We evaluated statistically the status of orthognathic surgery in our department between 2013 and 2018.
The results were as follows:
1．The number of orthognathic surgery operations increased yearly.
2．There were 194 patients （47 males and 147 females） in the 6 years.
3．The mean age at the time of operation was 24.7±7.8 years old （range: 15-55）. Patients in their twenties accounted for the largest number （39.1％）.
4．The most common diagnosis was mandibular protrusion （69.6％）, followed by maxillary retrusion （9.3％） and mandibular retrusion （8.2％）.
5．The most frequently performed operation was sagittal split ramus osteotomy （SSRO）, accounting for 61.3％, followed by the combination of SSRO and Le Fort Ⅰ osteotomy （SSRO+LF1） at 32.0％.
6．The average operation time and amount of bleeding for SSRO were 165.1 minutes and 129.2ml, and those for SSRO+LF1 were 256.3 minutes and 186.4ml, respectively.
7．The number of orthodontic clinics referring patients to our department is increasing.

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Introduction: For skeletal Class Ⅲ malocclusions requiring surgical orthodontic treatment, labial inclination of the mandibular incisors is often necessary to improve dental compensation. However, the alveolar bone width of the mandibular symphysis in these patients is prone to be narrower than in patients with individual normal occlusion so that movement of the lower incisors is limited. Therefore, we investigated the alveolar bone width of the mandibular symphysis and molar areas in skeletal Class Ⅲ malocclusion cases with either non-open bite or open bite without incisor attrition using cone-beam computed tomography （CBCT）.
Materials and Methods: Among patients 16 years old or older with skeletal Class Ⅲ malocclusion who underwent CBCT, we enrolled 30 patients with open bite without incisor attrition and 30 patients with non-open bite. Using CBCT, we measured the width of the lingual side cortical bone at 2.0, 4.0, 6.0, and 8.0 mm below the cementoenamel junction （CEJ） and the width of the alveolar bone of the symphysis at 10 mm below the CEJ of the lower central incisor.
Results: The mandibular anterior alveolar bone width, measured at 2.0, 4.0, 6.0, and 8.0 mm from the CEJ, was significantly narrower in the open-bite group than in the non-open-bite group. Between the distal root of the lower first molars and the second molars, the right buccal cortical bone of the open-bite group was significantly narrower at 6.0 mm and 8.0 mm from the CEJ than that of the non-open-bite group, but no significant difference was found in the left buccal cortical bone. Additionally, the right lingual cortical bone at 6.0 mm and the left lingual cortical bone at 2.0 mm and 4.0 mm from the CEJ were significantly narrower in the open-bite group than in the non-open-bite group. Furthermore, the width of the right alveolar bone was significantly narrower in the open-bite group than in the non-open-bite group at 8.0 mm from the CEJ.
Discussion: In the case of patients with skeletal Class Ⅲ malocclusion, there was less mechanical stimulation in the open-bite group than in the non-open-bite group. This suggests that the occlusal forces were smaller and the width of the mandibular molar alveolar and buccal cortical bone narrower in the open-bite group than in the non-open-bite group.

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Sagittal split ramus osteotomy （SSRO） is mainly performed for patients with mandibular deformity as orthognathic surgery, and is a versatile intraoral procedure to address various deformities of the mandible. One of the severe potential complications of SSRO is inferior alveolar nerve disturbance. The cause is the mandibular canal pattern and/or thin ramus, and there are many cases of neurosensory disturbance after SSRO. We have used intraoral inverted L ramus osteotomy （ILRO） to treat cases that were not amenable to SSRO and achieved good treatment outcomes.
At our department from 2006 to 2018, we intraorally treated 65 cases, 101 sides of ILRO and 52 cases with plate fixation procedures. We performed a retrospective clinical study of the cases treated by ILRO at our department, and found that a few cases of inferior alveolar nerve sensory disturbance by ILRO were completely resolved by 3 months after surgery. Therefore, the ILRO procedure is considered to be useful as a third method of mandibular osteotomy, following SSRO or intraoral vertical ramus osteotomy （IVRO）.

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In our previous study which examined cases of skeletal mandibular protrusion without asymmetry, deformation of cranial vaults was seen in many cases, ranging from moderate to severe degree, in a three-dimensional manner. The findings demonstrated that asymmetric cranial vaults having unilaterally longer sagittal length are associated with posteriorly located mandibular fossae on the same side. Interestingly, the mandibular body length compensated the bilateral difference in the sagittal position of the mandibular fossae to prevent lateral deviation of the mandible.
In contrast to symmetric cases, the asymmetric mandibular appearance is associated with excess growth in the unilateral mandibular body and/or ramus, rolling of the occlusal plane and mandible, and deformation of various mandibular internal structures. In asymmetric mandibular cases, the three-dimensional position of the mandibular fossae is unclear. To clarify this point and to consider the pathogenesis of lateral deviation of the mandible, 30 female cases with mandibular protrusion with more than 3mm laterally deviated Pog were examined using computed tomography.
As reported previously in cases without asymmetry, deformation of cranial vaults was also seen in many mandibular asymmetric cases, ranging from moderate to severe degree, in a three-dimensional manner. A significant correlation was seen between the bilateral difference in the sagittal length of cranial vaults and the bilateral difference in the sagittal position of mandibular fossae. Moreover, a significant correlation was seen between the bilateral difference in the transverse length of cranial vaults and the bilateral difference in the transverse position of mandibular fossae. These findings indicate that the unilateral mandibular fossae were located more posteriorly and laterally in association with the posteriorly and laterally deformed cranial vaults. All 30 cases had shorter mandibular bodies on the Pog-deviated side than on the non-deviated side. Twenty-four out of 30 cases exhibited more posteriorly located mandibular fossae on the Pog-deviated side than on the non-deviated side, which can worsen the mandibular asymmetry.
These findings indicate that the shape of the cranial vaults is related to the anterior-posterior and transverse position of mandibular fossae in cases of skeletal asymmetric mandibular protrusion. In contrast to our previous study which examined cases of skeletal mandibular protrusion without asymmetry, the bilateral difference of mandibular body lengths in asymmetric cases could not compensate the bilateral unbalance in the A-P position of mandibular fossae.

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Facial asymmetry is known to have various causes, one of which is hemimandibular hyperplasia. This condition causes malocclusion as well as facial asymmetry.
Here, we describe the combined surgery and orthodontic treatment performed for a patient with facial asymmetry accompanied by inclination of the maxillary occlusal plane as a result of mandibular asymmetry caused by hemimandibular hyperplasia. Based on the progress of bone scintigraphy, it was determined that accumulation in the mandible was ongoing and that condylectomy was required. Preoperative simulations conducted with the attending surgeon did not produce satisfactory occlusion with condylectomy alone, and it was therefore decided to simultaneously carry out maxillary and mandibular repositioning. Consequently, favorable occlusion was obtained during dynamic orthodontic treatment, and the facial features were improved. Furthermore, a satisfactory occlusal status was observed two years after the completion of dynamic orthodontic treatment.

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