Pharyngeal Airway Volume Changes and Patient-Reported Breathing and Sleep Comfort Following Class II Functional Orthodontic Treatment, Predominantly the Herbst Therapy, in Growing Children: A Retrospective CBCT Study

Objectives: To explore volumetric changes in the nasopharynx, oropharynx, hypopharynx, and total pharyngeal airway after Class II functional orthodontic treatment and to relate these anatomical changes to patient-reported breathing and sleep comfort. Methods: A retrospective observational study of 63 growing patients (11–14 years) with Class II mandibular retrusion was conducted. Pre- and post-treatment cone beam computed tomography (CBCT) scans (NewTom 5G) were exported as uncompressed digital imaging and communications in medicine (DICOM) files and analyzed with Dolphin Imaging v11.9. The pharyngeal airway was manually segmented into naso-, oro-, and hypopharyngeal regions; volumes were measured twice by a single examiner to assess reliability. Inter-examiner reliability was assessed in a 15-patient subgroup. Patients completed a 5-point Likert rating of perceived breathing and sleep changes. Statistical tests included Wilcoxon signed-rank, Friedman with Holm post hoc, Mann–Whitney U, and Spearman correlation; p < 0.05 was considered significant. Results: Intra-examiner reliability was excellent (ICC1 mean 0.988), and inter-examiner reliability was good to excellent (ICC2 0.87–0.95). Mean total pharyngeal airway volume during the treatment interval in growing Class II patients treated with functional appliances increased from 18,183.62 mm3 at T0 to 23,524.42 mm3 at T1—an average augmentation of approximately 5340.80 mm3 (~29.4%). Regional gains followed the following pattern: Oropharynx > Nasopharynx > Hypopharynx. Nasopharyngeal and total airway changes were found to be associated with improvements in reported breathing (ρ = 0.79 and 0.69) and sleep comfort (total airway ρ = 0.74). Conclusions: Functional mandibular advancement in growing Class II patients was associated with enlargement of the pharyngeal airway—most notably in the oropharynx—and these volumetric gains were followed by improved patient-reported breathing and sleep comfort within the limitations of retrospective study design.