Modeling facial movement: II. A dynamic analysis of differences caused by orthognathic surgery.

PURPOSE The purpose of this study was to determine the facial movement characteristics of patients who underwent orthognathic surgery. The specific aims were to determine the presurgery versus postsurgery differences in facial movements; to determine whether the presurgery facial movements were similar among patients with different dentofacial deformities; and to determine whether patients have a more similar post- than presurgery dentofacial morphology and soft tissue movement. The hypothesis was that there are differences between the pre- and postsurgery facial movements. PATIENTS AND METHODS The sample consisted of 19 patients (11 women, 8 men) with a mean age of 20.6 years (SD +/- 8.34). Facial movement and lateral cephalometric data were collected at presurgery, and at 6 and 12 months postsurgery. Measures of the facial skeletal differences were made from lateral cephalometric radiographs and facial movements were recorded by a video-based tracking system. Descriptive and inferential statistics were performed on principal component scores generated from the movement data. A linear mixed-effects model was used to test for significant differences in movement. RESULTS Differences were found between the presurgery and 12-month postsurgery visits for the instructed smile, lip purse, eye closure, grimace, and mouth opening movements as well as the natural smile. Also, there were significant differences at presurgery among the dentofacial groups for the lip purse movement but no differences were found at postsurgery for any of the movements. CONCLUSION These findings suggest that facial movements are effected by skeletal malocclusion and orthognathic surgical procedures.