Purpose: Concomitant occurrence of respiratory events can be often overlooked in the clinical practice of SB. This study assessed physiological characteristics of rhythmic masticatory muscle activity (RMMA) and concomitant respiratory events in young sleep bruxism (SB) subjects asymptomatic to obstructive sleep apnea (OSA). Methods: Twenty-two subjects (age: 24.1 +/- 1.9 years; F 8: M 14; BMI: 20.2 +/- 1.9 kg/m(2)) were polysomnographically diagnosed as moderate-severe SB. Sleep architecture, oromotor (RMMA and nonspecific masseter activity [NSMA]) and apnea/hypopnea events were scored. Results: All subjects showed normal sleep architecture whereas 6 exhibited respiratory events at a mild level of OSA. In all subjects, RMMA predominantly occurred in Stage N1 + N2 while NSMA occurred in Stage N1 + N2 (approximately 60 %) and in Stage R (up to 30 %). Up to 50 % of respiratory events were scored in Stage R. RMMA occurred more frequently in close association (e.g., within 10 s) with respiratory events in 6 subjects with OSA than those without. The percentage of RMMA occurring closely to respiratory events was positively correlated with apnea-hypopnea index (AHI) in Stage N1 + N2 only while that of NSMA was positively correlated with AHI in Stage N1 + N2 and Stage R. A sub-analysis in 6 subjects with OSA, RMMA after respiratory events was followed to arousals while those before respiratory events were mostly associated with central apnea. Conclusions: A subpopulation of young SB subjects can show concomitant respiratory events. Further large sample studies are needed to demonstrate that the occurrence of subclinical respiratory events represents a clinical subtype of SB. (C) 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

睡眠時ブラキシズム(Sleep Bruxism:以下 SB)は睡 眠中の非機能的咀嚼筋活動であり,国際睡眠関連疾患分 類では睡眠関連運動異常症に分類されている.その発生 率は成人では5~8%とされ中高年以降に減少するとさ れている.また,SBの存在は歯の咬耗, 破折や補綴装 置の破損,顎関節痛などの危険因子の一つに挙げられる. 病態生理学的特徴として,リズム性咀嚼筋活動(rhythmic masticatory muscleactivity:以下 RMMA)が頻発する こと,RMMAの発生の際,一過性の覚醒が先行するこ とが明らかになっている. 一方,閉塞性睡眠時無呼吸症候群(obstructive sleep apnea syndrome:以下 OSAS)の発生率は2~4%で 中高年以降に多いとされ,その症状は,いびき,頻回な 中途覚醒,日中傾眠などを示す.これら症状の原因は, 睡眠中に発生する無呼吸や低呼吸イベントによる頻回な 睡眠分断にある. これまでの疫学研究や OSAS患者を対象とした研究 で,SBと OSASの併存が報告されている .しかし, SBと OSASの病態生理学的な関連については不明な点 が多い.とりわけ RMMAは微小覚醒後に起こり,無呼 吸・低呼吸イベントは微小覚醒前に起こるが ,両者の 時間的関連性は強固なものではないことが示されてい る .また,OSAS 患者に無呼吸・低呼吸イベント後の 覚醒に反応してリズムを有さない咬筋活動(Non-specific activity,以下 NA)が発生する一方で,OSAS患者で あっても RMMAを生じない患者も多く存在する 3, . さらに,これまでの研究では睡眠自体が変調する中高 年男性の OSASを対象としていたり,OSASの症型が 混在することは考慮されていない. 本研究では,頻回な RMMAを有する若年被験者にお ける無呼吸・低呼吸イベントを認めた一群の睡眠構築や 臨床症状を調べ,RMMAと無呼吸・低呼吸イベントの 時間的関連を調べた.

PURPOSE To examine whether electrical stimulation of the masseter muscle triggered by heart rate elevation preceding sleep bruxism (SB) can actively suppress SB. MATERIALS AND METHODS Ten volunteers who were aware of their SB habits participated in the study. Baseline electromyogram (EMG) activity of the unilateral masseter muscle and electrocardiogram (ECG) signal were recorded on the first night. The individual mean sensation and pain thresholds to electrical stimulation of the unilateral masseter muscle were determined in awake subjects before the experiment. On the second night, electrical stimulations at either of the two threshold intensities were automatically generated and delivered to the masseter muscle on the opposite side from where electrodes were placed immediately after the heart rate exceeded 110%. On the third night, electrical stimulations at the other threshold intensity were delivered. RESULTS The numbers of SB events per night and per hour, the number of EMG bursts per SB event, and the duration of SB events decreased significantly on the nights when stimulation was applied compared with the baseline data. There were no significant differences between cases where the sensation threshold was used as the stimulation intensity and those in which the pain threshold was used as the stimulation intensity. CONCLUSION The results suggest that electrical stimulation of the masseter muscle triggered by heart rate elevation can significantly suppress SB.

Objetivos: Examinar si es posible identificar especificamente el bruxismo del sueno (BS) mediante un sistema de registro ambulatorio, que incluye un monitor biologico, el cual mide las variables del sueno y el balance simpatico-vagal (mecanismos de regulacion autonomica), y que el paciente puede utilizar en casa. Materiales y metodos: Se incluyeron 26 voluntarios, de los que 16 individuos tenian BS. Durante 3 noches consecutivas, cada participante resgistraba su electromiograma (EMG), el balance simpatico-vagal y el nivel de ruido, utilizando un registro audiovisual para identificar el BS. Se compararon los datos de las variables del sueno en las 3 noches experimentales. Los episodios se clasificaron en episodios de BS con y sin rechinamiento y episodios de no BS. Para determinar el umbral apropiado y detectar los episodios y el sonido de rechinar, se analizaron el patron EMG, la amplitud, el balance simpatico-vagal y el nivel de ruido en todos los episodios. A continuacion, se clasificaron en episodios de BS y de no BS utilizando los umbrales apropiados y se calcularon la sensibilidad y especificidad para detectar los episodios de BS. Resultados: En cuanto a las variables del sueno, no se dieron diferencias significativas, a excepcion de la latencia del sueno entre la primera y la segunda noche. Los patrones EMG apropiados fueron fasicos o mixtos, y los umbrales adecuados de amplitud se situaron en un 20% de contraccion voluntaria maxima, del balance simpatico-vagal en la media + 1 DE y del nivel de ruido en la media + 2 DE. La sensibilidad y la especificidad para detectar los episodios de BS fueron del 88,4% y 74,2% respectivamente. Conclusion: Los resultados indican que este sistema permite la deteccion de los episodios de BS en casa con una precision considerablemente alta y pocas interferencias con el sueno.

PURPOSE To investigate the hypothesis that sleep bruxism (SB) events could be predicted by an increase in heart rate. MATERIALS AND METHODS Fourteen sleep bruxers were recruited. Each participant recorded his or her own electromyography (EMG) and electrocardiography (ECG) at home for 2 consecutive nights using a portable telemetry system. Ten heartbeats before (B10 to B1) and three heartbeats after (A1 to A3) the onset of SB events were analyzed, and the threshold for the prediction of an SB event was determined. The validity of the threshold was tested by EMG and ECG recorded in the same manner for an additional night. The prediction accuracy of SB events was evaluated for sensitivity and specificity. RESULTS A gradual increase in heart rate was observed before an SB event, and B1, A1, A2, and A3 were significantly higher than B10 (P < .01). The threshold value was set at 110% when the mean of all heart rates of the second night of recording was set at 100%. A total of 324 SB events were observed and 299 were preceded by increased heart rate that exceeded the threshold (sensitivity, 92.3%). The total number of increased heart rate events was 1,239, and the total number of threshold applications was estimated to be 120,000. The specificity was 99.2%. CONCLUSION Over 90% of SB events could be predicted by an increasing heart rate of 110%. Since the sensitivity and specificity were extremely high, the hypothesis that SB events could be predicted by increased heart rate was positively verified.

PURPOSETo examine whether an ambulatory bruxism recording system, including a biologic monitor, that measures sleep variables and sympatho-vagal balance can specifically identify sleep bruxism (SB) at home.MATERIALS AND METHODSTwenty-six volunteers, including 16 SB subjects, were recruited. Each participant recorded his or her electromyogram (EMG), sympatho-vagal balance, and sound level for 3 consecutive nights using an audio-video recorder to identify SB. Data of sleep variables were compared among the 3 experimental nights. The episodes were classified into SB episodes with and without grinding and non-SB episodes. EMG patterns, amplitude, sympatho-vagal balance, and sound level of all episodes were analyzed so as to determine the appropriate thresholds to detect SB episodes and grinding sound. Then, all episodes without video-recording data were classified into SB and non-SB episodes by using the appropriate thresholds, and the sensitivity and specificity to detect SB episodes were calculated.RESULTSWith regard to sleep variables, there were no significant differences except for sleep latency between the first and second nights. The appropriate EMG pattern and thresholds of amplitude, sympatho-vagal balance, and sound level were phasic or mixed EMG pattern, 20% of maximum voluntary contraction, mean + 1 SD, and mean + 2 SDs, respectively. The sensitivity and specificity to detect SB episodes were 88.4% and 74.2%, respectively.CONCLUSIONThe results suggest that this system enables the detection of SB episodes at home with considerably high accuracy and little interference with sleep.

Purpose: This study aimed to investigate whether clenching aids performance in a task requiring mental concentration in healthy participants.Materials and methods: Twenty healthy participants (an average of 26.8 +/- 2.0 years, nine females and 11 males) were recruited from our department. Participants performed four sets of hundred-square calculations as a mental arithmetic task. Among these sets, the third and the fourth sets were randomly divided into two conditions: one condition where participants made an effort to not allow their teeth to touch ('no tooth-contact' condition), and another where they made a conscious effort to rhythmically clench their teeth ('clenching' condition) during the task. Surface EMG was recorded from the left masseter muscle. Arithmetic performance was compared between the tooth-contact and clenching conditions using paired t-tests. In addition, we computed Pearson product-moment coefficients of the correlations between the difference in EMG activity and arithmetic performance in the two conditions.Results: No significant change in arithmetic score was found between the no tooth-contact (68.8 +/- 12.2) and clenching conditions (66.5 +/- 12.7; P = 0.27). No significant correlation was found between the difference in EMG activity and changes in arithmetic performance (r = 0.32, P = 0.17).Conclusion: In healthy participants, conscious clenching was not associated with any benefit in arithmetic performance. Although our study was limited by only measuring the short-term effects of clenching on a simple arithmetic task, the results indicate that it may not be harmful for clinicians to encourage their patients to refrain from clenching their teeth. (C) 2011 Japan Prosthodontic Society. Published by Elsevier Ireland. All rights reserved.

Purpose: The aim of this study was to develop an ambulatory bruxism recording system capable of sleep-stage analysis.Methods: A portable EMG system was used to record masseter muscle activity. An EMG sensor was attached onto the masseter muscle belly at either side. EMG data were stored on a notebook type personal computer. A sound level meter was used to assess the sound level of bruxism. Sound level (dB) readings were taken every second and recorded on the same computer. A prototype of sleep sensor, a wristwatch-style biological signal sensor-recorder device, recorded and stored pulse wave, acceleration and temperature on a memory card. All stored data were transferred to a personal computer and analyzed.Results: The whole system was transportable within a protective case and weighed approximately 5 kg. Raw EMG signals were processed to derive integrated EMG data. TOSHIBA Sleep Analysis Program classified sleep-stages as awake, shallow sleep, deep sleep and REM based on the activity of the autonomic nervous system that was estimated from the fluctuations of pulse intervals. An EMG, sound level and sleep-stage analysis program was developed to analyze all data simultaneously. Using this program, the masseter muscle activity, sound level and sleep-stage could be quantified and correlated.Conclusion: We developed an ambulatory bruxism recording system that analyzes sleep-stage. We expect that this system will enable us to measure sleep bruxism activity in each sleep-stage on an electromyographical and auditory basis at the subject's home. (C) 2009 Japan Prosthodontic Society. Published by Elsevier Ireland. All rights reserved.

ObjectivesThis study aimed to investigate the influence of the occlusal form variation of a single molar crown on the smoothness of masticatory movement.MethodsThe subjects included 19 adults who visited the hospital seeking a single prosthetic restoration on a molar. Three types of crown were used: (i) an anatomical form, (ii) a flat occlusal table with occlusal contacts and (iii) a flat occlusal table without occlusal contacts. All restored the proximal contacts, and were temporarily cemented in random order. One week after each crown was cemented, the jaw movement trajectory was recorded during gum chewing and the normalized jerk-cost (NJC) was calculated for each chewing cycle. The mean and standard deviation of the chewing rhythms, pathways and peak speeds, were also calculated.ResultsRestoration by the anatomical occlusal form crown significantly decreased the standard deviation of the parameters for the chewing rhythm. The jerk analysis showed a significant NJC decrease after all types of crown were placed on the treated side. The smoothness of masticatory movement was more improved in the subjects who received each type of crown on their mandibular molar than those on the maxillary molar.ConclusionsThese results suggest that achieving occlusal and proximal contacts by a single crown treatment is associated with a reduction in the variability of jaw movements. These findings confirm the clinical importance of restoring occlusal contacts and proximal contacts even for a single tooth.

Purpose: To clarify the effects of deviated mandibular positions on the center of sole pressure in terms of fluctuations and positional changes.Methods: Of 100 subjects at Osaka University Graduate School of Dentistry, 30 faculty members and students who exhibited no mandibular deviation (i.e., who had a median menton angle and an SNB angle within one standard deviation of the mean) were selected. Using a machine capable of assessing the distribution of sole pressure, the center of sole pressure and the degree of fluctuations in the center of sole pressure corresponding to the mandibular positions, were measured at deviated mandibular positions. The mandible was moved 3 mm in the left, right, or anterior directions and maximally in the posterior direction. The data were analyzed statistically using a paired t test with a significance level of P=0.05.Results: No tendencies were observed between the positional changes in the center of sole pressure and the mandible moving from the intercuspal position. Whereas the degree of fluctuation increased significantly, irrespective of the direction of change, for the subjects in whom the position of the center of sole pressure did not change, or changed in the same direction as the deviated mandibular position, it did not increase for subjects in whom the position of the center of sole pressure changed in the direction opposite to that of the deviated mandibular position.Conclusion: The results of this study suggest the possibility that deviated mandibular positions do not affect the positional changes in the center of sole pressure, but do affect the fluctuations in relation to the direction of positional changes.

Purpose: The aim of this study was to investigate the relationship between chewing side continuity and masticatory performance.Methods: Twenty-two healthy subjects with normal occlusion who chewed alternately on both sides in a preliminary chewing task were selected for this study (15 males, 7 females; mean age, 25.9 years). To evaluate chewing side continuity, the subjects were asked to chew on one piece of gummy jelly for 20 seconds. This task was repeated three times, and the mean number of side-continuous strokes was calculated for each chewing side. The masticatory performance was determined by Manly's sieving method. The results obtained were analyzed for each chewing side, and the subjects were divided into two groups according to the length of chewing side continuity: the long chewing side continuity group (mean number of side-continuous strokes ≥ median) and the short chewing side continuity group (mean number of side-continuous strokes < median). The masticatory performance was compared between the two groups using the t-test, with statistical significance being established at P<0.05.Results: Among the 44 chewing sides, the most frequently encountered number of side continuous strokes was less than 4. The mean masticatory performance was 87.0% (SD, 7.5%). The long chewing continuity group showed significantly better masticatory performance than the shorter chewing continuity group (P=0.040).Conclusion: Our results suggest that long chewing continuity could be a measure of better masticatory performance in healthy young dentate subjects who do not have a preferred chewing side.

目的: 咀嚼の側性を客観的かつ定量的に評価する方法として, 左右側を指定しない自由咀嚼運動の左右側ストローク数より非対称性指数 (Asymmetry Index, 以下AI) を算出する方法を用い, 方法の妥当性, さらには食品による変化, 日間変動について検討することである.方法: 被験者として健常有歯顎者10名を選択し, チューイング・ガム, カマボコ, グミ・ゼリー, タクアン, スルメ, ピーナッツ, ジャイアント・コーンの計7種類を被験食品に用いた. 被験者に左右側を指定しない20秒間の自由咀嚼運動を行わせ, 左右側のストローク数を視覚的に数え, AIを算出した. 記録は各種食品1日1回, 1週間ごとに計3回行った.結果:(1) 左右側ストローク数からAIを算出することにより, 咀嚼の側性を定量的に表現できた.(2) 咀嚼の側性を捉える目安として, 3日間のAIの中央値, 範囲から, 各被験者を片側咀嚼型 (U型), 両側咀嚼型 (0型), 不定側咀嚼型 (V型) の3型に分類できた.(3) 軟性食品では0型が, 硬性食品ではU型が多い傾向があったが, 軟性食品内あるいは硬性食品内での性状による差は認められなかった.結論: 本実験で用いた咀嚼の側性の評価方法は客観的かつ定量的方法であり, 咀嚼の側性は各被験者において特徴的で, 食品の硬性により影響を受ける可能性が示唆された.

Mandibular movement occurs during chewing, speech and swallowing functionally or during bruxism and clenching parafunctionally. Further, the occlusal facet is caused by functional mandibular movement and parafunctional mandibular movement. However, it is not defined to what extent the occlusal facet is within the range of functional mandibular movement. The purpose of this study was to examine the extent of functional tooth grinding in chewing mandibular movement. One hundred dental students were used in this study, and the portion of correspondence of path of chewing and lateral border movement was measured using Sirognathograph Analyzing System III. As a result, some subjects had a large corresponding portion of path of chewing mandibular movement and path of lateral border movement. The extent of functional tooth grinding in chewing movement has been considered to be small near the centric occlusion, however, the results suggested that a large portion of the grinding surface was used by functional mandibular movement.

The purpose of this study was to analyze movements of the incisor point during chewing (chewing movements) of the patients with craniomandibular disorders (CMD) and healthy subjects, to classify the parameters of chewing movements and to clarify the relationship between classified parameters and CMD.Chewing movements of right and left sides were recorded with Sirognathograph Analysing System. The number of analyzed sides was 80 in 40 healthy subjects and 171 in 95 patients with CMD (90 in 50 patients with anterior disk displacement with reduction (Click), 42 in 25 patients with anterior disk displacement without reduction (Lock), and 39 in 20 patients with myofascial pain dysfunction syndrome (MPDS)). The 68 parameters of chewing movements were divided into 10 categories by a principal component analysis.The results were as follows:1. Distinctive parameters between healthy subjects and patients with CMD were irregularity of opening and closing path near the occluding point, unstable opening and closing speed, disturbance of rhythm, unstable occluding point and limitation of lateral closing path.2. Characteristics of chewing movements were delay of maximum opening and closing velocity and small degree of its occurring point in patients with Lock, and long opening and closing phase in patients with MPDS.