Effects of Andresen Activator on Pharyngeal Airway Volume in Growing Patients With Obstructive Sleep Apnea Syndrome: CBCT Evaluation

Aim: To assess the effects of Andresen functional appliance therapy on the pharyngeal airway passage (PAP) in growing Class II patients presenting with obstructive sleep apnea syndrome (OSAS). This update study incorporates new data from an extended sample and a revised follow-up period to evaluate changes in airway dimensions using cone beam computed tomography (CBCT). Methods: Fifty growing patients with Class II malocclusion, mandibular hypoplasia, and OSAS, aged 9–14 (±1.63) years, were recruited for the study group. An additional 15 untreated patients (seven females and eight males) matched for age, sex, and craniofacial morphology served as the control group. Each patient had a CBCT performed before treatment (T0) and posttreatment after follow-up (16–24 months-T1). Pharyngeal airway dimensions were measured via medical 3D analysis software. The following measurements were recorded: depth of the oropharynx (DOP), depth of the hypopharynx (DHP), MP-H (linear distance from mandibular plane to hyoid), posterior nasal spine (PNS)-U (soft palate length), posterior airway space (PAS), SNA, SNB, and ANB. Statistical analysis (t-tests for paired samples) was performed to compare T0–T1 changes within and between groups, with significance set at p < 0.05. Results: This study showed the effects of the Andresen appliance on Class II correction, with an increase in SNB and a reduction in ANB. PAS increased by 2.94 mm (p < 0.001). DOP and DHP showed improvements after expansion (p < 0.001), and MP-H decreased (3.62 mm; p < 0.001), suggesting upward movement of the hyoid bone. Conclusions: In growing Class II patients, correction of mandibular retrusion using the Andresen appliance contributes to a sagittal increase in the oropharyngeal airway. These dimensional changes in the PAP also provided clinical improvements in sleep-disordered breathing, supported by improved nocturnal polysomnographic (PSG) parameters. Such results might reduce anatomical and functional risk factors for pediatric OSAS. Functional orthopedic treatment performed during childhood has a role in airway patency promotion and long-term OSAS risk decrease. A multidisciplinary approach is advised for optimal care.