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AIM: To investigate the effect of restriction of mandibular movements during sleep on jaw-muscle activity. MATERIALS AND METHODS: Eleven healthy subjects (four men, seven women; mean age 25.9 ± 3.1 years) with self-reports and clinical indications of sleep-bruxism participated in three randomized sessions with three different types of oral appliances: 1) a full-arch maxillary and mandibular appliances which did not allow any mandibular movement, i.e., restrictive oral appliance (ROA), 2) full-arch maxillary and mandibular oral appliances (MMOA) with no restrictions of mandibular movements, and 3) a conventional full-arch flat stabilization appliance, i.e., maxillary oral appliance (MOA). Baseline recordings of jaw-muscle activity during sleep without any oral appliance were performed and followed by one week of nightly use of the oral appliances. After the baseline recording, subjects did three sessions with oral appliance during sleep. During the last night in each session, jaw-muscle activity was recorded and compared to baseline values. A detection threshold of 10 % of maximal voluntary clenching was used to analyze the electromyographic (EMG) activity from both sides of the masseter muscles and in accordance with published criteria (Lavigne et al. 1996). RESULTS: All subjects completed the experimental protocol. Regarding to the average of left and right sides, jaw-muscle activity expressed as number of EMG episodes per hour sleep was significantly lower during MOA (5.2 ± 1.1 episodes/h) compared to baseline values (6.7 ± 1.2, P < 0.01). Furthermore, the number of EMG bursts per hour sleep was significantly lower for ROA (28.3 ± 5.0 bursts/h) and MOA (25.0 ± 6.8) compared to baseline values (40.9 ± 7.7, P < 0.05). The number of phasic EMG episodes and bursts (ROA: 1.5 ± 0.4 episodes/h and 14.8 ± 2.8 bursts/h, MMOA: 1.9 ± 0.3 and 17.7 ± 4.0, MOA: 1.5 ± 0.5 and 15.1 ± 4.7) especially decreased for all three types of appliances compared to baseline (3.0± 0.5 and 29.2 ± 5.8, P < 0.05). CONCLUSION: The results indicated that restriction of mandibular movements with oral appliances may not have major influence on jaw-muscle activity during sleep but rather that the immediate effect of any combination of oral appliances lead to a suppression of EMG bursts per hour of sleep. |
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