Three-dimensional morphologic evaluation of the changes in the pharyngeal airway and hyoid bone after bimaxillary surgery in patients with skeletal Class III malocclusion with facial asymmetry: A preliminary study

Abstract

Introduction: The study aimed to evaluate the morphologic changes in the pharyngeal airway after bimaxillary surgery in skeletal Class III malocclusion patients with or without asymmetry. We also analyzed the correlation between positional changes in the menton, hyoid bone, and changes in the dimensions of the pharyngeal airway. Methods: We included 32 patients with skeletal Class III malocclusion who underwent bimaxillary surgery. There were 16 subjects in the symmetry group (10 male, 6 female; mean age, 22.44 +/- 5.14 years), and 16 in the asymmetry group (10 male, 6 female; mean age, 21.38 +/- 4.62 years). Preoperative and postoperative (2 months after surgery) cone-beam computed tomography scans were taken and then analyzed by comparing postoperative changes in each group. Results: The anteroposterior lengths at the uvula level (P2L) and epiglottis level (P3L) were significantly decreased in the symmetry group. The P2L was also significantly decreased in the asymmetry group, and a difference in the P3L was observed. However, there was no significant change in the width at the uvula level (P2W) and epiglottis level (P3W) in the symmetry group. In contrast, in the asymmetry group, P2W and P3W were significantly decreased. The cross-sectional ratio was significantly decreased P2 (P2L/P2W) and P3 (P3L/P3W) in the symmetry group. However, a statistically significant decrease occurred only at P3 in the asymmetry group. Anteroposterior positional changes of the menton and P2L (r = -0.370; P < .05), P3L (r = -0.414; P < 0.05), and P3L/P3W (r = -0.361; P < 0.05) were correlated. Conclusions: Differences in the morphologic features of the pharyngeal airway after bimaxillary surgery was observed in both the symmetry and asymmetry groups. Bimaxillary surgery with a mandibular setback in patients with skeletal Class III malocclusion worsened morbidity of the elliptical structure of the pharyngeal airway. However, it worsened less in the asymmetry group than in the symmetry group.