWMontien Manosudprasit, Khon Kaen, ThailandKen Marshall, Blaxland, NSWDomingo Martin, San Sebastian, SpainBrendan McCane, Dunedin, New ZealandAna Claudiá Melo, Curitiba, BrazilStephen Moate, Forestville, NSWRachel Moore, Dargaville, New ZealandAndrea Motta, Rio de Janeiro, BrazilJose Nelson Mucha, Rio de Janeiro, BrazilJohn Muir, Auckland, New ZealandShazia Naser-ud-Din, Brisbane, QDaniel Ngan, Sydney, NSWRick Olive, Brisbane, QKieran O’Neill, Invercargill, New ZealandDesmond Ong, Helensvale, QLynne Opperman, Texas, United States of AmericaStephen Papas, New Farm, QIan Patrick, Epping, NSWTimo Peltomaki, Tampere, FinlandAjith Polonowita, Bendigo, VicMaryam Poosti, Mashhad, IranZainul Rajion, Kelantan, MalaysiaSarbin Ranjitkar, Adelaide, SAMorris Rapaport, Bondi Junction, NSWHenry Rawls, Texas, United States of AmericaMike Razza, Booragoon, WADavid Rogers, Highgate, WAWayne Sampson, Adelaide, SA

Over the past year the following individuals have generously contributed their time, knowledge and expertise reviewing articles for the Journal. We sincerely thank them and acknowledge their considerable contributions which have improved the quality of the Journal.

28

00

1_

ao

j_o

rth

o_

jnl_

26

.2_

de

c 1

5:0

6:2

4 1

0-1

1-0

8 Y

ello

wM

ag

en

taC

ya

nB

lack

S

ect 9

Fro

nt




IN APPRECIATION

221

Philip Sanford, Invercargill, New ZealandSeyed Safavi, Tehran, IranMartyn Sherriff, London, United Kingdom Steven Singer, Kingsley, WAJane Spark, Epping, NSWJohn Stamatis, Booragoon, WASteve Stramotas, Chatswood, NSWMichael Swain, Dunedin, New ZealandArzu Tezvergil-Mutluay, Turku, FinlandGuilherme Thiesen, Florianópolis, BrazilAbi Thomas, Punjab, IndiaMurray Thomson, Dunedin, New ZealandMarcus Tod, Upper Mount Gravatt, QMartin Tyas, Melbourne, Vic

Christine Underhill, Edgecliff, NSWOktay Uner, Ankara, TurkeyTancan Uysal, Kayseri, TurkeyJan Van Gastel, Leuven, BelgiumVicky Vlaskalic, Hawthorn East, VicJeffrey Watts, Auckland, New Zealand Willliam Weekes, Gosford, NSW Tony Weir, Corinda, QGeoff Wexler, Toorak, VicGreg White, Camberwell, VicDilshan Wijayaratne, Sandy Bay, TasPeter Wilkinson, Benowa, QMatthew Williams, Wellington, New Zealand

28

00

1_

ao

j_o

rth

o_

jnl_

26

.2_

de

c 1

5:0

6:2

4 1

0-1

1-0

8 Y

ello

wM

ag

en

taC

ya

nB

lack

S

ect 9

Fro

nt




Lava digital modelThe new 3M Lava digital modeltools make it easy for doctors to dis-play models for new patients andanalyse models for treatment plan-ning. According to the manufac-turer, the Lava treatment manage-ment portal has new featuresincluding upgraded analytical tools

such as occlusal mapping, bite adjustment, grid measurementand email capability. For further information contact your 3M Unitek TerritoryManager Tel: 136 136 484

Cinch-back plier The new cinch-back plier fromDentaurum can bend NiTi wire inthe mouth, eliminating the need toremove the archwire. The manu-facturer states it can be used toform indentations (dimples) at themidline to ‘lock’ the archwirebetween the central incisor brackets.To order, please quote product number 003-355.For further information contact DentaurumTel: Australia: 1300 880 782; NZ: 0800 336 828Website: www.dentaurum.comEmail: [email protected]

Invisalign Invisalign uses a series ofclear, removable, active appli-ances and 3-D modelling soft-ware to design a series of cus-tom-made ‘aligners’ thatocclude the patient’s teeth inan aesthetic and comfortable

manner. The company states that Invisalign can be used alone for comprehensive orthodontic treatment or as a keycomponent of restorative or cosmetic dental work. ClinCheck, the virtual 3-D modelling software, allows the doctor to view the initial malocclusion and virtual final result,as well as the stages of movement in between. For furtherinformation contact InvisalignTel: 1800 468 472Website: www.invisalign.com.auEmail: [email protected]

Medical Indemnity Protection Society

Medical Indemnity Protection Society (MIPS) provides exten-sive indemnity cover for the dental profession. Members haveaccess to knowledgeable, professional and confidentialadvice from an experienced and sympathetic colleague on allmedico-legal matters.For further information contact MIPS Tel: 1800 061 113Website: www.mips.com.auEmail: [email protected]

topsOrtho version 4.0 releasedThe latest version of this Mac-based practice managementand imaging programmeoffers near instant retrieval ofdata and patient charts with

no loss of quality – even from satellite and home offices – aswell as enhanced image editing. Users no longer need buy orpay support fees for a separate imaging programme.For further information contact tops SoftwareEmail: [email protected]: topsOrtho.com

InVu aesthetic brackets with Readi-Base pre-applied adhesiveThe InVu aesthetic brackets with Readi-Base pre-applied adhesive were devel-oped to help orthodontists meet the ris-ing demand for aesthetic orthodontics.Features include exclusive colour-match-ing technology that allows the bracketsto blend naturally with individual teeth,and a pre-applied adhesive that makes bracket placementeasy and precise and reduces chair time, according to themanufacturer. For more information contact TP OrthodonticsTel: 1800 643 055 Website: www.InVu-Ortho.com

New products

New products are presented as a service to our readers, andin no way imply endorsement by the Australian OrthodonticJournal.



Australian Orthodontic Journal Volume 26 No.2 November 2010 223

2011January 21-23International Meeting of the Egyptian Orthodontic Society,Alexandria, Egypt.Email: [email protected]

March 2-5Mexican Association of Orthodontists’ Annual Congress,Cancún, Mexico.Email: [email protected]: www.amo.org.mx

March 4-6Australian Society of Orthodontists’ Foundation for Research andEducation Meeting, Melbourne, Australia.Website: www.aso.org.au

March 18-20Association of Orthodontists, Singapore, Biennial Conference,Conrad Centennial Hotel, Singapore.Email: [email protected]

May 13-17American Association of Orthodontists’ 111th AAO AnnualSession, McCormick Place, Chicago, Illinois, United States ofAmerica.Website: www.aaomembers.org

June 2-4Societe Francaise d’Orthopedie Dento-Faciale ScientificCongress, Lyon, France.Website: www.sfodf.org

June 19-2387th Congress of the European Orthodontic Society, Istanbul,Turkey.Website: www.eso2011.com

November 3-544th Annual Scientific Congress of the Korean Association ofOrthodontists, COEX Convention and Exhibition Center, Seoul,Korea.Email: [email protected]: http://www.kao.or.kr

2012February 11-1423rd Australian Orthodontic Congress, Perth, Western Australia,Australia.Website: aso2012perth.com

November 23-268th Asian Pacific Orthodontic Society and the 8th Asian PacificOrthodontic Conference, New Delhi, India.Website: www.ap-os.org

Orthodontic calendar

For a list of meetings and links to websites of national and international orthodontic societies, visit the World Federation of Orthodontics, www.wfo.orgFor inclusion in the Australian Orthodontic Journal please contact Dr Tony Collett Tel: (+61 3) 9756 0519.Email: [email protected]

Orthodontic position

An opportunity exists for a new graduate

or experienced orthodontist to join our

state-of-the-art group practice in

Newcastle, Australia.

Newcastle is a progressive coastal city

160 km North of Sydney.

The practice has a comprehensive range of

modern treatment facilities using modern

materials and techniques. It is fully

computerised, has an in-house laboratory,

a continuing education facility and the

philosophy of clinical autonomy with a

work/leisure balance.

For further information, please contact

Mari-Ann Phillips;

[email protected]




Author indexAbdel-Fattah E, 141Akhoundi M, 113Akkas I, 160Alaeddini M, 113Amasyali M, 10, 49Ang H, 66Armbruster P, 134Ballard R, 134Behnaz M, 149Bhalla N, 38Bolognese A, 27Bosco A, 90Bourauel C, 127Carman A, 189Cash A, 38Catal G, 33Celikoglu M, 160Çıldır S, 195Cobourne M, 42Cuoghi O, 90da Luz Fontes J, 78Dastjerdie E, 149Dause R, 42de Souza Araújo M, 16 Dehpour A, 113dos Santos R, 16, 73Dreyer C, 66, 207Ebin L, 165Eliades T, 61, 127Eraso F, 141Fardo D, 141Georgiou G, 119Ghoneima A, 141,Goldschmied F, 208Good S, 38Gu Y, 171Guerra C, 27Gunhan O, 49Hagan J, 134Harkness M, 95, 206Hartsfield J, 141Heravi F, 153

Herbison P, 189Jamilian A, 201Johnson G, 189Jones S, 119Kamak H, 160Karsliogu Y, 49Kharazifard M, 113Kilic N, 33, 56, 178Koyuturk A, 10Kula K, 141Kusakabe S, 84Lee B, 1Lee J, 119Lemke K, 134Makou M, 61, 127Martins F, 16May N, 78McDonald F, 38, 42Mendonça M, 90Miles P, 21, 109Miranda-Zamallou Y, 90Motta A, 27Mucha J, 27Noroozi H, 113O’Shea C, 189Oktay H, 160, 178Olmez H, 49Othman S, 165Ozcan S, 10Pandis N, 16, 127Pithon M, 16, 73Polychronopoulou A, 61Purmal K, 184Quick A, 189Rashed R, 153Rashidpour M, 113 Romanos M, 16Sagdic D, 10Sandallı N, 195Scougall-Vilchis R, 84Seifi M, 149Sherriff M, 38Showkatbakhsh R, 201

Sifakakis I, 61, 127Souza M, 27Sukumaran P, 184Thiesen G, 78Tondelli P, 90Trayalı G, 195Uysal T, 10, 49Weyant R, 21Xu X, 134Yamamoto K, 84Yoldas T, 49Zam Zam N, 165Zárate-Díaz C, 84Zarnegar H, 149Zastrow D, 78

Subject index

3-D evaluation

Skeletal and dental changes after rapidmaxillary expansion: a computertomography study, 141

Adhesive Remnant Index (ARI)

Bond strengths of different orthodonticadhesives after enamel conditioningwith the same self-etching primer, 84Does ozone water affect the bondstrengths of orthodontic brackets? 73Shear bond strength of buccal tubes,184

Alignment

Porcelain brackets during initial alignment: are self-ligating cosmeticbrackets more efficient? 21

Amorphous calcium phos-phate-containing composites

Amorphous calcium phosphate- con-taining orthodontic composites. Dothey prevent demineralisation aroundorthodontic brackets? 10

Band retention

Strength of attachment between bandand glass ionomer cement, 149

Index to Volume 26The Australian Orthodontic Journal

28

00

1_

ao

j_o

rth

o_

jnl_

26

.2_

de

c 1

5:0

6:2

4 1

0-1

1-0

8 Y

ello

wM

ag

en

taC

ya

nB

lack

S

ect 9

Fro

nt



Biocompatibility

Cytotoxicity of orthodontic separatingelastics, 16

Bond strength

Does ozone water affect the bondstrengths of orthodontic brackets? 73Strength of attachment between bandand glass ionomer cement, 149

Book reviews

Bruxism: Theory and Practice, 209Change Your Smile. Fourth Edition,212Current Therapy in Orthodontics, 97Dental Practice: Get in the Game,100Dental Implants: The Art and Science,213Head and Neck Anatomy for DentalMedicine, 209Implant Dentistry: A PracticalApproach. Second Edition, 214Introduction of Innovative OrthodonticConcepts Using Microimplant Anchor-age, 101Microimplants in Orthodontics, 211Minor Tooth Movement with Micro-implants for Prosthetic Treatment, 98Orthodontic and Dentofacial Ortho-pedic Treatment, 215Self-ligation in Orthodontics, 98

Buccal tubes

Shear bond strengths of buccal tubes,184

Case reports

Multidisciplinary treatment of a fractured root: a case report, 90Non-surgical treatment of mandibulardeviation: a case report, 201Orthodontic treatment of a trans-migrated mandibular canine: a casereport, 195The effect of a Clark twin block onmandibular motion: a case report,189

Cephalometric analysis

Cephalometric analysis of Malay chil-dren with and without unilateral cleftlip and palate, 165

Cephalometric norms

McNamara norms for Turkish adoles-cents with balanced faces and normalocclusion, 33

Cephalometric variables

Factors contributing to stability of pro-traction facemask treatment of Class IIImalocclusion, 171

Ceramic brackets

Bond strengths and debonding characteristics of two types of poly-crystalline ceramic brackets, 134

Clinical trial


Compression

Response of the expanded inter--premaxillary suture to intermittent compression. Early bone changes, 49

Computer tomography

Skeletal and dental changes afterrapid maxillary expansion: a comput-er tomography study, 141

Crossbite

Non-surgical treatment of a mandibu-lar deviation: a case report, 201

Curve of Spee

Effects of levelling of the curve of Spee on the proclination of mandib-ular incisors and expansion of dental arches: a prospective clinicaltrial, 61

Custom base

Indirect bonding – do custom basesneed a plastic conditioner? A ran-domised clinical trial, 109

Cytotoxicity


Demineralisation

Amorphous calcium phosphate-containing orthodontic composites.Do they prevent demineralisationaround orthodontic brackets? 10

Dental bonding

Bond strengths and debonding char-acteristics of two types of poly-crystalline ceramic brackets, 134

Dental changes

A comparison of dental changes produced by mandibular advance-ment splints in the management ofobstructive sleep apnoea, 66

Dental trauma

Multidisciplinary treatment of a fractured root: a case report, 90

Dentofacial changes

Effects of rapid-slow maxillary expan-sion on the dentofacial structures, 178

Discriminant analysis


Dolphin imaging

Cephalometric analysis of Malay children with and without unilateralcleft lip and palate, 165

Duoblock


Editorials

Can an optimal force be estimated?95Effective orthodontics, 206Retirement of Michael Harkness, 207

Efficiency


Elastics


Electromyography

Associations between upper lip activity and incisor position, 56


INDEX

225

28

00

1_

ao

j_o

rtho

_jn

l_2

6.2

_d

ec

15

:06

:24

10

-11

-08

Ye

llow

Ma

ge

nta

Cya

nB

lack

Se

ct 9

Fro

nt



Enamel microhardness

Amorphous calcium phosphate-containing orthodontic composites.Do they prevent demineralisationaround orthodontic brackets? 10

Eruption space

Effects of orthodontic treatment andpremolar extractions on the mandibu-lar third molars, 160

Facial asymmetry


Fatigue testing orthodonticadhesives

Initial and fatigue bond strengths ofchromatic and light-cured adhesives,119

Forced eruption

Multidisciplinary treatment of a fractured root: a case report, 90Orthodontic treatment of a trans-migrated mandibular canine: a casereport, 195

Friction


Glass ionomer cement

Strength of attachment between bandand glass ionomer cement, 149

Image analysis

Response of the expanded inter--premaxillary suture to intermittent com-pression. Early bone changes, 49

Incisor display

Display of the incisors as functions ofage and gender, 27

Incisor inclination


Incisor torque

A comparative assessment of theforces and moments generated at themaxillary incisors between conven-tional and self-ligating brackets usinga reverse curve of Spee NiTi arch-wire, 127

Indirect bonding


Intercanine width

Effects of levelling of the curve of Speeon the proclination of mandibular incisors and expansion of dental arches: a prospective clinical trial, 61

Intermolar width


Intrusion

A comparative assessment of theforces and moments generated at themaxillary incisors between con-ventional and self-ligating bracketsusing a reverse curve of Spee NiTiarchwire, 127

Korkhaus Analysis

Space planning sensitivity and specificity: Royal London SpacePlanning and Korkhaus Analyses, 42

Letter

Optimal force, 208

Lips at rest


Lower incisors


McNamara analysis


Malay children


Malocclusion

Lip – tooth relationships during smilingand speech: an evaluation of differentmalocclusion types, 153

Mandibular advancementsplint


Mandibular deviation


Mandibular displacement


Mandibular incisor inclination


Mandibular motion

The effect of a Clark twin block onmandibular motion: a case report,189

Maxillary expansion

Effects of rapid-slow maxillary expan-sion on the dentofacial structures, 178Response of the expanded inter-premaxillary suture to intermittent compression. Early bone changes, 49

Maxillary protraction

Incremental effects of facemask therapy associated with intermaxillarymechanics, 78

Methyl methacrylate monomer


Midline


Monobloc


Morphine

The effect of morphine on orthodontictooth movement in rats, 113

INDEX





INDEX

227

Naltrexone


Nickel titanium


Non-surgical treatment


Opioid antagonist


Optimal force

The dimensions of the roots of thehuman permanent dentition as aguide to the selection of optimal orthodontic forces, 1

Orbicularis oris muscle


Orthodontic adhesive

Bond strengths of different orthodonticadhesives after enamel conditioningwith the same self-etching primer, 84

Orthodontic brackets

Bond strengths and debonding characteristics of two types of poly-crystalline ceramic brackets, 134

Orthodontic extrusion

Multidisciplinary treatment of a fractured root: a case report, 90

Orthodontic tooth movement


Orthodontics

Cytotoxicity of orthodontic separatingelastics, 16Space planning sensitivity and specificity: Royal London SpacePlanning and Korkhaus Analyses, 42

Orthopaedic treatment


Overbite


Overjet


Ozonized water

Does ozone water affect the bondstrengths of orthodontic brackets? 73

Permanent dentition


Plastic conditioner


Porcelain


Premolar extractions


Projected root areas


Protraction facemask

Factors contributing to stability of protraction facemask treatment ofClass III malocclusion, 171

Randomised clinical trial

Indirect bonding – do custom basesneed a plastic conditioner? A randomised clinical trial, 109

Rapid maxillary expansion


Skeletal and dental changes afterrapid maxillary expansion: a com-puter tomography study, 141

Rapid-slow maxillary expansion


Rats

Response of the expanded inter--premaxillary suture to intermittent compression. Early bone changes, 49The effect of morphine on orthodontictooth movement in rats, 113

Reverse curve archwires


Root lengths

The dimensions of the roots of thehuman permanent dentition as aguide to the selection of optimalorthodontic forces, 1

Royal London Space Planning

Space planning sensitivity and specificity: Royal London SpacePlanning and Korkhaus Analyses, 42

Self-etching primer

Bond strengths of different orthodonticadhesives after enamel conditioningwith the same self-etching primer, 84

Self-ligating brackets

A comparative assessment of theforces and moments generated at themaxillary incisors between con-ventional and self-ligating bracketsusing a reverse curve of Spee NiTiarchwire, 127Assessment of slot sizes in self-ligatingbrackets using electron microscopy, 38Porcelain brackets during initial align-ment: are self-ligating cosmetic bracketsmore efficient? 21

Shear bond strength

Bond strengths and debonding char-acteristics of two types of poly-crystalline ceramic brackets, 134



INDEX

Volume 26 No. 2 November 2010228

Bond strengths of different orthodonticadhesives after enamel conditioningwith the same self-etching primer, 84Initial and fatigue bond strengths ofchromatic and light-cured adhesives,119Shear bond strengths of buccal tubes,184

Six degrees of freedom

The effect of a Clark twin block onmandibular motion: a case report,189

Skeletal Class III malocclusion


Slot dimensions

Assessment of slot sizes in self-ligatingbrackets using electron microscopy, 38

Slow maxillary expansion


Smile


Space analysis

Space planning sensitivity and speci-ficity: Royal London Space Planningand Korkhaus Analyses, 42

Space planning

Space planning sensitivity and speci-ficity: Royal London Space Planningand Korkhaus Analyses, 42

Speech


Stability


Third molar angulations


Transmigrated mandibularcanine

Orthodontic treatment of a transmi-grated mandibular canine: a casereport, 195

Transmigration

Orthodontic treatment of a trans-migrated mandibular canine: a casereport, 1

Turkish adolescents


Twin block

The effect of a Clark twin block onmandibular motion: a case report, 189

Unilateral cleft lip and palate


Upper incisors


Upper lip activity


Video imaging


Australian Orthodontic Journal

We hope to see you there. Program and registration form: www.aso.org.au

28

00

1_

ao

j_o

rtho

_jn

l_2

6.2

_d

ec

15

:06

:24

10

-11

-08

Ye

llow

Ma

ge

nta

Cya

nB

lack

Se

ct 9

Fro

nt


Documents

Cephalometric analysis of Malay children with and without unilateral cleft lip and palate