Akihito Gotouda

Temporal association between sleep apnea–hypopnea and sleep bruxism events

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.

Influence of motion and posture of the head on data obtained using the newly developed ultraminiature cordless bruxism measurement system

PURPOSE To elucidate the influence of motion and posture of head on the newly developed ultraminiature cordless bruxism measurement system (BMS), we examined masseteric electromyographic (EMG) data of BMS during turning-over movements in bed in comparison with those of a conventional polygraph system (PG). METHODS Twelve healthy subjects lay on their back and then turned to the right (right turn, 90 degrees) and then to the left (left turn, 180 degrees). Maximum amplitudes and root mean square (RMS) values of EMG data were calculated during the phase of turning movements. The data were high-pass filtered at 10 Hz, 30 Hz, 50 Hz, and 100 Hz. RESULTS Artifact signals were visibly observed in PG measurement for all subjects and in BMS measurement for three subjects. Maximum amplitudes during right turn measured by BMS were significantly smaller than those measured by PG, while there was no significant difference during left turn. During right turn, RMS values high-pass filtered at 10 Hz obtained by BMS were significantly smaller than those obtained by PG, while there was no significant difference between the data obtained by the two devices at the other cut-off frequencies. During left turn, there was no significant difference between RMS values obtained by the two devices. CONCLUSIONS Although BMS data were slightly affected by motion and posture of head during simulated sleep-turning, it was suggested that motion artifact of signals during BMS measurements is equivalent to or less than that during PG measurements, and BMS is thought to be suitable to measure sleep bruxism.

Day-to-day variations in salivary cortisol measurements

PURPOSE The purpose of this study was to clarify the day-to-day variations of salivary cortisol to discuss the appropriate timing for collecting saliva in a day for stress evaluation. MATERIALS AND METHODS Saliva samples from twelve healthy adults were collected by means of Salivette(®) (SARSTEDT Co.) three times per day, immediately after awakening (Time1), 6:00 PM (Time2) and 30 min before going to bed (Time3), on 5 nonconsecutive days. Cortisol concentration was measured using a radioimmunoassay. RESULTS Salivary cortisol concentration showed the larger value at Time1 than that at Time2. The mean value of %CV for day-to-day variation showed the smallest value at Time1 (mean: 43.1%) and the largest value at Time3 (mean: 100.3%). There were significant differences in %CV value between Time1 and Time3, Time2 (mean: 64.1%) and Time3. CONCLUSIONS There are considerable day-to-day variations in salivary cortisol concentration measurements. From the viewpoint of day-to-day variation, collecting saliva immediately after awakening in the morning is thought to be more advantageous for evaluating cortisol concentration.

The influence of tissue blood flow volume on energy metabolism in masseter muscles.

Abstract This study investigated the energy metabolism of masseter muscles by 31P-Magnetic Resonance Spectroscopy (MRS) during increased blood flow induced by hot pack application to clarify the influence of changes in blood flow on muscle fatigue. Twelve healthy subjects with no history of muscle pain in the masticatory system participated in this study. The 31P-MRS measurements were performed before and after hot pack application and the ratio of phosphocreatine (PCr) acting as the energy source to reproduce ATP to ß-ATP, the PCr/ß-ATP ratio, was analyzed. Results showed that PCr/ß-ATP ratios increased significantly by an average of 22.4% after the hot pack application. The results suggest that changes in blood flow volume influence the energy metabolism in masseter muscles and that blood flow increases due to the hot pack cause higher energy levels in masseter muscles and offer an advantageous condition for preventing and relieving muscle fatigue.

A newly developed ultraminiature wearable electromyogram system useful for analyses of masseteric activity during the whole day

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.

Rhythm and amplitude of rhythmic masticatory muscle activity during sleep in bruxers - comparison with gum chewing.

Objectives: The aim of this study was to elucidate characteristics of rhythmic masticatory muscle activity (RMMA) during sleep by comparing masseteric EMG (electromyogram) activities of RMMA with gum chewing. Method: The parts of five or more consecutive phasic bursts in RMMA of 23 bruxers were analyzed. Wilcoxon signed-rank test for matched pairs and Spearman’s correlation coefficient by the rank test were used for statistical analysis. Results: Root mean square value of RMMA phasic burst was smaller than that during gum chewing, but correlates to that of gum chewing. The cycle of RMMA was longer than that of gum chewing due to the longer burst duration of RMMA, and variation in the cycles of RMMA was wider. Discussion: These findings suggest that the longer but smaller EMG burst in comparison with gum chewing is one of the characteristics of RMMA. The relation between size of RMMA phasic bursts and gum chewing is also suggested.

Condylar movements of temporomandibular disorder patients with intermittent lock: a pilot study.

Abstract The purpose of this study was to clarify which direction of the condylar path is advantageous for releasing TMJ intermittent lock. The subjects were ten patients with temporomandibular disorders (TMD) and intermittent lock caused by anterior displacement of disks without obvious medial or lateral displacement. The patients could not open their mouths fully in habitual opening but could open fully in an intentional winding opening with reduction of the anteriorly displaced disks (winding opening). The two kinds of movement at the kinematic condylar point were measured in each subject and compared. The length of the condylar path in winding opening was significantly larger than that in habitual opening. The affected side condyle of winding opening traced medio-inferior paths in the early part of the condylar translation in comparison with habitual opening. From the viewpoint of the condylar path, the medio-inferior direction of condylar translation is thought to be advantageous for releasing intermittent lock.

The effect of physical therapy on masseteric blood flow : Comparison of hot pack and Myo-monitor^[○!R]

本研究では, マイオモニターに温罨法同様の咀嚼筋血流改善効果があるか否かを明らかにすることを目的に, 温罨法およびマイオモニター施行前後の咬筋組織内ヘモグロビン量, 酸素飽和度 (StO2) の変動を測定し, 比較検討した.被験者は顎口腔系に異常が認められない健常者で, 温罨法群10名, マイオモニター群10名とした.ヘモグロビン量とStO2の測定には近赤外分光血流計を用いた.測定項目は総ヘモグロビン量 (THb) , オキシヘモグロビン量 (OXHb) , デオキシヘモグロビン量 (deOXHb) , 酸素飽和度 (StO2) とし, 同時に脈拍 (HR) も測定した.温罨法群では, 温め後THb, OXHb, StO2に有意な増加が認められたのに対し, マイオモニター群ではTHb, OXHb, deOXHb, StO2, HRすべてにおいてマイオモニター後に有意な増加は認められなかった.また, 温罨法群とマイオモニター群の群間比較でも, 温罨法群のTHb, OXHb, StO2が, マイオモニター群よりも有意に大きな増加率を示した.一方, deOXHbとHRに有意差は認められなかった.以上から, 咬筋の血流改善の効果に関しては, マイオモニターより温罨法の方が有効であると考えられた.