Treatment of a Class II deepbite with microimplant anchorage · ter 12 months of treatment, buccal tubes were bonded onto the maxillary second molars, and the archwire Fig 4. The

CLINICIAN’S CORNER

Treatment of a Class II deepbite withmicroimplant anchorage

Hyo-Sang Park,a Ji-Yeun Kim,b and Tae-Geon Kwonc

Daegu, Korea

FromaProfebFellocAssoThe aucts oReprintistry,KoreaSubm0889-Copyrdoi:10

The goal of this report was to illustrate new treatment mechanics for using microimplants for the treatment ofaClass II Division 2 deepbitemalocclusion. A 29-year-old womanwith a deepbite was treatedwith the aid ofmicro-implant anchorage. Microimplants placed between the maxillary second premolars and first molars were used asanchorage to apply a distal force to the anterior teeth to correct the Class II canine andmolar relationships. A distalforce was applied to long hooks that were crimped between the lateral incisors and the canines. By applyinga backward force to the long hooks, themaxillary anterior teeth experienced palatal rootmovementwith no changein the vertical and anteroposterior positions of the incisal edges. The distal extrusive movement of the maxillarysecond molars achieved by disengaging the second molars from the archwire during distal force applicationand an anterior bite-block bonded on the lingual surface of the maxillary central incisors produced the increasein vertical dimension. The distal force to the long extended hooks from the microimplants was possibly good me-chanics for obtaining the palatal root movement and correcting the Class II canine and molar relationships. Theanterior bite-block and disengagement of themaxillary secondmolars during distal force applicationwere effectivefor increasing the vertical dimension. (Am J Orthod Dentofacial Orthop 2011;139:397-406)

A deepbite is considered a difficult malocclusionto treat. The treatment of deepbite has includedorthognathic surgery and orthodontic treatment

by intrusion of the anterior teeth or extrusion of theposterior teeth in either or both of the maxillary andmandibular arches.1 A decision for molar extrusion or in-trusion of incisors should be based on the causes and thevertical positions of the incisal edges of the maxillary in-cisors relative to the upper lip.

Distalization of the maxillary posterior teeth is oftenneeded in the treatment of Class II malocclusion whena nonextraction treatment is planned. Many extraoraland intraoral appliances have been developed to distal-ize the molars.2-5 Extraoral appliances can providereliable anchorage but only in compliant patients. Onthe other hand, all intraoral molar distalizingappliances produce adverse side effects such as labialtipping of the maxillary anterior teeth.6,7

the School of Dentistry, Kyungpook National University, Daegu, Korea.ssor and clinical director, Department of Orthodontics.w, Department of Orthodontics.ciate professor, Department of Oral and Maxillofacial Surgery.uthors report no commercial, proprietary, or financial interest in the prod-r companies described in this article.t requests to: Hyo-Sang Park, Department of Orthodontics, School of Den-Kyungpook National University, 188-2, Samduk 2-Ga, Jung-Gu, Daegu,700-412; e-mail, [email protected], January 2009; revised and accepted, February 2009.5406/$36.00ight � 2011 by the American Association of Orthodontists..1016/j.ajodo.2009.02.034

With the development of extradental skeletal anchor-age such as microimplants, clinicians can now moveteeth without anchorage loss to the specific plannedgoal. The tooth movement can also be precisely con-trolled with the help of microimplants. Many clinical re-ports and studies have focused on treating the varioustypes of malocclusions, including bialveolar protrusionrequiring maximum retraction of the anterior teeth,8,9

whole arch distal retraction,10,11 intrusion of a tooth orteeth,12,13 and protraction of the molars.14 However,there has been no report to illustrate the treatment me-chanics involved with microimplants in skeletal Class IIdeepbite treatment. In the treatment of a deepbite, themaxillary or mandibular incisors can be intruded by con-ventional or microimplant-aided mechanics.15 However,in a patient with proper vertically positioned maxillaryincisors, their intrusion is not desirable. Lingually tippedmaxillary incisors should be uprighted by distal rootmovement, which requires strong anchorage. The micro-implant can be used to provide anchorage for rootmovement of the maxillary incisors and distal retractionof the whole maxillary dentition to correct Class IIrelationships.

In this report, we illustrate effective microimplantmechanics for the treatment of Class II deepbitemalocclusion by palatal root movement of the max-illary anterior teeth, distal movement of the wholemaxillary dentition, and an increase of the verticaldimension.

397

mailto:[email protected]

Fig 1. Pretreatment records.

Table. Cephalometric measurements

Pretreatment PosttreatmentSNA (�) 80.5 78.9SNB (�) 79.7 78.1ANB (�) 0.7 0.8A to N-per (mm) 1.8 1.2Pog to N-per (mm) 1.1 1.0Co-A (mm) 93 90Co-Gn (mm) 121 121ANS-Me (mm) 62.6 66.3FMA (�) 14.1 16.7PFH/AFH 53/61.5 (0.86) 53.5/65 (0.82)FH to OP 6 6.4FH to UI 96.2 106.1IMPA (�) 95 98Z-angle (�) 85.4 85.8Nasolabial angle (�) 93 104Upper lip to E-line (mm) �3.7 �5.5Lower lip to E-line (mm) �5 �6

N-per, Nasion perpendicular line.

398 Park, Kim, and Kwon

CASE REPORT

A 29-year-old woman’s chief concern was a deepbite(Fig 1). She had a decreased vertical dimension, a deepmentolabial fold, and a negative E-line value. The ceph-alometric analyses showed that she had a Class IIIskeletal pattern. However, because of peg-shaped lateralincisors and lingually tipped maxillary incisors, thecanines and molars showed Class II relationships. Themaxilla was slightly retropositioned; the SNA anglewas 2� under normal, and the ANB angle was 0.8�

(Table). The patient had a severe brachyfacial pattern;the FMA angle was 14.1� and the gonial angle was107.3�. There was no apparent facial asymmetry ortransverse discrepancy.

Intraorally, the patient had a Class II Division 2 deep-bite malocclusion (Figs 1 and 2). The maxillary lateralincisors were peg-shaped, and the mandibular centralincisors exhibited severe attrition and discolorationfrom trauma 12 years previously. Overjet and overbitewere 2 and 6.5 mm, respectively, and arch-length

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Fig 2. Pretreatment digital dental models.

Fig 3. Periapical radiographs showing the microimplants(arrows) placed between the roots of themaxillary secondpremolar and the first molar.

Park, Kim, and Kwon 399

discrepancies in the maxilla and the mandible were 12and –5.8 mm, respectively. If the lateral incisors werebuilt up to normal size with composite resin, the arch-length discrepancy in the maxillary arch would become–3 mm. The vertical position of the maxillary incisorswas 1 mm relative to the reposed upper lip. There wereno signs and symptoms of temporomandibular jointdisorders or root resorption.

TREATMENT OBJECTIVES

Six treatment objectives were identified: (1) obtainClass I canine and molar relationships, (2) correct theoverbite by extrusion of the posterior teeth (3) obtainproper inclination and position of the maxillary anteriorteeth, (4) make space for cosmetic restoration of the

American Journal of Orthodontics and Dentofacial Orthoped

maxillary lateral incisors, (5) increase the vertical dimen-sion, and (6) obtain good retention.

TREATMENT PLAN

Distalization of the maxillary molars was planned tocorrect the Class II relationships. The inclination of thelingually tipped maxillary incisors also needed to be cor-rected. The distal movement of the posterior tooth seg-ment and palatal root movement of the maxillaryincisors required strong anchorage. For these reasons,the use of microimplants was proposed in the treatmentplan. The initial facial photos showed a favorable profile,and the anteroposterior position of the maxillary incisorswas planned not to change. The vertical position of themaxillary incisors relative to the upper lip was 1 mm, andtheir intrusion was not indicated. Instead, molar extru-sion was proposed to open the anterior bite and obtainenhanced vertical facial proportions. This was achievedby bonding an anterior bite-block on the palatal surfaceof the central incisors and inducing the extrusion of themaxillary second molars by disengaging them from thearchwire during distal force application.

TREATMENT PROGRESS

The traumatized mandibular central incisors weretreated. All teeth in the maxillary arch except the secondmolars were fitted with fixed preadjusted edgewise

ics March 2011 � Vol 139 � Issue 3

Fig 4. The anterior bite-block was bonded on the palatal surface of the maxillary central incisors.

Fig 5. The 0.019 3 0.025-in beta-titanium alloy archwire with hooks and torquing bend was placedwhile applying a distal force. A vertical step between the maxillary first and second molars is alsoshown.

Fig 6. Up-and-down elastics were used after the maxillary second molars were engaged to the lightmain archwire.


appliances, and a 0.014-in nickel-titanium (NiTi) align-ing archwire was ligated. Simultaneously, the microim-plants (diameter, 1.2 mm; length, 6 mm; Absoanchor,Dentos, Daegu, Korea) were placed into the buccal alve-olar bone between the maxillary second premolar andthe first molar on both sides (Fig 3). After 2 months oftreatment, an anterior bite-block was bonded on thepalatal surfaces of the maxillary central incisors to in-crease the vertical dimension (Fig 4). The braces weresubsequently bonded to all teeth in the mandibulararch. In the maxillary arch, a 0.016 3 0.022-in stainlesssteel archwire, with crimped 10-mm long hooks betweenthe lateral incisors and the canines, was placed. Distalforce was also applied from the microimplants to thehooks with NiTi coil springs. To increase the counter-clockwise moment to the maxillary anterior teeth, thelong hooks on the archwire were extended gingivally.

March 2011 � Vol 139 � Issue 3 American

After 5 months of treatment, there was distal movementof the maxillary posterior teeth. Vertical steps betweenthe maxillary first and second molars resulted from slightintrusion of the first molars, and distal tipping and ex-trusion of the second molars was observed. The distalforce transmitted to the maxillary posterior teeth hadcaused distal tipping and extrusion of the secondmolars.The vertical dimension was increased during treatmentby 3-point contacts—the anterior bite-block and 2 sec-ond molars. To control the axial inclination of the max-illary anterior teeth, a 0.0193 0.025 beta-titanium alloyarchwire with long hooks with a torquing bend betweenthe lateral incisors and the canines was used. The retrac-tion force was applied continuously by the NiTi coilsprings from long hooks to the microimplants (Fig 5). Af-ter 12 months of treatment, buccal tubes were bondedonto the maxillary second molars, and the archwire

Journal of Orthodontics and Dentofacial Orthopedics

Fig 7. Posttreatment records.


was switched to 0.016-in NiTi. Up-and-down elasticswere used to extrude the maxillary first molars to settlethe occlusion (Fig 6). After final arch coordination andminimal occlusal equilibration, all appliances were de-bonded. The microimplants were removed by unscrewingwithout anesthesia. The treatment time was 20 months.Lingual fixed retainers were bonded from the left first pre-molar to the right first premolar in the mandibular arch,and resin was built up on the maxillary lateral incisors.A wrap-around retainer with an anterior bite plate wasalso used to prevent relapse of the anterior overbite.

TREATMENT RESULTS

Class I canine and molar relationships were achieved(Figs 7 and 8). The maxillary posterior teeth had moveddistally by 3 mm, and a Class I molar relationship wasachieved. The vertical dimension had increased, andmasseter muscle weakness was also observed. The


cephalometric measurements showed that the FMAangle had increased from 14.1� to 16.7�, and theanterior facial height had increased from 61.5 to 65mm, along with the backward and downwardmovement of B-point (Fig 9). The extrusion of the max-illary and mandibular posterior teeth allowed a favorableposition for the mandible.

Overbite was improved remarkably from 6.5 to 1 mm.The angle of themaxillary incisor to the Frankfort horizon-tal plane was corrected from 96.2� to 106.1� after distalmovement of the roots. Root resorption was not signifi-cant, as observed in a panoramic radiograph. The 12-month follow-up records showed good retention withoutany obvious relapse (Fig 10). The occlusion was stable, andthe good facial harmony had also been retained.

DISCUSSION

Factors contributing to the development of an AngleClass II Division 2 deepbite malocclusion include


Fig 8. Posttreatment digital dental models.

Fig 9. Cephalometric superimposition between pretreatment (solid) and posttreatment (dotted).


enhanced dentoalveolar development with overeruptionof the anterior teeth, growth of the jaw, and function ofthe soft tissues. Supraeruption of the anterior teeth,infraocclusion of the posterior teeth, tooth-sizediscrepancy, maxillary prognathism with or withoutmandibular retrognathism, underdevelopment of ante-rior lower facial height, and other factors are gener-ally accepted as the causes of this type ofmalocclusion.1,16,17


Since the patient had low FMA and gonial angles, shewas diagnosed as having a deepbite with a hypodivergentskeletal pattern. Underdevelopment of molar height,normal growth of mandibular length, and counterclock-wise rotational growth resulted in the short anterior fa-cial height that led to the deepbite. The anterior deepbiteand tooth-size discrepancy between the maxilla and themandible due to the peg-shaped maxillary lateral inci-sors caused the Class II canine and molar relationships.


Fig 10. Retention records (12 months).


Since the patient was an adult and no further growthwas expected, distal movement of the maxillary posteriorteeth was considered a reasonable treatment option tocorrect the Class II canine and molar relationships. Thevertical position of the maxillary incisors was normalrelative to the upper lip. The short anterior facial heightand proper vertical positioning of the maxillary incisorsled to a treatment plan of not intruding the incisorsbut extruding the posterior teeth to correct the deepbite.

There are various conventional methods to correctClass II canine and molar relationships by distal move-ment of the maxillary molars. Headgear2 and Class IIintermaxillary elastics with the mandibular teeth asanchorage have been used routinely for many years.3

However, the success of these methods depends greatlyon patient cooperation. For this reason, many types ofintraoral devices and techniques for molar distalizationsuch as pendulum or distal jet appliances have beendeveloped.4,5 These methods are effective, but it isimpossible to avoid undesirable movements of teeth,


including mesial movement of the anterior teeth anddistal tipping of the molar crowns.6,7

With the help of skeletal anchorage, we can nowmove teeth to the specific goal precisely and reliably.Miniscrews were used to reinforce anchorage to thedistalizing appliances.18,19 The distal force applied tothe first molars might produce distal or mesial tippingof the molars when the force does not pass throughtheir center of resistance.18 The screw-reinforced molardistalizing appliance can result in distal tipping of themolars.19 A distal force, when applied to the canines todistalize the entire dentition, could bring about notonly distal movement of the molars but also intrusionof the molars.20 As a result, this can cause a decreasein the vertical dimension. Therefore, for this patient,we chose not to engage the second molars during distal-ization of the maxillary posterior teeth and bonded ananterior bite-block on the lingual surface of the maxil-lary central incisors. The distal force transmitted to themaxillary first molars exerts a distal and extrusive force


Fig 11. Biomechanics for the palatal root movement of the maxillary anterior teeth with microimplants:A, biomechanics to allow extrusion or B, to obtain intrusion of the maxillary anterior teeth.


to the second molars. The extrusion of the maxillarysecond molars and the anterior bite-block resulted inthe increase in the vertical dimension. After the retrac-tion was completed, the maxillary second molars werebonded. A light wire was placed, and up-and-down elas-tics were used to settle the maxillary first molars down toocclusion. Three-point contacts, the maxillary secondmolars on both sides, and an anterior bite-block can en-hance the increase in vertical dimension and minimizetrauma from the occlusion. This is also helpful whenbonding brackets on teeth in the mandibular arch in theearly stages of treatment. We had placed 2 bracket-headmicroimplants (diameter, 1.5-1.4 mm; length, 7 mm;BH1514-07, Absoanchor, Dentos) to apply extrusion forceto the mandibular arch, but mandibular microimplantswere not used because the treatment was successfulwith the maxillary microimplants, and 1 of 2 mandibularmicroimplants showed mobility during treatment.

A proper inclination of the maxillary anterior teethwas obtained by palatal root movement. In conventionalorthodontic treatment, the moment to achieve palatalroot torque of the maxillary anterior teeth can be appliedby twisting the rectangular archwire,21 an anteriortorquing arch,22 and helical torsion springs.23 However,with these mechanics, it is difficult to prevent labialcrown tipping and mesial movement of the anchorageposterior teeth. The later distal movement of labially tip-ped anterior teeth is a round-tripping movement thatmight cause root resorption.24 With skeletal anchorage,it is possible to overcome these side effects. There havebeen successful cases that obtained labial crown tippingand the root palatal torque of the maxillary anteriorteeth with intrusive force from microimplants placed be-low the anterior nasal spine.15 However, these mechanicscause intrusion of the maxillary anterior teeth, and thiswas not suitable in this patient with proper verticalpositioning of the anterior teeth relative to the upperlip. Therefore, pure root palatal movement of the maxil-lary anterior teeth without intrusion was 1 goal. Rootmovement requires strong anchorage and so too does


distal movement of the posterior teeth. Therefore, themicroimplants placed between the second premolarsand the first molars were used as anchorage. To applypalatal root torque, we crimped long hooks on the arch-wire, and a distal force was applied from the microim-plants. The distal force, as applied to the long hooks,could bring about distal movement of posterior teethas well as palatal root movement of the anterior teeth(Fig 11). To increase the counterclockwise moment tothe maxillary anterior teeth, a torquing bend of 3� wasapplied to the archwire between the lateral incisorsand the canines.

External apical root resorption is a common iatro-genic problem associated with orthodontic treatment.Parker and Harris25 reported that palatal root torque ofthe maxillary central incisors is strongly correlated withan increase in root resorption. This was also found inother studies.26,27 This can be explained by the factthat the torquing force is concentrated at the apex,which is the most resorption-sensitive area of thetooth.28 In this patient, the moment produced at the an-terior teeth of the maxilla could be high; thereby, rootresorption could occur. However, there was no evidenceof external apical root resorption posttreatment. It seemsthat force application with NiTi coil springs from micro-implants to long hooks on the archwire produces a moreprogressive and consistent moment to the anterior teeththan that with a twisted archwire in the bracket slots. Ac-cording to the finite element study of Jayade et al,24

third-order moments generated by rectangular twistedarchwires were often high and dropped suddenly whentooth movement started. Another reason might be thatmovement with the microimplants was not round trip-ping, which tended to increase root resorption. Evenso, although mechanics with microimplants producea continuous moment, clinicians must pay attention soas not to cause root resorption through periodic radio-graphic reviews.

To increase the horizontal component of force, theheads of the microimplants need to be positioned near


Fig 12. A, Frontal view of a clear model showing the inclination of the microimplant; B, bottom view ofa clear model showing the relationship of the apex of the microimplant and the roots; C, buccal view ofthe 3D image of the CT scans; D, bottom view of the 3D image of CT scan. Arrows indicate themicroimplant.


the gingival margin. Microimplants that are placedobliquely to the bone surface can reduce the chance ofroot contacts. Some authors prefer to place them30� to 40� to the long axes of adjacent teeth.9,29 Byinclining the microimplants, clinicians can put the apexof the microimplants at the apical area of roots wherethe space is wider and position the head of themicroimplant gingivally. The apex of the inclinedmicroimplant is sometimes located buccally to the rootof the second premolar, and this relationship wouldnot interfere with distal movement of the teeth. The3-dimensional reconstruction of the computedtomography scan images shows the inclination of themicroimplants and their relationships to adjacent roots(Fig 12). The apex of the microimplant was located buc-cally to the root of the second premolars in this patient.The interradicular space between the maxillary secondpremolar and the first molar was reported to reach 3.2mm at midroot level.29 Also, it increases toward theapex of the roots. According to some authors’ experience,3.5 mm of distal movement can be performed withouta deteriorating effect with buccally placed microim-plants.11However, ifmore than 4mmof distalmovement


is required, it is better to place the microimplant into thepalatal slope where there is more interradicular space. Ifthere is interference with distalization of the teeth,clinicians can place a new microimplant distally andremove the old one.

Several reports have shown the relationship be-tween jaw muscle volume and craniofacial form.30,31

The large masseter volumes were associated withbrachycephalism. The muscle activities were significantlyhigher in patients with deepbite than in patients withany other types of malocclusion.32 Our patient also hada brachyfacial pattern with a large masseter musclevolume. The strong muscular force from the massetermuscle might be a cause of relapse of the extrudedmolars. By adding the anterior bite-block, the patientexperienced weakening of the masseter muscle duringtreatment. The occlusal force generated from contactsat the anterior teeth is much lighter than that at the pos-terior teeth.33 This might be considered the result of dis-use atrophy from the decrease in the occlusal force fromthe anterior bite-block. The contractive capacity of themasseter muscle would be decreased, and this could aidin better treatment results and has advantages for long-



term retention. The use of a retainer with an anteriorbite plate appears to be sufficient for maintaining treat-ment results.

CONCLUSIONS

The distalization of the maxillary posterior teeth andpalatal root movement of the maxillary incisors could beeffectively achieved by microimplant-aided mechanics.The application of the distal force from the microim-plants to long hooks crimped between the lateral incisorsand the canines produced the counterclockwise momentto the maxillary incisors and the resultant palatal rootmovement without labial tipping and distal movementof the posterior teeth. The deepbite was corrected by ex-trusion of the molars by adding an anterior bite-blockand disengagement of the maxillary second molars tothe archwire. This brought about the increase in thevertical dimension and the weakening of the massetermuscle.

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Documents

Treatment of a Class II deepbite with microimplant anchorage · ter 12 months of treatment, buccal tubes were bonded onto the maxillary second molars, and the archwire Fig 4. The