Biomechanical Evaluation of Pre- and Post-bilateral Sagittal Split Mandibular Osteotomy on Three-Dimensional Models for Obstructive Sleep Apnea Using Finite Element Analysis

Abstract

Obstructive sleep apnea syndrome (OSA) is the hindrance of upper airway during sleep, associated with curtailment in blood oxygen saturation. It is characterized by subdual flow of oxygen to vital organs causing irregular heart rhythms. One of the triumphant surgeries to treat OSA is maxillo-mandibular advancement (MMA) which is found to be 90% successful for OSA patients (Phee 2015). In MMA, the lower jaw and the mid-face are progressed to augment the posterior airway space facilitating trouble-free breathing. In this research, we attempted to contemplate the von Mises stresses due to mastication in normal and osteotomed 3D models and identify the maximum stress that can be tolerated by the mandible using finite element analysis (FEA). FEA has been extensively used to solve complex problems in dentistry and researchers have found a high correlation between FEA simulation results and in vitro measurements for mandibular specimens (Erkmen et al. 2005). The location of screws and miniplate fixation in the 3D osteotomed models was determined by Champy’s lines in order to ensure stable fixation (Erkmen et al. 2005). We first evaluated the extent of movement of the posterior airway space that is mandatory for the OSA patients to breathe normally. It was evident that the airway constriction was corrected in the upper respiratory tract by the advancement of the mandible. The von Mises stress and displacement in the mandible before and after MMA by applying three different loads, incisal, contralateral compressive molar loads, and one-sided molar loads were analyzed to rule out the fixation and orthognathic issues. The stress distributions during mastication were furthermore compared for mandibular osteotomy models with two distinct lengths of advancement. In addition, the deflection by virtue of mastication on molars, incisors, and canines was also assessed. In line with the above-mentioned evaluation, we performed the computational fluid dynamics (CFD) analysis of the upper airway model with the pre- and post-surgical conditions to predict the airflow dynamics accordingly.