Eur J Orthod 2010 Jiang 693 7

7/27/2019 Eur J Orthod 2010 Jiang 693 7

http://slidepdf.com/reader/full/eur-j-orthod-2010-jiang-693-7 1/5

European Journal of Orthodontics 32 (2010) 693–697 © The Author 2010. Pubshed by Oxford Unversty Press on behaf of the European Orthodontc Socety.

doi:10.1093/ejo/cjp165 A rghts reserved. For permssons, pease ema: [email protected]

Advance Access Publication 22 March 2010

Introduction

Root resorpton s a common outcome of orthodontc

treatment. Harry and Sms (1982) found that some eve of

root resorpton exsted n most patents. Most resorpton

is clinically insignicant, but, if severe, root resorptionthreatens the ongevty of the teeth. Wth the mprovements

n orthodontc technques and the ncrease n patent

expectatons, orthodontsts need to be aware of ths ssue.

Most studes (Baumrnd et al., 1996; Jang et al., 2001) on

root resorpton and ts reatonshp wth orthodontc treatment

have found that there are mutpe factors assocated wth

root resorpton. Age, gender, nutrton, genetcs, the type

of appance, the amount of force used durng treatment,

extracton or non-extracton, duraton of treatment, and the

distance the teeth are moved all have some inuence on root

resorpton. Generay, the causes and mechansm of resorpton

are st uncear. The purpose of the present study was to

research and, f possbe, dentfy factors reated to root

resorpton durng orthodontc treatment.

Subjects and methods

Subjects

Nnety-sx patents aged from 9 to 34 years (34 maes and

62 females) who had undergone at least 12 months xed

appance orthodontc therapy (straghtwre, Roth vaue) were

randomy seected from subjects treated at the Orthodontc

Department, Pekng Unversty Schoo and Hospta of

Stomatoogy, Bejng, Chna. Panoramc radographs before

(T1) and after (T2) treatment were avaabe. Patents

who requred orthognathc surgery or had a ceft p and/or

palate were excluded from the study. Sixty-ve of thesubjects had undergone extracton therapy (four premoars

extracted, including the rst or second premolars) as part

of ther orthodontc treatment. Treatment duraton was

between 9 and 61 months (average 31 months).

Methodology

The roots of the maxary and mandbuar ncsors, cannes,

premolars, and rst molars were examined according to a

modied root resorption classication method, based on the

root resorpton score (Sharpe et al., 1987). Panoramc

radographs were used to score the root resorpton eve for

every patient at T1 and T2. The modied root resorptionmethod s shown n Fgure 1.

The mean root resorpton score (MRRS) for every patent

at T1 and T2 was cacuated for the upper anteror and

posteror and ower anteror and posteror teeth, usng the

formua:

Sum o t e scoresMean root resorption = .

Number of teeth

Gender, age, extracton or non-extracton therapy, and

treatment duraton were recorded.

Root resorption beore and ater orthodontic treatment: a clinical

study o contributory actors

Ruo-ping Jiang*, J.P. McDonald** and Min-kui Fu**Department o Orthodontics, Peking University School and Hospital o Stomatology, Beijing, China and**Orthodontic Department, Glasgow Dental Hospital, UK

Correspondence to: Dr Ruoping Jiang, Department o Orthodontics, Peking University School and Hospital o Stomatology, 22 Zhong Guan Cun Nan Da Jie, Beijing 100081, China. E-mail: [email protected]

SUMMARY This clinical study evaluated actors related to root resorption beore (T1) and ater (T2)orthodontic treatment. Ninety-six subjects between 9 and 34 years (34 males and 62 emales) whohad been treated using fxed appliances or at least 1 year and who had panoramic radiographsat T1 and T2 were selected. The relationship between root resorption at T1 and T2, with regard togender, age, extraction versus non-extraction patterns, specifc teeth and treatment duration wasinvestigated.

No statistically signifcant dierences in root resorption were ound in relation to gender. Signifcantdierences in root resorption (P = 0.000, P < 0.01) and also in treatment duration (P = 0.036, P < 0.05) werenoted between the extraction and non-extraction groups; extraction and treatment duration correlatedwith T2 mean root resorption. Patient age correlated with root resorption o the upper incisors at T1 andT2. Using multiple regression analysis, age and duration o treatment were ound to be more associatedwith root resorption than with extractions; the presence o root resorption at T1 was associated with T2root resorption, especially o the anterior teeth.



R.-P. JiANG ET Al.694

Statistical analysis

The patents were dvded nto dfferent groups dependng

on gender and whether extractons had been undertaken. A

t -test was performed between the MRRS of mae and

femae, and extracton and non-extracton groups. Bvarate

correaton anayss was undertaken between extracton,

duraton, and MRRS after treatment. Usng the MRRS

as the dependent varabe, and age, gender, extracton, and

duraton as the ndependent varabes, mutfactorca

regresson anayss was performed. When usng the T2

MRRS as the dependent varabe, the T1 score of the same

group was used as the ndependent varabe.

Error study

Assessment of root resorpton on the panoramc radographs

was performed by a snge examner (RPJ). To determne

reabty, 20 panoramc radographs were rechecked by the

same examner after a 10 day nterva. The MRRS between

these two examnatons were compared usng a pared

Wilcoxon test. The difference between the rst and second

measurements was not signicant.

Results

Gender

Statistical analysis did not demonstrate a signicant gender

dfference at T1 and T2.

Extraction therapy

Root resorpton vaues were compared between the

extracton (65 patents) and non-extracton (31 patents)

groups usng a t -test. There was no statistically signicant

dfference between the extracton and non-extracton groups

at T1. At T2, the MRRS n the extracton group was hgher than n the non-extracton group; the dfference was

statistically signicant ( P = 0.000, P < 0.01).

Treatment duration

The average treatment duraton n the extracton group was

32.1±9.7 months, somewhat onger than n the non-

extracton group (27.6±9.8 months). t -test anayss showed

that the difference was statistically signicant ( P = 0.036,

P < 0.05).

Bivariate correlation analysis

Bvarate anayss showed that there was no correaton between age and extracton, or between age and treatment

duraton. The reatonshp between age and MRRS score

was nconcusve—there was a postve correaton between

age and root resorpton wth respect to the upper teeth at

T1 and T2, but no correaton was found between age and

ower anteror and posteror teeth before or after treatment

(Tabe 1).

The correlation coefcient between extraction and

treatment duration was −0.21 ( P < 0.05), hence treatment

duraton n extracton cases was onger.

Wth the excepton of the upper anteror teeth, extractons

had a statistically signicant relationship with root resorption

after treatment (T2).

There was a postve reatonshp between T2 root

resorption and treatment duration, the correlation coefcients

rangng from 0.21 to 0.39. Ths ndcated that the onger the

treatment, the more severe the root resorpton.

Multiple regression analysis

MRRS were used as the dependent varabe and gender,

age, extracton, and duraton as the ndependent varabes.

The resuts are shown n Tabe 2.

Figure 1 The modied root resorption classication method. 0 degree: novsbe root resorpton. 1st degree: md resorpton, the root apex s bunted anddffuse. 2nd degree: moderate resorpton, the root apex dsappears, the rootapex ooks more ke a haf crce not a taper. The contour s sometmesdscontnuous or not smooth; the amount of root resorpton s aboutapproxmatey one-quarter of the root. 3rd degree: severe resorpton, the end of the root shows excessve buntng; the contour of the root apex s more keyto be dscontnuous; root resorpton s more than one-quarter of the root.



695ROOT RESORPTiON AND ORTHODONTiC TREATMENT

At T1, patient’s gender had no statistically signicant

correaton wth root resorpton. Patent’s age ony had acorreaton wth root resorpton for the upper teeth (0.52),

but no correaton wth the ower teeth. The resuts show

that at T1, n the upper posteror dentton, oder patents

tended to have more severe root resorpton. At T2, a

factors, apart from gender, had a correaton wth root

resorpton. Age and treatment duraton had a statstcay

signicant correlation with resorption in all parts of the

dentition. Extraction only had a statistically signicant

correaton wth resorpton of the ower anteror teeth. The

degree of root resorpton at T1 ony had a statstcay

signicant correlation with that of the anterior teeth at T2.

No statistically signicant correlation was found in the

posteror regon between T1 and T2 resorpton.

Discussion

Panoramic radiographs, cephalometric head lms, and

periapical lms have been used to study root resorption and

the reatonshp wth orthodontc treatment. When desgnng

ths study, these radographs were compared and t was

ntay decded that as cephaometrc radography s the

ony technque that uses ocazaton, ths woud be the best

method to compare the ength of ncsa roots before and

after treatment. However, patents wth maoccusons often

have crowding in the incisor region, which makes it difcultto dentfy the poston of root apces before treatment. in

addton, a prevous study (Kennedy et al., 1983) has shown

that most resorpton s n the regon of 1–2 mm, hence the

margn of error s extremey sma. The advantage of a

panoramic radiograph is that a single lm gives information

on a teeth, as we as the dentoaveoar bone and jaws. it s

not, however, a localized lm and has varying distortion of

dfferent teeth, for exampe, n upper ncsor retracton

where the ncsa root ength after treatment may appear

to be much onger than before treatment on a panoramc

radiograph. Periapical lm obtained using the crown

parae projectve technque (lnge and lnge, 1983, 1991;

levander et al., 1998) s ocazed and accurate, but the patent s subjected to an ncreased amount of radographc

exposure. it was therefore decded that panoramc

radography was the choce for the present study, but wth

some modications of the MRRS.

Two methods are used to assess root resorpton: one

measures the ength of the root drecty to determne the

amount of root resorpton; the other marks the degree of

root resorpton. The method cassfyng the degree of root

resorpton used n most prevous research (Remngton and

Joondeph, 1989) was smar to the four degree standard of

Table 1 Correlation coefcients of the bivariate correlation analysis between extraction, duration, age and mean root resorption score(MRRS) after treatment for the upper and ower anteror and posteror teeth.

Correlation coefcients MRRS MRRS MRRS MRRS Age Extracton Duraton

Upper posteror Upper anteror lower posteror lower anteror

Age 0.25* 0.28* 0.19 0.15 1.0 −0.09 −0.17Extracton −0.23* −0.19 −0.25* −0.34** −0.09 1.0 −0.21*Duraton 0.21* 0.23* 0.29** 0.39** −0.17 −0.21* 1.0

* P < 0.05, ** P < 0.01.

Table 2 Correlation coefcients of the multiple regression analysis of mean root resorption score (MRRS).

MRRS

Before treatment After treatment

Upper posteror Upper anteror lower posteror lower anteror Upper posteror Upper anteror lower posteror lower anteror

Gender −0.02 −0.06 0.13 0.06 0.04 −0.07 −0.13 −0.08Age 0.52** 0.23* −0.04 −0.06 0.29** 0.23* 0.21* 0.19*Extracton — — — — −0.15 −0.07 −0.17 −0.25**Duraton — — — — 0.26* 0.25** 0.28** 0.34**Cor-vaues — — — — 0.15 0.42** 0.13 0.19*

Cor-vaues: when the mean MRRS vaues post-treatment were used as the dependent varabe, the correspondng vaues pre-treatment were added to thendependent varabes.* P < 0.05; ** P < 0.01.



R.-P. JiANG ET Al.696

Sharpe et al. (1987): 0 degree = no root resorpton (0 mm);

1 degree = root apex bunted sghty (1–2 mm); 2 degree =

moderate buntng, resorpton up to one-quarter of the root

(2–4 mm); and 3 degree = severe buntng, resorpton more

than one-quarter of the root (greater than 4 mm). it s

beeved that ths method s accurate when used wth a

localized lm but not suitable for panoramic radiographs.The modied classication method in this study used the

change n shape of the root apex but not the ength of root

and s smar to the method of Sharpe et al. (1987). in a

prevous study (Jang et al., 2001), the same modied

method was used to nvestgate the endemc features of root

resorption; the ndings were in agreement with others who

used periapical lm (Sameshima and Sinclair, 2001a,b),

which supposedly is more accurate than panoramic lm.

No statistically signicant difference in root resorption

was found between mae and femae patents. Ths s

contrary to the studes of Spurrer and Ha (1990) and Kjær

(1995) who found femaes to have more resorpton than

maes but s n agreement wth most other research

(Sameshma and Sncar, 2001a,b; Kaey and Phps,

1991; Linge and Linge, 1991). No statistically signicant

dfference n treatment duraton between mae and femae

patents was found.

Seventy-nne of the 96 patents were under 15 years of

age. in a tra test, root resorpton was compared between

two groups subdvded at the age of 15 years, usng t -test

analysis. No statistically signicant difference was found.

When correaton anayss was ntroduced, a strong

correaton was found between age and root resorpton at

T2; at T1, there was aso a correaton between age and root

resorpton of the upper teeth. Ths ndcated that the oder the patent, the more severe the root resorpton. Ths s

contrary to the ndings of Sameshma and Sncar (2001a,b)

who found no correaton between age and resorpton of the

maxillary anterior teeth but that adults had signicantly

more resorpton of the mandbuar anteror teeth. lnge and

lnge (1983) found that patents startng treatment after 11

years of age experienced signicantly more root resorption

than those startng earer. it s beeved that age s an

mportant factor reated to root resorpton because of the

reduced abty to repar root resorpton n the oder patent.

Retan (1974) found that ‘n younger patents the anatomca

envronment consttutes an mportant factor, exstng

cementod on the root surface may deay the onset of rootresorpton, and f there s a thck ayer of predentne, any

apca or apca sde resorpton can hardy prevent further

deveopment of the root’. Therefore, the protectve

mechansm of precementum and predentne ocated at

young apices may also be an inuencing factor.

There were some interesting ndings on the relationship

between extracton, treatment duraton and root resorpton.

Baumrnd et al. (1996) and McFadden et al. (1989) found

patents who undergo extracton treatment tended to have

more root resorpton. Sameshma and Sncar (2001a,b)

also found that extraction pattern was a signicant factor

n root resorpton. However, after performng mutpe

regresson correaton anayss, ony the resorpton of ower

anteror teeth had a correaton wth extracton n the present

study; resorpton of upper and ower posteror teeth had

no reatonshp wth extracton. Ths mped that f other

factors were ncuded, such as gender, age, treatmentduraton, and pre-treatment resorpton, extracton became

ess mportant for resorpton than prevousy beeved. it

was noted that extracton and treatment duraton had a

statistically signicant correlation, and the duration between

the extraction and non-extraction groups was signicantly

dfferent. Furthermore, treatment duraton tsef had a

statistically signicant correlation with root resorption.

in reaton to the mandbuar ncsors, however, cases

nvovng extractons tended to have more root resorpton

even wth the same treatment duraton. Ths may be due to

the dfference between varous areas wthn the mouth

because of the anatomca structure of ths compexmandbuar area—the dstance between the cortca pates s

narrow and when the ncsors are retracted after premoar

extractons, the root apces tend to contact the cortex. The

contact between root and cortex was found to be an mportant

factor n root resorpton after orthodontc treatment

(Horuch et al., 1998).

The presence of previous resorption had an inuence on

resorpton after treatment but ony for the anteror teeth,

especay the maxary ncsors. Hence a patent who has

root resorpton wthout orthodontc treatment may we be

susceptbe to root resorpton as a resut of orthodontc

treatment. However, n a case–contro study (Kaey and

Phps, 1991), t was found that evdence of prevous rootresorpton was present as frequenty n contro patents as n

those wth severe resorpton.

Conclusions

The ndings of this study suggest that:

1. Gender was not an inuencing factor in root resorption

and treatment duraton n ths Chnese sampe.

2. Patient’s age would appear to be an inuencing factor

in root resorption. Older patients tend to have signicant

root resorpton after orthodontc treatment and an

eement of upper root resorpton before treatment.3. Extraction has some inuence on treatment duration

and root resorpton. Extracton cases have a onger

treatment duraton and more severe root resorpton

than non-extraction cases. The inuence of extraction

on root resorpton may be a consequence of treatment

duraton.

4. Treatment duration has a statistically signicant

correaton wth post-treatment root resorpton;

the onger the duraton, the more severe the root

resorpton.



697ROOT RESORPTiON AND ORTHODONTiC TREATMENT

5. The degree of pre-treatment root resorpton seems to

inuence root resorption after orthodontic treatment in

the maxary dentton.

Funding

Pekng Unversty Stomatoogy Research Fund.

References

Baumrnd S, Korn E l, Boyd R l 1996 Apca root resorpton northodontcay treated aduts. Amercan Journa of Orthodontcs andDentofaca Orthopedcs 110: 311–323

Harry M R, Sms M R 1982 Root resorpton n bcuspd ntruson: ascannng eectromcroscopc study. Ange Orthodontst 52: 235–258

Horuch A, Hotokezaka H, Kobayash K 1998 Correaton betweencortca pate proxmty and apca root resorpton. Amercan Journa of Orthodontcs and Dentofaca Orthopedcs 114: 311–318

Jang R P, Zhang D, Fu M K 2001 A cnca study of root resorpton beforeand after orthodontc treatment. Chnese Journa of Orthodontcs 8:108–110

Kaey J, Phps C 1991 Factors reated to root resorpton n edgewse practce. Ange Orthodontst 61: 125–132

Kennedy D B, Joondeph D R, Osterberg S K, ltte R M 1983 The effectof extractons and orthodontc treatment on dentoaveoar support.Amercan Journa of Orthodontcs 84: 183–190

Kjær i 1995 Morphoogca characterstcs of denttons deveopngexcessve root resorpton durng orthodontc treatment. EuropeanJourna of Orthodontcs 16: 25–34

levander E, Bajka R, Mamgren O 1998 Eary radographc dagnoss of apca root resorpton durng orthodontc treatment: a study of maxaryncsors. European Journa of Orthodontcs 20: 57–63

lnge B O, lnge l 1983 Apca root resorbton n upper anteror teeth.European Journa of Orthodontcs 5: 173–183

lnge B O, lnge l 1991 Patent characterstcs and treatment varabesassocated wth apca root resorpton durng orthodontc treatment.

Amercan Journa of Orthodontcs and Dentofaca Orthopedcs 99:35–43

McFadden W M, Engstrom C, Engstrom H, Anhom J M 1989 A study of the reatonshp between ncsor ntruson and root shortenng.Amercan Journa of Orthodontcs and Dentofaca Orthopedcs 96:390–396

Remngton D N, Joondeph D R 1989 long-term evauaton of rootresorpton occurrng durng orthodontc treatment. Amercan Journa of Orthodontcs and Dentofaca Orthopedcs 96: 43–46

Retan K 1974 inta tssue behavor durng apca root resorpton. AngeOrthodontst 44: 68–82

Sameshma G T, Sncar P M 2001a Predctng and preventng rootresorpton Part 1: dagnostc factors. Amercan Journa of Orthodontcsand Dentofaca Orthopedcs 119: 505–510

Sameshma G T, Sncar P M 2001b Predctng and preventng root

resorpton Part 2: treatment factors. Amercan Journa of Orthodontcsand Dentofaca Orthopedcs 119: 511–515

Sharpe W, Reed B, Subteny J D, Poson A 1987 Orthodontcreapse, apca root resorpton, and cresta aveoar bone eves.Amercan Journa of Orthodontcs and Dentofaca Orthopedcs 91:252–258

Spurrer S W, Ha S H 1990 A comparson of apca root resorpton durngorthodontc treatment n endodontcay treated vta teeth. AmercanJourna of Orthodontcs and Ora Orthopedcs 97: 130–134

Documents

Eur J Orthod 2010 Jiang 693 7