Retrospective 3D analysis of changes in the masseter muscles and soft tissues following orthognathic surgery for patients with maxillomandibular asymmetry: 12-month CBCT study

This retrospective study was performed to evaluate changes in the masseter muscles (MM) and gonial area soft tissues (GAST) in 20 patients with severe asymmetry (7 female, 13 male; age 19–45 years) who underwent bimaxillary orthognathic surgery. Preoperative and 1-year postoperative cone beam computed tomography scans were analysed for changes in the MM and GAST. No statistically significant difference in MM measurements (linear, cross-sectional, and volumetric) was observed between the preoperative and postoperative periods, or between the deviation side (side to which menton deviated) and non-deviation side. GAST measurements showed no significant difference between the sides, except for higher total soft tissue volume on the deviation side preoperatively (P = 0.028). Comparing the pre- and postoperative measurements, soft tissue thickness was significantly greater postoperatively at three points on the deviation side (Go5, P = 0.040; Go6, P = 0.023; Go7, P = 0.010) and one on the non-deviation side (Go3, P = 0.007). Skin volume was significantly greater postoperatively on the non-deviation side (P = 0.044). In conclusion, soft tissues may not fully compensate for underlying skeletal asymmetry. MM and GAST exhibit distinct morphological changes, underscoring the importance of considering both hard and soft tissue factors in treatment planning.