RESUMO
INTRODUCTION: This study aimed to determine the volumetric effects on the upper airways of growing patients with Class II malocclusion treated with the Herbst appliance (HA). METHODS: Volumetric measurements of the upper airways of 42 skeletal Class II malocclusion patients (mean age: 13.8 ± 1.2 years; ranging from 12.0 to 16.9 years) were assessed using cone-beam computed tomography scans acquired before treatment (T0) and approximately 1 year later (T1). The sample comprised a Herbst appliance group (HA group [HAG]; n = 24), and a comparison group (comparison group [CG]; n = 18) of orthodontic patients who had received dental treatments other than mandibular advancement with dentofacial orthopedics. RESULTS: In CG, nasopharynx and oropharynx volumes decreased slightly during the observation period (9% and 3%, respectively), whereas the nasal cavity volume increased significantly (12%; P = 0.046). In HAG, there was an increase in the volume of all regions (nasal cavity, 5.5%; nasopharynx, 11.7%; and oropharynx, 29.7%). However, only the oropharynx showed a statistically significant increase (P = 0.003), presenting significant volumetric changes along the time (T1-T0) in HAG. CONCLUSION: Mandibular advancement with the HA significantly increased the volume of the oropharynx, but no significant volumetric modifications were observed in the nasal cavity and nasopharynx.