Effect of mandibular contouring surgery on the stress distribution during various clenching tasks

A prominent mandibular angle produces a characteristic quadrangle with a coarse appearance. Asians prefer getting the shape of their jaws surgically corrected into a V-line, which is assumed to give a more intelligent, beautiful, and delicate appearance. According to many studies, mandibular contouring surgery may jeopardize mechanical stability. The aim of this study was to analyse the stress on the mandible during function after mandibular contouring surgery using finite element analysis. Based on computed tomography scans, the three-dimensional models of preoperative mandible, mandibular angle ostectomy, and sagittal cortical ostectomy of the mandibular ramus and body with angle ostectomy were obtained. Boundary conditions to restrict movement on both condyles and clenching tasks (incisal clench, right molar clench, and right group clench) were simulated. The sagittal cortical ostectomy model had the highest strain energy (48.51 J) and von Mises stress (77.39 MPa) during the right molar clench task. The maximum von Mises stress on the sagittal cortical ostectomy was increased by up to approximately four times compared with the cases of preoperative mandible. The stress was concentrated at the site of operation, mandibular condyle, and angle. In the case of the sagittal cortical ostectomy model, bone resorption may occur, and there is a possibility of fracture during the right molar clench task. These results suggest that mandibular contouring surgery may be related to the fragility of the mandible, since surgery significantly alters its biomechanics. The degree of surgery may be a determining factor in the stress and fracture risk of the mandible. Therefore, clinicians should establish an accurate and correct treatment plan for the safe prognosis of patients after surgery.