Correlation between the position of the glenoid fossa and condylar translational movement in skeletal Class III mandibular asymmetry patients

OBJECTIVES: Understanding the mechanism of mandibular asymmetry (MA) is important to provide suggestions for occlusal treatment and to know the developmental process of masticatory dysfunction. To investigate the morphological and functional effects on MA, we evaluated the three-dimensional position of the glenoid fossa and its relationship to asymmetrical condylar translational movement. METHODS: In this retrospective study, 50 subjects who previously underwent computed tomography for surgical purposes were divided into MA and control groups according to a menton deviation of at least 4 mm from the mid-sagittal plane. The glenoid fossae positions were evaluated using a three-dimensional analysis program. Condylar translational movements were recorded and measured by computerized axiography on protrusion. Side-to-side asymmetry was measured for each parameter. Asymmetry index value was calculated to assess the correlation between glenoid fossa position and condylar movement. Wilcoxon’s signed-ranked test, Mann–Whitney U-test, and Spearman’s rank correlation were used for the statistical analysis. RESULTS: In the MA group, glenoid fossa position on the shifted side was significantly inferior and posterior as compared to that on the non-shifted side and of the control group. Condylar path length and sagittal condylar inclination were significantly greater on the shifted side versus non-shifted side, while no significant difference was found in transverse condylar inclination. The asymmetry index of the anterior–posterior glenoid fossa position was significantly correlated with that of condylar path length and bilateral transverse condylar inclination. In the control group, there were no significant correlations among the morphological and functional parameters. LIMITATIONS: This study did not consider muscle activity and disc position, which may affect condylar movement. CONCLUSIONS: Functional asymmetry of condylar translational movements is closely related to asymmetry of glenoid fossa position in MA patients.