Quality assurance in orthognathic surgery using Brons-Mulié's soft tissue analysis, Nakamura's asymmetry index and a simple Enface analysis

The aim of orthognathic surgery should not only focus on correcting malocclusion alone, but also on achieving adequate facial aesthetics with a harmonious facial profile. However, it is often difficult to measure success of orthognathic surgery objectively due to the large number of parameters to be considered. Methods For objective assessment of success in orthognathic surgery, Brons-Mulié profile analysis, Nakamura's asymmetry index and a simple enface analysis were performed pre- and postoperatively. Comparative variance-based analysis of the different dimensions of the three methods were performed in order to analyze the variability of the individual parameters around their optimal value. F -test and Fligner-Killeen-Test were used to determine differences between pre- and post-operative variances. Results A total of 128 patients who underwent bimaxillary surgery between 2014 and 2019 were included in the study. All parameters showed a constant or reduced variance around their optimal value after orthognathic surgery. A significant reduction of the variance as an expression of surgical success ( p < 0.05) was found for the following parameters: Mandibulofacial height and lower lip inclination obtained from Brons-Mulié analysis, position of the nostrils, lip angles and jaw angles using Nakamura's Asymmetry Index and for chin position, occlusal plane inclination and midline position measured in the enface analysis. Conclusions The methodology used allows subjective aesthetic appearance to be visualized in an objective procedure. It can therefore be used as a valuable tool for preoperative surgical planning and for postoperative quality assurance in orthognathic surgery.