CASE REPORT
Correction of a skeletal Class II malocclusion with severe crowding by a specially designed rapid maxillary expander Honghong Wang,a Jing Feng,b Peijun Lu,a and Gang Shenc Shanghai, China
To correct an Angle Class II malocclusion or to create spaces in the maxillary arch by nonextraction treatment, distal movement of the maxillary molars is required. Various modalities for distalizing the buccal segment have been reported. Conventional extraoral appliances can be used to obtain maximum anchorage. However, many patients reject headgear wear because of social and esthetic concerns, and the success of this treatment depends on patient compliance. Intraoral appliances, such as repelling magnets, nickel-titanium coils, pendulum appliance, Jones jig appliance, distal jet appliance, and modified Nance appliance, have been introduced to distalize the molars with little or no patient cooperation. However, intraoral appliances can result in anchorage loss of the anterior teeth and distal tipping of the maxillary molars. In this case report, we introduce a diversified rapid maxillary expansion appliance that was custom designed and fabricated for the treatment of a growing girl with a skeletal Class II malocclusion and severe crowding from a totally lingually positioned lateral incisor. The appliance concomitantly expanded the maxilla transversely and retracted the buccal segment sagittally, distalizing the maxillary molars to reach a Class I relationship and creating the spaces to displace the malpositioned lateral incisor. The uniqueness of this special diversified rapid maxillary expansion appliance was highlighted by a series of reconstructions and modifications at different stages of the treatment to reinforce the anchorage. (Am J Orthod Dentofacial Orthop 2015;147:242-51)
T
o correct an Angle Class II malocclusion or to create spaces in the maxillary arch by nonextraction treatment, distalization of the maxillary molars is an alternative treatment approach. Various modalities in distalizing the buccal segment have been reported. Conventional extraoral appliances can be used to obtain maximum anchorage. However, many patients reject headgear wear because of social and esthetic concerns, and the success of this treatment depends on patient compliance.1 Beginning in the 1980s, intraoral appliances, such as repelling magnets,2
From the Department of Orthodontics, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University, Shanghai, China. a Postgraduate student. b Assistant professor. c Chair. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. Financial support from the National Natural Science Foundation of China, grant no. 81271182. Address correspondence to: Gang Shen, Department of Orthodontics, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University, Shanghai, China; e-mail, [email protected]. Submitted, November 2013; revised and accepted, December 2013. 0889-5406/$36.00 Copyright Ó 2015 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2013.12.032
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nickel-titanium coils,3 the pendulum appliance,4,5 the Jones jig appliance,6 the distal jet appliance,7 and the modified Nance appliance,8 have been introduced to distalize molars with little or no patient cooperation. However, intraoral appliances can result in anchorage loss of the anterior teeth and distal tipping of the maxillary molars.9 In this case report, we introduce a diversified rapid maxillary expander appliance (DRME) that was custom designed and fabricated for the treatment of a girl with a skeletal Class II malocclusion and severe crowding from a totally lingually positioned lateral incisor. The appliance concomitantly expanded the maxilla transversely and retruded the buccal segment sagittally, distalizing the maxillary molars to reach a Class I relationship and creating the spaces to align the remaining maxillary dentition. The uniqueness of this special DRME was highlighted by a series of reconstructions and modifications at different stages of the therapy to reinforce the anchorage. DIAGNOSIS AND ETIOLOGY
The patient was an 11-year-old Chinese girl with a chief complaint of crooked teeth. The initial clinical
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Fig 1. Pretreatment extraoral and intraoral photographs showing an acceptable facial appearance, a Class II molar relationship, and a lingually positioned maxillary right lateral incisor.
examination showed a slightly retrusive mandible with an obtuse nasolabial angle and an increased labiomental fold (Fig 1). The intraoral examination and study casts exhibited half-step Class II molar relationships on both sides. The maxillary right lateral incisor was completely palatally positioned (Fig 2). The maxillary midline was 4.0 mm off to the right of the facial midline, and the mandibular midline was symmetrically correct. Crowding in the maxilla was severe as a result of an ectopically placed right lateral incisor, whereas crowding in the mandible was mild. The maxilla was constricted, and a crossbite relationship was also noted in the left premolar area. Study cast analysis showed an overbite of 3.0 mm and an overjet of 2.5 mm. The lateral cephalometric analysis showed a Class II skeletal base (ANB, 5.7 ) with a protrusive maxilla (SNA, 86.5 ), and an average mandibular plane angle (FMA, 32.8 ) (Fig 3, Table). The U1-SN angle of 103.7 indicated a retroclined tendency of the maxillary incisors
that might have caused an obtuse nasolabial angle. An inspection of skeletal maturation by the cervical vertebrae suggested considerable growth potential. The panoramic radiograph showed that both maxillary second molars were under development, and the tooth buds of the maxillary third molars did not exist. Furthermore, no pathologic lesions, unusual root formations, or deformities of the maxillary right central or lateral incisors were identified with cone-beam computed tomography (Fig 4). TREATMENT OBJECTIVES
The treatment objectives for this patient were to (1) relieve crowding by bringing the palatally positioned lateral incisor into alignment, (2) correct the skeletal Class II, (3) restore a satisfactory occlusion with Class I molar and canine relationships, (4) correct the shifted midline, (5) create ideal overbite and overjet, and (6) improve the facial esthetics.
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Fig 2. Pretreatment study casts depicting the severity of crowding resulting from the malpositioned maxillary right lateral incisor.
Fig 3. Pretreatment cephalogram and panoramic radiograph.
TREATMENT ALTERNATIVES
This preteen patient had adequate growth potential, with an acceptable profile but with a retroclined maxillary anterior dentition. A maxillary lateral incisor was palatally positioned, but there were no signs of defects in the overlapping areas between the adjacent dentition (Fig 4). Furthermore, the maxillary second molars were
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not erupted, indicating that the timing for molar distalization might be an acceptable treatment modality. A nonextraction treatment plan was therefore proposed. The first step was orthopedic treatment with a specially designed DRME (Fig 5). This appliance was designed to expand the maxillary arch and distalize the maxillary molars simultaneously to create spaces for crowding
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Table. Cephalometric data SNA ( ) SNB ( ) SN-MP ( ) FMA ( ) ANB ( ) U1-NA (mm) U1-SN ( ) L1-NB (mm) IMPA ( ) Lower lip to E-plane (mm) Upper lip to E-plane (mm)
Norm Pretreatment Posttreatment Change 82.0 6 3.5 86.5 84.3 2.2 77.7 6 3.2 80.8 81.5 0.7 32.9 6 5.2 31.7 32.7 1.0 29.2 6 4.5 32.8 29.8 3.0 4.0 6 1.8 5.7 2.8 2.9 4.3 6 2.7 2.6 6.3 3.7 103.4 6 5.5 103.7 107.3 3.6 4.0 6 1.8 5.3 8.0 2.7 95.0 6 7.0 94.1 101.3 7.2 2.0 6 2.0 0.4 1.1 0.7 1.3 6 2.0
0.4
0.2
0.6
relief and restoration of the molar relationship. The second step was orthodontic treatment with fixed appliances to improve the buccal interdigitation and establish a proper incisal relationship. Microimplant anchorage devices (MIAs) could be applied in the maxilla to retract the frontal segment because the frontal anchorage might be partially lost as a result of buccal segmental distalization. In the maxillary arch, by moving the buccal dentition posteriorly, the maxillary left quadrant was to be distalized for midline correction, and crowding of the right quadrant was to be relieved. In the mandibular arch, mild crowding was to be relieved by expansion with broad archwires, whereas the sagittal position of the anterior teeth would remain to prevent further deepening of the labiomental fold. Over the whole course of orthopedic treatment, the adaptive modifications to the DRME would remain a constant endeavor to secure the frontal segment anchorage against the buccal distalization and vice versa. TREATMENT PROGRESS
The treatment began with the placement of the DRME. The device consisted of 3 expansion screws and 4 separate acrylic bases. The transverse expansion screw was used to expand the maxillary arch, and 2 sagittal expansion screws distalized the maxillary first molars. The first and second premolars were covered with a casting splint (Fig 5). The activation protocol for the 3 expansion screws was 1 turn every other day. After 3 months, interproximal spaces of 3 mm on both sides were obtained between the second premolars and the first molars (Fig 6). Preadjusted 0.022-in brackets (Shinye, Hangzhou, China) were bonded to the maxillary anterior teeth, and a 0.012-in nickel-titanium wire was engaged for prompt alignment of the maxillary front
teeth. Seven months into the treatment, 5 mm of expansion and 4 mm of distalization were obtained (Fig 7). At the same time, the maxillary anterior teeth were also aligned, the midline deviation was corrected, and a Class I molar relationship on both sides was achieved. The DRME was modified 7 months after the active treatment followed by 2 months of retention (Fig 8, A). The DRME was debonded and sent to the laboratory for reconstruction: the casting crowns covering the second premolars were removed so that we could proceed with distalization of the second premolars. The separate acrylic bases for the molars were fused together. The modified DRME was rebonded to the maxilla and served as a strong anchorage similar to a Nance appliance. At the same time, the second premolars were distalized, and brackets were bonded in the mandibular arch. When the second premolars were distalized to touch the first molars, the DRME was debonded again for a second modification, which was conducted by removing the anterior part of the DRME, so that it worked as a transpalatal arch to consolidate the distalized first molars (Fig 8, B). Sixteen months after the start of treatment, overjet increased. This might have been partly because of the unavoidable partial loss of anchorage in the frontal segment against the buccal distalization, and partly because of the eruptions of the maxillary second molars that pushed the anterior teeth forward. To retract the maxillary front teeth backward, 2 MIAs (1.6 3 11 mm; Cibei, Ningbo, China) were placed between the maxillary second premolar and first molar to enhance the retraction (Fig 9). Hawley retainers were prescribed upon completion of active treatment. TREATMENT RESULTS
Severe crowding that resulted from the correction of the lingually positioned maxillary right lateral incisor (Fig 10) was relieved. The dental midline deviation was corrected to become consistent with the facial midline. The posterior occlusal interdigitation was improved, and Class I canine and molar relationships on both sides were also achieved. Ideal overbite and overjet relationships were restored (Fig 11). The cephalometric analysis and superimposition are shown in Figures 12 and 13 and the Table. The overall superimposition indicated that the patient's Class II skeletal base changed to Class I. The regional superimpositions demonstrated that in the maxilla, the incisors were proclined about 3 , and the maxillary molars were distalized 4 mm on both sides; in the mandible, the incisors were proclined about 7 , and the molars remained unchanged. Model analysis showed that the
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Fig 4. Cone-beam computed tomography image identifying the position of the maxillary right lateral incisor and its proximity to adjacent teeth.
Fig 5. The specially designed DRME featuring the diversified transverse expansion and the sagittal distalizing mechanism.
intercanine, interpremolar, and intermolar widths increased by 1.2, 2.4, and 2.7 mm, respectively. The maxillary dental length, which was measured as a linear distance between the central incisors and the second molars, increased by 4.3 mm. The patient's facial esthetics were also improved. DISCUSSION
Distalization of the maxillary molars is often attempted in the correction of a Class II malocclusion. It has been demonstrated clearly that for molar distalization, intraoral appliances are more effective and acceptable than extraoral devices because they do not have an unesthetic
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appearance10 or undesirable intermittent forces, and they do not depend on patient cooperation.11 In addition, palatal-acting appliances consistently show less tipping for all teeth than do buccal-acting appliances.12-14 A possible reason for this is that the moment arm of the force produced by palatally acting appliances is smaller because its line of action is closer to the center of resistance of the specific tooth.15 In this case, the specially designed DRME is a palatalacting appliance that facilitated displacement of the maxillary teeth in 3 dimensions. In the transverse plane, the width of the maxilla was enlarged through the rapid maxillary expansion mechanism. The spaces created by maxillary expansion were mainly used to align the anterior teeth, especially the maxillary right lateral incisor, which required considerable space to be labialized. In the transverse plane, rotation of the maxillary first molars and premolars did not occur, a favorable phenomenon possibly attributed to the expanding force coupled with the distalizing one against the concerned buccal teeth. In the vertical plane, a previous study showed that vertical movements were also present, and extrusions of the incisors and premolars were observed with noncompliance intramaxillary appliances.15 However, in this patient, extrusion of the incisors, premolars, and first molars was not evident. This might have been due to the overall coverage of the casting frame to the dentition that might have prevented any vertical movement of individual teeth. The timing of the molar
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Fig 6. Three months into treatment: effective expansion and distalized molars.
Fig 7. Seven months into treatment: further transverse expansion and molar distalization.
Fig 8. The adaptive reconstructions of the DRME: A, the casting coverages to the second premolars were removed, and the posterior parts of the acrylic bases were fused to distalize the second premolars; B, the anterior part of the DRME was removed, and the posterior one remained to retract the maxillary labial segment.
distalization in this patient could also have been a factor. According to Kinzinger et al,16 the side effects—eg, tipping and extrusion—can be prevented or minimized in molar distalization with a favorable developmental status of the second molars, if their root formations are far from total completion. In the sagittal plane, it has been reported that noncompliance intramaxillary molar distalization appliances produce distal molar movement, which is a combination of distal crown movement and tipping, with a concomitant and unavoidable loss of anchorage.15 Anchorage loss is observed through premolar mesial movement and incisor mesial crown and tipping movements. The pendulum appliance is one of the most
popular palatal appliances. Although distal movement of the molars takes place remarkably, an adverse reaction of mesialization of the premolars of 1 to 2.5 mm and labial tipping of maxillary the incisors of 1.7 to 3.3 can occur.4,16-21 Therefore, on average, 55% to 80% of the space obtained comes from distalization of the molars and 20% to 45% from mesialization of the premolars and labial tipping of the incisors. In this patient, the anchorage against molar distalization was increased as a result of the unique design of the DRME, where the casting coverage of all premolars and the acrylic base on an increased area of the palate secured the anchorage rigidly. The anchorage control was further indicated by cast measurement, which
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Fig 9. MIAs were placed to enhance the anchorage for retraction of the maxillary labial segment.
Fig 10. Posttreatment extraoral and intraoral photographs showing an improved facial appearance, and correction of the malpositioned maxillary right lateral incisor and the Class II molar relationship.
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Fig 11. Posttreatment study casts.
Fig 12. Posttreatment cephalogram and panoramic radiograph.
showed distal movement of the molars of 4 mm and distal tipping of 1.7 , and mesial movement of the premolars of 0.4 mm and mesial tipping of 0.1 . Using the Nance appliance, Antonarakis and Kiliaridis15 reported molar distalization of 3.1 mm with 3.6 of distal tipping, and premolar mesialization of 1.3 mm with 0.1 of mesial tipping. The maxillary incisors, on the other hand, demonstrated 3.6 of labial tipping and 1.1 mm of labial movement, indicating a certain degree of
anchorage loss in the labial segment. The proclination of the maxillary incisors to some extent in this patient, however, was favorable because it allowed not only for the labial segment alignment, but also for the correction of the originally retroclined maxillary incisors. Undeniably, anchorage loss in this patient on the maxillary anterior teeth occurred during distalization of the maxillary first molars because the DRME was a tooth-and-tissue–supported appliance rather than a bone-supported
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Fig 13. Posttreatment cephalometric superimpositions. The overall superimposition shows a skeletal base change from Class II to Class I; the regional superimpositions show appropriate proclinations of the maxillary and mandibular segments and correction of the molar relationship.
one. Several types of MIAs have been used in the palate in conjunction with molar distalizing devices to provide better anchorage, thus presumably reducing the undesired side effects to the anterior dentition in the maxillary arch.22-24 In this case, MIAs were placed at the later stage in the posterior buccal alveolar bone as reinforcement of anchorage against the retraction of the maxillary labial segment. Upon the successful molar distalization and creation of spaces, it always remains a difficult and critical task to distalize the premolars and then to retract the maxillary labial segment without a substantial loss of anchorage burdened on the already distalized molars. One common clinical observation is that some posterior anchorage loss is visible when retraction of the anterior teeth is carried out in the second phase of treatment. In our patient, the constant design modifications and laboratory reconstructions of the DRME were implemented to reinforce the anchorage sustainability from the distalized molars. The first modification, where the casting coverage to the second premolars was removed and the posterior parts of the separated acrylic bases were merged (Fig 8, A), aimed to better distalize the premolars at no cost of anchorage
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loss in the first molars. The second modification, on the other hand, where the whole anterior part of the DRME was removed and the posterior part remained as a rigid transpalatal arch (Fig 8, B), was designed to better retract the maxillary labial segment without sacrificing the anchorage in the buccal segment. The phasic modifications and reconstructions of the DRME in this study may become a new protocol for stabilization of the already distalized molars and therefore secure the efficiency of the premolar distalization and the subsequent retraction of the maxillary front teeth. To treat this patient without extractions, a significant amount of maxillary molar distalization was critical. The timing of the molar displacement, as mentioned earlier, might have played a role. A favorable time to move molars distally appears to be in the mixed dentition before the eruption of the second molars.25 Kinzinger et al16 suggested that the best time to start therapy with a pendulum appliance is before the eruption of the second molars in young patients. They also suggested that if distalization of the first and second molars is considered, enucleation of the third molar tooth buds should be conducted simultaneously. Karlsson and
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Bondemark9 found that intraoral movement of the maxillary first molars before eruption of the maxillary second molars results in more effective molar movement and less anchorage loss than after eruption of the second molars. In this patient, a careful inspection of the panoramic radiograph showed the developmental status of the second molars with full crowns and the initial formation of the roots (Fig 3), suggesting good timing for molar distalization. CONCLUSIONS
A specially designed intraoral orthopedic appliance, the DRME, featuring transverse expansion and sagittal distalization mechanisms, was used to treat a growing patient diagnosed with a skeletal Class II base with severe crowding. The concomitant and diversified orthopedic forces contributed to creating spaces for relief of crowding in the labial segment and to achieving a Class I molar relationship in the buccal segment. The adaptive reconstructions of the DRME during different stages of the treatment strengthened the anchorage of the distalized molars to support the retraction of the premolars and the labial segment. ACKNOWLEDGMENT
We thank Dental Laboratory Ichban, Shanghai, China, for fabrication and reconstructions of the orthopedic appliance. REFERENCES 1. Clemmer EJ, Hayes EW. Patient cooperation in wearing orthodontic headgear. Am J Orthod 1979;75:517-24. 2. Bondemark L, Kurol J. Distalization of maxillary first and second molars simultaneously with repelling magnets. Eur J Orthod 1992;14:264-72. 3. Gianelly AA, Bednar J, Dietz VS. Japanese NiTi coils used to move molars distally. Am J Orthod Dentofacial Orthop 1991; 99:564-6. 4. Bussick TJ, McNamara JA Jr. Dentoalveolar and skeletal changes associated with the pendulum appliance. Am J Orthod Dentofacial Orthop 2000;117:333-43. 5. Chaques-Asensi J, Kalra V. Effects of the pendulum appliance on the dentofacial complex. J Clin Orthod 2001;35:254-7. 6. Brickman CD, Sinha PK, Nanda RS. Evaluation of the Jones jig appliance for distal molar movement. Am J Orthod Dentofacial Orthop 2000;118:526-34.
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7. Carano A, Testa M. The distal jet for upper molar distalization. J Clin Orthod 1996;30:374-80. 8. Puente M. Class II correction with an edgewise-modified Nance appliance. J Clin Orthod 1997;31:178-82. 9. Karlsson I, Bondemark L. Intraoral maxillary molar distalization. Angle Orthod 2006;76:923-9. 10. Bondemark L, Karlsson I. Extraoral vs intraoral appliance for distal movement of maxillary first molars: a randomized controlled trial. Angle Orthod 2005;75:699-706. 11. McLaughlin RP, Bennett JC. Anchorage control during leveling and aligning with a preadjusted appliance system. J Clin Orthod 1991;25:687-96. 12. Sayinsu K, Isik F, Allaf F, Arun T. Unilateral molar distalization with a modified slider. Eur J Orthod 2006;28:361-5. 13. Ferguson DJ, Carano A, Bowman SJ, Davis EC, Gutierrez Vega ME, Lee SH. A comparison of two maxillary molar distalizing appliances with the distal jet. World J Orthod 2005;6:382-90. 14. Bondemark L. A comparative analysis of distal maxillary molar movement produced by a new lingual intra-arch Ni-Ti coil appliance and a magnetic appliance. Eur J Orthod 2000;22:683-95. 15. Antonarakis GS, Kiliaridis S. Maxillary molar distalization with noncompliance intramaxillary appliances in Class II malocclusion. A systematic review. Angle Orthod 2008;78:1133-40. 16. Kinzinger GS, Fritz UB, Sander FG, Diedrich PR. Efficiency of a pendulum appliance for molar distalization related to second and third molar eruption stage. Am J Orthod Dentofacial Orthop 2004;125:8-23. 17. Ghosh J, Nanda RS. Evaluation of an intraoral maxillary molar distalization technique. Am J Orthod Dentofacial Orthop 1996;110: 639-46. 18. Byloff FK, Darendeliler MA. Distal molar movement using the pendulum appliance. Part 1: clinical and radiological evaluation. Angle Orthod 1997;67:249-60. 19. Byloff FK, Darendeliler MA, Clar E, Darendeliler A. Distal molar movement using the pendulum appliance. Part 2: the effects of maxillary molar root uprighting bends. Angle Orthod 1997;67: 261-70. 20. Chiu PP, McNamara JA Jr, Franchi L. A comparison of two intraoral molar distalization appliances: distal jet versus pendulum. Am J Orthod Dentofacial Orthop 2005;128:353-65. 21. Kinzinger GS, Wehrbein H, Diedrich PR. Molar distalization with a modified pendulum appliance—in vitro analysis of the force systems and in vivo study in children and adolescents. Angle Orthod 2005;75:558-67. 22. Karcher H, Byloff FK, Clar E. The Graz implant supported pendulum, a technical note. J Craniomaxillofac Surg 2002;30:87-90. 23. Gelgor IE, Buyukyilmaz T, Karaman AI, Dolanmaz D, Kalayci A. Intraosseous screw-supported upper molar distalization. Angle Orthod 2004;74:838-50. 24. Kircelli BH, Pektas ZO, Kircelli C. Maxillary molar distalization with a bone-anchored pendulum appliance. Angle Orthod 2006;76: 650-9. 25. Gianelly AA. Distal movement of the maxillary molars. Am J Orthod Dentofacial Orthop 1998;114:66-72.
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Correction of a skeletal Class II malocclusion with severe crowding by a specially designed rapid maxillary expander Honghong Wang,a Jing Feng,b Peijun Lu,a and Gang Shenc Shanghai, China
To correct an Angle Class II malocclusion or to create spaces in the maxillary arch by nonextraction treatment, distal movement of the maxillary molars is required. Various modalities for distalizing the buccal segment have been reported. Conventional extraoral appliances can be used to obtain maximum anchorage. However, many patients reject headgear wear because of social and esthetic concerns, and the success of this treatment depends on patient compliance. Intraoral appliances, such as repelling magnets, nickel-titanium coils, pendulum appliance, Jones jig appliance, distal jet appliance, and modified Nance appliance, have been introduced to distalize the molars with little or no patient cooperation. However, intraoral appliances can result in anchorage loss of the anterior teeth and distal tipping of the maxillary molars. In this case report, we introduce a diversified rapid maxillary expansion appliance that was custom designed and fabricated for the treatment of a growing girl with a skeletal Class II malocclusion and severe crowding from a totally lingually positioned lateral incisor. The appliance concomitantly expanded the maxilla transversely and retracted the buccal segment sagittally, distalizing the maxillary molars to reach a Class I relationship and creating the spaces to displace the malpositioned lateral incisor. The uniqueness of this special diversified rapid maxillary expansion appliance was highlighted by a series of reconstructions and modifications at different stages of the treatment to reinforce the anchorage. (Am J Orthod Dentofacial Orthop 2015;147:242-51)
T
o correct an Angle Class II malocclusion or to create spaces in the maxillary arch by nonextraction treatment, distalization of the maxillary molars is an alternative treatment approach. Various modalities in distalizing the buccal segment have been reported. Conventional extraoral appliances can be used to obtain maximum anchorage. However, many patients reject headgear wear because of social and esthetic concerns, and the success of this treatment depends on patient compliance.1 Beginning in the 1980s, intraoral appliances, such as repelling magnets,2
From the Department of Orthodontics, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University, Shanghai, China. a Postgraduate student. b Assistant professor. c Chair. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. Financial support from the National Natural Science Foundation of China, grant no. 81271182. Address correspondence to: Gang Shen, Department of Orthodontics, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University, Shanghai, China; e-mail, [email protected]. Submitted, November 2013; revised and accepted, December 2013. 0889-5406/$36.00 Copyright Ó 2015 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2013.12.032
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nickel-titanium coils,3 the pendulum appliance,4,5 the Jones jig appliance,6 the distal jet appliance,7 and the modified Nance appliance,8 have been introduced to distalize molars with little or no patient cooperation. However, intraoral appliances can result in anchorage loss of the anterior teeth and distal tipping of the maxillary molars.9 In this case report, we introduce a diversified rapid maxillary expander appliance (DRME) that was custom designed and fabricated for the treatment of a girl with a skeletal Class II malocclusion and severe crowding from a totally lingually positioned lateral incisor. The appliance concomitantly expanded the maxilla transversely and retruded the buccal segment sagittally, distalizing the maxillary molars to reach a Class I relationship and creating the spaces to align the remaining maxillary dentition. The uniqueness of this special DRME was highlighted by a series of reconstructions and modifications at different stages of the therapy to reinforce the anchorage. DIAGNOSIS AND ETIOLOGY
The patient was an 11-year-old Chinese girl with a chief complaint of crooked teeth. The initial clinical
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Fig 1. Pretreatment extraoral and intraoral photographs showing an acceptable facial appearance, a Class II molar relationship, and a lingually positioned maxillary right lateral incisor.
examination showed a slightly retrusive mandible with an obtuse nasolabial angle and an increased labiomental fold (Fig 1). The intraoral examination and study casts exhibited half-step Class II molar relationships on both sides. The maxillary right lateral incisor was completely palatally positioned (Fig 2). The maxillary midline was 4.0 mm off to the right of the facial midline, and the mandibular midline was symmetrically correct. Crowding in the maxilla was severe as a result of an ectopically placed right lateral incisor, whereas crowding in the mandible was mild. The maxilla was constricted, and a crossbite relationship was also noted in the left premolar area. Study cast analysis showed an overbite of 3.0 mm and an overjet of 2.5 mm. The lateral cephalometric analysis showed a Class II skeletal base (ANB, 5.7 ) with a protrusive maxilla (SNA, 86.5 ), and an average mandibular plane angle (FMA, 32.8 ) (Fig 3, Table). The U1-SN angle of 103.7 indicated a retroclined tendency of the maxillary incisors
that might have caused an obtuse nasolabial angle. An inspection of skeletal maturation by the cervical vertebrae suggested considerable growth potential. The panoramic radiograph showed that both maxillary second molars were under development, and the tooth buds of the maxillary third molars did not exist. Furthermore, no pathologic lesions, unusual root formations, or deformities of the maxillary right central or lateral incisors were identified with cone-beam computed tomography (Fig 4). TREATMENT OBJECTIVES
The treatment objectives for this patient were to (1) relieve crowding by bringing the palatally positioned lateral incisor into alignment, (2) correct the skeletal Class II, (3) restore a satisfactory occlusion with Class I molar and canine relationships, (4) correct the shifted midline, (5) create ideal overbite and overjet, and (6) improve the facial esthetics.
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Fig 2. Pretreatment study casts depicting the severity of crowding resulting from the malpositioned maxillary right lateral incisor.
Fig 3. Pretreatment cephalogram and panoramic radiograph.
TREATMENT ALTERNATIVES
This preteen patient had adequate growth potential, with an acceptable profile but with a retroclined maxillary anterior dentition. A maxillary lateral incisor was palatally positioned, but there were no signs of defects in the overlapping areas between the adjacent dentition (Fig 4). Furthermore, the maxillary second molars were
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not erupted, indicating that the timing for molar distalization might be an acceptable treatment modality. A nonextraction treatment plan was therefore proposed. The first step was orthopedic treatment with a specially designed DRME (Fig 5). This appliance was designed to expand the maxillary arch and distalize the maxillary molars simultaneously to create spaces for crowding
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Table. Cephalometric data SNA ( ) SNB ( ) SN-MP ( ) FMA ( ) ANB ( ) U1-NA (mm) U1-SN ( ) L1-NB (mm) IMPA ( ) Lower lip to E-plane (mm) Upper lip to E-plane (mm)
Norm Pretreatment Posttreatment Change 82.0 6 3.5 86.5 84.3 2.2 77.7 6 3.2 80.8 81.5 0.7 32.9 6 5.2 31.7 32.7 1.0 29.2 6 4.5 32.8 29.8 3.0 4.0 6 1.8 5.7 2.8 2.9 4.3 6 2.7 2.6 6.3 3.7 103.4 6 5.5 103.7 107.3 3.6 4.0 6 1.8 5.3 8.0 2.7 95.0 6 7.0 94.1 101.3 7.2 2.0 6 2.0 0.4 1.1 0.7 1.3 6 2.0
0.4
0.2
0.6
relief and restoration of the molar relationship. The second step was orthodontic treatment with fixed appliances to improve the buccal interdigitation and establish a proper incisal relationship. Microimplant anchorage devices (MIAs) could be applied in the maxilla to retract the frontal segment because the frontal anchorage might be partially lost as a result of buccal segmental distalization. In the maxillary arch, by moving the buccal dentition posteriorly, the maxillary left quadrant was to be distalized for midline correction, and crowding of the right quadrant was to be relieved. In the mandibular arch, mild crowding was to be relieved by expansion with broad archwires, whereas the sagittal position of the anterior teeth would remain to prevent further deepening of the labiomental fold. Over the whole course of orthopedic treatment, the adaptive modifications to the DRME would remain a constant endeavor to secure the frontal segment anchorage against the buccal distalization and vice versa. TREATMENT PROGRESS
The treatment began with the placement of the DRME. The device consisted of 3 expansion screws and 4 separate acrylic bases. The transverse expansion screw was used to expand the maxillary arch, and 2 sagittal expansion screws distalized the maxillary first molars. The first and second premolars were covered with a casting splint (Fig 5). The activation protocol for the 3 expansion screws was 1 turn every other day. After 3 months, interproximal spaces of 3 mm on both sides were obtained between the second premolars and the first molars (Fig 6). Preadjusted 0.022-in brackets (Shinye, Hangzhou, China) were bonded to the maxillary anterior teeth, and a 0.012-in nickel-titanium wire was engaged for prompt alignment of the maxillary front
teeth. Seven months into the treatment, 5 mm of expansion and 4 mm of distalization were obtained (Fig 7). At the same time, the maxillary anterior teeth were also aligned, the midline deviation was corrected, and a Class I molar relationship on both sides was achieved. The DRME was modified 7 months after the active treatment followed by 2 months of retention (Fig 8, A). The DRME was debonded and sent to the laboratory for reconstruction: the casting crowns covering the second premolars were removed so that we could proceed with distalization of the second premolars. The separate acrylic bases for the molars were fused together. The modified DRME was rebonded to the maxilla and served as a strong anchorage similar to a Nance appliance. At the same time, the second premolars were distalized, and brackets were bonded in the mandibular arch. When the second premolars were distalized to touch the first molars, the DRME was debonded again for a second modification, which was conducted by removing the anterior part of the DRME, so that it worked as a transpalatal arch to consolidate the distalized first molars (Fig 8, B). Sixteen months after the start of treatment, overjet increased. This might have been partly because of the unavoidable partial loss of anchorage in the frontal segment against the buccal distalization, and partly because of the eruptions of the maxillary second molars that pushed the anterior teeth forward. To retract the maxillary front teeth backward, 2 MIAs (1.6 3 11 mm; Cibei, Ningbo, China) were placed between the maxillary second premolar and first molar to enhance the retraction (Fig 9). Hawley retainers were prescribed upon completion of active treatment. TREATMENT RESULTS
Severe crowding that resulted from the correction of the lingually positioned maxillary right lateral incisor (Fig 10) was relieved. The dental midline deviation was corrected to become consistent with the facial midline. The posterior occlusal interdigitation was improved, and Class I canine and molar relationships on both sides were also achieved. Ideal overbite and overjet relationships were restored (Fig 11). The cephalometric analysis and superimposition are shown in Figures 12 and 13 and the Table. The overall superimposition indicated that the patient's Class II skeletal base changed to Class I. The regional superimpositions demonstrated that in the maxilla, the incisors were proclined about 3 , and the maxillary molars were distalized 4 mm on both sides; in the mandible, the incisors were proclined about 7 , and the molars remained unchanged. Model analysis showed that the
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Fig 4. Cone-beam computed tomography image identifying the position of the maxillary right lateral incisor and its proximity to adjacent teeth.
Fig 5. The specially designed DRME featuring the diversified transverse expansion and the sagittal distalizing mechanism.
intercanine, interpremolar, and intermolar widths increased by 1.2, 2.4, and 2.7 mm, respectively. The maxillary dental length, which was measured as a linear distance between the central incisors and the second molars, increased by 4.3 mm. The patient's facial esthetics were also improved. DISCUSSION
Distalization of the maxillary molars is often attempted in the correction of a Class II malocclusion. It has been demonstrated clearly that for molar distalization, intraoral appliances are more effective and acceptable than extraoral devices because they do not have an unesthetic
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appearance10 or undesirable intermittent forces, and they do not depend on patient cooperation.11 In addition, palatal-acting appliances consistently show less tipping for all teeth than do buccal-acting appliances.12-14 A possible reason for this is that the moment arm of the force produced by palatally acting appliances is smaller because its line of action is closer to the center of resistance of the specific tooth.15 In this case, the specially designed DRME is a palatalacting appliance that facilitated displacement of the maxillary teeth in 3 dimensions. In the transverse plane, the width of the maxilla was enlarged through the rapid maxillary expansion mechanism. The spaces created by maxillary expansion were mainly used to align the anterior teeth, especially the maxillary right lateral incisor, which required considerable space to be labialized. In the transverse plane, rotation of the maxillary first molars and premolars did not occur, a favorable phenomenon possibly attributed to the expanding force coupled with the distalizing one against the concerned buccal teeth. In the vertical plane, a previous study showed that vertical movements were also present, and extrusions of the incisors and premolars were observed with noncompliance intramaxillary appliances.15 However, in this patient, extrusion of the incisors, premolars, and first molars was not evident. This might have been due to the overall coverage of the casting frame to the dentition that might have prevented any vertical movement of individual teeth. The timing of the molar
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Fig 6. Three months into treatment: effective expansion and distalized molars.
Fig 7. Seven months into treatment: further transverse expansion and molar distalization.
Fig 8. The adaptive reconstructions of the DRME: A, the casting coverages to the second premolars were removed, and the posterior parts of the acrylic bases were fused to distalize the second premolars; B, the anterior part of the DRME was removed, and the posterior one remained to retract the maxillary labial segment.
distalization in this patient could also have been a factor. According to Kinzinger et al,16 the side effects—eg, tipping and extrusion—can be prevented or minimized in molar distalization with a favorable developmental status of the second molars, if their root formations are far from total completion. In the sagittal plane, it has been reported that noncompliance intramaxillary molar distalization appliances produce distal molar movement, which is a combination of distal crown movement and tipping, with a concomitant and unavoidable loss of anchorage.15 Anchorage loss is observed through premolar mesial movement and incisor mesial crown and tipping movements. The pendulum appliance is one of the most
popular palatal appliances. Although distal movement of the molars takes place remarkably, an adverse reaction of mesialization of the premolars of 1 to 2.5 mm and labial tipping of maxillary the incisors of 1.7 to 3.3 can occur.4,16-21 Therefore, on average, 55% to 80% of the space obtained comes from distalization of the molars and 20% to 45% from mesialization of the premolars and labial tipping of the incisors. In this patient, the anchorage against molar distalization was increased as a result of the unique design of the DRME, where the casting coverage of all premolars and the acrylic base on an increased area of the palate secured the anchorage rigidly. The anchorage control was further indicated by cast measurement, which
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Fig 9. MIAs were placed to enhance the anchorage for retraction of the maxillary labial segment.
Fig 10. Posttreatment extraoral and intraoral photographs showing an improved facial appearance, and correction of the malpositioned maxillary right lateral incisor and the Class II molar relationship.
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Fig 11. Posttreatment study casts.
Fig 12. Posttreatment cephalogram and panoramic radiograph.
showed distal movement of the molars of 4 mm and distal tipping of 1.7 , and mesial movement of the premolars of 0.4 mm and mesial tipping of 0.1 . Using the Nance appliance, Antonarakis and Kiliaridis15 reported molar distalization of 3.1 mm with 3.6 of distal tipping, and premolar mesialization of 1.3 mm with 0.1 of mesial tipping. The maxillary incisors, on the other hand, demonstrated 3.6 of labial tipping and 1.1 mm of labial movement, indicating a certain degree of
anchorage loss in the labial segment. The proclination of the maxillary incisors to some extent in this patient, however, was favorable because it allowed not only for the labial segment alignment, but also for the correction of the originally retroclined maxillary incisors. Undeniably, anchorage loss in this patient on the maxillary anterior teeth occurred during distalization of the maxillary first molars because the DRME was a tooth-and-tissue–supported appliance rather than a bone-supported
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Fig 13. Posttreatment cephalometric superimpositions. The overall superimposition shows a skeletal base change from Class II to Class I; the regional superimpositions show appropriate proclinations of the maxillary and mandibular segments and correction of the molar relationship.
one. Several types of MIAs have been used in the palate in conjunction with molar distalizing devices to provide better anchorage, thus presumably reducing the undesired side effects to the anterior dentition in the maxillary arch.22-24 In this case, MIAs were placed at the later stage in the posterior buccal alveolar bone as reinforcement of anchorage against the retraction of the maxillary labial segment. Upon the successful molar distalization and creation of spaces, it always remains a difficult and critical task to distalize the premolars and then to retract the maxillary labial segment without a substantial loss of anchorage burdened on the already distalized molars. One common clinical observation is that some posterior anchorage loss is visible when retraction of the anterior teeth is carried out in the second phase of treatment. In our patient, the constant design modifications and laboratory reconstructions of the DRME were implemented to reinforce the anchorage sustainability from the distalized molars. The first modification, where the casting coverage to the second premolars was removed and the posterior parts of the separated acrylic bases were merged (Fig 8, A), aimed to better distalize the premolars at no cost of anchorage
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loss in the first molars. The second modification, on the other hand, where the whole anterior part of the DRME was removed and the posterior part remained as a rigid transpalatal arch (Fig 8, B), was designed to better retract the maxillary labial segment without sacrificing the anchorage in the buccal segment. The phasic modifications and reconstructions of the DRME in this study may become a new protocol for stabilization of the already distalized molars and therefore secure the efficiency of the premolar distalization and the subsequent retraction of the maxillary front teeth. To treat this patient without extractions, a significant amount of maxillary molar distalization was critical. The timing of the molar displacement, as mentioned earlier, might have played a role. A favorable time to move molars distally appears to be in the mixed dentition before the eruption of the second molars.25 Kinzinger et al16 suggested that the best time to start therapy with a pendulum appliance is before the eruption of the second molars in young patients. They also suggested that if distalization of the first and second molars is considered, enucleation of the third molar tooth buds should be conducted simultaneously. Karlsson and
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Bondemark9 found that intraoral movement of the maxillary first molars before eruption of the maxillary second molars results in more effective molar movement and less anchorage loss than after eruption of the second molars. In this patient, a careful inspection of the panoramic radiograph showed the developmental status of the second molars with full crowns and the initial formation of the roots (Fig 3), suggesting good timing for molar distalization. CONCLUSIONS
A specially designed intraoral orthopedic appliance, the DRME, featuring transverse expansion and sagittal distalization mechanisms, was used to treat a growing patient diagnosed with a skeletal Class II base with severe crowding. The concomitant and diversified orthopedic forces contributed to creating spaces for relief of crowding in the labial segment and to achieving a Class I molar relationship in the buccal segment. The adaptive reconstructions of the DRME during different stages of the treatment strengthened the anchorage of the distalized molars to support the retraction of the premolars and the labial segment. ACKNOWLEDGMENT
We thank Dental Laboratory Ichban, Shanghai, China, for fabrication and reconstructions of the orthopedic appliance. REFERENCES 1. Clemmer EJ, Hayes EW. Patient cooperation in wearing orthodontic headgear. Am J Orthod 1979;75:517-24. 2. Bondemark L, Kurol J. Distalization of maxillary first and second molars simultaneously with repelling magnets. Eur J Orthod 1992;14:264-72. 3. Gianelly AA, Bednar J, Dietz VS. Japanese NiTi coils used to move molars distally. Am J Orthod Dentofacial Orthop 1991; 99:564-6. 4. Bussick TJ, McNamara JA Jr. Dentoalveolar and skeletal changes associated with the pendulum appliance. Am J Orthod Dentofacial Orthop 2000;117:333-43. 5. Chaques-Asensi J, Kalra V. Effects of the pendulum appliance on the dentofacial complex. J Clin Orthod 2001;35:254-7. 6. Brickman CD, Sinha PK, Nanda RS. Evaluation of the Jones jig appliance for distal molar movement. Am J Orthod Dentofacial Orthop 2000;118:526-34.
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7. Carano A, Testa M. The distal jet for upper molar distalization. J Clin Orthod 1996;30:374-80. 8. Puente M. Class II correction with an edgewise-modified Nance appliance. J Clin Orthod 1997;31:178-82. 9. Karlsson I, Bondemark L. Intraoral maxillary molar distalization. Angle Orthod 2006;76:923-9. 10. Bondemark L, Karlsson I. Extraoral vs intraoral appliance for distal movement of maxillary first molars: a randomized controlled trial. Angle Orthod 2005;75:699-706. 11. McLaughlin RP, Bennett JC. Anchorage control during leveling and aligning with a preadjusted appliance system. J Clin Orthod 1991;25:687-96. 12. Sayinsu K, Isik F, Allaf F, Arun T. Unilateral molar distalization with a modified slider. Eur J Orthod 2006;28:361-5. 13. Ferguson DJ, Carano A, Bowman SJ, Davis EC, Gutierrez Vega ME, Lee SH. A comparison of two maxillary molar distalizing appliances with the distal jet. World J Orthod 2005;6:382-90. 14. Bondemark L. A comparative analysis of distal maxillary molar movement produced by a new lingual intra-arch Ni-Ti coil appliance and a magnetic appliance. Eur J Orthod 2000;22:683-95. 15. Antonarakis GS, Kiliaridis S. Maxillary molar distalization with noncompliance intramaxillary appliances in Class II malocclusion. A systematic review. Angle Orthod 2008;78:1133-40. 16. Kinzinger GS, Fritz UB, Sander FG, Diedrich PR. Efficiency of a pendulum appliance for molar distalization related to second and third molar eruption stage. Am J Orthod Dentofacial Orthop 2004;125:8-23. 17. Ghosh J, Nanda RS. Evaluation of an intraoral maxillary molar distalization technique. Am J Orthod Dentofacial Orthop 1996;110: 639-46. 18. Byloff FK, Darendeliler MA. Distal molar movement using the pendulum appliance. Part 1: clinical and radiological evaluation. Angle Orthod 1997;67:249-60. 19. Byloff FK, Darendeliler MA, Clar E, Darendeliler A. Distal molar movement using the pendulum appliance. Part 2: the effects of maxillary molar root uprighting bends. Angle Orthod 1997;67: 261-70. 20. Chiu PP, McNamara JA Jr, Franchi L. A comparison of two intraoral molar distalization appliances: distal jet versus pendulum. Am J Orthod Dentofacial Orthop 2005;128:353-65. 21. Kinzinger GS, Wehrbein H, Diedrich PR. Molar distalization with a modified pendulum appliance—in vitro analysis of the force systems and in vivo study in children and adolescents. Angle Orthod 2005;75:558-67. 22. Karcher H, Byloff FK, Clar E. The Graz implant supported pendulum, a technical note. J Craniomaxillofac Surg 2002;30:87-90. 23. Gelgor IE, Buyukyilmaz T, Karaman AI, Dolanmaz D, Kalayci A. Intraosseous screw-supported upper molar distalization. Angle Orthod 2004;74:838-50. 24. Kircelli BH, Pektas ZO, Kircelli C. Maxillary molar distalization with a bone-anchored pendulum appliance. Angle Orthod 2006;76: 650-9. 25. Gianelly AA. Distal movement of the maxillary molars. Am J Orthod Dentofacial Orthop 1998;114:66-72.
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