上下顎歯列弓幅径の不調和を有し，CO-CRディスクレパンシーが大きい骨格性Ⅱ級・開咬症例に対し，正中2分割Le FortⅠ型骨切り術と下顎枝矢状分割術を施行した1例

It is known that stable orthodontic treatment for skeletal Class Ⅱ open-bite cases caused by retrognathia can attain over bite mandibular counterclockwise rotation due to intrusion of upper and lower molars. Evaluation the temporomandibular joint essential in these cases, as there may be progressive resorption condyle. Furthermore, it important plan surgical based on restoration position close centric relation （CR） possible. When disharmony arch width between both jaws a narrowed maxillary adult patients, dental or expansion used correct it. For expansion, distraction osteogenesis segmental Le Fort I osteotomy widely used. Compared has been reported post-orthodontic stability after difficult achieve with expansion. In this study, we report case class open posterior cross narrow CO-CR discrepancy, treated treatment. The patient was 19-year-8-month-old female whose chief complaint protrusion incisors masticatory disorder anterior teeth. To improve moderate crowding obtain an appropriate tooth axis, maxillomandibular bilateral first premolars were extracted, preoperative performed. Three months before orthognathic surgery, stabilization splint restore CR determining final amount movement jaw. During maxilla laterally expanded lateral segmented Ⅰ moved upward clockwise rotation. mandible, rotated set forward, resulting improved profile tight occlusion. currently under retention, occlusion generally maintained.