Takahiro Mizumori

An ambulatory bruxism recording system with sleep-stage analyzing function

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 5kg. 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 subjects home.

Restoration of occlusal and proximal contacts by a single molar crown improves the smoothness of the masticatory movement

OBJECTIVES This study aimed to investigate the influence of the occlusal form variation of a single molar crown on the smoothness of masticatory movement. METHODS The 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. RESULTS Restoration 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. CONCLUSIONS These 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.

Suppression of sleep bruxism: effect of electrical stimulation of the masseter muscle triggered by heart rate elevation.

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.

Identification of sleep bruxism with an ambulatory wireless recording system.

PURPOSE To 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 METHODS Twenty-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. RESULTS With 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. CONCLUSION The results suggest that this system enables the detection of SB episodes at home with considerably high accuracy and little interference with sleep.

Prediction of sleep bruxism events by increased heart rate.

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.

The occurrence of respiratory events in young subjects with a frequent rhythmic masticatory muscle activity: a pilot study

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±1.9years; F 8: M 14; BMI: 20.2±1.9kg/m2) were polysomnographically diagnosed as moderate-severe SB. Sleep architecture, oromotor (RMMA and non-specific 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 10s) 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.

A clinical study on relationship between occlusal curve and stomatognathic function

本研究は, 咬合彎曲の形態的, 機能的な重要性を明らかにする目的で, 咬合彎曲の矢状面的および側方的形態に関し, 健常者と顎口腔機能異常患者を対象に分析し, 咬合彎曲の形態的特徴と咀嚼運動との関連性について検討したものである.その結果, 咬合彎曲の強さは顎口腔機能異常との関連性を認め, 矢状面的および側方的咬合彎曲の強さが, 咀嚼運動のリズムや安定性および開閉口経路の形態に反映されることが明らかにされた.

Effect of Change in Occlusal Vertical Dimension on Chewing Movements. Part 1. Influences on the Rhythm of Chewing Movements.

Assessment of occlusal vertical dimension (OVD) is an essential in the dental treatment. However, physiolosical effects of the change in OVD remains unclear.The purpose of this study is to assess the effect of the change in OVD on the stomatognathic function by analyzing any chewing movements.Five subjects without any signs or symptoms of craniomandibular disorders and with normal occlusion (age: 24-28 years, 4 males and 1 female) were selected. Onlay-type appliance was fabricated to raise the OVD by about 2mm. The chewing movements were recorded and analyzed using the Sirognathograph Analyzing System III.As a result, no change was observed in cycle time of the chewing movements, however as for each duration, some changes was observed.

Diagnosis of stomatognathic function and dysfunction

Introduction Occlusion, masticatory muscles, and temporomandibula r joint (TMJ), together with the central nervous system, are integrated into the functional occlusion system, which plays an important role in the physiology of the stomatognathic system I). Abnormality in one of the three factors of the functional occlusion system causes disharmony of the system and is considered to be the most s ignif icant e t io logica l f a c t o r in the s tomatognathic dysfunction. There fore , exact diagnosis of the condition of the each factor is essential for the diagosis and treatment of stomatognathic dysfunction. P a t h o l o g y of the T M J is the stomatognathic dysfunction has not been clearly understood in the past. One of the reasons would have been lack of methodology to e v a l u a t e the T M J in the stomatognathic dysfunction in the clinical practice. But it is extremely important and significant to know and evaluate the information on the TMJ. Recently, TMJ radiography, which is one of the most effective methods for TMJ examination, has been developed to a stage that discrimination has been possible and the diagnosis of arthrogeneous TMJ dysfunction have been relatively easy and reliable. This article will summarize the results of our series of rediographic investigations 2-4) using simultaneous multilayer polytomography (polytom U, Philips Co.), which is one of the most available methods for the diagnosis of the arthrogenous TMJ dysfunction.Introduction Occlusion, masticatory muscles, and temporomandibula r joint (TMJ), together with the central nervous system, are integrated into the functional occlusion system, which plays an important role in the physiology of the stomatognathic system I). Abnormality in one of the three factors of the functional occlusion system causes disharmony of the system and is considered to be the most s ignif icant e t io logica l f a c t o r in the s tomatognathic dysfunction. There fore , exact diagnosis of the condition of the each factor is essential for the diagosis and treatment of stomatognathic dysfunction. P a t h o l o g y of the T M J is the stomatognathic dysfunction has not been clearly understood in the past. One of the reasons would have been lack of methodology to e v a l u a t e the T M J in the stomatognathic dysfunction in the clinical practice. But it is extremely important and significant to know and evaluate the information on the TMJ. Recently, TMJ radiography, which is one of the most effective methods for TMJ examination, has been developed to a stage that discrimination has been possible and the diagnosis of arthrogeneous TMJ dysfunction have been relatively easy and reliable. This article will summarize the results of our series of rediographic investigations 2-4) using simultaneous multilayer polytomography (polytom U, Philips Co.), which is one of the most available methods for the diagnosis of the arthrogenous TMJ dysfunction.

A clinical Study on Chewing Movements in Open Bite. Part I. Effect of the Range of Open Bite on Chewing Movements.

It is important to grasp the functional characteristics of open bite, because those who are open bite have problems on anterior guidance and many of them show TMJ dysfunction. However the effect of open bite on stomatognathic function has not been clarified.The purposes of this study are to investigate 1) the characteristics of chewing patterns in subjects with open bite and 2) the relationship between each chewing pattern and the location of open bite.14 normal subjects were selected as a control group, and 14 open bite subjects were selected and clinically classified by the location of open bite, as follows1) anterior open bite2) anterior and posterior open biteChewing movements of each subject were recorded and qualitatively analysed by Sirognathograph Analysing System II.As a result, characteristic chewing patterns were observed in subjects with open bite, and some of which have relationships with the location of open bite.