Effect of Bone Buttressing at the Vertical Osteotomy Site on Postoperative Stability After Mandibular Setback Surgery

This study aimed to assess the effect of bone buttressing at the vertical osteotomy site on postoperative stability after mandibular setback surgery and determine factors contributing to postoperative relapse. This retrospective study was conducted on patients who received mandibular setback surgery using bilateral sagittal split ramus osteotomy. Patients were divided into two groups: group I, intimate bony contact, and group II, bony gap of 2 mm or more. Using lateral cephalograms taken before surgery, 1 week after surgery, and 6 months after surgery, surgical changes, and postoperative relapse were compared between 2 groups. To assess associations between postoperative relapse and other variables, Pearson correlation analysis and multiple linear regression analysis were performed. Twenty-eight patients were evaluated (17 in group I and 11 in group II). Mean relapse was greater in group II (1.8 mm) than in group I (1.2 mm), although there were no significant differences between 2 groups (P = 0.203). Postoperative relapse was significantly associated with intraoperative clockwise rotation of the proximal segment (P < 0.001) and the amount of mandibular setback (P = 0.038). Bony gap was only correlated with postoperative counterclockwise rotation of the proximal segment (P = 0.014). In the regression analysis, intraoperative clockwise rotation of the proximal segment significantly predicted postoperative relapse (P < 0.001, R2 = 0.388). The absence of bone buttressing at the vertical osteotomy site may not significantly affect postoperative stability after mandibular setback surgery, and it is important to minimize intraoperative clockwise rotation of the proximal segment for better postoperative stability.