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Treatment of unilateral posterior crossbite with facial asymmetry in a female patient with transverse discrepancy
CASE REPORT
Treatment of unilateral posterior crossbite with facial asymmetry in a female patient with transverse discrepancy Seok-Ki Junga and Tae-Woo Kimb Seoul, Korea
A unilateral posterior crossbite with facial asymmetry is difficult to correct with orthodontic treatment alone. This case report describes the orthodontic treatment and additional plasty without orthognathic surgery for a 19-yearold woman with a transverse discrepancy. The posterior crossbite was resolved by expansion of the narrow maxillary arch and space closure in the mandibular arch. This accelerated the correction of the functional shift of the mandible. After resolution of the unilateral posterior crossbite, the problems of the anteroposterior molar relationship were treated using orthodontic mini-implants. Mandibular angle reduction plasty was performed for the asymmetric mandibular border to improve the facial appearance. After treatment, the patient had a more symmetrical facial appearance, normal overjet and overbite, and midline coincidence. The treatment results remained stable 1 year after treatment. This case report demonstrates that a minimally invasive treatment can successfully correct a unilateral posterior crossbite with a transverse discrepancy. (Am J Orthod Dentofacial Orthop 2015;148:154-64)
G
enerally, when we establish the treatment plan for patients with facial asymmetry, surgery is included1 because facial asymmetry is usually caused by skeletal problems.2 Orthodontic treatment alone is a difficult choice in this situation.3 Patients with facial asymmetry and a skeletal Class III malocclusion must be treated by orthognathic surgery even if there is no facial asymmetry. However, more consideration is needed to treat patients with facial asymmetry and a skeletal Class I relationship. Because correction of the asymmetry is the only goal of the orthognathic surgery in this case, satisfaction with the treatment may be low after surgery. Moreover, patients with facial asymmetry and a transverse discrepancy can be treated with orthodontics alone.4 This case report describes the treatment of a woman with a unilateral posterior
a Postgraduate student, Department of Orthodontics, School of Dentistry, Dental Research Institute, Seoul National University; clinical instructor, Department of Orthodontics, Korea University Ansan Hospital, Seoul, Republic of Korea. b Professor, Department of Orthodontics, School of Dentistry, Dental Research Institute, Seoul National University, Seoul, Republic of Korea. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. Address correspondence to: Tae-Woo Kim, Department of Orthodontics, School of Dentistry, Dental Research Institute, Seoul National University, 101 Daehakro, Jongro-Gu, Seoul 110-749, Republic of Korea; e-mail, [email protected]. Submitted, June 2014; revised and accepted, September 2014. 0889-5406/$36.00 Copyright Ó 2015 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2014.09.023
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crossbite and facial asymmetry. She had a skeletal Class I relationship. Her chin and mandibular midline were deviated to the left side with a left posterior crossbite. Because there was a transverse discrepancy, a nonsurgical approach for the correction of the occlusion could be planned. Mandibular angle reduction plasty was planned for the asymmetrical mandibular inferior border. By avoiding orthognathic surgery, it was possible to minimize the patient's discomfort. DIAGNOSIS AND ETIOLOGY
The patient was a 19-year-old woman who visited Seoul National University Dental Hospital in South Korea for an orthodontic consultation. No specific medical problems or temporomandibular joint symptoms were observed. She had a skeletal Class I relationship and facial asymmetry, with the chin deviated 4.5 mm to the left. A slight maxillary deficiency and a normal vertical growth pattern were seen. A Class I molar relationship on the right and a Class II molar relationship on the left were observed, and a posterior crossbite from the left lateral incisor to the left second molar was observed (Fig 1). The mandibular dental midline was deviated 6.5 mm to the left. There was space between the mandibular anterior teeth (Fig 2). The cant of the occlusal plane was minor. In the lateral cephalometric analysis, no mouth protrusion or problems of anterior tooth inclination were found (Table I). The major
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Fig 1. Pretreatment facial and intraoral photographs.
problems were summarized as frontal asymmetry, deviation of the chin, left posterior crossbite, and mandibular dental midline deviation. Furthermore, the patient had a slight transverse centric occlusion–centric relation discrepancy. This functional shift of the mandible caused mandibular asymmetry, which could be observed in the panoramic and posteroanterior radiographs (Fig 3). In particular, the mandibular left inferior border was much bulkier than right inferior border. This difference in mass was the cause of the facial asymmetry. TREATMENT OBJECTIVES
The treatment objectives for the dentition were correction of the left posterior crossbite, making the maxillary and mandibular midlines coincident, and closing the mandibular arch space. The treatment objectives for the skeleton were improving the facial asymmetry, including
the deviation of the chin, and improving the transverse discrepancy. Thus, facial symmetry, normal overjet and overbite, and Class I canine-to-molar relationships could be obtained. TREATMENT ALTERNATIVES
Facial asymmetry and unilateral posterior crossbite are difficult to treat with orthodontics alone. Therefore, the first plan was orthodontic treatment accompanied by orthognathic surgery. Extraction of the 2 maxillary third molars was planned. Leveling of maxillary and mandibular arches and space closure of the mandibular arch were planned as the presurgical orthodontic treatment. After that, the asymmetries of the chin and mandible could be corrected with orthognathic surgery. Postsurgical orthodontic treatment would finish correction of the malocclusion.
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Fig 2. Pretreatment dental casts.
Table I. Comparison of cephalometric measurements ANB angle ( ) A to N perpendicular (mm) Pog to N perpendicular (mm) Bj€ ork sum ( ) FMA ( ) U1 to FH ( ) U1 to SN ( ) IMPA ( ) Interincisal angle ( ) Upper lip to E-line (mm) Lower lip to E-line (mm) Nasolabial angle ( )
Pretreatment 2.4 1.2 5.9 393.0 22.3 108.7 98.0 104.2 124.8 2.3 0.1 96.6
Posttreatment 2.4 1.2 5.5 401.4 30.7 108.4 97.7 88.3 132.6 4.9 1.8 93.4
This plan has the advantage of eliminating the patient's skeletal asymmetry, but at the cost of surgical risk and financial burden. The second plan was orthodontic treatment and additional plasty without orthognathic surgery. Expansion of a narrow maxillary arch can help to correct the transverse discrepancy by releasing the locking in the left posterior teeth. After that, maxillary left molar distalization and mandibular left molar mesialization were planned to correct the left molar relationship and the dental midline. Mandibular angle reduction plasty and genioplasty were planned for the bulky left inferior border of the mandible. This plan would minimize the burden of surgery while maximizing the reduction of asymmetry. The downside is that it is difficult to eliminate the asymmetry completely.
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The patient selected the second option because she did not want orthognathic surgery. TREATMENT PROGRESS
Metal self-ligating brackets (0.022-in slot, Damon Q; Ormco, Glendora, Calif) were used for this treatment. Initial leveling progressed with a 0.014-in nickeltitanium archwire. A lingual sheath was attached to the palatal side of the maxillary first molar, and an expansion transpalatal arch was inserted into the lingual sheath (Fig 4). Buccal root torque was given to the expansion transpalatal arch to decompensate the inclination of the maxillary left first molar (Fig 5). The relationship of the left posterior teeth was improved to an edge bite after 4 months of leveling and expansion of the maxillary arch. To resolve the minor cant of the maxillary left anterior teeth, a titanium orthodontic mini-implant (OMI; diameter, 1.6 mm; length, 6.0 mm; Jeil Medical, Seoul, South Korea) was inserted between the mandibular left premolars. Intermaxillary elastics were applied from the OMI to the maxillary left canine and premolars. After leveling of the mandibular arch, elastomeric modules were used to close the remaining space. After 7 months of treatment, the unilateral posterior crossbite was corrected (Fig 6). Expansion of the maxillary arch relieved the functional shift of the mandible (Fig 5, B). In addition, the reduced mandibular intermolar width helped reduce the functional shift (Table II). After resolution of the unilateral posterior crossbite, mandibular angle reduction plasty and genioplasty were done to improve the bulky left inferior border of the mandible. Despite
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Fig 3. Pretreatment lateral and frontal cephalograms and panoramic radiograph.
Fig 4. Intraoral photographs during initial alignment.
the improvement of the left posterior crossbite, a Class II molar relationship remained. Distalization of the maxillary left molars and mesialization of the mandibular left molars were planned to improve the molar
relationships and the mandibular dental midline. At first, a titanium OMI was inserted between the maxillary second premolar and the first molar. After ligation between the OMI and the second premolar, the molars were
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Fig 5. A, Pretreatment molar relationships; B, mechanics to resolve the crossbite.
Fig 6. Intraoral photographs after resolving the crossbite.
Table II. Comparison of intercanine and intermolar
widths Maxillary intercanine width (mm) Mandibular intercanine width (mm) Maxillary intermolar width (mm) Mandibular intermolar width (mm)
Pretreatment Posttreatment Retention 33.17 37.55 37.55 31.83
27.84
28.14
55.47
57.46
57.37
52.10
48.89
49.36
distalized during 3 months using open-coil springs between the second premolar and the first molar (Fig 7). After that, the OMI was moved between the maxillary first and
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second molars, and distalization of the remaining anterior teeth was performed. At the same time, an OMI was inserted between the mandibular left lateral incisor and the canine. The mandibular left molars were mesialized using elastomeric modules from the OMI. After 13 months, active treatment was finished, and all fixed orthodontic appliances were removed. Fixed lingual retainers were attached to both arches, and circumferential retainers were placed additionally. The instructions to the patient included full-time retainer use for 3 months and then nighttime use for 2 years at least. TREATMENT RESULTS
The final records (Figs 8-10) show that the unilateral posterior crossbite was resolved, and the dental midline
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Fig 7. Intraoral photographs during molar distalization.
was coincident. The space in the mandibular arch was closed, and the minor crowding of the maxillary arch was resolved. The skeletal facial asymmetry was partly resolved by the recovery of the mandibular functional shift. The mandibular angle reduction plasty and the genioplasty markedly improved the patient's frontal appearance. Distalization of the maxillary left posterior teeth was successful, and it contributed to the normal overjet and the Class I canine-to-molar relationship. The panoramic radiographs (Fig 10) show well-aligned parallel roots of the teeth, and there are no signs of root resorption. Comparison of measurements before and after treatment (Table I) shows the increment of the Frankfort-mandibular plane angle resulting from the mandibular angle reduction plasty. In addition, normalization of the inclination of the mandibular anterior teeth was accomplished by space closure. In the comparison of the dental casts before and after treatment (Table II), maxillary intercanine and intermolar widths increased by 4.4 and 2.0 mm, respectively. The mandibular intercanine and intermolar widths decreased by 4.0 and 3.2 mm, respectively. These changes were well maintained during the retention period. The superimposition of the frontal cephalometric radiographs showed expansion of the maxillary arch, constriction of the mandibular arch, and coincidence of dental midlines (Fig 11). A minor movement of the mandibular condyle was also observed while correcting the functional shift. The superimposition of the lateral cephalometric radiographs showed the results of the mandibular angle reduction plasty and the genioplasty, the distalization of the maxillary molars, and the mesialization of the
mandibular molars. The patient returned for reevaluation at 1 year after debonding (Figs 12 and 13). Her occlusion was well maintained. The occlusal relationships of the premolars and molars were improved by settling. The facial photographs showed a harmonious, acceptable, and symmetrical appearance. DISCUSSION
A compensated dentition is often found in patients with a unilateral posterior crossbite.5 In this case report, the buccal inclination of maxillary left molars and the lingual inclination of mandibular left molars were kept to compensate for the left posterior crossbite. If a simple unilateral expansion of the maxillary dentition and constriction of mandibular dentition had been done, the compensatory movement of dentition would have been intensified.6 This means that the buccal inclination of the maxillary left molars and the lingual inclination of the mandibular left molars would have been worse.7 These changes can cause adverse effects such as interference with lateral movements of the mandible by the opposite side. Therefore, the first choice of treatment for unilateral posterior crossbite is orthognathic surgery followed by decompensation of the inclination of the posterior teeth. However, in patients with a transverse discrepancy such as our patient, bodily movement of the mandible can be obtained partly by appropriate centric-relation guidance. Thereby, improvement of the occlusion can be obtained without orthognathic surgery or without worsening of the compensation. In this patient, habitual maximal intercuspation caused narrow maxillary posterior teeth and wide
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Fig 8. Posttreatment facial and intraoral photographs.
Fig 9. Posttreatment dental casts.
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Fig 10. Posttreatment lateral and frontal cephalograms and panoramic radiograph.
Fig 11. Superimposition of the lateral and frontal cephalograms at pretreatment (black) and posttreatment (red).
mandibular posterior teeth.8 To solve this problem, normalization of the width is needed before everything else.9 Locked posterior teeth can be resolved by expansion of the maxillary arch, and thereby, the functional
shift of the mandible can be also resolved. In addition, generalized spacing in the mandibular arch was observed in this patient. Generalized spacing can have a variety of causes, such as a tongue-thrusting habit,
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Fig 12. One-year follow-up facial and intraoral photographs.
low tongue posture, small tooth sizes, and a broad arch.10 However, the cause in this patient was a little different because there was no space in the maxillary arch. Moreover, there was no mandibular prognathism or a broad mandibular arch. A locked maxillary dentition seemed to cause the generalized spacing in the mandibular arch.11 As the treatment progressed, space closure in the mandibular arch helped to decrease the intercanine and intermolar widths. Reduction of the width of the mandibular arch also helped to form the proper overjet of the posterior teeth. After elimination of the locked maxillary posterior dentition and the functional shift of the mandible, the patient maintained the proper occlusion with a proper overjet. Meanwhile, molar distalization and mesialization with OMIs were attempted in this patient. OMIs were an important part of her orthodontic treatment.12
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Difficult tooth movements with traditional techniques can be achieved using OMIs.13 Molar distalization is just one of these techniques. There are several studies about molar distalization with OMIs.14-16 There are many ways to try, but most methods have reported good results. In this report, we used open coil springs and OMIs. The advantages of this method are that it can prevent binding and heavy forces compared with the total distalization method. Also, the total distalization method often requires a complex apparatus, but the open-coil method requires only a simple device. The disadvantage of the open-coil method is that reinsertion of the OMIs to the distal side is needed after the molar distalization. However, it is recommended because distalization of the anterior portion after distalization of the molars can guarantee reliable movements of the teeth.
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Fig 13. One-year follow-up dental casts.
Intermaxillary elastics should be used minimally in a patient with a transverse discrepancy because excessive use of intermaxillary elastics can cause temporomandibular disorder.17 In addition, relapse in the retention period can be high.18 Therefore, for these patients, actual tooth movements using OMIs are recommended. Normalization of the intermaxillary relationship after decompensation of the teeth causes recompensation of the teeth.19,20 The new balance obtained can protect the teeth in lateral and protrusive movements of the mandible.21 This helps to maintain oral health.22 Orthognathic surgery has the disadvantages of surgical risks and costs. These are especially considerable for orthognathic surgery in a patient with skeletal Class I asymmetry. In view of these risks and because correcting the asymmetry is the only goal of treatment, the patient's satisfaction can be low after orthognathic surgery. In short, the differences after surgery might not be significant compared with the presurgical status. Therefore, a well-established treatment plan and diagnosis are important. If orthodontic treatment without orthognathic surgery is possible, it can decrease the surgical risks and costs and increase of satisfaction of the patient. CONCLUSIONS
This patient had a unilateral posterior crossbite with a transverse discrepancy. She was treated successfully using an expansion transpalatal arch and OMIs. Good alignment and occlusion were maintained 1 year after appliance removal. Consideration of a hidden functional
shift is important. Orthognathic surgery may not be necessary in patients with Class I facial asymmetry. Minimally invasive treatment can be planned for a patient with a unilateral posterior crossbite and a transverse discrepancy. REFERENCES 1. Sekiya T, Nakamura Y, Oikawa T, Ishii H, Hirashita A, Seto K. Elimination of transverse dental compensation is critical for treatment of patients with severe facial asymmetry. Am J Orthod Dentofacial Orthop 2010;137:552-62. 2. Suda N, Tominaga N, Niinaka Y, Amagasa T, Moriyama K. Orthognathic treatment for a patient with facial asymmetry associated with unilateral scissors-bite and a collapsed mandibular arch. Am J Orthod Dentofacial Orthop 2012;141:94-104. 3. Harrison JE, Ashby D. Orthodontic treatment for posterior crossbites. Cochrane Database Syst Rev 2000;CD000979. 4. Bishara SE, Burkey PS, Kharouf JG. Dental and facial asymmetries: a review. Angle Orthod 1994;64:89-98. 5. O'Byrn BL, Sadowsky C, Schneider B, BeGole EA. An evaluation of mandibular asymmetry in adults with unilateral posterior crossbite. Am J Orthod Dentofacial Orthop 1995;107:394-400. 6. Burstone CJ. Diagnosis and treatment planning of patients with asymmetries. Semin Orthod 1998;4:153-64. 7. Erdinc AE, Ugur T, Erbay E. A comparison of different treatment techniques for posterior crossbite in the mixed dentition. Am J Orthod Dentofacial Orthop 1999;116:287-300. 8. Ferro F, Spinella P, Lama N. Transverse maxillary arch form and mandibular asymmetry in patients with posterior unilateral crossbite. Am J Orthod Dentofacial Orthop 2011;140:828-38. 9. Bartzela T, Jonas I. Long-term stability of unilateral posterior crossbite correction. Angle Orthod 2007;77:237-43. 10. Primozic J, Franchi L, Perinetti G, Richmond S, Ovsenik M. Influence of sucking habits and breathing pattern on palatal constriction in unilateral posterior crossbite—a controlled study. Eur J Orthod 2013;35:706-12.
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11. Volk J, Kadivec M, Music MM, Ovsenik M. Three-dimensional ultrasound diagnostics of tongue posture in children with unilateral posterior crossbite. Am J Orthod Dentofacial Orthop 2010;138: 608-12. 12. Bechtold TE, Kim JW, Choi TH, Park YC, Lee KJ. Distalization pattern of the maxillary arch depending on the number of orthodontic miniscrews. Angle Orthod 2013;83:266-73. 13. Grec RH, Janson G, Branco NC, Moura-Grec PG, Patel MP, Castanha Henriques JF. Intraoral distalizer effects with conventional and skeletal anchorage: a meta-analysis. Am J Orthod Dentofacial Orthop 2013;143:602-15. 14. Sar C, Kaya B, Ozsoy O, Ozcirpici AA. Comparison of two implantsupported molar distalization systems. Angle Orthod 2013;83: 460-7. 15. Chung KR, Kim SH, Chaffee MP, Nelson G. Molar distalization with a partially integrated mini-implant to correct unilateral Class II malocclusion. Am J Orthod Dentofacial Orthop 2010;138:810-9. 16. Choi YJ, Lee JS, Cha JY, Park YC. Total distalization of the maxillary arch in a patient with skeletal Class II malocclusion. Am J Orthod Dentofacial Orthop 2011;139:823-33.
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17. Janson G, de Freitas MR, Araki J, Franco EJ, Barros SE. Class III subdivision malocclusion corrected with asymmetric intermaxillary elastics. Am J Orthod Dentofacial Orthop 2010;138:221-30. 18. Burstone C, Filleul MP, Pigeot V. Stability of orthodontic treatment of occlusal asymmetry. Orthod Fr 2000;71:197-205. 19. Petren S, Bjerklin K, Bondemark L. Stability of unilateral posterior crossbite correction in the mixed dentition: a randomized clinical trial with a 3-year follow-up. Am J Orthod Dentofacial Orthop 2011;139:e73-81. 20. Wong CA, Sinclair PM, Keim RG, Kennedy DB. Arch dimension changes from successful slow maxillary expansion of unilateral posterior crossbite. Angle Orthod 2011;81:616-23. 21. Wattanachai T, Yonemitsu I, Kaneko S, Soma K. Functional lateral shift of the mandible effects on the expression of ECM in rat temporomandibular cartilage. Angle Orthod 2009;79:652-9. 22. Takeda H, Nakamura Y, Handa H, Ishii H, Hamada Y, Seto K. Examination of masticatory movement and rhythm before and after surgical orthodontics in skeletal Class III patients with unilateral posterior cross-bite. J Oral Maxillofac Surg 2009;67: 1844-9.
American Journal of Orthodontics and Dentofacial Orthopedics
Treatment of unilateral posterior crossbite with facial asymmetry in a female patient with transverse discrepancy Seok-Ki Junga and Tae-Woo Kimb Seoul, Korea
A unilateral posterior crossbite with facial asymmetry is difficult to correct with orthodontic treatment alone. This case report describes the orthodontic treatment and additional plasty without orthognathic surgery for a 19-yearold woman with a transverse discrepancy. The posterior crossbite was resolved by expansion of the narrow maxillary arch and space closure in the mandibular arch. This accelerated the correction of the functional shift of the mandible. After resolution of the unilateral posterior crossbite, the problems of the anteroposterior molar relationship were treated using orthodontic mini-implants. Mandibular angle reduction plasty was performed for the asymmetric mandibular border to improve the facial appearance. After treatment, the patient had a more symmetrical facial appearance, normal overjet and overbite, and midline coincidence. The treatment results remained stable 1 year after treatment. This case report demonstrates that a minimally invasive treatment can successfully correct a unilateral posterior crossbite with a transverse discrepancy. (Am J Orthod Dentofacial Orthop 2015;148:154-64)
G
enerally, when we establish the treatment plan for patients with facial asymmetry, surgery is included1 because facial asymmetry is usually caused by skeletal problems.2 Orthodontic treatment alone is a difficult choice in this situation.3 Patients with facial asymmetry and a skeletal Class III malocclusion must be treated by orthognathic surgery even if there is no facial asymmetry. However, more consideration is needed to treat patients with facial asymmetry and a skeletal Class I relationship. Because correction of the asymmetry is the only goal of the orthognathic surgery in this case, satisfaction with the treatment may be low after surgery. Moreover, patients with facial asymmetry and a transverse discrepancy can be treated with orthodontics alone.4 This case report describes the treatment of a woman with a unilateral posterior
a Postgraduate student, Department of Orthodontics, School of Dentistry, Dental Research Institute, Seoul National University; clinical instructor, Department of Orthodontics, Korea University Ansan Hospital, Seoul, Republic of Korea. b Professor, Department of Orthodontics, School of Dentistry, Dental Research Institute, Seoul National University, Seoul, Republic of Korea. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. Address correspondence to: Tae-Woo Kim, Department of Orthodontics, School of Dentistry, Dental Research Institute, Seoul National University, 101 Daehakro, Jongro-Gu, Seoul 110-749, Republic of Korea; e-mail, [email protected]. Submitted, June 2014; revised and accepted, September 2014. 0889-5406/$36.00 Copyright Ó 2015 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2014.09.023
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crossbite and facial asymmetry. She had a skeletal Class I relationship. Her chin and mandibular midline were deviated to the left side with a left posterior crossbite. Because there was a transverse discrepancy, a nonsurgical approach for the correction of the occlusion could be planned. Mandibular angle reduction plasty was planned for the asymmetrical mandibular inferior border. By avoiding orthognathic surgery, it was possible to minimize the patient's discomfort. DIAGNOSIS AND ETIOLOGY
The patient was a 19-year-old woman who visited Seoul National University Dental Hospital in South Korea for an orthodontic consultation. No specific medical problems or temporomandibular joint symptoms were observed. She had a skeletal Class I relationship and facial asymmetry, with the chin deviated 4.5 mm to the left. A slight maxillary deficiency and a normal vertical growth pattern were seen. A Class I molar relationship on the right and a Class II molar relationship on the left were observed, and a posterior crossbite from the left lateral incisor to the left second molar was observed (Fig 1). The mandibular dental midline was deviated 6.5 mm to the left. There was space between the mandibular anterior teeth (Fig 2). The cant of the occlusal plane was minor. In the lateral cephalometric analysis, no mouth protrusion or problems of anterior tooth inclination were found (Table I). The major
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Fig 1. Pretreatment facial and intraoral photographs.
problems were summarized as frontal asymmetry, deviation of the chin, left posterior crossbite, and mandibular dental midline deviation. Furthermore, the patient had a slight transverse centric occlusion–centric relation discrepancy. This functional shift of the mandible caused mandibular asymmetry, which could be observed in the panoramic and posteroanterior radiographs (Fig 3). In particular, the mandibular left inferior border was much bulkier than right inferior border. This difference in mass was the cause of the facial asymmetry. TREATMENT OBJECTIVES
The treatment objectives for the dentition were correction of the left posterior crossbite, making the maxillary and mandibular midlines coincident, and closing the mandibular arch space. The treatment objectives for the skeleton were improving the facial asymmetry, including
the deviation of the chin, and improving the transverse discrepancy. Thus, facial symmetry, normal overjet and overbite, and Class I canine-to-molar relationships could be obtained. TREATMENT ALTERNATIVES
Facial asymmetry and unilateral posterior crossbite are difficult to treat with orthodontics alone. Therefore, the first plan was orthodontic treatment accompanied by orthognathic surgery. Extraction of the 2 maxillary third molars was planned. Leveling of maxillary and mandibular arches and space closure of the mandibular arch were planned as the presurgical orthodontic treatment. After that, the asymmetries of the chin and mandible could be corrected with orthognathic surgery. Postsurgical orthodontic treatment would finish correction of the malocclusion.
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Fig 2. Pretreatment dental casts.
Table I. Comparison of cephalometric measurements ANB angle ( ) A to N perpendicular (mm) Pog to N perpendicular (mm) Bj€ ork sum ( ) FMA ( ) U1 to FH ( ) U1 to SN ( ) IMPA ( ) Interincisal angle ( ) Upper lip to E-line (mm) Lower lip to E-line (mm) Nasolabial angle ( )
Pretreatment 2.4 1.2 5.9 393.0 22.3 108.7 98.0 104.2 124.8 2.3 0.1 96.6
Posttreatment 2.4 1.2 5.5 401.4 30.7 108.4 97.7 88.3 132.6 4.9 1.8 93.4
This plan has the advantage of eliminating the patient's skeletal asymmetry, but at the cost of surgical risk and financial burden. The second plan was orthodontic treatment and additional plasty without orthognathic surgery. Expansion of a narrow maxillary arch can help to correct the transverse discrepancy by releasing the locking in the left posterior teeth. After that, maxillary left molar distalization and mandibular left molar mesialization were planned to correct the left molar relationship and the dental midline. Mandibular angle reduction plasty and genioplasty were planned for the bulky left inferior border of the mandible. This plan would minimize the burden of surgery while maximizing the reduction of asymmetry. The downside is that it is difficult to eliminate the asymmetry completely.
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The patient selected the second option because she did not want orthognathic surgery. TREATMENT PROGRESS
Metal self-ligating brackets (0.022-in slot, Damon Q; Ormco, Glendora, Calif) were used for this treatment. Initial leveling progressed with a 0.014-in nickeltitanium archwire. A lingual sheath was attached to the palatal side of the maxillary first molar, and an expansion transpalatal arch was inserted into the lingual sheath (Fig 4). Buccal root torque was given to the expansion transpalatal arch to decompensate the inclination of the maxillary left first molar (Fig 5). The relationship of the left posterior teeth was improved to an edge bite after 4 months of leveling and expansion of the maxillary arch. To resolve the minor cant of the maxillary left anterior teeth, a titanium orthodontic mini-implant (OMI; diameter, 1.6 mm; length, 6.0 mm; Jeil Medical, Seoul, South Korea) was inserted between the mandibular left premolars. Intermaxillary elastics were applied from the OMI to the maxillary left canine and premolars. After leveling of the mandibular arch, elastomeric modules were used to close the remaining space. After 7 months of treatment, the unilateral posterior crossbite was corrected (Fig 6). Expansion of the maxillary arch relieved the functional shift of the mandible (Fig 5, B). In addition, the reduced mandibular intermolar width helped reduce the functional shift (Table II). After resolution of the unilateral posterior crossbite, mandibular angle reduction plasty and genioplasty were done to improve the bulky left inferior border of the mandible. Despite
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Fig 3. Pretreatment lateral and frontal cephalograms and panoramic radiograph.
Fig 4. Intraoral photographs during initial alignment.
the improvement of the left posterior crossbite, a Class II molar relationship remained. Distalization of the maxillary left molars and mesialization of the mandibular left molars were planned to improve the molar
relationships and the mandibular dental midline. At first, a titanium OMI was inserted between the maxillary second premolar and the first molar. After ligation between the OMI and the second premolar, the molars were
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Fig 5. A, Pretreatment molar relationships; B, mechanics to resolve the crossbite.
Fig 6. Intraoral photographs after resolving the crossbite.
Table II. Comparison of intercanine and intermolar
widths Maxillary intercanine width (mm) Mandibular intercanine width (mm) Maxillary intermolar width (mm) Mandibular intermolar width (mm)
Pretreatment Posttreatment Retention 33.17 37.55 37.55 31.83
27.84
28.14
55.47
57.46
57.37
52.10
48.89
49.36
distalized during 3 months using open-coil springs between the second premolar and the first molar (Fig 7). After that, the OMI was moved between the maxillary first and
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second molars, and distalization of the remaining anterior teeth was performed. At the same time, an OMI was inserted between the mandibular left lateral incisor and the canine. The mandibular left molars were mesialized using elastomeric modules from the OMI. After 13 months, active treatment was finished, and all fixed orthodontic appliances were removed. Fixed lingual retainers were attached to both arches, and circumferential retainers were placed additionally. The instructions to the patient included full-time retainer use for 3 months and then nighttime use for 2 years at least. TREATMENT RESULTS
The final records (Figs 8-10) show that the unilateral posterior crossbite was resolved, and the dental midline
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Fig 7. Intraoral photographs during molar distalization.
was coincident. The space in the mandibular arch was closed, and the minor crowding of the maxillary arch was resolved. The skeletal facial asymmetry was partly resolved by the recovery of the mandibular functional shift. The mandibular angle reduction plasty and the genioplasty markedly improved the patient's frontal appearance. Distalization of the maxillary left posterior teeth was successful, and it contributed to the normal overjet and the Class I canine-to-molar relationship. The panoramic radiographs (Fig 10) show well-aligned parallel roots of the teeth, and there are no signs of root resorption. Comparison of measurements before and after treatment (Table I) shows the increment of the Frankfort-mandibular plane angle resulting from the mandibular angle reduction plasty. In addition, normalization of the inclination of the mandibular anterior teeth was accomplished by space closure. In the comparison of the dental casts before and after treatment (Table II), maxillary intercanine and intermolar widths increased by 4.4 and 2.0 mm, respectively. The mandibular intercanine and intermolar widths decreased by 4.0 and 3.2 mm, respectively. These changes were well maintained during the retention period. The superimposition of the frontal cephalometric radiographs showed expansion of the maxillary arch, constriction of the mandibular arch, and coincidence of dental midlines (Fig 11). A minor movement of the mandibular condyle was also observed while correcting the functional shift. The superimposition of the lateral cephalometric radiographs showed the results of the mandibular angle reduction plasty and the genioplasty, the distalization of the maxillary molars, and the mesialization of the
mandibular molars. The patient returned for reevaluation at 1 year after debonding (Figs 12 and 13). Her occlusion was well maintained. The occlusal relationships of the premolars and molars were improved by settling. The facial photographs showed a harmonious, acceptable, and symmetrical appearance. DISCUSSION
A compensated dentition is often found in patients with a unilateral posterior crossbite.5 In this case report, the buccal inclination of maxillary left molars and the lingual inclination of mandibular left molars were kept to compensate for the left posterior crossbite. If a simple unilateral expansion of the maxillary dentition and constriction of mandibular dentition had been done, the compensatory movement of dentition would have been intensified.6 This means that the buccal inclination of the maxillary left molars and the lingual inclination of the mandibular left molars would have been worse.7 These changes can cause adverse effects such as interference with lateral movements of the mandible by the opposite side. Therefore, the first choice of treatment for unilateral posterior crossbite is orthognathic surgery followed by decompensation of the inclination of the posterior teeth. However, in patients with a transverse discrepancy such as our patient, bodily movement of the mandible can be obtained partly by appropriate centric-relation guidance. Thereby, improvement of the occlusion can be obtained without orthognathic surgery or without worsening of the compensation. In this patient, habitual maximal intercuspation caused narrow maxillary posterior teeth and wide
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Fig 8. Posttreatment facial and intraoral photographs.
Fig 9. Posttreatment dental casts.
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Fig 10. Posttreatment lateral and frontal cephalograms and panoramic radiograph.
Fig 11. Superimposition of the lateral and frontal cephalograms at pretreatment (black) and posttreatment (red).
mandibular posterior teeth.8 To solve this problem, normalization of the width is needed before everything else.9 Locked posterior teeth can be resolved by expansion of the maxillary arch, and thereby, the functional
shift of the mandible can be also resolved. In addition, generalized spacing in the mandibular arch was observed in this patient. Generalized spacing can have a variety of causes, such as a tongue-thrusting habit,
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Fig 12. One-year follow-up facial and intraoral photographs.
low tongue posture, small tooth sizes, and a broad arch.10 However, the cause in this patient was a little different because there was no space in the maxillary arch. Moreover, there was no mandibular prognathism or a broad mandibular arch. A locked maxillary dentition seemed to cause the generalized spacing in the mandibular arch.11 As the treatment progressed, space closure in the mandibular arch helped to decrease the intercanine and intermolar widths. Reduction of the width of the mandibular arch also helped to form the proper overjet of the posterior teeth. After elimination of the locked maxillary posterior dentition and the functional shift of the mandible, the patient maintained the proper occlusion with a proper overjet. Meanwhile, molar distalization and mesialization with OMIs were attempted in this patient. OMIs were an important part of her orthodontic treatment.12
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Difficult tooth movements with traditional techniques can be achieved using OMIs.13 Molar distalization is just one of these techniques. There are several studies about molar distalization with OMIs.14-16 There are many ways to try, but most methods have reported good results. In this report, we used open coil springs and OMIs. The advantages of this method are that it can prevent binding and heavy forces compared with the total distalization method. Also, the total distalization method often requires a complex apparatus, but the open-coil method requires only a simple device. The disadvantage of the open-coil method is that reinsertion of the OMIs to the distal side is needed after the molar distalization. However, it is recommended because distalization of the anterior portion after distalization of the molars can guarantee reliable movements of the teeth.
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Fig 13. One-year follow-up dental casts.
Intermaxillary elastics should be used minimally in a patient with a transverse discrepancy because excessive use of intermaxillary elastics can cause temporomandibular disorder.17 In addition, relapse in the retention period can be high.18 Therefore, for these patients, actual tooth movements using OMIs are recommended. Normalization of the intermaxillary relationship after decompensation of the teeth causes recompensation of the teeth.19,20 The new balance obtained can protect the teeth in lateral and protrusive movements of the mandible.21 This helps to maintain oral health.22 Orthognathic surgery has the disadvantages of surgical risks and costs. These are especially considerable for orthognathic surgery in a patient with skeletal Class I asymmetry. In view of these risks and because correcting the asymmetry is the only goal of treatment, the patient's satisfaction can be low after orthognathic surgery. In short, the differences after surgery might not be significant compared with the presurgical status. Therefore, a well-established treatment plan and diagnosis are important. If orthodontic treatment without orthognathic surgery is possible, it can decrease the surgical risks and costs and increase of satisfaction of the patient. CONCLUSIONS
This patient had a unilateral posterior crossbite with a transverse discrepancy. She was treated successfully using an expansion transpalatal arch and OMIs. Good alignment and occlusion were maintained 1 year after appliance removal. Consideration of a hidden functional
shift is important. Orthognathic surgery may not be necessary in patients with Class I facial asymmetry. Minimally invasive treatment can be planned for a patient with a unilateral posterior crossbite and a transverse discrepancy. REFERENCES 1. Sekiya T, Nakamura Y, Oikawa T, Ishii H, Hirashita A, Seto K. Elimination of transverse dental compensation is critical for treatment of patients with severe facial asymmetry. Am J Orthod Dentofacial Orthop 2010;137:552-62. 2. Suda N, Tominaga N, Niinaka Y, Amagasa T, Moriyama K. Orthognathic treatment for a patient with facial asymmetry associated with unilateral scissors-bite and a collapsed mandibular arch. Am J Orthod Dentofacial Orthop 2012;141:94-104. 3. Harrison JE, Ashby D. Orthodontic treatment for posterior crossbites. Cochrane Database Syst Rev 2000;CD000979. 4. Bishara SE, Burkey PS, Kharouf JG. Dental and facial asymmetries: a review. Angle Orthod 1994;64:89-98. 5. O'Byrn BL, Sadowsky C, Schneider B, BeGole EA. An evaluation of mandibular asymmetry in adults with unilateral posterior crossbite. Am J Orthod Dentofacial Orthop 1995;107:394-400. 6. Burstone CJ. Diagnosis and treatment planning of patients with asymmetries. Semin Orthod 1998;4:153-64. 7. Erdinc AE, Ugur T, Erbay E. A comparison of different treatment techniques for posterior crossbite in the mixed dentition. Am J Orthod Dentofacial Orthop 1999;116:287-300. 8. Ferro F, Spinella P, Lama N. Transverse maxillary arch form and mandibular asymmetry in patients with posterior unilateral crossbite. Am J Orthod Dentofacial Orthop 2011;140:828-38. 9. Bartzela T, Jonas I. Long-term stability of unilateral posterior crossbite correction. Angle Orthod 2007;77:237-43. 10. Primozic J, Franchi L, Perinetti G, Richmond S, Ovsenik M. Influence of sucking habits and breathing pattern on palatal constriction in unilateral posterior crossbite—a controlled study. Eur J Orthod 2013;35:706-12.
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17. Janson G, de Freitas MR, Araki J, Franco EJ, Barros SE. Class III subdivision malocclusion corrected with asymmetric intermaxillary elastics. Am J Orthod Dentofacial Orthop 2010;138:221-30. 18. Burstone C, Filleul MP, Pigeot V. Stability of orthodontic treatment of occlusal asymmetry. Orthod Fr 2000;71:197-205. 19. Petren S, Bjerklin K, Bondemark L. Stability of unilateral posterior crossbite correction in the mixed dentition: a randomized clinical trial with a 3-year follow-up. Am J Orthod Dentofacial Orthop 2011;139:e73-81. 20. Wong CA, Sinclair PM, Keim RG, Kennedy DB. Arch dimension changes from successful slow maxillary expansion of unilateral posterior crossbite. Angle Orthod 2011;81:616-23. 21. Wattanachai T, Yonemitsu I, Kaneko S, Soma K. Functional lateral shift of the mandible effects on the expression of ECM in rat temporomandibular cartilage. Angle Orthod 2009;79:652-9. 22. Takeda H, Nakamura Y, Handa H, Ishii H, Hamada Y, Seto K. Examination of masticatory movement and rhythm before and after surgical orthodontics in skeletal Class III patients with unilateral posterior cross-bite. J Oral Maxillofac Surg 2009;67: 1844-9.
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