Oropharyngeal muscle training has emerged as a novel adjunctive treatment approach, involving training of the swallowing muscle group and tongue muscles to prevent tongue collapse, reduce tongue base volume during sleep, and strengthen muscle tension. Therefore, the objective is to assess changes in oropharyngeal muscle strength, ultrasonographic tongue morphology, severity of sleep related breathing interruptions, clinical symptoms, and correlations among these factors. Oropharyngeal muscle training for patients with residual OSA using MAD can significantly 1. increase muscle strength and endurance. 2. reduce the severity of sleep-related breathing interruptions. 3. decrease clinical symptoms. 4. improve tongue morphology.