ORIGINAL ARTICLE

Deepbite correction with incisor intrusion inadults: A long-term cephalometric study

Selin Kale Varlık,a €Od€ul Onur Alpakan,b and Ca�grı T€urk€ozc

Ankara, Turkey

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414

Introduction: The purpose of this study was to investigate the long-term stability of deep overbite correction withmandibular incisor intrusion with utility arches in adult patients. Methods: Pretreatment, posttreatment, and5-years postretention lateral cephalograms of 31 patients (mean age, 26.8 years; range, 24.1-30.9 years)with Class II Division 1 malocclusion and deepbite, treated by maxillary first premolar extraction andmandibular incisor intrusion, were traced and measured. Results: Significant decreases in overjet and overbite(6.46 1.2 and 3.96 0.7 mm, respectively), significant retroclination (17� 6 1.9�) and retraction (3.86 1.1 mm)of the maxillary incisors, and significant increases in protrusion (0.8 6 1.5 mm), proclination (0.6� 6 0.9�), andintrusion (2.66 1.4 mm) of the mandibular incisors were observed at posttreatment. At postretention, there werestatistically significant but clinically unimportant increases in overjet and overbite (0.4 6 0.2 and 0.8 6 0.4 mm,respectively) and extrusion of the mandibular incisors (0.8 6 1.1 mm). Conclusions: Correction of deepbite innongrowing patients by mandibular incisor intrusion with a utility arch can be considered effective and stable.(Am J Orthod Dentofacial Orthop 2013;144:414-9)

Correction of deepbite is often a challenging stepin orthodontic treatment. Untreated deepbitecan cause increased anterior crowding, maxillary

dental flaring, periodontal problems, and temporoman-dibular joint problems and can interfere with lateral andanterior mandibular movements.1-3

Deepbite can be treated orthodontically by intrusionor flaring of the incisors, extrusion or passive eruptionof the buccal segments, or a combination of these.4-6

The choice of treatment depends on several factors.Extrusion of the posterior dentition, although aneffective method of bite opening in growing patients,7,8

is not indicated in patients with normal incisor displayor normal or long lower facial height; its stability isquestionable in nongrowing patients with average tolow mandibular plane angles.6,9-14 Intrusion of themaxillary incisors is indicated in patients with excessiveincisor and gingival display and a large interlabial

ciate professor, Department of Orthodontics, Faculty of Dentistry, Gazirsity, Ankara, Turkey.te practice, Ankara, Turkey.tant professor, Department of Orthodontics, Faculty of Dentistry, Gazirsity, Ankara, Turkey.thors have completed and submitted the ICMJE Form for Disclosure oftial Conflicts of Interest, and none were reported.t requests to: Selin Kale Varlık, Gazi University, Faculty of Dentistry, BiskekSok. No: 4 06510 Emek, Ankara, Turkey; e-mail, kaleselin@yahoo.com.itted, February 2013; revised and accepted, April 2013.5406/$36.00ight � 2013 by the American Association of Orthodontists./dx.doi.org/10.1016/j.ajodo.2013.04.014

gap.13-15 Considering these facts, mandibular incisorintrusion is the most suitable deepbite treatment foradults with normal incisor and gingival display and anormal or high mandibular plane angle.

Although many studies have examined the stabilityof deepbite treatment, most included growing subjects.In some studies, different malocclusions or differenttreatment methods were assessed together, and in othersthe follow-up durations were short.16-19 Two studies ofnongrowing subjects did not include information aboutlong-term follow-up results and treatment stability.20,21

The purpose of this study was to investigate the long-term stability of deepbite correction with mandibularincisor intrusion with utility arches in adult patients.The null hypothesis was that dental deepbite correctionwith mandibular incisor intrusion in adults is stable.

MATERIAL AND METHODS

In this retrospective longitudinal study, pretreatment(T1), posttreatment (T2), and postretention (T3) lateralcephalograms of 31 patients (24 women, 7 men) withClass II Division 1 malocclusion treated with a 1-phasemaxillary first premolar extraction protocol by either ofthe first 2 authors were used. Their mean age at thebeginning of treatment was 26.8 years (range,24.1-30.9 years). The inclusion criteria were (1) stan-dardized lateral cephalograms available at 3 timeperiods, T1, T2, and T3; (2) deepbite of at least4.5 mm; (3) normal vertical dimension represented by

Fig. Cephalometric landmarks.

Kale Varlık, Onur Alpakan, and T€urk€oz 415

lower face height of 47� 6 3�; (4) 3 to 4 mm or less ofmaxillary incisor display at rest; (5) overjet of at least6 mm; and (6) 4 mm or less crowding in the maxillaryand mandibular arches.

Because of the retrospective nature of the study andbecause no additional x-rays were taken, ethicalapproval was not needed; informed consent had beenobtained at T1 from all patients as the routine protocol.

The treatment protocol included intrusion of themandibular incisors to correct the deepbite and extrac-tion of the maxillary first premolars to correct the over-jet. All patients had transpalatal arches on the maxillaryfirst molars before the extractions. All patients had0.018-in slot preadjusted metal brackets with the Rothprescription. In the maxillary arch, after alignment,the canines were retracted with nickel-titanium coilsprings (Sentalloy; GAC International, Central Islip, NY)exerting 150 g of force on 0.016 3 0.022-in stainlesssteel archwires (Accuform; GAC International). Theincisors were retracted by 0.017 3 0.025-in beta-titanium alloy archwires (Resolve; GAC International)with mushroom loops.

The mandibular incisors and premolars were leveledby 0.016-in nickel-titanium segments if necessary.After leveling, custom-made mandibular utility arches(0.016 3 0.022-in Blue Elgiloy wires; Ormco, Glen-dora, Calif), activated to exert 40 g of force, wereused for incisor intrusion. During this period, 0.0163 0.022-in stainless steel stabilizing sections extend-ing from the first molars to the first premolars wereplaced. The intrusive force of 40 g was checked beforetying the archwire, and the force levels were checkedevery 4 weeks. Intrusion was considered completewhen a 2-mm overbite was achieved, and a 0.016 30.022-in Blue Elgiloy stabilization utility arch wasplaced. At this point, the mandibular canines weretied to the stabilizing utility arch with elastic threadif their intrusion was necessary; 0.017 3 0.025-instainless steel wires were used for finishing in botharches. The mean active treatment time was 2.7 years(range, 2.4-3 years). Immediately after debonding,maxillary and mandibular wraparound retainers weredelivered. The patients were instructed to wear the re-tainers 24 hours a day for the first year and only atnight after that. The retention period lasted 1.5 years.

The same author (S.K.V.) hand-traced the lateralcephalograms and identified all landmarks. All hand-tracings were scanned with a scanner at 200 dpi, andDolphin software (version 10; Dolphin Imaging & Man-agement Solutions, Chatsworth, Calif) was used toobtain the cephalometric measurements. The measure-ments are shown in the Figure and Table I. The centerof resistance (a point located at one-third of the distance

American Journal of Orthodontics and Dentofacial Orthoped

of the root length apical to the alveolar crest) was used toevaluate the vertical positions of both the mandibularand maxillary central incisors.22

Sixty randomly chosen lateral cephalograms were re-traced and redigitized, and method error was calculatedwith Dahlberg’s formula.23

Statistical analysis

Statistical analysis was completed using the Statisti-cal Package for Social Sciences (version 13; SPSS, Chi-cago, Ill).

Because the Shapiro-Wilks test showed that all datawere normally distributed, treatment (T2-T1), postreten-tion (T3-T2), and overall changes (T3-T1) werecompared by repeated measurements analysis of vari-ance (ANOVA), followed by multiple comparisons withthe Bonferroni adjustment. The significance level wasset at P\0.05.

RESULTS

The method error ranged from 0.15 mm (U1CR to PP)to 0.55 mm (L6 to MP) for the linear measurements, andfrom 0.25� (L1 to MP) to 0.45� (U1 to L1) for the angularmeasurements.

Because the sample size was 31 subjects and the0.8-mm change in overbite in postretention period wasstatistically significant, the power of the study at a sig-nificance level of 0.05 was 0.86.

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Table I. Cephalometric measurements

SN to MP (�) Angle formed by the sella-nasion line andmandibular plane* (MP)

ANS toXi/Xi-PM (�)

Angle formed by the line extending fromanterior nasal spine to Xiy and corpusaxis (Xi-PMz)

Overbite (mm) Distance between incisal edges of maxillaryand mandibular central incisors,perpendicular to occlusal plane§ (OP)

Overjet (mm) Distance between incisal edges of maxillaryand mandibular central incisors, parallelto OP

U1CR to PP (mm) Perpendicular distance between the centerof resistancek (CR) of maxillary centralincisor and palatal plane (PP)

U1 to PP (�) Angle formed by the long axis of maxillarycentral incisor and palatal plane

U1 to APg (mm) Perpendicular distance from maxillaryincisor incisal edge to A-point–pogonionline

U6 to PP (mm) Perpendicular distance from the mesiobuccalcusp tip of maxillary first molar to PP

L1CR to MP (mm) Perpendicular distance between the CR ofmandibular central incisor andmandibular plane (MP)

L1 to MP (�) Angle formed by the long axis of mandibularcentral incisor and MP

L1 to APg (mm) Perpendicular distance from mandibularincisor incisal edge to A-point–pogonion(APg) line

L6 to MP (mm) Perpendicular distance from the mesiobuccalcusp tip of mandibular first molar to MP

U1 to L1 (�) Angle formed by the long axes of maxillaryand mandibular incisors

*Mandibular plane (MP): formed by a line through menton, tangentto the lower border of the angle of the mandible; yXi: the geometriccenter of the ramus of the mandible; zPM: protuberance menti pointselected at the anterior border of the symphysis between Point B andpogonion where the curvature changes from concave to convex;§Occlusal plane (OP): formed by a line bisecting the overlappingcusps of the first molars and the incisal overbite; kCenter of resis-tance (CR): a point located at one-third of the distance of the rootlength apical to the alveolar crest.

Table II. Cephalometric measurements at the 3 evalu-ations

Measurement

Pretreatment Posttreatment Postretention

Mean 6 SD Mean 6 SD Mean 6 SDSN to MP (�) 32.7 6 2.4 33.2 6 2.6 33.4 6 2.3ANS to Xi/Xi-PM (�) 47.1 6 1.9 47.3 6 1.2 47.3 6 1.9Overbite (mm) 5.9 6 0.7 2.0 6 0.1 2.8 6 0.4Overjet (mm) 8.6 6 1.3 2.1 6 0.3 2.3 6 0.2U1CR to PP (mm) 12.9 6 1.8 12.6 6 2.1 12.8 6 1.6U1 to PP (�) 132.2 6 5.4 115.2 6 5.1 115.3 6 5.4U1 to APg (mm) 8.1 6 1.4 4.3 6 0.7 4.3 6 0.6U6 to PP (mm) 28.5 6 4.1 28.4 6 3.9 28.6 6 3.9L1CR to MP (mm) 28.2 6 2.9 26.4 6 2.1 27.3 6 2.9L1 to MP (�) 94.2 6 2.8 94.6 6 2.5 94.4 6 2.6L1 to APg (mm) 2.1 6 0.9 2.8 6 0.8 2.8 6 0.6L6 to MP (mm) 36.0 6 2.5 36.9 6 2.7 36.5 6 2.6U1 to L1 (�) 110.2 6 3.8 131.7 6 3.9 131.6 6 4.1

416 Kale Varlık, Onur Alpakan, and T€urk€oz

The mean values for the cephalometric measure-ments at T1, T2, and T3 are shown in Table II, and thetreatment, postretention, and overall changes and theircomparisons are shown in Table III.

Of the treatment changes (T2-T1), overjet and over-bite significantly decreased by 6.4 6 1. and 3.9 6 0.7mm, respectively (Table I). Significant retroclination(17� 6 1.9�) and retraction (3.8 6 1.1 mm) of themaxillary incisors were observed. There were significantincreases in the protrusion (0.86 1.5 mm) and proclina-tion (0.6� 6 0.9�) of the mandibular incisors. Theinterincisal angle increased by 21.5� 6 5.1�. Therewere no significant changes in the vertical positionsof the maxillary incisors and first molars. In the

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mandibular arch, significant intrusion of the incisors(�2.6 6 1.4 mm) and extrusion of the molars(0.8 6 0.6 mm) were observed. The SN to MP and ANSto Xi/Xi-PM angles did not change significantly.

Among the postretention (T3-T2) changes, there weresignificant increases in overjet and overbite (0.4 6 0.9and 0.8 6 0.4 mm, respectively). In the mandibulararch, significant extrusion of incisors (0.8 6 1.1 mm)was observed. Other variables did not show any changes.

During the overall period (T3-T1), the maxillary inci-sors were retroclined (16.9� 6 0.4�) and retracted(�3.7 6 1 mm), and the mandibular incisors were pro-truded (0.7 6 1.1 mm) significantly; these changescontributed to a significant decrease in overjet(�6.3 6 1.2 mm) and an increase in the interincisalangle (21.4� 6 5.2�). The mandibular molars wereextruded, and the mandibular incisors were intrudedsignificantly; these changes resulted in a significantreduction in overbite. The vertical positions of the maxil-lary incisors and molars and the proclination of themandibular incisors had no significant changes fromT1 to T3.

DISCUSSION

The aim of this study was to evaluate the long-termstability of deepbite correction in adults with mandibularincisor intrusion using the bioprogressive sectional archtechnique. The null hypothesis was that dental deepbitecorrection with mandibular incisor intrusion in adults isstable; based on our results, the null hypothesis was notrejected.

The mean overbite correction at T2 was 3.9 mm,which corresponded to 66.1% of the pretreatment over-bite. This ratio is higher than the ratio reported in thestudy of Weiland et al20 using adult patients. In that

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Table III. Descriptive statistics and statistical comparisons of the treatment, postretention, and overall changes

Measurement

Treatment changes (T2-T1) Postretention changes (T3-T2) Overall changes (T3-T1)

Mean 6 SD Sig Mean 6 SD Sig Mean 6 SD SigSN to MP (�) 0.5 6 1.6 NS �0.2 6 1.3 NS 0.6 6 1.6 NSANS to Xi/Xi-PM (�) 0.2 6 3.7 NS �0.1 6 3.7 NS 0.2 6 3.8 NSOverbite (mm) �3.9 6 0.7 * 0.8 6 0.4 * �3.1 6 0.8 *Overjet (mm) �6.4 6 1.2 * 0.4 6 0.9 * �6.3 6 1.2 *U1CR to PP (mm) �0.3 6 0.9 NS 0.1 6 0.6 NS �0.2 6 0.9 NSU1 to PP (�) �17.0 6 1.9 * �0.2 6 0.8 NS �16.9 6 0.4 *U1 to APg (mm) �3.8 6 1.1 * 0.1 6 1.3 NS �3.7 6 1.0 *U6 to PP (mm) �0.1 6 0.8 NS 0.2 6 0.6 NS 0.1 6 0.8 NSL1CR to MP (mm) �2.6 6 1.4 * 0.8 6 1.1 * �2.1 6 0.9 *L1 to MP (�) 0.6 6 0.9 * �0.2 6 0.9 NS 0.3 6 0.8 NSL1 to APg (mm) 0.8 6 1.5 * �0.1 6 1.3 NS 0.7 6 1.1 *L6 to MP (mm) 0.8 6 0.6 * �0.3 6 0.5 NS 0.5 6 0.6 *U1 to L1 (�) 21.5 6 5.1 * �0.1 6 1.7 NS 21.4 6 5.2 *

Sig, Significance; NS, not significant.*P\0.001.

Kale Varlık, Onur Alpakan, and T€urk€oz 417

study, 2 different mechanics were used, and the correc-tion values were 3.17 and 3.56 mm, corresponding to58.8% and 58.1%, respectively. The difference couldbe because in our study, the posttreatment overbitevalue was slightly lower than that reported by Weilandet al. In our study, a statistically significant but clinicallyinsignificant relapse of 0.8 mm was observed at T3, andthe mean overbite (2.8 mm) at T3 was acceptable. In pre-vious studies, either similar or higher relapse valuesranging from 0.1 to 2.1 mm were reported.7,8,16,17,24-27 However, when our results were compared withthose of previous studies, there are differences in termsof factors that were previously reported to haveaffected overbite stability, such as the subjects' growthpotential, growth pattern, muscle strength, adaptationcapacity, follow-up and retention durations, initial over-bite value, and retainer type.8,14,21,26-31

We used incisor centroid as a reference point andevaluated true intrusion, as was proposed by Nget al.32 At the end of the treatment, 2.6 mm of mandib-ular incisor intrusion was achieved. Similar mean intru-sion values between 1.1 and 3 mm were reported inprevious studies where deepbite correction was accom-plished by only mandibular incisor intrusion withsegmental or sectional arches.10,33,34 An importantconsideration with regard to centroid while evaluatingthe mean incisor intrusion value is that although itwas claimed to be independent of any change in theaxial inclination, the possibility that centroid canslightly move apically because of proclination of theincisors, resulting in somewhat higher than actualintrusion values, cannot be ruled out.14,32 In thisstudy, an 0.8-mm relapse was observed at T3. Althoughthis relapse was statistically significant, it was not

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clinically important because the overbite value at T3was well within the normal range, and the overall intru-sion value of 2.1 mm was quite remarkable.

The interincisal angle is believed to play a criticalrole in the stability of deepbite correction. Berg28

suggested that the interincisal angle should be lessthan 140� at the end of treatment for stability of deep-bite treatment. According to Houston,35 an approximateinterincisal angle of 135� inhibits incisor overeruptionand thus has an impact on the stability of deepbitetreatment. In this study, the mean interincisal angle,which was below the normal range at T1, increasedsignificantly after treatment mainly because of retrac-tion of the maxillary incisors; it approached the normvalues proposed by several authors and did not changeat T3.36-38 The substantial stability of overbitecorrection in this study seems to support the validityof the interincisal angle values suggested for stabilityby Berg and Houston.

An intrusive force that is labial to the center of resis-tance of the incisors would intrude them but also tipthem labially.12 Labial tipping tends to decrease overbitebecause it influences the vertical incisal edge position,and depending on the original inclination of the incisors,it can be advantageous in deepbite correction.33,34,39,40

However, flaring has been associated with an increasedincidence of relapse.8,10,13,17 In this study, statisticallysignificant increases in both proclination andprotrusion of the mandibular incisors were observedafter treatment. The mean increases in L1 to APg andL1 to MP were 0.8 mm and 0.6�, respectively.Although statistically significant, these values weremuch lower than the values reported in other studiesin which intrusion utility arches were used.10,34,39 Less

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418 Kale Varlık, Onur Alpakan, and T€urk€oz

incisor flaring could be due to the use of 0.0163 0.022-in utility arches in this study, thus providing better tor-que control.

Relapse of proclined incisors is thought to be relatedto distortion of the perioral neuromuscular balance13 orthe tendency of incisors that were upright at the begin-ning of treatment to return to their original positions.8

The changes in the sagittal position of the mandibularincisors in our study were stable in the postretentionperiod. The reason for no relapse might be that the L1to APg and L1 to MP measurements were within normalranges at T1; despite some flaring, they remained withinthe normal ranges at T2 and therefore caused no neuro-muscular imbalance.

This study involved nongrowing patients with normalvertical dimensions; therefore, prevention of posteriorextrusion that could result in relapse and opening rota-tion of mandible was intended. To this end, sectionalarches were used for intrusion, and stabilization sectionswere used to enhance the vertical anchorage of themandibular molars and premolars.41,42 Still, despitethese measures, extrusion of 0.8 mm occurred in themandibular molars. This value was lower than reportedin other studies in which mandibular incisor intrusionwas performed with segmental or sectional arches. Inthe study of Dake and Sinclair,10 when the mandibularincisors were intruded with utility arches, they reported2.6 mm of mandibular molar extrusion. Al Buraikiet al16 used lever arches and reported 1.6 mm ofmandib-ular molar extrusion. One explanation for the lowervalue in our study could be that these 2 studies wereconducted with growing subjects who had a likelihoodof continuing molar eruption.31 Moreover, the intrusionforce used in this study was lower than that was used byDake and Sinclair; an intrusion force of 40 g might nothave affected the posterior vertical anchorage. Accord-ing to Nanda and Kuhlberg,13 1 mm of maxillary ormandibular molar extrusion effectively reduces incisoroverlap by 1.5 to 2.5 mm. In our study, the mean over-bite reduction was 3.96 0.7 mm, and themeanmandib-ular incisor intrusion was 2.6 6 1.4 mm. That is,together with the modest increases in the proclinationand protrusion of the mandibular incisors, molar extru-sion might have contributed to overbite correction.

Seemingly, 0.8 mm of mandibular molar extrusiondid not result in mandibular posterior rotation becausethe mandibular plane and lower facial height anglesdid not change at either T2 or T3. The molars retainedtheir new vertical positions in the postretention period;thus, the 0.8-mm relapse in overbite cannot be attrib-uted to a posttreatment change in molar position. Simi-larly, Burzin and Nanda14 also found no relationshipbetween molar extrusion and overbite relapse.

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This study had some limitations because of its retro-spective design without randomization. Althoughconsecutively treated subjects were included without re-gard to treatment and postretention outcomes and 2 or-thodontists with similar experience provided theorthodontic treatment, adhering strictly to treatmentand retention protocols, the potential for selection biasstill exists. Therefore, these findings must be regardedwith some caution.

CONCLUSIONS

1. With mandibular intrusion utility arches, 2.6 mm oftrue incisor intrusion was obtained. Only 0.8 mm ofmolar extrusion was observed.

2. Five years after the end of the retention period, a sta-tistically significant but clinically unimportant relapseof 0.8 mm (which corresponded to approximately30% of the total intrusion amount) was observed inmandibular incisor intrusion and overbite.

3. Deepbite treatment with mandibular incisor intru-sion with utility arches was effective and appearedto be stable in nongrowing patients.

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