Evaluation of the Therapeutic Effect of Bi-Maxillary Osteotomy Using the Stress Distribution on the Temporomandibular Joint When Doing Anterior Teeth Occlusion.

The purpose of this study was to investigate how sagittal split ramus osteotomy (SSRO) and Le Fort 1 osteotomy affected the stress distribution of the temporomandibular joint (TMJ) during an anterior teeth bite using the three-dimensional (3D) finite element (FE) method. Fourteen orthognathic surgery patients were examined with mandibular prognathism, facial asymmetry, and mandibular retraction. They underwent Le Fort 1 osteotomy in conjunction with SSRO. In addition, ten asymptomatic subjects were recruited as the control group. The 3D models of the mandible, disc, and maxilla were reconstructed according to cone-beam computed tomography (CBCT). Contact was used to simulate the interaction of the disc-condyle, disc-temporal bone, and upper-lower dentition. Muscle forces and boundary conditions corresponding to the anterior occlusions were applied on the models. The stresses on the articular disc and condyle in the pre-operative group were significantly higher than normal. The contact stress and minimum principal stress in TMJ for patients with temporomandibular disorder (TMD) were abnormally higher. The peak stresses of the TMJ of the patients under anterior occlusions decreased after bimaxillary osteotomy. No postoperative TMD symptoms were found. Maxillofacial deformity led to excessive stress on the TMJ. Bimaxillary osteotomy can partially improve the stress distributions of the TMJ and relieve the symptoms of TMD.

Effect of sagittal split ramus osteotomy on morphologic parameters of temporomandibular joint in patients with mandibular prognathism.

The purpose of this study was to evaluate the change in three-dimensional morphology and clinical symptoms of temporomandibular joint (TMJ) in class III dentofacial deformity patients postoperatively for 6 months after sagittal split ramus osteotomy (SSRO).Seventeen patients with skeletal Class III malocclusion and 10 asymptomatic volunteers (classified as Control group) were recruited for the study and underwent cone-beam computed tomography scanning. The geometries of the maxilla and mandible were reconstructed using MIMICS (Materialise, Leuven, Belgium). The morphologic measurements of the patients' TMJs were done before surgery and at 6-month follow-up - named as Pre and Post groups, respectively.The joint spaces (medial joint space, superior joint space, lateral joint space, anterior joint space, and posterior joint space) of the Control group were significantly greater than those of the Pre and Post groups (P < .05), and SSRO did not significantly change the TMJ morphology parameters. Five patients were found to have preoperative temporomandibular disorder (TMD) symptoms, and 3 of them were relieved at 6 months after surgery. Postoperative TMD symptom was observed in 1 patient without preoperative TMD symptom.SSRO did not markedly alter the TMJ morphology of the patients with mandibular prognathism. The effects of SSRO on TMD symptoms should be related to the type of deformity.