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.