Horizontal changes of the proximal mandibular segment after mandibular setback surgery using 3-dimensional computed tomography data.

OBJECTIVES: To evaluate horizontal changes of the proximal mandibular segment after mandibular setback surgery using 3-dimensional computed tomography (3-D CT). STUDY DESIGN: This study included 66 patients who underwent bilateral sagittal split ramus osteotomy for correction of mandibular prognathism. With the use of 3-D CT data obtained preoperatively (T1), immediately postoperatively (T2), and 6 months postoperatively (T3), horizontal changes of the proximal mandibular segment, including the intercondylar width, the intergonial width, and the frontal-ramal inclination were evaluated. RESULTS: The value of the right frontal-ramal inclination was 11.43 +/- 1.36 degrees at T1, 11.91 +/- 1.96 degrees at T2, and 10.7 +/- 1.5 degrees at T3. The values of the left frontal-ramal inclination were 6.10 +/- 1.03 degrees at T1, 8.17 +/- 1.66 degrees at T2, and 7.66 +/- 1.65 degrees at T3. The values of the intergonial width were 99.67 +/- 1.67 mm at T1, 98.24 +/- 1.72 mm at T2, and 97.08 +/- 1.71 mm at T3. The intergonial width was significantly decreased at T3 compared with T1 (P < .001). The values of the intercondylar width were 123.51 +/- 1.66 mm at T1, 123.9 +/- 1.66 mm at T2, and 122.88 +/- 1.58 mm at T3. CONCLUSIONS: Lower facial width at mandibular angle region decreased immediately after mandibular setback surgery and showed further decreases during the postoperative period.