Postoperative Stability and Occlusal Plane Alternation by Orthgnathic Surgery of Skeletal Class Ⅲ Malocclusion with Anterior Open Bite

Abstract

The purpose of this study is to investigate the stability of counterclockwise rotation

of mandible by sagittal split ramus osteotomy to correct the skeletal Class Ⅲ

malocclusion with anterior open bite. Twenty five skeletal ClassⅢ open bite

patients(mean age 20.6 years) who were treated by the sagittal split ramus osteotomies with rigid fixation were examined in this study. Cephalometric radiographs were taken for ach patients preoperative(T1), early postoperative(T2), and late postoperative period(T3). Mean postoperative period(T3).Mean postoperative period was 8.0 months.

Cephalomerric analysis was done and data from T1, T2, and T3 were analyzed

statistically by paired t-test and pearson correlation analysis. The following results were obtained.

1. Mandibular plane angle decreased 2.9° and mandibular occlusal plane angle related to

SN plane decreased 2.7° after orthognathic surgery(T2). At 6 months after orthgnathic

surgery(T3), mandibular plane angle increased 1.0°, but mandibular occlusal plane angle did not changed.

2. The amount of horizontal relapse long time after orthornathic surgery(T3) was 1.6㎜ at B point and it was 22％ of the total posterior movements. There was no vertical

relapse in the anterior facial height.

3. The related factor with horizontal relapse at late postoperative period was mandibular plane angle(p＜0.01). The related factors with decreasing posterior facial height were amount of mandibular setback(p＜0.01), increasing of mandibular ramus height(p＜0.01), and decrease of the mandibular plane angle during operation(p＜0.01).

4. There was no relationship between the amount of changes in mandibular occlusal

plan angle during operation and the amount of relaspe after surgery.