Purpose: The purpose of this study was to examine the relationship between the morphologies of the masseter muscle and the ramus and occlusal force before and after sagittal split ramus osteotomy (SSRO) in patients with mandibular prognathism.
Patients and methods: The study group consisted of 26 patients with mandibular prognathism. All patients underwent bilateral SSRO as well as 3-dimensional computed tomography on which the masseter muscle, ramus, and condyle were measured preoperatively and at 1 year postoperation. Occlusal force and contact area were also recorded with pressure-sensitive sheets.
Results: In the cross-sectional area of the masseter muscle, there were no significant differences between the pre- and postoperative status. However, postoperative ramus width and area were significantly larger than preoperative values (P < .0001). Postoperative right condylar area was significantly larger than the preoperative value (P = .0120). Occlusal force and contact area 1 year after surgery were significantly larger than the preoperative values (P = .0016, P = .0190).
Conclusion: This study suggested that the masseter muscle area did not significantly differ from preoperative status 1 year after SSRO, although occlusal force, contact area, and ramus area and width increased significantly 1 year after SSRO.