Effects of Web-Based Orofacial Myofunctional Therapy on Hyoid Bone Position in Adults with Mild to Moderate Obstructive Sleep Apnea: Evidence from an Estonian Substudy of a Randomized Controlled Trial

<b>Background</b>: Orofacial myofunctional therapy (OMT) is an emerging adjunctive treatment for obstructive sleep apnea (OSA), but its effects on upper airway structural support, particularly the hyoid complex, are not well defined. This study assessed the short-term effects of OMT on hyoid bone position and sleep-related indices in adults with mild to moderate OSA. <b>Methods</b>: In this assessor-blinded randomized controlled trial (ClinicalTrials.gov Identifier: NCT06079073), 13 adults with mild to moderate OSA were randomized to a 12-week web-based OMT program (<i>n</i> = 9) or a waitlist control group (<i>n</i> = 4). Cone-beam computed tomography (CBCT) and three-night home sleep testing were performed at baseline and follow-up. The primary outcome was change in axis-based cephalometric hyoid position measures; secondary outcomes included sleep parameters such as the apnea-hypopnea index (AHI). <b>Results</b>: No significant within- or between-group differences were observed in AHI, oxygen desaturation index, or mean nocturnal SpO₂ after 12 weeks (all <i>p</i> > 0.05). However, several cephalometric variables showed significant between-group differences. The waitlist group exhibited greater posterior-inferior hyoid displacement than the OMT group, with large effect sizes across multiple vector measures (all <i>p</i> ≤ 0.045; r = 0.56-0.66). Posterior and inferior hyoid displacement was associated with higher AHI and lower SpO₂, whereas increased lower pharyngeal airway width was associated with lower AHI. <b>Conclusions</b>: Short-term OMT did not improve sleep-disordered breathing indices but was associated with stabilization of hyoid bone position. These findings suggest that structural stabilization may precede functional improvement and highlight the clinical relevance of vector-based hyoid analysis.