Comparison of the mandibular hinge axis in adult patients with facial asymmetry with and without posterior unilateral crossbite

Background/Objectives: Although it has been suggested that adult patients with facial asymmetry with posterior unilateral crossbite (PUXB) may have a more tilted mandibular hinge axis (MHA) than those without PUXB, whether craniofacial morphology is associated with the MHA remains unclear. The purpose of this study was to compare the craniofacial morphology and MHA in adult subjects with post-growth facial asymmetry with and without PUXB. Subjects/Methods: Thirty pre-orthodontic patients (PUXB and non-PUXB groups, n = 15 each, 9 females and 6 males, mean age: 23.2 years) participated in the study. The MHA was measured by computerized axiography and duplicated on posteroanterior and submentovertex cephalometric radiographs. Morphological asymmetry was evaluated for both skeletal and dental components and positional deviation of the mandible by cephalometric analysis. The Mann-Whitney U-test and Spearman's correlation coefficient by rank were used for statistical analysis. The level of statistical significance was set at P < 0.05. Results: Significant differences in both skeletal and dental components were found between the PUXB and non-PUXB groups. In both the frontal and horizontal dimensions, the inclination of the MHA towards the mandibular shifted side was greater in the PUXB group than in the non-PUXB group. Conclusions/Implications: The present findings suggest that facially asymmetric adult subjects with malocclusions associated with PUXB exhibit not only mandibular asymmetry but also remodelling of the condylar head and glenoid fossa that accompanies the three-dimensional shifting of the MHA.