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Purpose This study aimed to measure masseter muscle activity throughout the day in outpatients suspected of having awake bruxism (AB) and/or sleep bruxism (SB) and examine the relationship between AB and SB by comparing muscle activity during daytime wakefulness and nighttime sleep.Methods Fifty outpatients with suspected SB and/or AB participated in this study. A single-channel wearable electromyogram (EMG) device was used for EMG recording. The selected EMG bursts were divided into bursts during sleep (S-bursts) and bursts during awake state (A-bursts). The number of bursts per hour, average burst duration, and ratio of burst peak value to maximum voluntary contraction were calculated for both the S- and A-bursts. These values of the S- and A-bursts were then compared, and the correlations between them were analyzed. Additionally, the ratios of phasic and tonic bursts in the S- and A-bursts were compared.Results The number of bursts per hour was significantly higher for A-bursts than for S-bursts. No significant correlation was found between the numbers of S- and A-bursts. The ratio of phasic bursts was large and that of tonic bursts was small in both the S- and A-bursts. A comparison of the S- and A-bursts showed that the S-bursts had a significantly lower ratio of phasic bursts and higher ratio of tonic bursts than the A-bursts.Conclusions The number of masseteric EMG bursts during wakefulness did not show any association with that during sleep. It became clear that sustained muscle activity was not dominant in AB.

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OBJECTIVE: This study aimed to clarify frequency distribution of number and peak amplitude of electromyographic (EMG) waveforms of sleep bruxism (SB) in outpatients with clinical diagnosis of SB (probable bruxer: P-bruxer). METHODS: Subjects were 40 P-bruxers. Masseteric EMG during sleep was measured at home using a wearable EMG system. EMG waveforms with amplitude of more than two times the baseline and with duration of 0.25 s were extracted as SB bursts. Clusters of bursts, i.e. SB episodes, were also scored. RESULTS: There were large variations among the subjects in numbers of SB bursts and episodes and in burst peak amplitude. As for burst peak amplitude within a subject, a wide right-tailed frequency distribution was shown with the highest frequency at the class of 5-10% maximum voluntary contraction. CONCLUSION: The number and amplitude of SB waveforms for P-bruxers were distributed over a wide range, indicating the existence of large individual differences.

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Developing support and an environment for patients with dementia in hospitals is important. This study aims to assess the immediate effect of one-session cognitive stimulation intervention on the mood of patients with dementia in a hospital as preliminary evidence. This study included 33 female patients. The cognitive stimulation intervention was conducted in the day room of the hospital ward by two occupational therapists. The patients participated in one or more sessions. The cognitive stimulation intervention was designed to discuss current affairs that implicitly stimulate memory, executive function, and language skills, according to the cognitive stimulation definition. Outcomes were evaluated using a two-dimensional mood scale. The primary outcome was pleasure. The before and after session scores for the first session and the average score before and after each session at multiple times were compared. The patients' pleasure showed significant improvements in both analyses. These results may indicate that one-session Cognitive stimulation intervention in a hospital effectively improves a mood of pleasure immediately. This study is the first report to provide preliminary evidence on the beneficial alterations of mood after one-session cognitive stimulation intervention for patients with dementia in hospitals. Cognitive stimulation intervention may be an effective non-pharmacotherapy for these patients.

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PURPOSE: We aimed to clarify the relationship between the number of sleep bruxism (SB) bursts at home and in a laboratory equipped with polysomnography with audio-video recording (PSG-AV). We applied an identical single-channel wearable electromyography (EMG) device for both types of SB burst scorings. METHODS: The subjects were 20 healthy student volunteers (12 men and 8 women; mean age, 21.9 years) who were clinically diagnosed with bruxism based on the criteria set forth by the International Classification of Sleep Disorders (ICSD-2). We used a wearable EMG device attached to the masseteric area (the FLA-500-SD [FLA]), for scoring SB bursts at home and in the laboratory. PSG-AV was set within the laboratory environment as well. The mean interval for both sleep studies was 28.8 days. EMG bursts with amplitudes greater than twice the baseline amplitude and with durations of longer than 0.25 s were selected. EMG bursts with amplitudes ≥5% MVC (maximum voluntary contraction), ≥10% MVC, and ≥20% MVC were selected as well. A cluster of bursts was defined as an episode. RESULTS: In all the conditions for selecting EMG bursts specified above, the number of SB bursts and episodes recorded under laboratory conditions was statistically significantly smaller than that recorded at home. There were no statistically significant differences between the data obtained on the first and second recording days. CONCLUSION: The results of this study suggest that the unfamiliar environment of a sleep laboratory equipped with PSG-AV affects the emergence of SB as compared with home conditions.

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Objective: Assessments of diurnal awake bruxism (d-AB) using masseteric electromyogram (EMG) during various lengths of measurement time within a day were examined as the first step of research to clarify the minimum measurement time required for assessment of d-AB by subject.Methods: Subjects were 33 outpatients. Assessment of d-AB by EMG during partial measurement time (PMT) with durations ranging from 30 minutes to 6 hours was compared with that during total measurement time (TMT) used as the reference standard.Results: No significant difference was found between TMT data and PMT data. There were significant correlations in all combinations between TMT data and PMT data. Accuracy was 0.909 or more for 2.5 hours or longer.Discussion: The results suggest that the tendency of daytime muscle activity in 1 day can be assessed even by using masseteric EMG data obtained during a relatively short measurement time.

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Evaluation of sleep bruxism (SB) in clinical practice is currently conducted based on clinical findings, i.e., clinical diagnostic criteria consisting of medical interview, findings of tooth wear, and symptoms of temporomandibular joint (TMJ) and muscles. However, there are many unclear points about validity of the criteria. In this study, validity tests were conducted to clarify the accuracy of the clinical diagnostic criteria for SB by comparison with a reference standard using a single-channel masseteric electromyogram (EMG) obtained with ultraminiature electromyographic devices. The subjects included 30 'probable' bruxers (P-bruxers) who were clinically diagnosed as having SB and 30 non-bruxers. EMG was recorded during sleep under unrestrained and accustomed condition at each subject's home using ultraminiature cordless EMG devices. Bursts with amplitudes of more than 5%, 10%, 20% of the maximum voluntary contraction (MVC) value (EMG-burst-5%, EMG-burst-10%, and EMG-burst-20%) and episodes of sleep bruxism (EMG-episode) were selected for analyses. In all conditions for burst selection, the P-bruxer group showed a significantly larger number of bursts and episodes than those in the non-bruxer group. Accuracy of the clinical diagnosis criteria was 66.7% with the reference standard using EMG-burst-5%/h and 58.3% with that using EMG-episodes/h. By applying single-channel EMG as the reference standard, we were able to conduct validity tests of clinical diagnostic criteria with a larger sample. It was clarified that the level of accuracy of clinical diagnostic criteria for SB were not high despite using the combination of an interview and clinical findings.

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PURPOSE: The purpose of this study was to clarify the validity of assessment of sleep bruxism (SB) by using single-channel electromyogram (EMG) and a cut-off value with optimum sensitivity and specificity. METHODS: The subjects were twenty volunteers with clinical diagnosis of SB. Assessment by masseteric EMG data only by using a wearable EMG was compared with reference standard assessment by masseteric EMG data using polysomnography with audio-visual recording (PSG-AV). From EMG activities recorded by single-channel EMG, bursts of more than two times the baseline amplitude with a duration of 0.25s or more were selected by a burst unit (EMG-burst-all). Furthermore, from EMG-burst-all, bursts that were more than 5-20% of the maximum voluntary contraction value (EMG-burst-5%, EMG-burst-10%, EMG-burst-20%) were selected. By an episode unit, phasic, tonic, and mixed episodes were selected by single-channel EMG (EMG-episodes). Among the EMG-episodes, further, reference standard episodes of SB (PSG-episodes) were selected by PSG-AV assessment. RESULTS: Sixteen subjects were diagnosed as bruxers based on PSG-AV (PSG-episodes/h >2). By a burst unit and an episode unit, there were significant correlations between assessment variables of SB by single-channel EMG and PSG-AV except for EMG-burst-20%/h. When the cut-off value in EMG-episodes/h was 5.5/h for sleep bruxers, both sensitivity and specificity were 100%. As for variables by a burst unit, EMG-burst-all/h and EMG-burst-5% had higher values of sensitivity and specificity. CONCLUSIONS: The results suggested that single-channel EMG is valid for diagnosis of SB if a cut-off value that is appropriate for single-channel EMG is used.

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Rhythmic masticatory muscle activity (RMMA), which is defined as three or more consecutive phasic bursts, accounts for a large part of sleep bruxism (SB). RMMA is thought to be characterized by co-contraction, a jaw muscle activity in which jaw-opening muscles contract during the active phase of jaw-closing muscles, which is different from that during mastication. However, there has been limited information about co-contraction. The aim of the present study was to clarify the amplitudes and patterns of jaw-opening muscle activity during the active phase of jaw-closing muscles in RMMA. Data from 14 healthy volunteers with bruxism, which was diagnosed by using polysomnographic recording with audio-video, were analysed. RMMA with electromyographic amplitudes of more than two times the baseline amplitude was selected. From the selected RMMA, burst groups consisting of five or more consecutive phasic bursts, including tonic bursts, were selected for analyses. Electromyographic activities during gum chewing were also recorded before sleeping. The minimum, maximum and average value of the amplitudes of jaw-opening muscle activity during the active phase of jaw-closing muscles were calculated. Jaw-opening muscle activity during the active phase of jaw-closing muscles in RMMA was closer to the baseline than that in gum chewing. The minimum, maximum and average values of amplitudes of jaw-opening muscle activity during the phase were significantly smaller than those of gum chewing. Contrary to our hypothesis prior to the study, the obtained results suggested that the pattern of electromyogram activity of jaw-opening and jaw-closing muscles in RMMA was not necessarily co-contraction.

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PURPOSE: We describe the characteristics of a new data-logger-type ultraminiature electromyogram (EMG) system (FLA-500-SD) and methods used for recording and we show its potential in clinical applications by presenting an example of a clinical case. METHOD: FLA contains electrodes, an amplifier, 12-bit analog-to-digital (A/D) converter at a sampling frequency of 1kHz, 16-bit CPU, a 3.7-V coin-shaped lithium battery, and a micro SD card. The size of FLA is 37.0×23.5×8.6mm, and its weight is 6g (9g with a battery inserted). The device is wearable and patients can attach the device and operate it by themselves in daily life. Data recorded in the micro SD card are transferred to a personal computer and analyzed. Although the device is ultraminiature and wearable, it has the capacity for recording a precise and clear masseteric surface electromyogram that is not inferior to that recorded by conventional stationary-type EMG recording systems. CONCLUSIONS: To our knowledge, the device is the smallest and lightest device with capacity for the longest consecutive measuring time as a data-logger-type electromyograph with built-in electrodes and memory. The device is useful for analyses of masseteric activity during the whole day. In the future, it is expected that applications of the device will expanded to observation, evaluation and diagnosis of normal or abnormal gnathic functions, e.g., assessment of sleep and awake bruxism and observation of the chewing state in daily life.

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PURPOSE: No definitive associations or causal relationships have been determined between obstructive sleep apnea-hypopnea (OSAH) and sleep bruxism (SB). The purpose of this study was to investigate, in a population reporting awareness of both OSAH and SB, the associations between each specific breathing and jaw muscle event. METHODS: Polysomnography and audio-video data of 59 patients reporting concomitant OSAH and SB history were analyzed. Masseteric bursts after sleep onset were scored and classified into three categories: (1) sleep rhythmic masticatory muscle activity with SB (RMMA/SB), (2) sleep oromotor activity other than RMMA/SB (Sleep-OMA), and (3) wake oromotor activity after sleep onset (Wake-OMA). Spearman's rank correlation coefficient analyses were performed. Dependent variables were the number of RMMA/SB episodes, RMMA/SB bursts, Sleep-OMA, and Wake-OMA; independent variables were apnea-hypopnea index (AHI), arousal index(AI), body mass index(BMI), gender, and age. RESULTS: Although all subjects had a history of both SB and OSAH, sleep laboratory results confirmed that these conditions were concomitant in only 50.8 % of subjects. Moderate correlations were found in the following combinations (p < 0.05); RMMA/SB episode with AI, RMMA/SB burst with AI and age, Sleep-OMA burst with AHI, and Wake-OMA burst with BMI. CONCLUSIONS: The results suggest that (1) sleep arousals in patients with concomitant SB and OSAH are not strongly associated with onset of RMMA/SB and (2) apnea-hypopnea events appear to be related to higher occurrence of other types of sleep oromotor activity, and not SB activity. SB genesis and OSAH activity during sleep are probably influenced by different mechanisms.

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There is some evidence suggesting that obstructive sleep apnea-hypopnea syndrome is concomitant with sleep bruxism. The aim of this study was to investigate the temporal association between sleep apnea-hypopnea events and sleep bruxism events. In an open observational study, data were gathered from 10 male subjects with confirmed obstructive sleep apnea-hypopnea syndrome and concomitant sleep bruxism. Polysomnography and audio-video recordings were performed for 1 night in a sleep laboratory. Breathing, brain, heart and masticatory muscle activity signals were analysed to quantify sleep and sleep stage duration, and number and temporal distribution of apnea-hypopnea events and sleep bruxism events. Apnea-hypopnea events were collected within a 5-min time window before and after sleep bruxism events, with the sleep bruxism events as the pivotal reference point. Two temporal patterns were analysed: (i) the interval between apnea-hypopnea events termination and sleep bruxism events onset, called T1; and (ii) the interval between sleep bruxism events termination and apnea-hypopnea events onset, called T2. Of the intervals between sleep bruxism events and the nearest apnea-hypopnea event, 80.5% were scored within 5 min. Most intervals were distributed within a period of <30 s, with peak at 0-10 s. The T1 interval had a mean length of 33.4 s and was significantly shorter than the T2 interval (64.0 s; P < 0.05). Significantly more sleep bruxism events were scored in association with the T1 than the T2 pattern (P < 0.05). Thus, in patients with concomitant obstructive sleep apnea-hypopnea syndrome and sleep bruxism, most sleep bruxism events occurred after sleep apnea-hypopnea events, suggesting that sleep bruxism events occurring close to sleep apnea-hypopnea events is a secondary form of sleep bruxism.