RESUMO
INTRODUCTION: The muscles of mastication are important in positioning the mandible and can therefore affect the patency of the upper airway. The aim of this study was to determine whether resting masticatory muscle activity influences the response to mandibular advancement splint treatment in patients with obstructive sleep apnea. METHODS: Thirty-eight adult patients with obstructive sleep apnea were recruited for the study. Baseline electromyographic activities of the right anterior and posterior temporalis, masseter, and submandibular muscles were recorded with surface electrodes while the patients were awake, in the upright and supine positions, with the jaw in the postural position, and with and without a mandibular advancement splint. Muscle activity of the patients with obstructive sleep apnea was compared between responders (apnea-hypopnea index change ≥50%, and <10 events per hour) and nonresponders (apnea-hypopnea index change <50%) to mandibular advancement splint treatment. RESULTS: There were 18 responders and 20 nonresponders to mandibular advancement splint treatment. The responders had a trend for increased muscle activity in all muscle groups and scenarios. The resting muscle activity of the submandibular and masseter muscles while lying at rest and of the submandibular and posterior temporalis muscles while lying with the mandibular advancement splint in place were significantly greater (P <0.05) in the responders than in the nonresponders. CONCLUSIONS: Inherent baseline differences in muscle activity between responders and nonresponders to mandibular advancement splint treatment in adults with obstructive sleep apnea were observed. This preliminary study suggests that there might be a correlation between responsiveness with mandibular advancement splint treatment and baseline muscle activity.