Changes in nasopharynx,oropharynx,soft and hard tissues around pharyngeal airway after bimaxillary surgery for patients with skeletal Class III malocclusion

Objective: To compare the changes of nasopharynx,oropharynx,soft and hard tissues around the pharyngeal airway in the patients with skeletal Class Ⅲ malocclusion after bimaxillary surgery.Methods: 19 patients(12 women,7 men,average age:23.8) with skeletal Class Ⅲ malocclusion underwent bimaxillary surgery were involved in this study.Cone Beam Computer Tomography(CBCT) examination was performed 1 week before and 3 months after the surgery.The nasopharynx and oropharynx for volumetric analysis was conducted by the use of 3D CBCT images built by Mimics 10.01.Results: After surgery the oropharynx volume and the pharyngeal airway(including nasopharynx and oropharynx) decreased(P0.05).On average the oropharynx volume and pharyngeal airway decreased by 8.37% and 6.91% respectively.The cross-sectional area behind the soft palate decreased by 19.83%(P0.05).The position of the hyoid bone and the morphology of the soft palate changed significantly(P0.05).Pharyngeal airway space was correlated with the position of the hyoid bone(H-X,H-Y) or the morphology of the soft palate(PNS-UT,U-T,UT/ANS).The morphology of the soft palate was correlated with the position of the hyoid bone.Conclusion: Bimaxillary surgery can not prevent pharyngeal airway space from narrowing in the correction of Class Ⅲ malocclusion.