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Applying transverse genioplasty for facial asymmetry and profile improvement-case report YI-JYUN CHEN1,3 TSUI-HSIEN HUANG1,3 CHIH-YU PENG1,3 CHIA-TZE KAO2,3 1 Institute of Stomatology, College of Oral Medicine, Chung Shan Medical University, Taichung, Taiwan, ROC. Institute of Oral Material Science, College of Oral Medicine, Chung Shan Medical University, Taichung, Taiwan, ROC. 3 Department of Dentistry, Chung Shan Medical University Hospital, Taichung, Taiwan, ROC. 2 An 18-year-old healthy man with marked facial and dental asymmetry due to unilateral mandibular condylar hyperplasia was treated with pre-adjusted fixed appliance therapy combined with transverse genioplasty. The total treatment time was 28 months. Although the compromised treatment did not exactly correct the asymmetry, a more-balanced proportion of facial features and a better profile were achieved. The mentalis muscle tone was also relieved, presenting a smooth labiomental fold with a satisfying outcome. (J Dent Sci, 3(2):108-116 , 2008) Key words: facial asymmetry, transverse genioplasty, labiomental fold, profile. Most of the time, people view themselves from the front rather than from other aspects1, and it is also easier for patients and orthodontists to identify facial asymmetry from a frontal view2-5. For an adult patient with a skeletal Class III malocclusion and a midline deviation, combined surgical-orthodontic therapy is often the treatment of choice because of its satisfying outcome and stability6. Camouflage treatment with selective extractions is usually considered only for borderline patients. A Class III malocclusion is caused by any combination of deficient maxillary growth and excessive mandibular growth. However, injury to the condylar region can result in growth arrest, and consequently a characteristic distortion of the mandibular form producing facial asymmetry7. Many schematic diagrams of the “ideal” position of the chin as described by Ricketts8, Steiner9, Burstone10, and Holdway11 are all discussed in the horizontal anteroposterior direction; therefore, genioplasty has become one of the best choices of surgical procedures for correcting chin deformities12-14. Received: February 18, 2008 Accepted: May 13, 2008 Reprint requests to: Dr. Chia-Tze Kao, Institute of Oral Material Science, Chung Shan Medical University, No. 110, Chien-Kuo North Road, Section 1, Taichung, Taiwan 40201, ROC. 108 In contrast, transverse genioplasty is an option for correcting mandibular asymmetry12; and although it is less effective for overall facial balance, fewer risks are involved14. Sometimes, the treatment plan consists of orthodontic treatment combined with compromised minor surgery rather than the most ideal surgical procedures, or even no surgery is involved15-17. The ultimate benefit to the patient has always been the primary concern of clinicians providing coordinated orthodontic and orthognathic surgical treatment18. The present case report describes an example of orthodontic compensatory treatment combined with transverse genioplasty of an adult patient with a class III malocclusion and facial asymmetry. Transverse genioplasty decreased the degree of facial asymmetry and significantly improved the facial profile by simultaneously relieving the mentalis muscle tone. CASE PRESENTATION An 18-year-old male presented with the chief complaint of “I don’t like my asymmetric chin position which makes me look quite different from other people” (Figure 1A). His medical history showed no contraindication to orthodontic therapy. According to the interview data, he had received a J Dent Sci 2008‧Vol 3‧No 1 Transverse genioplasty for facial profile improvement Figure 1. An 18-year-old male patient with a class III malocclusion and dentofacial midline deviation (A, B). (A, C) The mentalis hyperfunction has had a detrimental effect on the facial esthetics in both frontal and profile views. (D) The asymmetry is the result of unilateral condylar hypoplasia. traumatic injury to the left side of the chin at 7 years of age with a residual scar (Figure 2); a family history of mandibular prognathism was denied. A facial examination showed constricted mentalis muscle tone (mentalis muscle hypertension) and an anterior bulge of the labiomental skin, with the chin deviated to the left side. There was a 5-mm deviation of the chin button from the facial midline. On an intraoral examination, the teeth were well aligned in both arches, and a huge amalgam restoration was found on J Dent Sci 2008‧Vol 3‧No 1 the mandibular first molar, which also revealed an edge-to-edge incisor relationship (Figure 1B). The facial asymmetry originated from the cranial base, maxilla, and mandible (Figure 3A). Furthermore, the asymmetrical mandible body length and ramus height (Figures 1D, 3A) resulted in a class III malocclusion on the right side with a buccal crossbite between the lower left canine and lower left first premolar (Figure 1B), with both dental midlines deviating to the left. The cephalometric analysis (Figure 3B, Table 1) 109 Y.J. Chen, T.H. Huang, C.Y. Peng, et al. Figure 2. A scar on the left side of the patient’s chin. confirmed the skeletal class III pattern (with an ANB of -1) with bimaxillary dental protrusion (with a U1-L1 angle of 108°) and an average mandibular plane angle (FMA) of 28°. He was diagnosed as having an Angle’s Class III malocclusion with incisor edge-to-edge occlusion, a dental midline deviation, an asymmetric skeletal Class III jaw base relationship, and a normal mandibular plane angle. Treatment plan During consultations with the patient and his parents, a treatment plan was devised based on the concept of non-extraction orthodontic treatment involving compensatory dental changes with genioplasty for the skeletal discrepancy. The treat- ment plan consisted of the following stages: (1) achievement of Class I molar occlusion and normal incisor relationships with 0.022-inch-slot pre-adjusted edgewise appliances and inter-arch asymmetrical mechanics; (2) a deferred surgical procedure to identify the cessation of skeletal growth using serial cephalometric radiographs; (3) extraction of the right maxillary and mandibular third molars; and (4) retention of the upper and lower removable retainers. Treatment progress At the age of 18 years and 5 months, the pre-adjusted 0.022-inch-slot edgewise appliances were put in place. After the initial leveling was accomplished, the maxillary anterior teeth were Figure 3. Superimposition of cephalometric tracings before and after treatment. 110 J Dent Sci 2008‧Vol 3‧No 1 Transverse genioplasty for facial profile improvement Table 1. Summary of the cephalometric analysis Measurement Norm Initial Finish SNA 82° 84° 84° SNB 80° 85° 83° ANB 2° -1° 1° SND 76°~77° 83° 81° U1-UA 4 mm 13 mm 13 mm U1-UA 22° 38° 41° L1-NB 4 mm 10 mm 9 mm L1-NB 25° 35° 36° 0 mm 1 mm Pog-NB U1-L1 131° 108° 100° OccI-SN 14° 10° 9° GoGn-SN 32° 30° 30° Max.L(A’-C’) 50 mm 48 mm 48 mm Mand.L(B’-D’) 50 mm 52 mm 51 mm ALFH(A’-B’) 67 mm 68 mm PLFH(C’-D’) 50 mm 50 mm Aver ALFH=(ALFH+FLFH)/2 58.5 59 FMA 31±5° 28° 32° IMPA 94±6° 98° 99° FMIA 55±6° 54° 49° Wits(A/B to OccI. PI) -1.4±2.6 mm mix.: -0.8~1.5 -7 mm -3.5 mm retracted with a 0.019 × 0.025-inch rectangular stainless steel arch wire with vertical loops as hooks between the maxillary central and lateral incisors, and a mandibular 0.019×0.025-inch rectangular stainless steel arch wire for further alignment. The lower arch wire with a reverse curve of Spee was used to tip back the molars in order to achieve a better molar relationship. After a 7-month period of leveling, the right lower and upper third molars were sequentially extracted. The malocclusion correction was done and J Dent Sci 2008‧Vol 3‧No 1 was completed using inter-arch asymmetric mechanics and vertical elastics. After 25 month of edgewise treatment, Class I incisor and molar relationships with good buccal segment interdigitation had been achieved (Figure 4), and further consultation focused on surgical correction of the facial asymmetry (Figure 5). After an extraoral facial analysis, a transverse sliding osteotomy shift to the right side of 5.0 mm without mandibular advancement was agreed upon. Two months later, transverse sliding genioplasty 111 Y.J. Chen, T.H. Huang, C.Y. Peng, et al. Figure 4. Pre-surgical evaluation. (A) The mentalis muscle is still in hypertension. (B) Finished stage, with good interdigitation. with wire fixation was performed with the patient under general anesthesia (Figure 6). One month after this, wrap-around retainers were applied to both dental arches following removal of the pre-adjusted edgewise appliances. Treatment results Figure 5. Frontal view of the patient with a bite stick in place to show the canting of the occlusal plane. 112 Facial photographs (Figure 7A) show significant improvement in the facial profile and few class III facial characteristics. Although there was still mild facial and dental asymmetry, the patient is now pleased with his dental and facial appearance. After active treatment, his upper lip was coincident with the E line, and the lower lip was 2.0 mm anterior to the E line. The following treatment goals set in the pretreatment planning were attained, and the malocclusion was compromisingly treated: (1) achieving solid intercuspation of the teeth with Class I J Dent Sci 2008‧Vol 3‧No 1 Transverse genioplasty for facial profile improvement Figure 6. Transverse genioplasty with a 5-mm shift to the right side. molar and normal incisor relationships; (2) improving the lateral crossbite; (3) decreasing the maxillary and mandibular dental midline deviations; and (4) achieving an acceptable facial profile (Figure 7). The distance from the chin button to the facial midline was reduced from 5 to 2 mm. The occlusion was reduced to a class I molar relationship and a Class I cuspid relationship occlusion with a normal overjet and overbite. The composite cephalometric tracings superimposed on the S-N line at sella illustrate the treatment changes (Figure 3B). The mandibular incisors remained in the same approximate position with an IMPA angle of 99°. The FMA angle increased (32°), which increased the facial height but also helped to ameliorate the Class III appearance, and the SNB angle decreased to 83°. A posttreatment panoramic radiograph confirmed that no pathosis or root resorption had occurred (Figure 7C). There were neither signs nor symptoms of temporomandibular disorders (TMDs) during the treatment or retention periods. The patient was given maxillary and mandibular wrap-around retainers. The treatment time was 28 months. The right mandibular first molar was then restored for better long-term stability (Figure 8). DISCUSSION The secret to facial beauty is balanced proportions of all facial features19,20. The appearance J Dent Sci 2008‧Vol 3‧No 1 of any face is a composite of all of the anatomic elements—teeth, bone, and soft tissues—and their relationships to one another21. The chin is a prominent facial feature, which plays an important role in the overall facial appearance22. The position of the chin is important in establishing correct facial proportions. The chin gives the appearance of strength to the face13. A “crooked chin” is the most difficult chin deformity to properly assess and correct (Figure 1A). This deformity generally results from a truly 3-dimensional skeletal abnormality20. Because patients’ views of themselves are usually in a mirror, discrepancies of the chin's projection are often not even recognized by the patient. For these reasons, surgical correction of minor deformities of the chin is infrequently requested13,20. In contrast, asymmetrical chin deformities are easily detected by patients, and corrections are often asked for. Mandibular asymmetries may be related not only to asymmetrical positioning, but also to an asymmetrical morphology of the mandible23. Differences in the length of the body of the mandible, as well as differences in the height of the developing ramus, can lead to asymmetries. The developing asymmetries may begin early in fetal life24 but may also be the result of disturbances in postnatal development, including trauma to the mandibular condyle25. Condylar hypoplasia may also result in skeletal asymmetry in which the mandible deviates toward the affected side26. Compensatory maxillary asymmetry and canting of the occlusal plane may be associated with such skeletal asymmetries (Figure 5). A significantly asymmetrical condylar height can also be detected with a radiographic examination (Figure 1D). Management of axial inclination asymmetries depends on the treatment plan. Patients who do not undergo extraction may require maintenance of asymmetrical compensatory axial inclinations, although a more-ideal symmetry can be achieved in patients willing to undergo surgical and extraction procedures27. Malocclusion in a young adult who presents with a Class I occlusion on 1 side and a Class III occlusion on the other side can be of both skeletal and dental origins. Asymmetrical mechanics can be used to correct a Class III malocclusion with a midline deviation26. An anterior crisscross elastic can effectively decrease the dental midline deviation, but may produce the undesirable side effect of canting the occlusal plane27. The use of a combination of Class II 113 Y.J. Chen, T.H. Huang, C.Y. Peng, et al. Figure 7. Patient after treatment, showing dramatic improvement in the lower facial profile and an elegant appearance from genioplasty (A~D). Frontal cephalogram showing the extent of the underlying skeletal asymmetry (E). and III elastics can produce rotation of the entire arch. One side effect of interarch elastics, molar extrusions, can be minimized by an upper arch wire with a curve of Spee and a lower arch wire with a reverse curve of Spee. In addition, tipping back the right mandibular molars greatly helped decrease the dental midline deviation and crossbite correction in this case 114 (Figure 3D). Finally, in order to obtain a better surgical evaluation, the transverse genioplasty was postponed until the final stage (Figure 4). In the present case, the prepubertal traumatic history of the chin may have been the reason for the mandibular asymmetry, which caused condylar growth arrest on the left side and mandibular hyperplasia on J Dent Sci 2008‧Vol 3‧No 1 Transverse genioplasty for facial profile improvement Figure 8. Right mandibular first molar after being restored. the right. Although a non-extraction treatment involving compensatory dental changes was selected, a minor skeletal correction by transverse genioplasty was performed to reduce the jaw deformity. Transverse genioplasty without advancement (Figure 7D), which downsizes the surgical risks compared to other osteotomies for mandibular deformities, is seldom considered as a simultaneous adjunct to orthodontic treatment. This case, however, illustrates the benefits that it can contribute to the final outcome. The patient’s esthetic appearance was dramatically enhanced by genioplasty, combined with marked improvement in the harmonious profile of the lower third of the face and the chin-neck contour, owing to relief of the muscle tone by transverse genioplasty (Figure 7A). Genioplasty is chin surgery. The chin is a prominence of the mandible and overlying tissues. Two notable muscles on the chin are the genioglossus and mentalis. The genioglossus is behind the chin under the tongue. It is the muscle that pulls the tongue forward when you breathe, swallow, and stick out your tongue. The mentalis is on the front of the chin. It pushes the lip up, and when used, produces a puckered appearance28 (Figure 1A). Continued hyperfunction of this muscle may have played a role in creating this deformity. Surgeons have been using botulinum toxin A with good success to manage hyperfunctional facial lines28,29. The paralytic effect, however, lasts only 3~6 months, although some investigators have reported a longer duration in patients exposed over a prolonged period of time29. Therefore, relaxing the mentalis muscle may have J Dent Sci 2008‧Vol 3‧No 1 resulted in anterosuperior rotation of the genial segment30, which presents a more-satisfying profile (Figures 3B, 7A). Aesthetic surgery of the chin is an extremely useful procedure, which can aid in achieving balanced proportions of the facial features. Although augmentation of the chin using alloplasts can camouflage an anteroposterior chin deficiency, this technique is not effective in correcting vertical or transverse deformities of the lower face and chin31. Therefore, transverse sliding genioplasty was a better choice for a surgical procedure in this case. Only by critical clinical, lateral cephalometric, and P-A cephalometric radiographic analyses (Figure 7E) with soft-tissue markers can these various aspects be totally appreciated and accordingly appraised32,33. In a case like the present one, when correcting a rather gross developmental facial deformity, improvement can be achieved by lessexacting surgery, and patient satisfaction is frequently good. However, when dealing with a more-subtle esthetic variety of deformity, such as an isolated crooked chin, the patient is generally seeking and only satisfied with subtle, precise change1,20. Facial appearances tend to influence the impressions of those we meet, and our social interactions are heavily dependent on how we look to others34-36. Accordingly, the treatment plan should be closely congruent with and responsive to the patient's wants, needs, and preferences, and it should also consider the psychological, social, cultural, and economic dimensions of the patient in addition to physical findings18. After all, patient-centered outcomes can never be overemphasized. 115 Y.J. Chen, T.H. Huang, C.Y. Peng, et al. REFERENCES 1. Steenbergen E, Litt MD, Nanda R. Presurgical satisfaction with facial orthognathic surgery patients. Am J Orthod Dentofac Orthop, 110: 653-659, 1996. 2. Burke PH, Beard LF. Stereophotogrammetry of the face. Am J Orthod, 53: 769-782, 1967. 3. Burke PH. Stereophotogrammetric measurement of normal facial asymmetry in children. Hum Biol, 4: 536-548, 1971. 4. Jerrold L, Lowenstein LJ. The midline: Diagnosis and treatment. Am J Orthod Dentofac Orthop, 97: 453-462, 1990. 5. Arnett GW, Bergman RT. Facial keys to orthodontic diagnosis and treatment planning-part II. 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Burstone CJ. Diagnosis and treatment planning of patients with asymmetry. Semin Orthod, 4: 153-164, 1998. 28. Bentsianov B, Blitzer A. Facial Anatomy. Clinics in Dermatology, 22: 3-13, 2004. 29. Binder WJ, Blitzer A, Brin MF. Treatment of hyperfunctional lines of the face with botulinum toxin A. Dermatol Surg, 24: 1198-1205, 1998. 30. Ayoub AF, Stirrups DR, Moos KF. Evaluation of changes following advancement genioplasty using finite element analysis. Br J Oral Maxillofac Surg, 31: 217-222, 1993. 31. Sykes JM, Frodel JL Jr. Genioplasty. Operative Techniques in Otolaryngology-Head and Neck Surgery, 6: 319-323, 1995. 32. Edler R, Wertheim D, Greenhill D. Outcome measurement in the correction of mandibular asymmetry. Am J Orthod Dentofacial Orthop, 125: 435-443, 2004. 33. Kusayama M, Motohashi N, Kuroda T. Relationship between transverse dental anomalies and skeletal asymmetry. Am J Orthod Dentofacial Orthop, 123: 329-337, 2003. 34. Feingold A. Gender differences in effects of physical attractiveness on romantic attraction: A comparison across five research paradigms. J Personality Social Psychol, 59: 981-993, 1990. 35. Cowley G. The biology of beauty. Newsweek, 127: 60-67, 1996. 36. Hunt OT, Hepper PG, Burden DJ. The psychosocial impact of orthognathic surgery: A systematic review. Am J Othod Dentofac Orthop, 120: 490-497, 2001. J Dent Sci 2008‧Vol 3‧No 1