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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外科的矯正治療が必要となる骨格性下顎前突症においては，術前矯正を行う事が一般的である。この際，dental compensationを解消させるために下顎前歯の唇側傾斜が必要となる。しかし骨格性下顎前突症患者は正常咬合者に比べてsymphysisの歯槽部幅径が小さく，歯の移動が制限される。そこで，本研究は骨格性下顎前突症患者において前歯に咬耗のない開咬を伴う症例と開咬伴わない症例のsymphysisと下顎臼歯部の歯槽骨幅径に関連があるかcone-beam computed tomography（以下，CBCT）を用いて分析，解明することを目的とした。
CBCTを撮影した16歳以上の骨格性下顎前突症患者のうち，前歯部咬耗がない開咬を伴う下顎前突症患者30名（開咬群）と開咬を伴わない下顎前突症患者30名（非開咬群）の計60名を選択した。CBCT画像を用いて，InVivo5（Anatomage，San Jose，CA）を使用し下顎中切歯，下顎臼歯部のcemento-enamel junction（以下，CEJ）から各2，4，6，8，10mm下方のsymphysisと下顎臼歯部の唇舌側（頰舌側）皮質骨，下顎歯槽骨幅径の距離を計測した。統計処理は，距離計測の比較にMann-Whitney’s U testを用いた。統計解析用ソフトJMP Pro 14（SAS Institute Inc.，Cary，NC）を用いて，優位性を危険率5％で検定した。
計測の結果，非開咬群と比較して，開咬群のconvexity，A-B Plane angle，Mandibular plane angle， gonial angleは有意に大きな値を示し2群の間で差が認められた。下顎前歯部歯槽骨幅径はCEJから2.0mm，4.0mm，6.0mm，8.0mmの平均値で開咬群が非開咬群に対し有意に小さな値を示した。下顎第一大臼歯遠心根・第二大臼歯間においては，開咬群の右側頰側皮質骨はCEJから6.0mm，8.0mmにおいて非開咬群に対して有意に小さい値を示したが，左側頰側皮質骨には有意差が認められなかった。また，開咬群の右側舌側皮質骨はCEJから6.0mm，左側舌側皮質骨はCEJから2.0mm，4.0mmにおいて非開咬群に対して有意に小さい値を示した。さらに，開咬群の右側歯槽骨幅径はCEJから8.0mmにおいて非開咬群に対して有意に小さい値を示した。
1）前歯部の咬合刺激低下によりsymphysisの歯槽骨幅径が小さくなった。2）骨格性下顎前突症患者の場合，開咬群の咬合力は非開咬群より小さく，機械的刺激が低下するため，下顎臼歯部歯槽骨幅径，頰側皮質骨幅径の一部で非開咬群に比べて小さい値を示す，と示唆された。以上より，成長期の骨格性下顎前突傾向のある患者に意図的に矯正装置による咬合刺激を与え，symphysis等の厚みを変化させることで，術前矯正における下顎前歯移動の制限や歯根吸収，歯肉退縮を予防出来る可能性があると考えた。

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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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