Abstract
BACKGROUND: This study evaluated the outcomes of bimaxillary surgery for class III asymmetry and lip cant, and identified factors associated with lip cant and facial midline correction. MATERIALS AND METHODS: Fifty adult patients (22 females, 28 males; mean age: 24.8 ± 5.1 years) with class III asymmetry and lip cant who underwent bimaxillary surgery were prospectively and consecutively analyzed. Cone-beam computed tomography scans obtained preoperatively and at postoperative follow-up were superimposed to assess surgical jaw movements in six degrees of freedom and their effects on lip cant and facial midline symmetry. RESULTS: Significant reductions were observed in lip cant (1.6 ± 1.6 mm), lower lip deviation (2.4 ± 1.7 mm), chin deviation (5.8 ± 4.2 mm), and facial midline deviation (9.7 ± 7.2 mm). Multiple linear regression analysis identified mandibular roll correction (β = 0.456, p < 0.01) and pre-treatment lip cant severity (β = 0.394, p < 0.01) as significant factors of lip cant reduction. Additionally, chin shift (β = 0.495, p < 0.01) and mandibular shift (β = 0.461, p < 0.01) were significant factors of facial midline correction. CONCLUSION: Bimaxillary surgery significantly improved lip cant and facial midline deviation in patients with class III asymmetry and lip cant. Mandibular roll correction and pre-treatment lip cant severity were key factors associated with lip cant correction, while chin and mandibular shift correction were associated with facial midline improvement.