The influence of initial incisal overlap on mandibular plane rotation, 3D airway dimensions, and hyoid bone changes following surgery-first mandibular setback in skeletal Class III patients: A pilot study.

BACKGROUND/PURPOSE: Skeletal Class III malocclusion often requires mandibular setback, which can affect airway patency and skeletal stability, particularly when managed with a surgery-first orthognathic approach (SFOA). This study evaluated the influence of initial incisal overlap on mandibular plane (MP) rotation, pharyngeal airway volume, and hyoid bone position following surgery-first isolated mandibular setback in skeletal Class III patients.

MATERIALS AND METHODS: Nineteen patients (mean age, 24.5 ± 4.22 years) treated with a SFOA were grouped by initial overbite (OB): Group 1 (OB ≥ 0 mm; n = 11) and Group 2 (OB < 0 mm; n = 8). Cone-beam computed tomography and cephalograms were analyzed at pretreatment, 1 month, and 1 year postoperatively. Changes in airway volumes, minimum cross-sectional area (MCSA), hyoid position, and MP angle were assessed. Statistical comparisons and correlation analyses were performed (P < 0.05).

RESULTS: Group 1 showed significantly greater total horizontal mandibular setback and more pronounced clockwise (CW) MP rotation. Both groups demonstrated postero-inferior hyoid bone displacement; Group 1 exhibited greater vertical displacement, whereas Group 2 showed significantly greater upward hyoid bone movement. Total airway volume decreased significantly in both groups, primarily due to oropharyngeal volume reduction. No significant correlations were found between skeletal changes and airway volume.

CONCLUSION: Initial incisal overlap appeared to influence postoperative MP rotation, skeletal stability, hyoid bone adaptation, and airway changes in SFOA-treated skeletal Class III patients. This suggested that controlling MP rotation and maintaining anterior occlusal support may minimize skeletal relapse and postoperative airway compromise.