CLINICIAN'S CORNER

Esthetic orthodontic treatment with a doubleJ retractor and temporary anchorage devices

Jae Hyun Park,a Kiyoshi Tai,b Masato Takagi,c Kuniaki Miyajima,d Yukio Kojima,e and Bo-Hoon Joof

Mesa, Ariz, Okayama and Nagoya, Japan, St Louis, Mo, and Seoul, Korea

aAssoSchooscholabVisitzonapracticPrivadAdjusity, SeAssoof TecfAdjunCollegSeoulThe aucts oReprinSchooAZ 85Subm0889-Copyrdoi:10

796

This clinical article reports an esthetic treatment option for managing a Class II malocclusion in an adult. Thepatient, a woman aged 24 years 2 months, had crowding and a convex profile. She was treated with maxillaryfirst premolar extractions, a double J retractor, and temporary skeletal anchorage devices in the maxillary arch.Posttreatment records after 2 years showed excellent results with good occlusion and long-term stability. (Am JOrthod Dentofacial Orthop 2012;141:796-805)

The correction of dental crowding is a common or-thodontic treatment that can be performed witha removable or fixed appliance or a combination

of both. Until recently, the process of straightening teethhas typically involved appliances including brackets,bands, and wires, but many adult patients are reluctantto wear fixed appliances. Consequently, the desire fora cosmetic solution for misaligned teeth has causedmore patients to seek veneers, crowns, and otherlaboratory-fabricated cosmetic restorations.

Clear brackets can be placed for esthetic reasons, butthey can irritate soft tissues because of their size. Lingualbrackets might be a great alternative for those who de-sire straight teeth without visible brackets, but, althoughlingual orthodontic techniques have improved, theygenerally require more chair time and might not becost-effective.1,2 Clear removable appliances have thebenefits of improved oral hygiene and esthetics.3-6

ciate professor and chair, Postgraduate Orthodontic Program, Arizonal of Dentistry & Oral Health, A. T. Still University, Mesa, Ariz; internationalr, Graduate School of Dentistry, Kyung Hee University, Seoul, Korea.ing adjunct assistant professor, Postgraduate Orthodontic Program, Ari-School of Dentistry & Oral Health, A. T. Still University, Mesa, Ariz; privatece, Okayama, Japan.te practice, Okayama, Japan.nct professor, Center for Advanced Dental Education, Saint Louis Univer-t Louis, Mo.ciate professor, Department of Mechanical Engineering, Nagoya Institutehnology, Nagoya, Japan.ct professor, Department of Orthodontics, Samsung Medical Center,e of Medicine, Sungkyunkwan University, Seoul, Korea; private practice,, Korea.uthors report no commercial, proprietary, or financial interest in the prod-r companies described in this article.t requests to: Jae Hyun Park, Postgraduate Orthodontic Program, Arizonal of Dentistry & Oral Health, A. T. Still University, 5835 E Still Cir, Mesa,206; e-mail, JPark@atsu.edu.itted, August 2010; revised and accepted, January 2011.5406/$36.00ight � 2012 by the American Association of Orthodontists..1016/j.ajodo.2011.01.024

These appliances have become increasingly popularamong adults who want to straighten their teethwithout using conventional brackets. However, inorthodontics, precisely controlled force application isrequired to achieve the final alignment.

The purpose of this article is to report the use ofa modified type of lingual retractor, the double J retrac-tor, and temporary skeletal anchorage devices for en-masse retraction of the 6 anterior teeth in a patientwith premolar extractions.7

DIAGNOSIS AND ETIOLOGY

A woman aged 24 years 2 months was referred bya general dentist for evaluation of anterior crowding.Her chief complaint was the appearance of her maxillaryanterior teeth and upper lip (Fig 1). She did not want tohave fixed orthodontic appliances in the maxillary archbecause of their appearance, especially when smiling.She had a convex profile and a Class II skeletal pattern,with a Class II Division 1 malocclusion. Her facial formwas mesocephalic, with good symmetry, a mildly in-creased lower facial height, and a retrognathic chin.Lip competence could be achieved but with some men-talis strain. There were no signs of temporomandibularjoint dysfunction, andmandibular movements were nor-mal, with no evidence of deviation. Intraorally, her max-illary and mandibular midlines were centered relative toher facial midline. All permanent teeth were present, andshe had fair oral hygiene and probing depths within thenorms. The patient was in good general health and hadno history of major systemic diseases. She had no historyof dental trauma or parafunctional habits, and theetiology of her occlusion was believed to be heredity.

Pretreatment records showed that the patient had anend-onClass II relationship on the right and the left at the

Fig 1. Pretreatment facial and intraoral photographs.

Park et al 797

firstmolars and canines. Therewasmoderate crowding inthe maxillary arch and mild crowding in the mandibulararch with a severe curve of Spee. She had a 6.3-mm over-jet and an 80%overbite. The teethwere free of caries withno pathologies. The third molars were missing.

The cephalometric analysis indicated skeletal Class II(ANB, 8.4�; Wits, 3.6 mm) with a hyperdivergent growthpattern (SN-MP, 44.9�). The maxillary incisors wereslightly retroclined (U1-SN, 96.2�) caused by bilateralrotation of the maxillary central incisors, and themandibular incisors showed a slight retroclincation(IMPA, 88.3�) (Fig 2; Table).

TREATMENT OBJECTIVES AND PLAN

The treatment objectives were to obtain normal over-jet and overbite, establish Class I canine and molar rela-tionships, relieve the crowding in both arches, level the

American Journal of Orthodontics and Dentofacial Orthoped

curve of Spee, and improve the patient's profile withoutthe use of labial fixed appliances in the maxillary arch.

With temporary skeletal anchorage devices, distalmovement of the anterior or posterior teeth or both, with-out anchorage loss, would be possible.8,9 This patientwanted to retract her upper lip as much as possible, sothe maxillary first premolars were extracted, but, tocamouflage the skeletal Class II pattern, the mandibularsecond premolars were not extracted.

TREATMENT ALTERNATIVES

With no growth modification possible, correction ofthe Class II molar relationship could be accomplishedby nonextraction molar distalization treatment, extrac-tion of the maxillary first premolars and the mandibularsecond premolars, or extraction of only the maxillaryfirst premolars.

ics June 2012 � Vol 141 � Issue 6

Fig 2. Pretreatment panoramic radiograph and lateral cephalogram.

Table. Cephalometric measurements

Measurement Japanese norm Pretreatment Posttreatment 2 years posttreatmentSNA (�) 82.0 83.5 82.1 79.9SNB (�) 80.0 75.0 74.9 75.1ANB (�) 2.0 8.4 7.2 4.8Wits (mm) 1.1 3.6 4.7 2.7SN-MP (�) 32.0 44.9 45.2 45.0FH-MP (�) 25.0 35.0 35.9 35.3LFH (ANS-Me/N-Me) (%) 55.0 57.1 57.4 57.3U1-SN (�) 104.0 96.2 90.7 94.7U1-NA (�) 22.0 12.8 8.5 14.8IMPA (�) 90.0 88.3 91.7 88.3L1-NB (�) 25.0 28.2 31.0 28.7U1/L1 (�) 124.0 130.6 133.2 131.7Upper lip (mm) 1.2 4.1 0.8 0.6Lower lip (mm) 2.0 4.8 2.2 2.0

798 Park et al

To accomplish the treatment objectives, conven-tional esthetic treatment options for the maxillaryorthodontic appliances included lingual orthodonticappliances or clear removable appliances. However, a dif-ficult problem to overcome in lingual orthodontics hasbeen torque control of the anterior teeth. A potentialdisadvantage of clear removable appliances is that theyhighly depend on patient compliance.6 The other signif-icant weakness is the aligner cannot move the root apexefficiently which results in the tipping of teeth especiallyin extraction cases. Compared with those 2 esthetic or-thodontic appliances, the double J retractor offered aneffective tool for producing translational tooth move-ment during anterior retraction; a treatment plan wasdeveloped that included extraction of the maxillary firstpremolars, delivery of the double J retractor, and use oftemporary skeletal anchorage devices to achieve bodilytranslation.

Because of the skeletal discrepancies that resultedfrom an unfavorable growth pattern, bilateral sagittal

June 2012 � Vol 141 � Issue 6 American

split osteotomy was discussed for mandibular advance-ment combined with orthodontic treatment. Upon com-pletion of the orthodontic treatment, genioplasty wouldbe another option to improve her profile, but the patientdeclined all surgical options.

TREATMENT PROGRESS

Before orthodontic treatment, the patient was re-ferred to an oral surgeon to extract her maxillary firstpremolars.

Because she had high esthetic demands and was un-willing to tolerate the extraction spaces, esthetic ponticswere bonded to the distal aspects of the maxillary ca-nines. The double J retractor is an alternative methodfor obtaining the desired direction of force on the max-illary anterior teeth.10-12 We used bonding pads insteadof mesh brackets, which were common with earlierlingual retractors. The anterior lever arm hooks werebent in the wire approximately 20 mm from the pad so

Journal of Orthodontics and Dentofacial Orthopedics

Fig 3. A, Schematic showing the double J retractor and palatal temporary anchorage devices: 1 and 2,palatal temporary skeletal anchorage devices; 3, anterior lever arm hooks; 4, posterior lever arm hooks.B,Maxillary occlusal photograph during treatment with a double J retractor and temporary skeletal an-chorage devices. C, Maxillary occlusal photograph showing the bonded fixed appliance.

Park et al 799

that the line of action of the force passed through thecenter of resistance. The posterior lever arm hooks wereextended from the lingual crown surfaces of thecanines. Both hooks can be used for space closing withelastic chains or superelastic closed-coil springs, andthe posterior hooks can be used for torque control withClass II elastics. In this case, however, to minimize extru-sion of the posterior mandibular teeth, the patient worethe Class II elastics at night only when it was necessary.After the retractor was adjusted to the lingual surfaceof the anterior teeth, it was bonded to them. Transbond(3M Unitek, Monrovia, Calif) was used, in addition to thecustomary bonding adhesive, to resist the shearing forcesthat occur when loading the retractor.13 Three temporaryskeletal anchorage devices were placed (OSAS, Tuttlin-gen, Germany). Two (diameter, 1.6 mm; length, 8.0mm) were placed palatally between the maxillary firstand second molars, and 1 temporary anchorage device(diameter, 1.6 mm; length, 7.0 mm) was placed in themidpalate. Elastic chains or superelastic closed-coilsprings were stretched from the anterior hooks to thetemporary skeletal anchorage devices (Fig 3).

A cephalometric film was used to determine the pointof force application of the appliance with the aid ofa gutta-percha cone as a radiopaque guide. Power elas-tic chains or nickel-titanium closed-coil springs that de-livered 200 g per side provided the retraction force forspace closure.14 In addition, the intrusion force of thelingual retractor was 60 g per side.15

Biomechanically, the position of the hook in the leverarm wire can change the point of force application withrespect to the center of resistance of the teeth to be in-truded and retracted. During lingual retraction, the max-illary left posterior temporary skeletal anchorage devicefailed, so another (diameter, 1.6 mm; length, 8.0 mm;OSAS) was installed between the maxillary left secondpremolar and first molar. After 6 months, the anteriorteeth were retracted so that only 1 to 1.5 mm of space

American Journal of Orthodontics and Dentofacial Orthoped

remained between the canines and the second premo-lars. At this point, the patient was satisfied with the re-sults, and she agreed to allow the fixed appliances bebonded for axial control and root movement. The0.022 3 0.028-in edgewise ceramic brackets werebonded in both arches. After leveling, 0.018 3 0.025-in stainless steel wires were placed for the remainingspace closure in the maxillary arch. At this point, the pa-tient wanted to retract her upper lip a bit more. Becauseof her request during the space closure, the maxillaryanterior teeth were slightly tipped lingually (Fig 3).

In the mandibular arch, during the leveling stage,a sectional 0.016-in copper-nickel-titanium wire wasused between the mandibular incisors to achieve theirinitial leveling. Then a mandibular utility archwire wasconstructed with 0.016 3 0.022-in stainless steel wire.With a mandibular utility archwire, intrusive forceswere applied to the mandibular incisors labially to thecenter of resistance. It produced a labial crown momentthat resulted in proclination of the mandibular inci-sors.16 To minimize this side effect, labial root torquewas included in the incisor region of the mandibular util-ity archwire.17,18 To produce approximately 60 g ofincisor intrusion force, 20� of distal molar crown tipwas activated.18 To prevent the need for mandibularmolar extrusion, buccal root torque and expansionwere applied to the molars by establishing cortical an-chorage.18 After leveling the mandibular arch, a flat0.016 3 0.022-in nickel-titanium archwire was used.At the finishing stage, a mild curve of Spee in the max-illary archwire and a mild reverse curve of Spee in themandibular archwire were placed by using 0.018 30.025-in stainless steel wires.

To establish acceptable overbite and overjet, intrep-roximal reduction was done on the mandibular anteriordentition during the finishing stage. A tooth positionerwas used for final detailing. After treatment, the curveof Spee of the mandibular arch was found to be

ics June 2012 � Vol 141 � Issue 6

Fig 5. Retraction forces with A and B, temporary skeletal anchorage devices and C, elastics producerotation of the anterior segment around the center of resistance.

Fig 4. Three-dimensional finite element model for tooth-periodontal ligament system.

800 Park et al

successfully leveled. Active treatment time was 18months. For a better esthetic result, an advancementgenioplasty could have been considered. After treat-ment, maxillary and mandibular Essix retainers (Dents-ply Raintree Essix, Sarasota, Fla) were delivered. Thepatient was instructed to wear them 24 hours per dayfor 1 year and then at night only. Recall visits for retainerchecks occurred at 1, 3, and 6 months during the firstyear. To ensure continued satisfactory posttreatmentalignment of the mandibular and maxillary anterior den-tition, the use of retainers was recommended indefi-nitely.19

The detailed calculation method has already beendescribed in previous articles.20,21

For our patient, the double J retractor was con-structed of a segmented archwire bonded to the 6

June 2012 � Vol 141 � Issue 6 American

anterior teeth, and lever arms extended from the seg-mented archwire. Both were made of a stiff 0.028-insteel wire (Young's modulus, 200 GPa), and forceswere applied at the ends of the lever arm. Assuming sym-metry on both sides of the arch, a model of only the leftside was fabricated. A lateral view of the finite elementmodel is shown in Figure 4.

By using this method, orthodontic tooth movementis calculated based on bone remodeling: ie, resorptionand apposition of the alveolar bone. The bone-remodeling rate is assumed to be in proportion to stressin the periodontal ligament.

Jang et al7 reported that the center of resistance ofthe 6 maxillary anterior teeth is located vertically 12.2mm (55.6%) and apically to the incisal edges of centralincisors. Those authors also demonstrated that

Journal of Orthodontics and Dentofacial Orthopedics

Fig 6. Posttreatment facial and intraoral photographs.

Park et al 801

temporary skeletal anchorage devices located 8 mm api-cally to the cervical line of the first molars achievedbodily anterior retraction with a double J retractor.The center of resistance of the anterior teeth was deter-mined from movement patterns when changing the lo-cation of the lever arm end. Figure 4 shows themovement patterns of the 6 anterior teeth and the stressdistributions in the periodontal ligament after retractionof the teeth by 4 mm. When an extension line of theforce passed through the center of resistance of the 6 an-terior teeth, the teeth moved bodily and intruded by 0.5mm. When an extension line of the force was coronal tothe center of resistance, the anterior teeth tipped lin-gually. When an extension line of the force was apicalto the center of resistance, there was lingual root move-ment (Fig 5).

TREATMENT RESULTS

The posttreatment records demonstrate that thetreatment objectives were achieved. The facial

American Journal of Orthodontics and Dentofacial Orthoped

photographs showed improved smile and profile es-thetics (Fig 6). Class I canine and Class II molar relation-ships were established with a canine-protectedocclusion. The dental midlines were maintained withthe facial midline, and ideal overbite and overjet wereachieved, and the curve of Spee was successfully leveled.

The posttreatment panoramic radiograph showedproper space closure and acceptable root parallelism, ex-cept for the mandibular left first premolar. There were nosignificant signs of bone or root resorption (Fig 7).

Posttreatment lateral cephalometric analysis and su-perimposition showed no significant skeletal changes inthe maxillary skeletal base (SNA, 82.1�) and the mandib-ular skeletal base (SNB, 74.9�). The maxillary anteriorteeth were retracted and slightly tipped lingually. Therewas no significant improvement in the anteroposteriorchin position since growth had already finished beforetreatment, so the patient still had a relatively convexprofile (Fig 8; Table). To superimpose the multi-planarreconstruction images and for volume rendering, a newregistration technique developed by Tai et al22,23

ics June 2012 � Vol 141 � Issue 6

Fig 7. Posttreatment panoramic radiograph and lateral cephalogram.

Fig 8. Cephalometric superimposition: black line, pretreatment; red line, posttreatment.

802 Park et al

(Fig 9) was performed. At the 24-month follow-up, shehad a stable occlusion, with the results of the orthodontictreatment maintained (Fig 10).

DISCUSSION

A Class II malocclusion is difficult to treat. A station-ary anchorage is 1 main factor that determines the suc-cess of the treatment. Stationary anchorage means thatthe anchorage unit does not move in reaction to theapplied forces and moments.24 Conventional extraoral

June 2012 � Vol 141 � Issue 6 American

appliances are routinely used to establish maximum an-chorage. However, many patients reject headgear wearbecause of social and esthetic concerns, and the successof this treatment solely depends on patient compli-ance.25 In many cases, lack of compliance results inthe loss of anchorage and unsatisfactory treatment re-sults. The growing demand for treatments requiringmaximum curative effects with minimal cooperationhas made temporary skeletal anchorage devices morepromising as an excellent alternative to traditional or-thodontic anchorage.

Journal of Orthodontics and Dentofacial Orthopedics

Fig 9. Superimposingmultiplanar reconstruction (MPR) images (A andB) and volume rendering (C-E)with 3D superimposition technique.

Park et al 803

In patients with Class II Division 1 malocclusions, thechief complaint is usually an exaggerated horizontaloverlap of the incisors. Patients and parents are routinelyinformed that, although there are no tooth size-archlength discrepancies, an anteroposterior skeletal dis-crepancy is present. Proffit26 stated that approximately80% of white Class II patients have some mandibulardeficiency, whereas only approximately 20% have exces-sive maxillary development. In the most severe Class IIDivision 1 malocclusions, orthognathic surgery to ad-vance the mandible is often indicated.

During the treatment of a patient with a high-angleClass II malocclusion, it is important to prevent extrusionof the mandibular posterior teeth with Class II forces.

Another consideration in our patient was the correc-tion of a deep overbite. To correct a deep overbite, forexample, leveling a mandibular curve of Spee can beachieved by extrusion of posterior teeth.27 However,extrusion of the premolars and molars will result in in-creased lower facial height, steepening of the occlusal

American Journal of Orthodontics and Dentofacial Orthoped

plane, and downward and backward rotation of themandible with a worsened Class II skeletal relation-ship.28,29 The long-term stability of such a correctionis questionable. Intrusion of the maxillary anterior teethto correct a deep overbite might be indicated in patientswith a gummy smile.29 However, when the patient hasan ideal smile arc, any maxillary incisor intrusion shouldbe carefully monitored during treatment to prevent flat-tening of the smile arc.30

When smiling, our patient displayed 95% of her max-illary incisors but did not show any gingivae. Eventhough she did not have a gummy smile, to controlthe vertical dimension, a slight intrusion of the maxillaryanterior teeth was indicated for her.

Anterior bodily retraction is achieved by either directlyapplying a moment and force to an edgewise bracket orusing lever-arm mechanics to change the point of forceapplication closer to the center of resistance.31 In a le-ver-arm system, the desired tooth movement is obtainedby adjusting the length of the lever arm and the point of

ics June 2012 � Vol 141 � Issue 6

Fig 10. Two-year posttreatment facial and intraoral photographs.

804 Park et al

force application.31 In this system, a transpalatal arch isneeded to control the point of force application in theposterior area.12 Instead of a transpalatal arch, tempo-rary skeletal anchorage devices can be placed palatallyto control the point of force application.

The point of force application and the line of actionof the force can be planned from the lateral cephalomet-ric radiograph.32 Increasing the vertical forces in the an-terior and posterior areas will reinforce anchorage, butincreasing the intrusive force in the anterior segmentmakes torque control more complicated and flattensthe occlusal plane.33 If vertical bowing of the lingualarchwire occurs during space closure, the anterior andposterior vertical force differences should be checked.

In this patient, instead of using high-pull headgear toreinforce the posterior anchorage unit during en-masseretraction of the maxillary anterior teeth, we used tem-porary skeletal anchorage devices. There are several ad-vantages with lingual retractor (double J retractor)mechanics.34 This technique requires no complicatedwire bending and can easily control retraction of the

June 2012 � Vol 141 � Issue 6 American

maxillary incisors. When compared with the conven-tional lingual segmental approach, no brackets need tobe bonded to the anterior portion during the retractionperiod, so practitioners can easily apply this technique.

CONCLUSIONS

The double J retractor is an esthetic, effective, andsimplified option for closing spaces caused by tooth ex-tractions. It uses a single point force, so by controllingthe magnitude and direction of the force, it is easy toprevent unwanted tooth movements. Since it can easilyretract the maxillary anterior dentition in the variousvertical dimensions, it could be an effective alternativein appropriate situations for patients who are reluctantto use conventional fixed appliances.

REFERENCES

1. Alexander RG. The Alexander discipline. Glendora, Calif: Ormco;1986. p. 371-94.

2. Scuzzo G, Takemoto K. Invisible orthodontics. Berlin, Germany:Quintessence; 2003. p. 15-21.

Journal of Orthodontics and Dentofacial Orthopedics

Park et al 805

3. Lagrav�ere MO, Flores-Mir C. The treatment effects of Invisalign or-thodontic aligners: a systematic review. J Am Dent Assoc 2005;136:1724-9.

4. Wong BH. Invisalign A to Z. Am J Orthod Dentofacial Orthop 2001;121:540-1.

5. Womack WR, Ahn JH, Ammari Z, Castillo A. A new approach tocorrection of crowding. Am J Orthod Dentofacial Orthop 2002;122:310-6.

6. Boyd RL, Miller RJ, Vlaskalic V. The Invisalign system in adult or-thodontics: mild crowding and space closure cases. J Clin Orthod2000;34:203-12.

7. Jang HJ, Roh WJ, Joo BH, Park KH, Kim SJ, Park YG. Locatingthe center of resistance of maxillary anterior teeth retracted bydouble J retractor with palatal miniscrews. Angle Orthod 2010;80:1023-8.

8. Chen Y, Kyung HM, Zhao WT, Yu WJ. Critical factors for thesuccess of orthodontic mini-implants: a systematic review. Am JOrthod Dentofacial Orthop 2009;135:284-91.

9. Park HS, Kwon DG, Sung JH. Nonextraction treatment with micro-screw implant. Angle Orthod 2004;74:539-49.

10. Chung KR, Oh MY, Ko SJ. Corticotomy-assisted orthodontics.J Clin Orthod 2001;35:331-9.

11. Isaacson RJ, Lindauer SJ. Closing anterior openbites: the extrusionarch. Semin Orthod 2001;7:34-41.

12. Park YC, Choi KC, Lee JS, Kim TK. Lever-arm mechanics in lingualorthodontics. J Clin Orthod 2000;34:601-5.

13. Kucher G, Weiland FJ, Bantleon HP. Modified lingual lever armtechnique. J Clin Orthod 1993;27:18-22.

14. Vanden Bulcke MM, Dermaut LR, Sachdeva RC, Burstone CJ. Thecenter of resistance of anterior teeth during intrusion using thelaser reflection technique and holographic interferometry. Am JOrthod Dentofacial Orthop 1986;90:211-20.

15. Kim SH, Park YG, Chung KR. Severe Class II anterior deep bite mal-occlusion treated with a C-lingual retractor. Angle Orthod 2004;74:280-5.

16. Nikolai RJ. Forces and structural analyses of representativeorthodontic mechanics. In: Nikolai RJ, editor. Bioengineeringanalysis of orthodontic mechanics. Philadelphia: Lea and Febiger;1985. p. 372-436.

17. AlQabandi A, Sadowsky C, BeGole EA. A comparison of the effectsof rectangular and round archwires in leveling the curve of Spee.Am J Orthod Dentofacial Orthop 1999;116:522-9.

18. AlQabandi A, Sadowsky C, Sellke T. A comparison of continuousarchwires and utility archwires for leveling the curve of Spee. WorldJ Orthod 2002;3:159-65.

American Journal of Orthodontics and Dentofacial Orthoped

19. Little RM, Riedel RA,�Artun J. An evaluation of changes in mandib-ular anterior alignment from 10 to 20 years postretention. Am JOrthod 1988;93:423-8.

20. Kojima Y, Fukui H, Miyajima K. The effect of friction and flexuralrigidity of the archwire on canine movement in sliding mechanics:a numerical simulation with a 3-dimensional finite elementmethod. Am J Orthod Dentofacial Orthop 2006;130:275.e1-10.

21. Kojima Y, Mizuno Y, Fukui H. A numerical simulation of toothmovement produced by molar uprighting spring. Am J OrthodDentofacial Orthop 2007;132:630-8.

22. Tai K, Hotokezaka H, Park JH, Tai H, Miyajima K, Choi M, et al.Preliminary cone-beam computed tomography study evaluating den-tal and skeletal changes after treatment with a mandibular Schwarzappliance. Am J Orthod Dentofacial Orthop 2010;138:262.e1-11.

23. Tai K, Park JH, Mishima K, Hotokezaka H. Using superimpositionof 3-dimensional cone-beam computed tomography imageswith surface-based registration in growing patients. J Clin PediatrDent 2010;34:361-8.

24. Diedrich P. Different orthodontic anchorage systems: a criticalexamination. Fortschr Kieferorthop 1993;54:156-71.

25. Egolf RJ, Begole EA, Upshaw HS. Factors associated with ortho-dontic patient compliance with intraoral elastic and headgearwear. Am J Orthod Dentofacial Orthop 1990;97:336-48.

26. Proffit WR. Contemporary orthodontics. 3rd ed. St Louis: C. V.Mosby; 1996. p. 2-22.

27. Bernstein RL, Preston CB, Lampasso J. Leveling the curve of Speewith a continuous archwire technique—a long-term cephalometricanalysis. Am J Orthod Dentofacial Orthop 2007;131:363-71.

28. Shroff B, Lindauer SJ, Burstone CJ, Leiss JB. Segmented approachto simultaneous intrusion and space closure: biomechanics of thethree-piece base arch appliance. Am J Orthod Dentofacial Orthop1995;107:136-43.

29. Burstone CR. Deep overbite correction by intrusion. Am J Orthod1977;72:1-22.

30. Sarver DM. The importance of incisor positioning in the esthetic smile:the smile arc. Am J Orthod Dentofacial Orthop 2001;120:98-111.

31. Gjessing P. Controlled retraction of maxillary incisors. Am J OrthodDentofacial Orthop 1992;101:120-31.

32. Keles A, Erverdi N, Sezen S. Bodily distalization of molars with ab-solute anchorage. Angle Orthod 2003;73:471-82.

33. Creekmore T. Lingual orthodontics—its renaissance. Am J Orthod1989;96:120-37.

34. Kim SH, Park YG, Chung KR. Severe anterior open bite malocclu-sion with multiple odontoma treated by C-lingual retractor andhorseshoe mechanics. Angle Orthod 2003;73:206-12.

ics June 2012 � Vol 141 � Issue 6