Portable and wearable electromyographic devices for the assessment of sleep bruxism and awake bruxism: A literature review

Association between waking-state oral behaviors and health, anxiety, and distress in adolescents. A cross-sectional study

OBJECTIVE

To examine the relationship between non-physiological awake oral behaviors (NPAOB) and awake bruxism (AB) and symptoms of depression, distress, anxiety and somatization in adolescents.

METHODS

A total of 100 adolescents aged 12-15 from Medellín, Colombia participated, with 79 completing the assessments after excluding those with known health conditions. The frequency of NPAOB and AB was evaluated using the oral behavior checklist (OBC). Symptoms of depression, anxiety, distress, and somatization were assessed with standardized instruments (PHQ-A, GAD-7, PSS-C and PHQ-15).

RESULTS

Symptoms of depression did not represent a significant predictor of NPAOB, but it is of AB. The occurrence of anxiety symptoms led to a twofold increase in the likelihood of having NPAOB (OR>2; p<0.05), while anxiety, distress and somatization was associated with a more than three times higher probability of NPAOB and AB (OR>2;p<0.05).

CONCLUSION

Distress, anxiety, depression and somatization significantly influences NPAOB and AB in adolescents.

Comparison Between Ecological Momentary Assessment and Self-Report of Awake Bruxism Behaviours in a Group of Healthy Young Adults

OBJECTIVE

The aim of this investigation was to compare the self-reported frequency of awake bruxism (AB) behaviours by means of a validated single-observation point questionnaire (i.e., Oral Behaviour Checklist [OBC]) with the frequency reported in real-time with an Ecological Momentary Assessment (EMA) over 1 week.

MATERIALS AND METHODS

One hundred healthy young adults took part in the study. The frequency of some activities belonging to the spectrum of AB behaviours (i.e., teeth contact, mandible bracing, teeth clenching, teeth grinding) was evaluated using the EMA approach with smartphone technology support over 1 week. The OBC questionnaire was used to evaluate the self-reported frequency of the same AB behaviours. Spearman's rank correlation coefficient was adopted to test the correlation between the average score of each OBC question considered (i.e., teeth contact, mandible bracing, teeth clenching, teeth grinding) and the average frequency of the corresponding EMA item.

RESULTS

Statistical analysis showed a weak-to-moderate level of correlation between the two different AB assessment methods. Mandible bracing showed the highest level of correlation, while teeth grinding had the lowest one.

CONCLUSIONS

While the OBC represents a valid and easy-to-administer screening tool for evaluating bruxism behaviours, the EMA approach provides a more detailed real-time report on AB behaviours.

Prevalence and Severity of Sleep Bruxism in Edentulous Patients: A Cross-Sectional Study

Aims: Edentulous patients can also suffer from sleep bruxism (SB), just like dentate patients. This study aims to evaluate the prevalence and severity of SB in edentulous patients using the definitive method. Methods: Twenty-three edentulous patients underwent treatment with new conventional complete dentures. Definitive SB was evaluated using the Bruxoff (portable electromyography device) while sleeping at home. The prevalence of SB was assessed by the Bruxmeter software, where SB was evaluated as "absent" (score zero), "light" (<2 episodes), "moderate" (between 2 and 4 episodes), or "severe" (>4 episodes). The prevalence was expressed with descriptive statistics in percentage using the number of detected cases out of the total number of patients. Results: Eighteen patients (78.26%) were diagnosed with SB. The severity of SB was 55.5%, 5.5%, and 39% for the light, moderate, and severe scores, respectively. Conclusions: Almost 8 out of 10 edentulous patients have SB. Approximately half of the SB-detected patients showed moderate to severe severity of bruxism as measured by a commercial, at-home device.

Awake bruxism behaviors frequency in a group of healthy young adults with different psychological scores

OBJECTIVE

To assess the frequency of awake bruxism (AB) behaviors in a group of undergraduate dentistry students and correlate it with the status of anxiety and depression.

MATERIALS AND METHODS

The frequency of five oral behaviors (i.e., relaxed jaw muscle, teeth contact, mandible bracing, teeth clenching, teeth grinding) was evaluated using a smartphone-based ecological momentary assessment (EMA) approach. The anxiety and depression status was investigated with the four-item patient health questionnaire for anxiety and depression (PHQ-4). ANOVA with Tukey post-hoc test was used to assess the difference in frequency of AB behaviors among the four PHQ-4 groups.

RESULTS

Among the four groups, there was a statistically significant difference in the frequency of relaxed jaw muscle, teeth contact, mandible bracing, and teeth clenching, but not for teeth grinding.

CONCLUSION

Based on this cross-sectional study's findings, psyche seems to have a determinant impact on AB behaviors, which is significantly higher in individuals with anxiety and depression traits.

Effects of orthodontic aligners on 24-hour masseter muscle activity: a multiple-day electromyographic study

OBJECTIVE

This study aimed to assess the effects of aligners on masseter muscle activity by using an electromyographic device in the home environment.

METHODS

The study was performed on healthy patients who required orthodontic treatment. Three different 24 h-EMG recording sessions were performed in different conditions: without aligners, with passive aligners, and with active aligners. The non-functional MMA work index (nfMMA-WI) and the non-functional MMA time index (nfMMA-TI) for both awake and sleep hours were assessed. ANOVA test was used to compare the average activity during the three recording conditions.

RESULTS

On average, a total recording time of 204.7 ± 7.9 hours were provided for each patient. For most patients, ANOVA test showed an absence of significant differences between the recording sessions.

CONCLUSIONS

The impact of our results is not negligible: clinicians can find remarkable support to the hypothesis that the use of aligners affects the MMA only in a minority of subjects.

Cannabidiol Intervention for Muscular Tension, Pain, and Sleep Bruxism Intensity-A Randomized, Double-Blind Clinical Trial

Background: Temporomandibular disorders (TMDs) are the most prevalent non-dental pain issues in the maxillofacial region. Despite advancements, diagnosing and managing TMDs continues to pose challenges. This study aimed to assess the efficacy of cannabidiol (CBD) formulations, with different concentrations, in patients experiencing sleep bruxism and muscle-related TMDs, with a particular emphasis on their myorelaxant, pain-relieving, and bruxism-reducing properties. Methods: The Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMDs) was utilized as the diagnostic framework. Sixty patients completed the study, which followed a parallel-group, three-arm, randomized, double-blind clinical trial design, with a 1:1:1 allocation ratio across three groups: 1a, 1b, and 2. Groups 1a and 1b received CBD formulations at concentrations of 10% and 5%, respectively, while Group 2 received a placebo formulation. The trial consisted of four main visits, namely screening, baseline, first follow-up after 14 days, and second follow-up after 30 days, during which surface electromyography (sEMG), the visual analogue scale (VAS) for pain assessment, and Bruxoff examinations were conducted. Results: The reduction in pain, as measured by the visual analogue scale (VAS), among patients using the 10% CBD formulation was 57.4% (p < 0.05), accompanied by a decrease in sEMG activity by 42.1% (p < 0.05). Conversely, individuals using the 5% CBD formulation experienced a 40.8% (p < 0.05) decrease in pain. Regarding the decrease in the sleep bruxism index, users of the 10% CBD formulation saw the highest reduction of 51% (p < 0.05). These findings underscore the efficacy of the proposed treatment in both experimental groups, with a notable advantage observed in Group 1a. Conversely, the outcomes of the selected variables for the control group did not exhibit significant differences throughout the study. Conclusions: The intraoral use of CBD formulations in patients with TMDs have proven to be a successful treatment for reducing pain, muscle tension, and bruxing activity in individuals with sleep bruxism and muscle-related TMDs. Specifically, a concentration of 10% CBD has demonstrated superior results compared to 5% CBD.

Inflammatory Markers and Sleep Architecture in Sleep Bruxism-A Case-Control Study

Background: Sleep bruxism (SB) is a common sleep-related movement behavior with a multifaceted etiology and a deficiently understood pathophysiology. A recent hypothesis suggests a link between SB and systemic inflammation. The scope of the study was to determine whether bruxers have altered sleep structure and different levels of inflammatory parameters compared to nonbruxers. Methods: A total of 83 adults underwent full-night polysomnography. The polysomnograms were evaluated using the American Academy of Sleep Medicine (AASM) guidelines. Then, the blood samples were obtained from the participants by venipuncture and the analyses were performed. The study group was divided based on bruxism episode index (BEI) into two groups: BEI ≤ 4 and BEI > 4. Results: In comparison with nonbruxers, the oxygen desaturation index (ODI) was significantly higher in severe bruxers (7.5 ± 11.08 vs. 3.33 ± 5.75, p < 0.005), as well as the arousal parameters (7.77 ± 4.68 vs. 4.03 ± 2.97, p < 0.001), and the mean oxygen desaturation (3.49 ± 0.69 vs. 3.01 ± 0.67, p < 0.05). Moreover, the differences in sleep architecture and deprivation of the deep sleep phase were observed, the non-REM sleep stage 3 was significantly shorter in severe bruxers (p < 0.03). Differences were also noted in non-REM sleep stage 1 and REM sleep phase. In the investigated group, there were no statistical differences in inflammatory cytokines levels between bruxers and nonbruxers. Conclusions: Sleep bruxism is associated with sleep structure alterations and may be associated with deep sleep phase deprivation. The inflammatory markers are not linearly correlated with the severity of sleep bruxism expressed as BEI.

Association between Psychological Distress and Possible, Probable, and Definite Sleep Bruxism-A Comparison of Approved Diagnostic Procedures

(1) Background: The relationship between sleep bruxism (SB) and psychological distress has been investigated in numerous studies and is heterogeneous. Different diagnostic procedures have been applied to determine SB. The aim of this study was to directly compare the association between psychological distress and SB diagnosed by different accepted methods. (2) Methods: Data of N = 45 subjects were analyzed, including group comparisons and correlation analyses. Following diagnostic methods for the determination of SB were used in one sample: self-report, clinical assessment, polysomnography with audio-video recording and a novel diagnostic sheet with analyzing software. Psychological distress was measured using the global severity index (GSI) of the Symptom Checklist-90-Standard (SCL-90-S). (3) Results: The GSI did not differ significantly between subjects with and without SB, regardless of the underlying diagnostic classification (p > 0.05). In-depth correlation analyses of self-report and clinical data revealed a weak-to-medium correlation with the GSI (r = 0.12-0.44). Due to non-normally distributed data, a test of statistical significance was not possible. Variables of instrumental methods such as the SB index (amount of SB activity per hour) of polysomnography (PSG) showed almost no correlation with psychological distress (r = -0.06-0.05). (4) Conclusions: Despite these limitations, the results provide an indication that the choice of diagnostic procedure may elucidate the variance in the correlation between SB and psychological distress.

Examination of the relationship between masseter muscle activity during sleep and wakefulness measured by using a wearable electromyographic device

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.

Novel Diagnostic and Therapeutic Approaches to Temporomandibular Dysfunction: A Narrative Review

Temporomandibular dysfunction (TMD) is a burgeoning area of study within the dental field. TMD is caused by abnormalities in the temporomandibular joint or muscles of mastication and can lead to pain, loss of function, and other complications. As this area of patient care receives increased focus, the ability to accurately diagnose TMD becomes paramount. The aim of this review is to summarize novel diagnostic and therapeutic techniques that have been proposed within the last approximately 3 years in order to inform readers of the cutting-edge advances in the field of TMD diagnosis and management, while also analyzing the clinical relevance of each study. A PubMed search was completed on 1 March 2023, using MeSH terms related to TMD diagnosis and treatment. The search yielded seven articles that pertained to the aim of this review article. The main findings from each study are summarized in this review article. These novel methods of diagnosing and treating TMD may improve our ability to assess and treat patients suffering from TMD.

Wearables for personalized monitoring of masticatory muscle activity - opportunities, challenges, and the future

Wearable devices are worn on or remain in close proximity of the human body. The use of wearable devices specific to the orofacial region is steadily increasing. Orofacial applications of wearable devices include supplementing diagnosis, tracking treatment progress, monitoring patient compliance, and understanding oral parafunctional behaviours. In this short communication, the role of wearable devices in advancing personalized dental medicine are highlighted with a specific focus on masticatory muscle activity monitoring in naturalistic settings. Additionally, challenges, opportunities, as well as future research areas for successful use of wearable devices for precise, personalized care of muscle disorders are discussed.

Frequency distribution of the number and amplitude of electromyographic waveforms of the masseter muscle during sleep in patients with a clinical diagnosis of sleep bruxism

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.

Nutrients Associated with Sleep Bruxism

Background: The purpose of the present research was to identify nutrients related to sleep bruxism and to establish a hypothesis regarding the relationship between sleep bruxism and nutrients. Methods: We recruited 143 Japanese university students in 2021 and assigned them to sleep bruxism (n = 58) and non-sleep bruxism groups (n = 85), using an identical single-channel wearable electromyography device. To investigate nutrient intakes, participants answered a food frequency questionnaire based on food groups. We assessed differences in nutrient intakes between the sleep bruxism and non-sleep bruxism groups. Results: Logistic regression modeling showed that sleep bruxism tended to be associated with dietary fiber (odds ratio, 0.91; 95% confidence interval, 0.83–1.00; p = 0.059). In addition, a subgroup analysis selecting students in the top and bottom quartiles of dietary fiber intake showed that students with sleep bruxism had a significantly lower dietary fiber intake (10.4 ± 4.6 g) than those without sleep bruxism (13.4 ± 6.1 g; p = 0.022). Conclusion: The present research showed that dietary fiber intake may be related to sleep bruxism. Therefore, we hypothesized that dietary fiber would improve sleep bruxism in young adults.

Dental sleep-related conditions and the role of oral healthcare providers: A scoping review

Dental sleep medicine as a discipline was first described about a quarter of a century ago. Snoring, obstructive sleep apnea, sleep bruxism, xerostomia, hypersalivation, gastroesophageal reflux disease, and orofacial pain were identified as dental sleep-related conditions. This scoping review aimed to: i) identify previously unidentified dental sleep-related conditions; and ii) identify the role of oral healthcare providers in the prevention, assessment, and management of dental sleep-related conditions in adults. A systematic literature search was conducted in PubMed, Embase.com, Web of Science, and Cochrane. Studies that reported an actual or likely role of oral healthcare providers in the prevention, assessment, and/or management of sleep-related conditions were included. Of the 273 included studies, 260 were on previously listed dental sleep-related conditions; the other 13 were on burning mouth syndrome. Burning mouth syndrome was therefore added to the list of dental sleep-related conditions for the first aim and categorized into sleep-related orofacial pain. For the second aim, the role of oral healthcare providers was found to be significant in the prevention, assessment, and management of obstructive sleep apnea and sleep bruxism; in the assessment and management of snoring, sleep-related orofacial pain, and oral dryness; and in the assessment of sleep-related gastroesophageal reflux condition.

Wearable Orofacial Technology and Orthodontics

Wearable technology to augment traditional approaches are increasingly being added to the arsenals of treatment providers. Wearable technology generally refers to electronic systems, devices, or sensors that are usually worn on or are in close proximity to the human body. Wearables may be stand-alone or integrated into materials that are worn on the body. What sets medical wearables apart from other systems is their ability to collect, store, and relay information regarding an individual's current body status to other devices operating on compatible networks in naturalistic settings. The last decade has witnessed a steady increase in the use of wearables specific to the orofacial region. Applications range from supplementing diagnosis, tracking treatment progress, monitoring patient compliance, and better understanding the jaw's functional and parafunctional activities. Orofacial wearable devices may be unimodal or incorporate multiple sensing modalities. The objective data collected continuously, in real time, in naturalistic settings using these orofacial wearables provide opportunities to formulate accurate and personalized treatment strategies. In the not-too-distant future, it is anticipated that information about an individual's current oral health status may provide patient-centric personalized care to prevent, diagnose, and treat oral diseases, with wearables playing a key role. In this review, we examine the progress achieved, summarize applications of orthodontic relevance and examine the future potential of orofacial wearables.

Artifact removal from sEMG signals recorded during fully unsupervised daily activities

Objective

In this study, we propose a method for removing artifacts from superficial electromyography (sEMG) data, which have been widely proposed for health monitoring because they encompass the basic neuromuscular processes underlying human motion.

Methods

Our method is based on a spectral source decomposition from single-channel data using a non-negative matrix factorization. The algorithm is validated with two data sets: the first contained muscle activity coupled to artificially generated noises and the second comprised signals recorded under fully unsupervised conditions. Algorithm performance was further assessed by comparison with other state-of-the-art approaches for noise removal using a single channel.

Results

The comparison of methods shows that the proposed algorithm achieves the highest performance on the noise-removal process in terms of signal-to-noise ratio reconstruction, root means square error, and correlation coefficient with the original muscle activity. Moreover, the spectral distribution of the extracted sources shows high correlation with the noise sources traditionally associated to sEMG recordings.

Conclusion

This research shows the ability of spectral source separation to detect and remove noise sources coupled to sEMG signals recorded during unsupervised daily activities which opens the door to the implementation of sEMG recording during daily activities for motor and health monitoring.

Ecological Momentary Assessment of Masseter Muscle Activity in Patients with Bruxism

According to the International Bruxism Consensus, bruxism refers to the activity of the masticatory muscles reflecting contraction disorders, regardless of whether it is during sleep (SB) or an awake (AB) state. The objective of the present study was to evaluate the activity of the masseter muscle by surface electromyographic (sEMG) recordings. This study was performed on 20 participants with self-reported “possible bruxism” (study group) and 20 participants with no self-reported bruxism (control group); all participants underwent an evaluation of the masseter muscle activity using the dia-BRUXO device, which provides numerical parameters regarding sEMG (the total duration and the type of bruxism specific events, the effort made by the masticatory muscles during the recording period, and the personal bruxism index of each participant). Participants from the study group presented more clenching events during AB, three times more frequent than the control group (p = 0.002, Mann−Whitney U test); for SB, the frequency of clenching and grinding events was comparable within the study group, being more frequent than for the control group; the mean value of the effort index was higher for AB (1.177%) than SB (0.470%) and the same for the duration index, with a mean value of 2.788% for AB and 1.054% for SB. All participants from the control group presented reduced values for all acquired parameters. Overall, the personal bruxism index in AB was approximately four times higher for the study group (2.251%) compared to the control group (0.585%) (p < 0.005, Mann−Whitney U test). Similar values were obtained for SB. All participants with “possible bruxism” from the study group presented a higher activity of the masseter muscle, which is specific for bruxism, thus being defined as “definite bruxism”.

Accuracy of Surface Electromyography in the Diagnosis of Pain-Related Temporomandibular Disorders in Children with Awake Bruxism

The study assessed masticatory muscle electromyographic (EMG) activity in both children diagnosed with pain-related temporomandibular disorders (TMD-P) and awake bruxism (AB) and in children without TMD, as well as the diagnostic value of surface electromyography (sEMG) in diagnosing TMD-P in subjects with AB. After evaluation based on the Axis I of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD), 30 children diagnosed with myofascial pain were included in the myofascial pain group and 30 children without TMD diagnosis comprised the control group (mean age of 9.49 ± 1.34 years). The activity of the anterior temporal (TA) and masseter (MM) muscle was assessed bilaterally using a DAB-Bluetooth device (zebris Medical GmBH, Germany) at rest and during maximum voluntary clenching (MVC). The receiver operating characteristic (ROC) curve was used to determine the accuracy, sensitivity, and specificity of the normalized sEMG data. Statistically significant intergroup differences were observed in TA and MM muscle EMG activity at rest and during MVC. Moderate degree of sEMG accuracy in discriminating between TMD-P and non-TMD children was observed for TAmean, left MM, and MMmean EMG muscle activity at rest. sEMG can be a useful tool in assessing myofascial TMD pain in patients with AB.

Signal acquisition and analysis of ambulatory electromyographic recordings for the assessment of sleep bruxism: A scoping review

BACKGROUND

Ambulatory electromyographic (EMG) devices are increasingly being used in sleep bruxism studies. EMG signal acquisition, analysis and scoring methods vary between studies. This may impact comparability of studies and the assessment of sleep bruxism in patients.

OBJECTIVES

(a) To provide an overview of EMG signal acquisition and analysis methods of recordings from limited-channel ambulatory EMG devices for the assessment of sleep bruxism; and (b) to provide an overview of outcome measures used in sleep bruxism literature utilising such devices.

METHOD

A scoping review of the literature was performed. Online databases PubMed and Semantics Scholar were searched for studies published in English until 7 October 2020. Data on five categories were extracted: recording hardware, recording logistics, signal acquisition, signal analysis and sleep bruxism outcomes.

RESULTS

Seventy-eight studies were included, published between 1977 and 2020. Recording hardware was generally well described. Reports of participant instructions in device handling and of dealing with failed recordings were often lacking. Basic elements of signal acquisition, for example amplifications factors, impedance and bandpass settings, and signal analysis, for example rectification, signal processing and additional filtering, were underreported. Extensive variability was found for thresholds used to characterise sleep bruxism events. Sleep bruxism outcomes varied, but typically represented frequency, duration and/or intensity of masticatory muscle activity (MMA).

CONCLUSION

Adequate and standardised reporting of recording procedures is highly recommended. In future studies utilising ambulatory EMG devices, the focus may need to shift from the concept of scoring sleep bruxism events to that of scoring the whole spectrum of MMA.

Awake Bruxism-Single-Point Self-Report versus Ecological Momentary Assessment

Assessment of awake bruxism (AB) is problematic due to the inability to use continuous recordings during daytime activities. Recently, a new semi-instrumental approach was suggested, namely, ecological momentary assessment (EMA), via the use of a smartphone application. With the application, subjects are requested to report, at least 12 times per day, the status of their masticatory muscle activity (relaxed muscles, muscle bracing without tooth contact, teeth contact, teeth clenching, or teeth grinding). The aim of the present study was to test the association between a single observation point self-report and EMA assessment of AB. The most frequent condition recorded by the EMA was relaxed muscles (ca. 60%) and the least frequent was teeth grinding (less than 1%). The relaxed muscle condition also showed the lowest coefficient of variance over a seven-day period of report. Additionally, only the relaxed muscles and the muscle bracing conditions presented an acceptable ability to assess AB-positive and AB-negative subjects, as defined by single-point self-report questions. The combination between self-report and EMA may have the potential to promote our ability to assess AB. We suggest to re-consider the conditions of teeth contact and teeth grinding while using EMA to evaluate AB.

Associations among masticatory muscle activity, physical activity and self-reported oral behaviours in adult women

OBJECTIVES

To examine the relationship between masticatory muscle activity (MMA), self-reported oral behaviours (OBs) and overall physical activity (PA) in adult women.

MATERIALS AND METHODS

MMA and PA were assessed by a wearable electromyography (EMG) device and accelerometer respectively, worn over 2 non-consecutive days by 53 women (mean age 27.5 ± 6.4 years). Following the second recording day, self-reported OBs were assessed. MMA was assessed by the number, amplitude and duration of masseter contraction episodes. Masseter muscle EMG outcome measures were number of contraction episodes per hour (CEs/h) and the relative contraction time (RCT%). PA was assessed by time accumulated in moderate to vigorous physical activity (MVPA) and 10-min bouts of MVPA per hour. Data were analysed using mixed model analysis.

RESULTS

MMA in free-living conditions consisted mostly of low-amplitude (<10% maximum voluntary clenching) and short-duration (<10 s) contraction episodes. Masseter CEs/h were not associated with self-reported levels of OB. Masseter CEs/h were positively associated with time accumulated in MVPA (F = 9.9; p = 0.002) and negatively associated with 10-min bouts of MVPA/h (F = 15.8; p <0.001). RCT% was not significantly associated with either.

CONCLUSIONS

Objectively assessed MMA is not associated with self-reported OB in free-moving adult females. Moderate to vigorous exercise and physical inactivity are accompanied with an increase in the number of masseter muscle contractions and thus possibly tooth clenching activity.

CLINICAL RELEVANCE

OB can be influenced by the type and extent of PA. Subjective assessment of MMA by questionnaire and/or interviews may be invalid.

Electromyographic Patterns and the Identification of Subtypes of Awake Bruxism

The future of awake bruxism assessment will incorporate physiological data, possibly electromyography (EMG) of the temporal muscles. But up to now, temporal muscle contraction patterns in awake bruxism have not been characterized to demonstrate clinical utility. The present study aimed to perform surface EMG evaluations of people assessed for awake bruxism to identify possible different subtypes. A 2-year active search for people with awake bruxism in three regions of the country resulted in a total of 303 participants (223 women, 38 ± 13 years, mean and SD). Their inclusion was confirmed through non-instrumental approaches for awake bruxism: self-reported questionnaire and clinical exam, performed by three experienced and calibrated dentists (Kappa = 0.75). Also, 77 age- and sex-matched healthy controls were recruited (49 women, 36 ± 14 years). Temporalis surface EMG was performed with a portable device (Myobox; NeuroUp, Brazil). EMG signals were sent to a computer via Bluetooth 4.0 at a sampling rate of 1,000 Hz. Digital signal processing was performed using the commercial neuroUP software, transformed in RMS and then normalized for peak detection (EMG peaks/min), in a 10 min session. Cluster analysis revealed three distinct subtypes of awake bruxism: phasic, tonic, and intermediate. Individuals with a predominance of EMG peaks/min were classified as the "phasic" subtype (16.8%). Those with the highest EMG rest power were classified as the "tonic" subtype (32.3%). There was also an "intermediate" subtype (50.8%), when both variables remained low. Characterization of awake bruxism physiology is important for future establishment of instrumental assessment protocols and treatment strategies.