A cone beam CT study on the changes in oropharyngeal airway parameters and hyoid position in skeletal Class Ⅱ adult female patients with different vertical skeletal types treated with maxillary anterior teeth retraction with maximum anchorage

To investigate the changes in oropharyngeal airway parameters and hyoid position in skeletal ClassⅡ adult female patients with different vertical skeletal types who were treated with maxillary anterior teeth retraction with maximum anchorage, and to provide a reference for orthodontic clinical diagnosis and treatment.

This study was reviewed and approved by the Medical Ethics Committee, and informed consent was obtained from patients. Sixty adult female patients with skeletal ClassⅡ were selected and divided into a skeletal ClassⅡ normodivergent group and a skeletal ClassⅡ hyperdivergent group based on the patients’mandibular plane angle. In both groups, the bilateral maxillary first premolars were extracted and the maxillary anterior teeth were retracted with maximum anchorage. Cone beam CT(CBCT) images were collected before and after treatment, and three-dimensional measurement software was used to analyze oropharyngeal airway-related parameters.

After retraction of the maxillary anterior teeth with maximum anchorage, the 10 parameters related to the oropharyngeal airway did not exhibit statistically significant differences in the normodivergent group (P＞0.05), but the perpendicular distance from the highest point of the hyoid bone to the vertical line passing through the sella (H-X) value decreased (P＜0.001). In the hyperdivergent group, the oropharyngeal area at the level of the epiglottis tip (OPA-E), anterior-posterior diameters of the oropharynx at the level of the epiglottis tip (E-AP), most constricted axial area of the oropharynx (OPA-MCA), and anterior-posterior diameters of MCA area of the oropharynx (MCA-AP) decreased after treatment (P＜0.001). In addition, the oropharyngeal volume (OPV) decreased after treatment (P＜0.05), and the perpendicular distance from the highest point of the hyoid bone to the horizontal line passing through the sella (H-Y) and the highest point of the hyoid bone to the epiglottis base (H-Eb) values increased after treatment (P＜0.05).

After retraction of the maxillary anterior teeth with maximum anchorage, there is no change in the oropharyngeal airway in skeletal ClassⅡ normodivergent female adult patients, while skeletal ClassⅡ hyperdivergent female adult patients have a risk of reduction in the oropharyngeal airway after maximuim anchorage retraction of the maxillary anterior teeth.