Clinical Effectiveness of a Separated-Type Oral Appliance for Obstructive Sleep Apnea in Japanese Patients

Background/Objectives: Oral appliance (OA) therapy is an established treatment option for patients with mild-to-moderate obstructive sleep apnea (OSA). Although OAs of various designs have been developed, clinical evidence regarding the effectiveness of separated-type OAs in OSA remains limited. We evaluated the clinical outcomes of patients with OSA treated using a custom-made separated-type OA. Methods: This retrospective study included 47 Japanese patients with OSA who were diagnosed using polysomnography and referred for OA therapy between March 2015 and March 2025. Baseline demographic and clinical characteristics were obtained from medical records for all patients. Treatment effectiveness was analyzed in the 27 patients who underwent both baseline and follow-up polysomnography. The normality of within-patient Apnea-Hypopnea Index (AHI) differences was assessed using the Shapiro-Wilk test, and paired comparisons were performed using the paired t-test. Results: Follow-up polysomnography after OA therapy was performed in 27 patients (57.4%). In these patients, AHI significantly decreased from 17.4 ± 8.6 events/h at baseline to 8.2 ± 5.1 events/h after OA therapy (mean reduction, 9.23 events/h; 95% CI, 6.33-12.12; paired t-test, p < 0.001). OSA severity classification improved after treatment, and no patients were classified as having severe OSA at follow-up. Conclusions: Treatment with a custom-made separated-type OA was associated with a significant reduction in AHI among patients who underwent follow-up polysomnography, suggesting that separated-type OAs may be a useful option for selected patients with mild-to-moderate OSA. These findings should be interpreted with caution because of the retrospective design and incomplete follow-up data.