The three-dimensional morphology of mandible and glenoid fossa as contributing factors to menton deviation in facial asymmetry—retrospective study

BACKGROUND: The aim of this study is to evaluate whether the three-dimensional (3D) morphology of the mandibular condyle, glenoid fossa, and mandible correlated with menton deviation in facial asymmetry. SUBJECTS AND METHODS: Thirty adults (15 males and 15 females; mean age, 23.2 ± 3.8 years) with facial asymmetry were included. Linear, angular, and volumetric measurements of the 3D morphology of the mandibular condyle, glenoid fossa, and mandible were recorded using computed tomography (CT) images. The right/left differences were obtained by subtracting the left value from the right value, and an independent t test was used to compare the differences between the females and males. Multiple regression analysis was performed to identify the correlation between the right/left difference of the 3D morphology and menton deviation. RESULTS: The results of the comparative analysis did not show any statistical difference between the females and males (P > .05), so the females and males were combined. Multiple regression analysis for the mandibular condyle, glenoid fossa, and mandible showed that neck length, ramus length, and frontal ramal inclination had positive influences on menton deviation, with 76.5% of explanatory power. The neck length and head volume of the mandibular condyle when only the mandibular condyle was considered, and the ramus length and frontal ramal inclination when only the mandible was considered had positive influence on menton deviation with 69.9% and 68.6% explanatory power, respectively. On the other hand, when only considering glenoid fossa, the glenoid fossa had little effect on menton deviation with 15.7% of explanatory power. CONCLUSIONS: In facial asymmetry, the right/left differences in mandibular condyle and mandible have more impact on the menton deviation than the right/left differences in glenoid fossa. TRIAL REGISTRATION: CNUDH, CNUDH-EXP-2017-016. Registered 28 September 2017