Absence of joint pain identifies high levels of sleep masticatory muscle activity in myofascial temporomandibular disorder

Although the development of reliable diagnostic criteria for temporomandibular disorders (TMDs) has operationalised identification of a subgroup with myofascial pain (mTMD), causal mechanisms remain elusive. This study examines masticatory muscle activity (MMA) in more homogenous research subgroups of mTMD. Data from an existing case‐control study of women were used to subcategorise mTMD cases based on joint pain with palpation to isolate muscle‐only pain (M‐pain) vs muscle and joint pain (MJ‐pain). Differences in laboratory indicators of MMA, specifically research diagnostic criteria for sleep bruxism (SB) and high background EMG activity, and other clinical and sociodemographic indicators were examined between groups. Compared to controls, the MJ‐pain subgroup did not show elevated background EMG or sleep bruxism. In contrast, the M‐pain subgroup showed significantly higher background EMG and a trend towards elevated prevalence of sleep bruxism. These results may explain why it has been difficult for studies of SB in mixed TMD and even mTMD samples to find a consistent positive association, since a positive association may be limited to mTMD without joint pain. The subcategorising of mTMD based on joint pain with palpation (ie M‐pain, MJ‐pain) appears to reveal subgroups with relatively high and low sleep masticatory muscle‐specific activity. Findings need replication in a larger study with updated mTMD diagnostic criteria, but may prove useful for understanding mechanism of pain maintenance in mTMD with and without joint pain.     

Comparison of ambulatory and polysomnographic recording of jaw muscle activity during sleep in normal subjects

Clinicians and investigators need a simple and reliable recording device to diagnose or monitor sleep bruxism (SB). The aim of this study was to compare recordings made with an ambulatory electromyographic telemetry recorder (TEL-EMG) with those made with standard sleep laboratory polysomnography with synchronised audio-visual recording (PSG-AV). Eight volunteer subjects without current history of tooth grinding spent one night in a sleep laboratory. Simultaneous bilateral masseter EMG recordings were made with a TEL-EMG and standard PSG. All types of oromotor activity and rhythmic masseter muscle activity (RMMA), typical of SB, were independently scored by two individuals. Correlation and intra-class coefficient (ICC) were estimated for scores on each system. The TEL-EMG was highly sensitive to detect RMMA (0·988), but with low positive predictive value (0·231) because of a high rate of oromotor activity detection (e.g. swallowing and scratching). Almost 72% of false-positive oromotor activity scored with the TEL-EMG occurred during the transient wake period of sleep. A non-significant correlation between recording systems was found (r = 0·49). Because of the high frequency of wake periods during sleep, ICC was low (0·47), and the removal of the influence of wake periods improved the detection reliability of the TEL-EMG (ICC = 0·88). The TEL-EMG is sensitive to detect RMMA in normal subjects. However, it obtained a high rate of false-positive detections because of the presence of frequent oromotor activities and transient wake periods of sleep. New algorithms are needed to improve the validity of TEL-EMG recordings.     

Relationship between self‐reported sleep bruxism and pain in patients with temporomandibular disorders

The aim of this study was to evaluate the association between self‐reported sleep bruxism and the age, gender, clinical subtypes of temporomandibular disorders (TMD), pain intensity and grade of chronic pain in patients previously diagnosed with TMD. Thousand two‐hundred and twenty patients of the Andalusian Health Service were examined using the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) questionnaire. The inclusion and exclusion criteria were those included in the RDC/TMD criteria. The bruxism diagnosis was drawn from the question, ‘Have you been told, or do you notice that you grind your teeth or clench your jaw while sleeping at night?’ in the anamnestic portion of the questionnaire. A bivariate analysis was conducted, comparing the presence of perceived parafunctional activity with age (over age 60 and under age 60), gender, different subtypes of TMD, pain intensity, grade of chronic pain and presence of self‐perceived locked joints. The overall prevalence of self‐reported sleep bruxism (SB) was 54·51%. A statistically significant association was found between the presence of SB and patients under age 60, women, greater pain intensity, greater pain interference with activities of daily living, and the axis‐I groups affected by both muscular and articular pathology. There is a statistically significant association between self‐reported sleep bruxism and women under age 60 who have painful symptoms of TMD. There is also a positive association between this parafunctional habit and the presence of chronic pain. However, more studies that cover larger samples and differentiate between sleep bruxism and awake bruxism are needed.     

Ultrasonographic evaluation of jaw elevator muscles in young adults with bruxism and with and without attrition-type tooth wear: A pilot study

ABSTRACT

Objective

This pilot study was planned to analyze masticatory activation in bruxism patients with and without attrition by ultrasonographic evaluation of mandibular adductor muscles.     

Oro-facial activities in sleep bruxism patients and in normal subjects: a controlled polygraphic and audio-video study

Summary  To our knowledge, the large spectrum of sleep motor activities (SMA) present in the head and neck region has not yet been systematically estimated in normal and sleep bruxism (SB) subjects. We hypothesized that in the absence of audio–video signal recordings, normal and SB subjects would present a high level of SMA that might confound the scoring specificity of SB. A retrospective analysis of several SMA, including oro-facial activities (OFA) and rhythmic masticatory muscle activities (RMMA), was made from polygraphic and audio–video recordings of 21 normal subjects and 25 SB patients. Sleep motor activities were scored, blind to subject status, from the second night of sleep recordings. Discrimination of OFA included the following types of activities: lip sucking, head movements, chewing-like movements, swallowing, head rubbing and scratching, eye opening and blinking. These were differentiated from RMMA and tooth grinding. The frequency of SMA per hour of sleep was lower in normal subjects in comparison with SB patients ( P  < 0·001). Up to 85% of all SMA in normal subjects were related to OFA while 30% of SMA in SB patients were related to OFA scoring ( P  < 0·001). The frequency of RMMA was seven times higher in SB patients than in normal subjects ( P  < 0·001). Several SMA can be observed in normal and SB subjects. In the absence of audio–video signal recordings, the discrimination of various types of OFA is difficult to achieve and may lead to erroneous estimation of SB-related activities.     

The effects of stabilization splint treatment on the volume of masseter muscle in sleep bruxism patients

Objective: The aim of this study was to evaluate, quantitatively, the volumetric effects of stabilization splint therapy on the masseter muscle of sleep bruxism (SB) patients.

Methods: The magnetic resonance (MR) images of 16 SB patients diagnosed by polysomnography (PSG) who used stabilization splints for four months were obtained before and after the therapy. The masseter muscle volume was calculated using Cavalieri’s principle on the MR images.

Results: After the splint therapy, the mean volume of the masseter muscle did not reduce significantly. The fat and/or water content of the muscles did not change either.

Discussion: The stabilization splint therapy had no effect on the volume, fat and/or water content of the masseter muscle; however the discomfort was reduced in the patients. Although the effect of splint therapy is not fully understood, the non-invasive and reversible stabilization splint can be used in SB patients because of its relaxation effect on muscles.     

The relationship between selective sleep deprivation, nocturnal jaw-muscle activity and pain in healthy men

The relationship between nocturnal jaw-muscle activity and temporomandibular disorders (TMD) is still controversial. The aim of this study was to investigate the effect of selective slow wave sleep (SWS = non-rapid-eye-movement (NREM) stage 3 + 4) deprivation on jaw-muscle activity using a new automatic system. Ten healthy men without signs of symptoms of TMD participated. The subjects slept in the laboratory for six continuous nights including one adjustment night, one baseline night, three nights with experimental sleep deprivation and one recovery night. Polysomnographic recordings of electroencephalography (EEG) and electromyography (EMG) were obtained for recognition of sleep stages and masseter muscle activity. During the three experimental nights, computer-controlled sound stimulation (60--90 dB(A), 1000 Hz) were given as long as the subjects were in SWS. Maximum voluntary occlusal force (MVOF), pain pressure threshold (PPT) and visual analogue scales (VAS) were used to assess the state of the masseter muscles every morning and evening during the study period. The results showed that the time spent in SWS was significantly decreased during the first sleep deprivation night, but there were no significant effects on nocturnal EMG activity (i.e. the numbers of bruxism episodes per hour of sleep, bruxism bursts per episodes bruxism bursts per hour of sleep), MVOF, VAS or PPT. Furthermore, the automatic system only deprived the SWS in five subjects for the following two nights although the sound stimulation was given at the maximum intensity. These results suggest that deprivation of SWS may not interact immediately with nocturnal jaw-muscle activity and jaw-muscle pain.     

Changes in oxygen and carbon dioxide in the genesis of sleep bruxism: a mechanism study

PurposeRhythmic masticatory muscle activity (RMMA), a biomarker of sleep bruxism (SB), has been associated with mild hypoxia and/or big breaths in some adults with non-sleep-disordered breathing. The purpose of this study was to investigate that concurrent oxygen and carbon dioxide fluctuations are among the physiological variables that contribute to RMMA onset.MethodsTwelve subjects (5 female, 7 male, mean age: 43 ± 11) underwent polysomnography recording in a sleep laboratory. RMMA index and apnea-hypopnea index were calculated. Oxygen saturation (SpO₂) was estimated by finger pulse oximeter and end-tidal CO₂ (ETCO₂) by nasal airflow cannula before and after RMMA onset. Given the expected response time delay between actual arterial hypoxemia and fingertip pulse detection, we adjusted the SpO₂ desaturation onset to the onset of masseter muscle activity using a 17 s criterion based on ETCO₂ shifts.ResultsSpO₂ was slightly but significantly lower than at baseline (max: −0.6%) in the 6–4 s before RMMA onset and significantly higher in the 6–18 s after onset (0.9%; p < 0.05). Although ETCO₂ before RMMA onset did not differ from baseline, it decreased at 8–10 s after onset (−1.7 mmHg: p < 0.05). No changes in SpO₂ or ETCO₂ in relation to RMMA onset reached a critical clinical threshold.ConclusionsThe mild transient hypoxia observed before RMMA onset was not associated with a change in ETCO_2. The mild and brief oxygen fluctuations before RMMA onset may reflect a physiological response that seems to have little influence on SB genesis.     

Effect of contingent electrical stimulation on jaw muscle activity during sleep: A pilot study with a randomized controlled trial design

Abstract

Objective. To determine the effect of contingent electrical stimulation (CES) on jaw muscle activity during sleep in a double-blinded randomized controlled trial (RCT). Materials and methods. Eleven patients with myofascial TMD (mean age 37 years) and with a clinical diagnosis of bruxism were included. EMG activity (Grindcare®) was recorded from the anterior temporalis muscle during sleep and analyzed online. Jaw muscle activity related to clenching or grinding triggered an electrical square-wave pulse train (450 ms) adjusted to a clear, but non-painful intensity. TMD patients were randomized into two groups: active treatment with CES or no CES (placebo). Number of EMG episodes/hour sleep was the primary outcome parameter. The following variables were assessed as secondary outcome parameters; number of painful muscles, maximum pain-free jaw opening, characteristic pain intensity, depression scores and Oral Health Impact Profile scores. Numerical Rating Scale scores for self-reported pain and muscle tension were registered for at least 4 nights per week during the experiment. Results. The number of EMG episodes/hour sleep was significantly reduced (52 ± 12%) in the CES group during the sessions with CES (ANOVA: p = 0.021) compared to baseline. There were no significant differences in the secondary outcome parameters (ANOVA: p > 0.513) or pain or muscle tension scores between groups (p = 0.645). The average duration of sleep hours during the nights with and without CES was not significantly different (p = 0.646). Conclusions. These results demonstrate a significant inhibitory effect of CES on jaw muscle EMG activity during sleep in a RCT, but with no effects on self-reported pain.     

Changes in heart rate related to rhythmic masticatory muscle activities and limb movements in patients with sleep bruxism

Most sleep bruxism (SB) episodes are accompanied by an increase in sympathetic tone and heart rate (HR). To characterise heart rate (HR) changes in relation to rhythmic masticatory muscle activities (RMMAs) in SB patients, polysomnographic recordings were performed on 10 SB patients and 11 normal controls. The duration of movement events, amplitude and duration of HR increases, and time to reach HR peak associated with RMMAs and limb movements (LMs) were determined, and the relationships of the parameters of HR increases with types of movements and RMMAs were analysed. All of the parameters of HR increases associated with three types of movements (RMMAs, RMMAs + LMs and LMs) and masseter activities (phasic, tonic and mixed) were significantly different (two-way ANOVA, P < .001 for all) in both SB patients and controls. The duration of RMMAs/LMs was positively correlated with the parameters (SB patients: R² = .24-.85, P < .0001; controls: R² = .23-.68, P < .0001). The amplitude of HR increases was also positively correlated with respiration changes in the SB patients (R² = .3258, P < .0001) and controls (R² = .09469, P < .05). The proportions of phasic RMMAs associated with awakenings, microarousals and no cortical arousals were significantly different and so were the proportions of tonic and mixed RMMAs (Friedman's tests, P < .05-.001). The HR increases associated with RMMAs may be intrinsic to the cortical arousal response and autonomic activation, and differences in HR increases associated with different types of movements and RMMAs might be related to the changes in respiration and differences in cortical arousal levels.     

下颌咀嚼运动与夜磨牙症特征相关性的初步探究

目的 探讨夜磨牙症各临床诊断标准和睡眠时下颌咀嚼运动发生频率的相互关系。方法 运用视频多导睡眠监测方法,对20例健康成人,具有至少以下一项临床症状和体征且诊断为夜磨牙症的实验参与者进行记录：1）有牙齿频繁磨耗的报告;2）至少有3颗牙的咬合面有牙齿磨损与牙本质暴露;3）早晨咀嚼肌症状;4）咬肌肥大。对咀嚼肌节律性运动（RMMA）和孤立强直性咀嚼肌收缩发作事件进行评分。将这些变量与临床症状和体征存在的相关性进行比较。对孤立下颌强直运动发作的患者和RMMA受试者的颞下颌关节紊乱病（TMD）发生率进行调查。结果 20例受试者中,RMMA事件发作的频率为（5.8±3.1）次·h-1,孤立强直性发作的频率为（2.1±0.9）次·h-1。室友报告有磨牙体征的RMMA事件显著高于磨牙体征者（P<0.05）;牙齿磨耗者的RMMA事件显著高于无牙齿磨耗者（P<0.05）。但是,RMMA事件的发生与早晨咀嚼肌症状或咬肌肥大之间无差异。RMMA发生者的TMD发生率显著高于孤立下颌强直运动发作者。结论 常用于诊断夜磨牙症的临床症状和体征可体现在睡眠期间不同的临床和生理方面的下颌运动,即在睡眠期间RMMA可反映牙齿磨耗的发生,而且TMD的发生风险更大。     

Sleep bruxism and sleep arousal: an experimental challenge to assess the role of cyclic alternating pattern

Rhythmic masticatory muscle activity (RMMA) is the characteristic electromyographic pattern of sleep bruxism (SB), a sleep-related motor disorder associated with sleep arousal. Sleep arousals are generally organised in a clustered mode known as the cyclic alternating pattern (CAP). CAP is the expression of sleep instability between sleep maintaining processes (phase A1) and stronger arousal processes (phases A2 and A3). This study aimed to investigate the role of sleep instability on RMMA/SB occurrence by analysing CAP and electroencephalographic (EEG) activities. The analysis was performed on the sleep recordings of 8 SB subjects and 8 controls who received sensory stimulations during sleep. Baseline and experimental nights were compared for sleep variables, CAP, and EEG spectral analyses using repeated measure ANOVAs. Overall, no differences in sleep variables and EEG spectra were found between SB subjects and controls. However, SB subjects had higher sleep instability (more phase A3) than controls (P= 0·05). The frequency of phase A3 was higher in the pre-REM sleep periods (P < 0·001), where peaks in RMMA/SB activity were also observed (P = 0·05). When sleep instability was experimentally increased by sensory stimuli, both groups showed an enhancement in EEG theta and alpha power (P = 0·04 and 0·02, respectively) and significant increases in sleep arousal and all CAP variables. No change in RMMA/SB index was found within either groups (RMMA/SB occurred in all SB subjects and only one control during the experimental night). These findings suggest that CAP phase A3 may act as a permissive window rather than a generator of RMMA/SB activity in predisposed individuals.