This study compared the jaw-muscle electromyographic (EMG) activity during sleep in patients with craniofacial pain (n = 63) or no painful conditions (n = 52) and between patients with tension-type headache (TTH: n = 30) and healthy control individuals (n = 30). All participants used a portable single-channel EMG device (Medotech A/S) for four nights. There was no significant difference in EMG activity between craniofacial pain (24.5 ± 17.9 events/hr) and no painful conditions (19.7 ± 14.5), or between TTH (20.8 ± 15.0) and healthy control individuals (15.2 ± 11.6, p >.050). There were positive correlations between EMG activity and number of painful muscles (r = 0.188; p = 0.044), characteristic pain intensity (r = 0.187; p = 0.046), McGill Pain Questionnaire (r = 0.251; p = 0.008), and depression scores (r = 0.291; p = 0.002). Patients with painful conditions had significantly higher night-to-night variability compared with pain-free individuals (p < 0.050). This short-term observational study suggests that there are no major differences between patients with different craniofacial pain conditions and pain-free individuals in terms of jaw-muscle EMG activity recorded with a single-channel EMG device during sleep. However, some associations may exist between the level of EMG activity and various parameters of craniofacial pain. Longitudinal studies are warranted to further explore the relationship between sleep bruxism and craniofacial pain.

The aim of this study was to investigate effects of interocclusal distance (IOD) on bite force and masseter electromyographic (EMG) activity during different isometric contraction tasks. Thirty-one healthy participants (14 women and 17 men, 21·2 ± 1·8 years) were recruited. Maximal Voluntary Occlusal Bite Force (MVOBF) between the first molars and masseter EMG activity during all the isometric-biting tasks were measured. The participants were asked to bite at submaximal levels of 20%, 40%, 60% and 80% MVOBF with the use of visual feedback. The thickness of the force transducer was set at 8, 12, 16 and 20 mm (= IOD), and sides were tested in random sequence. MVOBF was significantly higher at 8 mm compared with all other IODs (P < 0·001). Only in women, IOD always had significant influence on the corresponding root-mean-square (RMS) value of EMG (P < 0·011). When biting was performed on the ipsilateral side to the dominant hand, the working side consistently showed higher masseter EMG activity compared with the balancing side (P < 0·020). On the contralateral side, there was no difference between the masseter EMG at any IODs. The results replicated the finding that higher occlusal forces can be generated between the first molars at shorter IODs. The new finding in this study was that an effect of hand dominance could be found on masseter muscle activity during isometric biting. This may suggest that there can be a general dominant side effect on human jaw muscles possibly reflecting differences in motor unit recruitment strategies.

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).

Tanosoto T, Arima T, Tomonaga A, Ohata N, Svensson P. Effect of PASAT-inducedmental stress on human heart rate variability, masseter EMG activity and haemodaynamics. Eur J Oral SciThis study aimed to determine autonomic and jaw-muscle EMG responses to acute experimental mental stress in humans. Eleven healthy men (25.2 ± 3.0 years old) and five women (23.0 ± 3.7) performed a standardized mental stress task, Paced Auditory Serial Addition Task (PASAT). Autonomic function, such as heart rate variability (HRV), and haemodynamic changes in addition to bilateral masseter electromyographic (EMG) activity were recorded simultaneously. The success rate of PASAT (first session: 84.6 ± 15.8%) decreased during the sessions (fourth session: 61.2 ± 16.1%, P < 0.001) probably due to increased pace and difficulty of PASAT. Low frequency (5.8 ± 1.1 ms 2 ) and high frequency (5.3 ± 0.6 ms 2

It is proved that the evaluation method using the facet index of occlusal splint for sleep bruxism is a reliable means of estimating how long the restoration will last. The results showed that sleep bruxism influences the dislodgement of restorations. To protect restorations, it might be effective to control the load from sleep bruxism.