Influence of Oral Appliances for OSA on Mastication-related Muscle Activity

Objectives: It is unknown how the forced positioning of the mandible forward and downward with oral appliance (OA), used for the treatment of obstructive sleep apnea (OSA), affects the stomatognathic system. The purpose of this study is to define the appropriate design of OA in male and female subjects in human subjects.

Methods: Twelve healthy adults participated in the present study. With the appliance, the mandible was advanced 0, 45, 60 or 75% of maximum protrusion capacity and bite raising between the first molars was 10mm (OA10-0, 10-45, 10-60 or 10-75). Electromyographic (EMG) activity was recorded from the right masseter (Mm), anterior (Ta) and posterior temporal (Tp), and sternocleidomastoid muscles (Scm) following maximum voluntary clenching. The EMG activities in each muscle was analyzed before wearing OA (stage B), 1 hour and 6 hours after wearing (stage A1, A6), and 1 hour after removal (stage R1). EMG activity was integrated and the activity index (Mm•Ta) was calculated. These data were studied in comparison with stage B, and activity index in male and female subjects was precisely analyzed in each OA stage.

Results: Mm EMG activity had a tendency to be lower significantly in female (p < 0.05). Tp activity had a tendency to be lower significantly in male. Scm activity had a tendency to be higher significantly in male, and lower significantly in female. Activity index (Mm•Ta) of male was significantly higher than that of female in stage A6 of OA10-0, stage A6 and R1 of OA10-45.

Conclusion: These findings suggested that the design and duration of OA usage should be different in male and female OSA patients. It was also suggested that the appropriate approach in different muscles should be considered for OSA treatment in male and female patients.