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