A literature review was performed concerning the changes of orthognathic functions, especially of the lip, tongue and masticatory muscle functions, by the treatment of dentofacial deformity. Improvement of maxillofacial morphology by surgical orthodontic treatment results in normalization of the resting and functional behaviors of the lip and tongue, and the lip pressure during rest and function decreases. No significant correlation has been reported among the changes in tongue pressure and amount of surgical correction and relapse. The importance of tongue posture associated with respiration is suggested.
In patients with dentofacial deformity, the masticatory muscle function was impaired before surgery, and also immediately after surgery. Muscle atrophy and functional deterioration due to surgical invasion and intermaxillary fixation occur. After six months, functional recovery gradually occurred, and it reached that of the control group at 4 years or more. It is suggested that improvement of occlusion brings about this change and that the adaptation of masticatory muscle may differ depending on maxillofacial morphology. Although the effectiveness of masticatory muscle training is advocated, further research is required.

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　Aim: Facial asymmetry not only affects the mandible, but jaw deformation also extends to the cranial base, maxilla, alveolar bone, and dentition. The position of teeth and the form of the dental arch, which are located on the alveolar bone, are also affected by jaw deformity. The purpose of this study was to analyze the tooth position and arch form of mandibular dentition in skeletal Class Ⅲ facial asymmetry patients.
　Materials and methods: Skeletal ClassⅢ patients diagnosed with facial asymmetry who had undergone surgical orthodontic treatment were selected as subjects. The control group consisted of skeletal ClassⅢ patients without facial asymmetry who had undergone surgical orthodontic treatment. Twenty patients （10 males and 10 females） were selected for each group. For evaluation, mandibular study models of selected patients were scanned using a laser scanner. Using a 3D digital model, the cusp-tip and facial axis points were projected on the occlusal plane, and point dimensions were measured using modeling software. Arch forms of the two groups were drawn and compared using a polynomial formula and compared.
　Results: In the molar region of the facial asymmetry group, the cusp-tip and facial axis points were located lingually on the deviated side and buccally on the non-deviated side, and a significant difference was indicated. A symmetric arch form was expressed with the 6th polynomial formula in the facial symmetry group. Meanwhile, an asymmetric arch form with an S curve on the deviated side was expressed with a 6th polynomial formula in the facial asymmetry group.
　Conclusion: This study confirmed that the asymmetrical arch form is caused by differences in transverse positioning of the molars in cases with skeletal Class Ⅲ facial asymmetry.

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　The results of virtual surgery performed using simulation software based on acquired CBCT image data were transferred to actual two-jaw surgery using a navigation system to treat seven patients with deformities. Osteotomy was applied and the accuracy of navigation surgery was investigated.
　Patients with congenital anomalies such as cleft lip and palate were excluded. An impression of the dentition was prepared for each of the patients about 14 days before surgery and a splint was prepared. Another splint with reference points for navigation registration was prepared by adding references to the first splint using contrast-enhancing resin. The patients were fitted with the splint and CBCT images of centric occlusion were acquired. Simulation proceeded using preoperative CBCT image data, and then the osteotomy line, as well as the direction and distance of bone segment movement, were set. Standard registration was achieved using the splint with the reference points to match the three-dimensional CT image with positional information about the patient. Surgery then proceeded following the standard method. The position of the osteotomy line and the direction of maxillary movement were confirmed while also confirming the three-dimensional position using a navigation pointer. The mandible was moved according to the maxillary position. We investigated errors of maxillary position between the position set on the simulation and that after movement in actual surgery as follows. The preoperative simulation image and postoperative three-dimensional CT image were superimposed, and anteroposterior, vertical, and horizontal errors were measured at five points. When the maxilla had moved forward, the error between the maxillary positions on simulation and after actual surgery was within 2mm at most measurement points, and highly accurate, but the errors were relatively large when facial asymmetry required movement in three dimensions.
　Therefore, to clarify the usefulness of orthognathic surgery through a linkage between simulation and navigation, close analysis involving many cases might be necessary to establish a method of addressing three-dimensional movement of the maxilla.

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　A statistical analysis was performed for patients who underwent orthognathic surgery during the last 12 years, from 2005 to 2016, in the Department of Oral and Maxillofacial Surgery, Faculty of Medicine, Tokyo Medical University.
　The results were as follows:
　1．The number of orthognathic surgery operations increased yearly.
　2．There were 313 patients （109 males and 204 females） in the 12 years.
　3．The average age of the patients was 29.0 years old （range: 16-58）. Patients in their twenties accounted for the largest number （47.9％）.
　4．The most common diagnosis was mandibular prognathism （50.5％）, followed by mandibular retrognathism （11.8％）, and mandibular prognathism with open bite （9.3％）.
　5．The most frequently performed operation was sagittal split ramus osteotomy （SSRO）, accounting for 47.9％, followed by the combination of Le Fort I osteotomy and SSRO （L1＋SSRO） at 27.5％.
　6．The average operation time and amount of bleeding for SSRO were 231 minutes and 316ml, and those for L1＋SSRO were 408min and 810ml, respectively.
　7．The number of clinics referring patients to our department is increasing.

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We report a case of adult mandibular prognathism with missing maxillomandibular molar teeth.
A 46-year-old man had mandibular protrusion with maxillomandibular molars lost due to periodontal disease and dental caries. After 5months of preoperative orthodontic treatment, a sagittal split ramus osteotomy was performed using bite plates to stabilize the molar occlusion.
The amount of setback was 6.5mm on the right side and 4.0mm on the left. After the surgery, the mandibular prognathism improved. After performing orthodontic treatment, the molar occlusion was reconstructed with an implant prosthesis. It has been almost 2years since the surgical treatment and there has been no significant relapse and the occlusion has remained stable. We think that malocclusion with jaw deformity is one of the risk factors for collapse of the occlusion. In patients with multiple missing teeth, we should consider both prosthodontic treatment and comprehensive dental therapy, including surgical orthodontic treatment.

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We report a case of skeletal mandibular retrusion with a narrow maxillo-mandibular dental arch in which satisfactory occlusion was achieved by lateral expansion of maxillary and mandibular bones with horizontal distraction osteogenesis followed by maxillo-mandibular advancement. The patient was a female aged 24 years and 5 months at the first visit with a chief complaint of maxillary protrusion. She had a convex facial profile with prominent tension around the lips when her mouth was closed. When she smiled, she showed a gummy smile with large buccal corridor. The molar relationship was Angle Class Ⅱ. Cephalometric findings revealed retrusion of the mandibular bone and labial inclination of the anterior maxillo-mandibular teeth.
Lateral expansion was performed for the maxilla by 6.0 mm and for the mandible by 7.0 mm at the median of the maxillo-mandibular bones using horizontal distraction osteogenesis. Three months after completing expansion, preoperational orthodontic treatment was started, and maxillo-mandibular advancement was performed 1 year and 6 months after the expansion. The screws were removed and genioplasty was performed 8 months after the operation. Then, screws were further removed from the corresponding site at 5 months, and as appropriate occlusion was achieved, we completed the active treatment 12 months after the orthognathic surgery and started maintenance. The treatment required 3 years. Her large buccal corridor was resolved after lateral expansion of the dental arch using horizontal distraction osteogenesis. With this extra space, maxillo-mandibular growth was achieved and labial inclination of the anterior teeth was improved. Furthermore, her gummy smile was improved with maxillo-mandibular advancement, and her convex facial profile was also improved by concomitant use of genioplasty.

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Crouzon syndrome is a type of craniofacial dysostosis characterized by early fusion of certain skull bones, which can affect the shape of the head and face. Signs and symptoms of Crouzon syndrome include bulging eyes, underdeveloped upper jaw and severe mandibular prognathism. This case report describes a patient with Crouzon syndrome who received maxillary distraction osteogenesis using a rigid extraoral distractor （RED） system and sagittal split ramus osteotomy （SSRO）. A boy, 10 years and 1 month old, was referred to our clinic to treat mandibular prognathism. He had already undergone cranioplasty at 1 year old, maxillary distraction at 7 years old, and surgical closure of the occipital region at 9 years old at another hospital. He showed a concave profile and also had an abnormal swallowing habit. The overjet and overbite were −1.0mm and 2.0mm respectively. ∠ANB was −10.0°, ∠SNA was 71.0°, and ∠SNB was 81.0°. We applied orthodontic expansion and a maxillary protractive appliance at the first phase of treatment. However, at 17 years and 0 months, overjet became −3.0mm and ∠ANB worsened to −15.8°. Therefore, at the second phase of treatment, we performed alveolar osteotomy with maxillary expansion, maxillary distraction osteogenesis using a RED system for maxillary advancement and SSRO for mandibular setback. As a result, overjet improved to 2.0mm and ∠ANB changed to −4.5°. Although the skeletal discrepancy was not improved enough, his concave facial profile was changed to almost a straight profile by the orthognathic surgery. The active treatment period was 2 years and 5 months and the patient’s occlusal relationship remained stable during the retention period.

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