Position of mandibular canal and ramus morphology before and after sagittal split ramus osteotomy.

PURPOSE The purpose of this study was to evaluate changes in the mandibular canal and ramus morphology before and after a sagittal split ramus osteotomy. PATIENTS AND METHODS The subjects were 30 patients (60 sides) with mandibular prognathism who had undergone bilateral sagittal split ramus osteotomy setback surgery. The mandibular canal position and ramus morphology were measured at the 3 horizontal planes under the mandibular foramen level (level A), 1 cm lower than level A (level B), and 2 cm lower than level A (level C) preoperatively and 1 year postoperatively by computed tomography. RESULTS Postoperative ramus width, lateral distance, lateral marrow distance, and canal length were significantly larger than the preoperative values at the foramen, 1 cm lower, and 2 cm lower. The mandibular canal completely contacted the lateral cortex without lateral bone marrow in 6 sides (10%) in levels A and B and 4 sides (6.7%) in level C preoperatively and 6 sides (10%) in level C postoperatively. CONCLUSION This study suggested that postoperative mandibular canal position was located more posteriorly and the postoperative lateral bone marrow became thicker compared with the preoperative state.