3D lip changes in skeletal Class III patients with premolar extraction: A prospective cohort study comparing surgery-first and orthodontics-first approaches.

Objective: To investigate the three-dimensional (3D) changes in lip morphology introduced by different surgical orthodontic treatment approaches in skeletal Class III patients. Methods: Forty Class III patients were treated using the surgery-first approach (SFA, n = 20) or a three-stage approach (TSA, n = 20), both involving bimaxillary surgery and maxillary premolar extractions. Cephalograms and facial scans were obtained at different time points (T0-T5) throughout the treatment period. T tests and repeated measures analysis of variance were compared to 3D lip morphology between groups. Correlation analysis and stepwise linear regression were used for prediction. Results: After debonding, mandibular incisors in the SFA group were positioned more lingually (L1MP: SFA 80.75 ± 5.73°, TSA 89.78 ± 5.88°, Conclusions: Both methods significantly improved the aesthetics of lip morphology in skeletal Class III patients. When the extraction space was closed, the lip shape was nearly stable in the SFA; TSA was stabilized 6 months post-surgery. The lips exhibited a compensatory response to differences in hard tissue and showed a moderate association with changes in dental and skeletal measurements.