Changes in masseter muscle morphology after surgical-orthodontic treatment in skeletal Class III patients with mandibular asymmetry: the automatic masseter muscle segmentation model
Introduction: This study evaluated the masseter muscle changes after surgical-orthodontic treatment in skeletal Class III patients using automatic segmentation. Methods: Images of 120 skeletal Class III malocclusion patients were obtained and reconstructed at T0 (pre-treatment), T1 (preoperative), and T2 (6–12 months postoperative). The patients were divided into symmetrical and asymmetrical groups. The volume, major axis length, maximum cross-sectional area (CSAM), horizontal cross-sectional area 5 mm above the mandibular foramen (CSAF), and orientation were calculated automatically. Results: In the asymmetrical group, the volume and major axis length on the deviated side were lesser than on the non-deviated side at T0, T1, and T2 (p < 0.05). There were no significant differences in CSAM and CSAF bilaterally. The orientation was coronally more vertical and sagittally more forward on the deviated side (both p < 0.001). In the symmetrical group, there were no significant bilateral differences at T0, T1, and T2. The volume, major axis length, and CSAF decreased, and the coronal orientation was more vertical on the non-deviated side at T2 compared to T0 in both groups (p < 0.05). The coronal plane orientation was more inclined on the deviated side at T2 compared to T0 in the asymmetrical group (p < 0.05). Conclusions: The smaller volume on the deviated side at T2 indicates the need for myofunctional training after surgery. The masseter muscle volume and cross-sectional area did not recover to the pre-orthodontic levels. Studies with longer follow-up durations are needed to confirm these findings.
Beijing Municipal Science and Technology Commission, Adminitrative Commission of Zhongguancun Science Park