Comparative Analysis of Root Resorption in Surgery-first Approach vs Conventional Orthognathic Approach: A Cone Beam Computed Tomography Study

Objective: This retrospective clinical study aimed to compare root resorption between the surgery-first approach (SFA) and conventional orthognathic approach (COA) using cone-beam computed tomography (CBCT). Methods: Forty-one skeletal class III patients who underwent combined orthognathic surgery and non-extraction orthodontic treatment were included. According to surgical timing, participants were divided into the conventional orthognathic approach (COA) group (n=21) and the surgery-first approach (SFA) group (n=20). Root length and volume were measured on pre- and post-treatment CBCT scans. Intra-group changes in root dimensions were analyzed using paired t tests. Inter-group differences were evaluated using independent-samples t tests for tooth-specific analyses and a linear mixed model for overall assessment. Results: Root resorption was observed in both groups after treatment completion. Compared with the COA group, the SFA group exhibited a lower prevalence of mild-to-moderate root resorption and a higher proportion of unaffected teeth. Significant inter-group differences in root length reduction were observed across all maxillary teeth and mandibular incisors ( P <0.05). The linear mixed model revealed a reduction of 0.21 mm in overall root resorption in the SFA group ( P =0.002), although its clinical significance may be limited. Regarding volume loss, no significant differences were observed between the groups, except for the maxillary central incisors ( P =0.037). Consistent with these findings, the linear mixed model demonstrated no significant difference in volume loss between the two groups ( P =0.238). Conclusion: Compared with COA, SFA did not increase the risk of root resorption and might have a protective potential in non-extraction cases.