Comprehensive three-dimensional morphological changes of mandibular incisors and surrounding alveolar bone in patients with skeletal Class III malocclusion following surgery-first or conventional bimaxillary orthognathic surgery.

This retrospective clinical and radiographic study aimed to quantitatively compare root resorption of mandibular incisors and surrounding alveolar bone remodeling in skeletal Class III malocclusion patients treated with surgery-first approach (SFA) or conventional orthognathic surgery (COS). Sixty-two eligible patients with skeletal Class III malocclusion treated with COS (n = 31) or SFA (n = 31) at our institution between January 2020 and December 2024 were included. CBCT scans were obtained at the following time points: before treatment (T0), completed presurgical orthodontic treatment (T1)-only for COS patients, and 1-2 weeks after postsurgical orthodontics completed and debonding (T2). Skeletal and dental parameters at diverse stages were determined by Dolphin Imaging software. Incisor roots were segmented into eight regions and their length and volume were measured by Mimics 21.0. Moreover, alveolar bone height surrounding the mandibular incisors was measured and compared at diverse stages. Root resorption and alveolar bone loss were found in the lower incisors after treatment irrespective of SFA or COS. SFA induced less root resorption and alveolar bone reduction as compared to COS. Moreover, root resorption was positively correlated with increased incisor inclination in SFA patients and alveolar bone loss was positively associated with increased incisor inclination among COS patients. Initial buccal alveolar bone height negatively associated with bone reduction after treatment in both groups. Taken together, our results indicate that SFA has advantages in reduced root resorption and alveolar bone loss in the mandibular incisors as compared to COS in skeletal Class III malocclusion, thus highlighting the need to monitor these changes in patients receiving combined orthognathic and orthodontic treatment.