Effects of vertical control on anatomic and aerodynamic characteristics of the oropharyngeal airway during premolar extraction treatment of Class II hyperdivergent nonsevere crowding malocclusion.

Introduction: This study aimed to analyze the effects of premolar extraction treatment with vertical control on changes in the anatomy and aerodynamics of the oropharynx in Class II hyperdivergent malocclusion with nonsevere crowding.

Methods: Thirty-nine patients with Class II hyperdivergent malocclusion were enrolled consecutively. All the participants underwent 4 premolar extractions. The high-pull J-hook and mini-implants were used to provide vertical control. Cone-beam computed tomography was performed before and after treatment. The participants were divided into a decreased lower vertical facial height group (n = 23) and an increased lower vertical facial height group (n = 16) on the basis of superimposition. The aerodynamic characteristics, including airway resistance (inspiration, R; expiration, R) and maximum velocity (inspiration, Vmax; expiration, Vmax) at inspiration and expiration, were calculated using computational fluid dynamics. Anatomic characteristics, including volume and cross-sectional area (CSA), were measured using the Dolphin Imaging software (Dolphin Imaging and Management Solutions, Chatsworth, Calif).

Results: After treatment, the median volume and CSA increased by 2357 mm and 43 mm, respectively, and median R and Vmax decreased by 0.15 Pa/L/min and 0.24 m×s, respectively, in decreased lower vertical facial height group. In contrast, the median CSA decreased by 9.5 mm in the increased lower vertical facial height group. All the changes were statistically significant (all P <0.05). Significant differences in volume, CSA, R, and Vmax were observed between the 2 groups.

Conclusions: Vertical control might improve the anatomic and aerodynamic characteristics of the oropharyngeal airway during premolar extraction treatment of Class II hyperdivergent malocclusion with nonsevere crowding.