Study of the characteristics and correlation of the chin and airway in skeletal Class Ⅱ adult female patients with mandibular retraction

To explore the characteristics and correlation of the chin and airway in females with skeletal Class Ⅱ mandibular retraction for reference for clinical diagnosis and therapy.

This study was approved by the hospital Medical Ethics Committee. Forty cases of skeletal Class Ⅱ mandibular retraction adult females with average angle were selected as the research group, and sixty cases of skeletal Class Ⅰ patients with average angle were selected as the control group. Cone-beam computed tomography (CBCT) images for all subjects were analyzed using threedimensional modeling software. Measurements included the chin morphology, position, and upper airway morphology.

Compared with skeletal Class Ⅰ patients, patients with skeletal Class Ⅱ mandibular retraction had smaller anterior chin thickness, base bone volume, chin total volume, and larger chin angle, chin depression, chin curvature, and alveolar area with statistically significant differences (P<0.05). Gn-V, Gn-H, Po-NB distance, and facial angle were smaller, and the Y-axis angle was larger in patients with skeletal Class Ⅱ mandibular retraction with statistically significant differences (P<0.05). Upper airway total volume, transverse and sagittal diameter of the glossopharynx upper boundary were smaller in patients with skeletal Class Ⅱ mandibular retraction with statistically significant differences (P<0.05). The correlation analysis between the morphology and position of the chin and the morphology of the upper airway in patients with Class Ⅱ mandibular retraction showed that there was a negative correlation between chin angle and laryngopharynx length in patients with Class Ⅱ mandibular retraction (r = -0.277, P<0.01). There was a negative correlation between Po-NB distance and palatopharyngeal length (r = -0.222, P<0.05). Chin height (r = -0.261, P<0.01) and basal bone area (r = -0.225, P<0.05) were negatively correlated with the transverse diameter of the palatopharyngeal upper boundary.The minimum chin thickness (r = 0.245, P<0.05), chin angle (r = 0.249, P<0.05), and alveolar area (r = 0.213, P<0.05) were positively correlated with the sagittal diameter of the palatopharyngeal upper boundary. Gn-V (r = 0.217, P<0.05) and Po-NB distance (r = 0.208, P<0.05) were positively correlated with the transverse diameter of the glossopharynx upper boundary. Anterior chin thickness was negatively correlated with the sagittal diameter of the laryngopharynx upper boundary (r = -0.211, P<0.05). Chin depression was negatively correlated with the sagittal diameter of the laryngopharynx lower boundary (r = -0.237, P<0.05). Chin curvature was positively correlated with the transverse diameter of the laryngopharynx lower boundary (r = 0.231, P<0.05).

Patients with skeletal Class Ⅱ mandibular retraction exhibit thinner chins. The sagittal position of the chin is backward, and the vertical position is upward. Patients with skeletal Class Ⅱ mandibular retraction have a narrow glossopharyngeal airway. There is a correlation between the morphology and position of the chin and the morphology of the upper airway in patients with Class Ⅱ mandibular retraction.