Effects of Two-Phase Treatment with the Herbst and Preadjusted Edgewise Appliances on the Upper Airway Dimensions

Aims. To assess the effects of two-phase treatment with the Herbst and the preadjusted edgewise appliances on upper airway dimensions and to investigate the correlation between changes in the upper airway dimensions and skeletal morphologies. Methods. A total of 27 Chinese male adolescents aged 12.8 ± 1.3 years were selected. Lateral cephalograms were collected to assess the skeletal morphology and upper airway dimensions. Results. Following Herbst appliance treatment, the upper airway space was significantly enlarged, with the retropalatal (U-MPW) increasing by 1.1 ± 1.6 mm (P < 0.001), the retroglossal (PASmin) increasing by 1.3 ± 2.9 mm (P < 0.05), and the hypopharynx (V-LPW) enlarging by 1.6 ± 3.0 mm (P < 0.01). PASmin was found to show a negative correlation to the mandibular plane angle (MnPl-SN) by r = −0.413 (P < 0.05). There was no significant change (P > 0.05) in upper airway dimensions during the second-phase treatment. Conclusions. Herbst appliance treatment increased the oropharyngeal and hypopharyngeal airway dimensions among adolescents with Class II malocclusion, and the effects were maintained throughout the second treatment phase with a preadjusted edgewise appliance. There was a negative correlation between the change in the depth of the retroglossal pharynx and the mandibular plane angle.