Biomechanical comparison of temporomandibular joints after orthognathic surgery before and after design optimization.

The aim of this study is to analyse the biomechanical effects of bilateral sagittal split ramus osteotomy (BSSRO) on temporomandibular joints (TMJs) of a patient with mandibular prognathism. Two three-dimensional models of the maxilla, mandible, and articular disc were constructed based on pre- and postoperative cone-beam computed tomography (CBCT) images of the patient's head. Meanwhile, based on the preoperative model, numerical surgery of BSSRO was performed to predict the optimized postoperative model (named Num-post). Contact elements were used to simulate the interactions between the discs and articular cartilages and between the upper and lower dentitions. Muscle forces and boundary conditions corresponding to centric occlusion were applied on the models. Stresses on the disc, condylar, and temporal cartilages were significantly reduced after the optimized numerical surgery. Meanwhile, the stress distributions in the TMJ in the Num-post-operative model were uniform without stress concentration compared to Pre-operative model and Post-operative model, which suggests that the optimized numerical surgery can be beneficial to orthognathic surgeries.