Sleep bruxism, bite force, morning symptoms, and home electromyography: a cross-sectional study

Sleep bruxism, bite force, morning symptoms, and home electromyography: a cross-sectional study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Sleep bruxism, bite force, morning symptoms, and home electromyography: a cross-sectional study Oanh Nguyen-Ngoc Hoang, Xuan Vinh TRAN, Anh Nguyen Ho Quynh, Ngan Nguyen Gia Kieu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8889308/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 10 You are reading this latest preprint version Abstract Background Sleep bruxism is a common parafunctional activity marked by involuntary tooth grinding or clenching during sleep and has been linked to tooth wear, masticatory muscle discomfort, and temporomandibular joint loading. However, its association with maximum bite force and awakening masticatory symptoms remains unclear. This study aimed to compare maximum bite force and morning masticatory symptoms between adults with and without sleep bruxism using a combined clinical assessment and multi-night, at-home surface electromyography monitoring. Methods This cross-sectional study enrolled 60 adults aged 18–45 years (30 with sleep bruxism and 30 controls). Sleep bruxism was identified using a multimodal approach that combined self-report, clinical signs, and three nights of at-home single-channel surface electromyography recorded over the masseter muscle with the FLA-500-SD device (GC Corporation, Japan), in accordance with the American Academy of Sleep Medicine criteria. Participants completed a structured questionnaire on awakening masticatory symptoms and underwent a standardized assessment of occlusal wear. Maximum bite force was measured bilaterally at the first molar, second premolar, and central incisor regions using a digital occlusal force gauge (BFM, 4th generation, Vietnam). Three measurements were conducted per site, and the highest value was used for analysis. Electromyography outcomes included the bruxism episode index and the percentage of maximum voluntary contraction. Between-group differences were evaluated using the independent-samples t-test or the Mann-Whitney U test, with a two-sided significance level of 0.05. Results Participants with sleep bruxism reported more frequent awakening symptoms, including jaw stiffness, jaw fatigue, and temporal headache (p < 0.01). Maximum bite force at the molar region did not differ between groups, whereas values at the premolar and incisor regions were higher in the sleep bruxism group (p < 0.05). Across all tooth regions, men showed higher maximum bite force than women (p < 0.01). Conclusions Adults with sleep bruxism showed higher anterior bite force and more frequent awakening masticatory symptoms than controls, while molar bite force did not differ. However, awakening symptoms alone are insufficient for identifying sleep bruxism. A multimodal approach that integrates clinical assessment with instrumental measures, such as electromyography, may improve diagnostic accuracy. Trial registration Not applicable. sleep bruxism maximum bite force electromyography masticatory symptoms parafunctional habits Figures Figure 1 Introduction Bruxism is considered common and may have a substantial impact on oral health. This activity can occur both during sleep and while awake ( 1 ). In individuals with bruxism, clinical manifestations may involve multiple components of the masticatory system: teeth (occlusal wear, cracks or fractures, hypersensitivity, mobility), muscles (hyperactivity, pain or fatigue, hypertrophy), and the temporomandibular joint (intra-articular disorders, changes in joint tissues, disc displacement). These consequences are largely attributed to prolonged and repetitive muscle contraction that exceeds physiological tolerance, resulting in cumulative tissue damage over time ( 2 ). Current evidence regarding maximum bite force in patients with sleep bruxism remains limited. Todic and colleagues suggested that bruxism increases maximum bite force and proposed maximum bite force as a potential indicator for diagnosis and for understanding the pathophysiology of this parafunctional activity ( 3 ). Helkimo and Ingervall reported that maximum bite force increased only in the incisor region, whereas Cosme and colleagues ( 4 ) concluded that bruxism does not affect maximum bite force ( 5 ). Other authors have reported a 54.5% increase in maximum bite force among individuals with bruxism ( 6 ). To date, conclusions about the effect of bruxism on maximum bite force remain inconsistent. Such discrepancies may reflect differences in diagnostic criteria, study design, sample characteristics (sex, tooth loss, temporomandibular disorders), or the measurement site and method. In clinical practice, bruxism diagnosis is still largely based on questionnaires, history taking, and clinical signs. However, these approaches lack objectivity and have limited diagnostic value ( 7 ). In 2023, the American Academy of Sleep Medicine, through successive revisions of the International Classification of Sleep Disorders, issued clinical diagnostic criteria for sleep bruxism that have been widely used in research as a screening tool. In parallel, advances in surface electromyography have enabled more objective assessment. Yamaguchi T. and colleagues introduced the FLA-500-SD surface electromyography device, which allows accurate multi-night, at-home recording of masseter activity and supports clinical identification of sleep bruxism ( 8 , 9 ). Surface electromyography does more than classify sleep bruxism: it quantifies masticatory muscle activation during sleep, thereby contextualizing maximum bite force findings. These data link functional measurements to underlying muscle activity rather than symptoms alone. If maximum bite force truly changes in individuals with bruxism, measuring this parameter could become a useful quantitative tool for diagnosis and risk stratification ( 3 ). This study aimed to assess awakening masticatory symptoms using a questionnaire aligned with the American Academy of Sleep Medicine framework, compare site-specific maximum bite force between adults with and without sleep bruxism identified using at-home surface electromyography, and evaluate between-group differences in electromyography indices, including the bruxism episode index and the percentage of maximum voluntary contraction. Methods Study design and participant recruitment This study aimed to compare site-specific maximum bite force and awakening masticatory symptoms between adults with and without sleep bruxism, and to examine electromyography indices across groups. This cross-sectional study was conducted at the Dental Speciality Clinic, University of Medicine and Pharmacy at Ho Chi Minh City. Participants were recruited by convenience sampling from adults attending the dental clinic for routine dental care during the study period; recruitment was not restricted to individuals presenting with suspected bruxism. Eligible participants were adults aged 18–45 years with full natural dentition in both arches (28 teeth excluding third molars), a bilateral Angle Class I molar relationship, and no severe systemic disease, regardless of sleep bruxism status. Exclusion criteria included anterior or posterior crossbite; history of maxillofacial trauma or surgery; fixed prostheses or restorations on the functional surfaces of first molars, premolars, or incisal edges; active dental pathology such as pulpitis, periapical or periodontal disease; and use of medications affecting neuromuscular activity, such as analgesics, anxiolytics, antidepressants, or antipsychotics. Participants were also excluded if they had a pain-related temporomandibular disorder (according to DC/TMD classification) with moderate to severe pain lasting at least three months or were undergoing treatment for TMD, orthodontic therapy, or bruxism. All participants underwent clinical screening and diagnostic procedures, including surface electromyographic monitoring, as part of the study protocol. Sample size An a priori sample size calculation was performed to compare two independent means with equal group allocation. Parameter estimates were derived from a previous study by Dıraçoğlu and colleagues in which maximum bite force was measured at the incisor region. Assuming a two-sided significance level of 0.05 and 80% power (β = 0.20), with expected mean (standard deviation) values of 105.1 (34.2) and 81.3 (31.0), the minimum required sample size was 30 participants per group (total n = 60). This target sample size was therefore adopted for recruitment and group comparisons in the present study. Group allocation based on sleep bruxism status Participants were classified into two groups, those with SB and those without, based on a three-step diagnostic process integrating subjective, clinical, and instrumental criteria in accordance with the International Classification of Sleep Disorders (ICSD-3-TR, 2023). • Step 1: History-based screening using a structured questionnaire All participants completed a standardized SB Questionnaire (Fig. 1 ) adapted from the criteria described by the American Academy of Sleep Medicine and validated through previous literature ( 10 ). A participant fulfilled this criterion if they answered “Yes” to item 1 (self- or bed partner-reported grinding/clenching noises) or item 2 (awareness of abnormal tooth wear), and “Yes” to at least one of the listed morning symptoms (e.g., jaw stiffness, clenching sensation, headache, limited mouth opening, joint clicking). Participants satisfying these conditions were considered positive for the history-based criterion (A). • Step 2: Clinical examination for suspected bruxism-related tooth wear A calibrated dental specialist conducted a comprehensive examination of all tooth surfaces to identify patterns of occlusal wear indicative of SB. Participants were deemed to fulfill the clinical criterion (B) if at least one pair of opposing teeth exhibited wear facets that were flat, glossy, sharply demarcated, and demonstrated interlocking morphology characteristic of bruxism-related attrition. • Step 3: Instrumental confirmation using home surface electromyography Participants were instructed to wear the FLA-500-SD surface electromyography (sEMG) device at home for three consecutive nights. The first night served as an adaptation period during which the device was worn without activation, allowing subjects to become accustomed to its presence. On the following two nights, the device was activated to record jaw muscle activity. A bruxism episode index of ≥ 5.5 episodes/hour (averaged across the two recorded nights) was used as the instrumental criterion, based on prior validation studies for this device. Meeting this threshold constituted the instrumental diagnostic criterion (C). Final classification Participants who met all three diagnostic criteria: subjective report (A), clinical signs (B), and instrumental confirmation via EMG (C), were classified into the SB group. Conversely, those who did not meet any of the three criteria were assigned to the control (non-SB) group. Individuals who satisfied only one or two criteria were considered diagnostically inconclusive and were therefore excluded from further analysis to maintain the diagnostic specificity of the comparison groups. Maximum bite force measurement Participants were seated upright with the head in a natural position, facing forward, and feet flat on the floor. Maximum bite force (MBF) was measured within one week of EMG recording using a custom-built digital strain-gauge occlusal force gauge (BFM 4th generation, Vietnam) ( 11 ). Measurements were taken bilaterally at three sites: first molars, premolars, and central incisors. At each site, participants were instructed to bite maximally for 3 seconds. Three trials were performed per site, with a 2-minute rest between measurements to minimize muscle fatigue. For each tooth region, the highest of three trials was recorded for each side, and the final value used for analysis was the mean of the left and right maxima ( 11 ). Data analysis Data were analyzed using SPSS 26. Normality was assessed with the Shapiro-Wilk test. Continuous variables (MBF and EMG indices) are presented as mean ± standard deviation or median (interquartile range) where appropriate. Categorical variables are shown as frequencies and percentages. Intergroup comparisons of MBF and BEI were made using independent-samples t -tests or Mann-Whitney U -tests. Sex-stratified differences were analyzed similarly. Chi-square or Fisher’s exact tests compared symptom frequencies. A significance level of 0.05 was adopted. Results Participant characteristics A total of 60 subjects (30 SB, 30 controls) completed the study (Table 1 ). The SB group had a median age of 23.0 years (range 19–43) and included 14 men and 16 women; controls had a median age of 25.0 years (19–44) with 13 men and 17 women. The age and sex distributions did not differ significantly (p > 0.05). Table 1 Demographic characteristics and self-reported awareness of sleep bruxism Characteristic SB group (n = 30) Control group (n = 30) p-value a Age (years), median (range) 23 (19–43) 25 (19–44) > 0.05 Male, n (%) 14 (46.7%) 13 (43.3%) > 0.05 Female, n (%) 16 (53.3%) 17 (56.7%) Self-aware 8 (26.7%) 3 (10.0%) Not self-aware 22 (73.3%) 27 (90.0%) Self-awareness was defined as a “Yes” response indicating that the participant personally noticed sleep-related grinding or clenching; participants without personal awareness were classified as not self-aware, regardless of bed-partner report Morning masticatory symptoms Morning masticatory symptoms were more common in the sleep bruxism group (Table 2 ). Fatigue or pain on awakening (93.3% vs 20.0%) and clenching sensation/oral soreness on awakening (50.0% vs 6.7%) were both significantly higher in participants with sleep bruxism than in controls (both p 0.05). Table 2 Frequency of morning masticatory symptoms Symptom Sleep bruxism (n = 30) Control (n = 30) p-value Jaw feels sore or stiff on awakening 28 (93.3%) 6 (20.0%) < 0.001 Upper and lower teeth tightly together (clenching) or mouth hurts on awakening 15 (50.0%) 2 (6.7%) < 0.001 Forehead feels tense on awakening 12 (40.0%) 8 (26.7%) 0.411 Trouble opening the mouth wide on awakening 3 (10.0%) 0 (0%) 0.237 Jaw feels tense on awakening and tension decreases after moving the lower jaw 2 (6.7%) 0 (0%) 0.492 Clicking sound/feeling in the jaw on awakening that goes away afterwards 10 (33.3%) 8 (26.7%) 0.778 Values are n (%). P values were calculated using the chi-square test or Fisher’s exact test, as appropriate (Fisher’s exact test was used when expected cell counts were < 5). Maximum bite force Mean maximum bite force values are shown in Table 3 . Compared with controls, participants with sleep bruxism had higher maximum bite force at the premolar (495.3 ± 79.5 N vs 447.6 ± 63.5 N; p = 0.002) and incisor regions (268.7 ± 41.1 N vs 235.6 ± 41.2 N; p = 0.003), whereas no difference was observed at the first molar site (597.6 ± 61.2 N vs 574.9 ± 77.3 N; p = 0.21). Sex-stratified analyses showed the same pattern in men and women (premolar and incisor: all p 0.05). Across groups and sites, men exhibited higher maximum bite force than women (p 0.4), indicating similar relative force distribution along the arch. Values are mean ± SD. p values were calculated using the independent-samples t-test. Table 3 Maximum bite force (MBF) by site and group Tooth region Sleep bruxism (n = 30) Mean ± SD (N) Control (n = 30) Mean ± SD (N) p-value First molars 597.6 ± 61.2 574.9 ± 77.3 0.210 Premolars 495.3 ± 79.5 447.6 ± 63.5 0.002 Central incisors 268.7 ± 41.1 235.6 ± 41.2 0.003 Electromyography results The SB group exhibited a significantly higher bruxism episode index (BEI), averaging 10.5 ± 3.4 episodes/hour compared to 3.2 ± 1.5 in controls (p < 0.001), confirming increased nocturnal muscle activity (Table 4 ). In contrast, the average percentage of maximum voluntary contraction (%MVC) did not differ significantly between groups (20.9% ± 13.0% in SB vs. 19.7% ± 13.7% in controls; p = 0.72), suggesting comparable contraction intensity during episodes. Table 4 Electromyographic indices Parameter SB group (Mean ± SD) Control group (Mean ± SD) p-value a Bruxism Episode Index (BEI) 10.5 ± 3.4 3.2 ± 1.5 < 0.001 % MVC 20.9 ± 13.0 19.7 ± 13.7 0.72 a: two sample t-tests in comparison between SB group and control group Discussion This study applied a multimodal diagnostic approach to sleep bruxism, integrating both subjective and objective assessments: (i) a structured history-based questionnaire, (ii) clinical examination for tooth wear, and (iii) recording of masticatory muscle activity using the FLA-500-SD electromyography device. The FLA-500-SD is a portable single-channel electromyography system positioned over the masseter muscle, enabling multi-night, at-home recording during sleep. Previous studies have reported high sensitivity and specificity compared with audio–video polysomnography, particularly when using a calibrated bruxism episode index threshold ( 8 ). In the present study, participants wore the device for three consecutive nights; the first night was an adaptation night without recording to facilitate habituation and minimize behavioral changes when first using the device. Multi-night recording in a familiar sleep environment may reduce the “first-night effect” commonly observed with audio–video polysomnography and may better reflect sleep bruxism frequency under real-world conditions ( 12 , 13 ). This is consistent with findings reported by Sakuma and colleagues, who noted stable device performance both in the laboratory and at home compared with polysomnography ( 14 ). Overall, given its feasibility for research and its ability to provide quantitative indices (e.g., bruxism episode index and percentage of maximum voluntary contraction) that characterize the intensity and patterns of masticatory muscle activity, the FLA-500-SD appears suitable for supporting the identification and monitoring of sleep bruxism. Several previous studies have suggested that diagnosing sleep bruxism using questionnaires and clinical examination based on ICSD-3 criteria has limited accuracy; when compared with single-channel electromyography, this approach yielded a sensitivity of 63.2% and specificity of 72.7% ( 15 ). These findings indicate a substantial risk of missed sleep bruxism cases when relying on clinical assessment alone ( 15 – 17 ). In our study, the ICSD-3-based classification was broadly consistent with the electromyography-based diagnosis, although 73.3% of participants did not self-report awareness of bruxism and therefore met only the remaining two questionnaire criteria. The questionnaire proposed by Yunisa and colleagues has a notable advantage in its two-stage screening structure: it is easy to administer yet includes a threshold that may reduce false positives compared with single-item screening. Specifically, participants are classified as suspected sleep bruxism when they respond “Yes” to Question 1 or Question 2 (night-time grinding/clenching or perceived abnormal tooth wear) and report at least one morning symptom in Question 3 (e.g., jaw pain or stiffness, forehead tension, difficulty opening the mouth, jaw tension relieved by moving the mandible, or joint clicking) ( 10 ). Compared with the American Academy of Sleep Medicine screening questions, which include only two brief items for sleep bruxism (morning jaw pain and sleep grinding), the Yunisa questionnaire broadens the symptom spectrum while retaining a simple yes/no format suitable for large-scale surveys. In the present study, symptoms on awakening such as jaw pain/fatigue (93.3%) and a clenching sensation (50.0%) were more frequent in the sleep bruxism group than in controls, with statistically significant differences. These symptoms may reflect repeated masticatory muscle contractions during sleep and have high screening value, whereas symptoms such as temporal pain or jaw stiffness appear less specific. In addition, we observed occlusal wear patterns suspected to be related to bruxism. Maximum bite force followed the expected anteroposterior gradient, with the highest values at the first molar region and progressively lower values at the premolar and incisor regions in both sexes. When comparing groups, sleep bruxism was associated with higher maximum bite force at the premolar and incisor regions, whereas molar values were comparable to those of controls. This site-specific pattern aligns with prior reports showing no between-group difference when bite force was assessed only at the first molar, as in studies by Calderon and by Chrcanovic and colleagues ( 18 ), and anterior differences without posterior changes as reported by Helkimo and Ingervall ( 5 ). Importantly, those earlier studies relied on questionnaires and clinical signs to define bruxism (probable bruxism), whereas our classification incorporated multi-night, at-home surface electromyography, supporting a definite bruxism diagnosis. Using an instrumental criterion may reduce exposure misclassification and improve the internal validity of site-specific bite force comparisons across groups. Bruxism involves involuntary masticatory muscle contraction that occurs during sleep ( 19 ). Repeated occlusal loading associated with bruxism may lead the masticatory muscles, particularly the masseter and temporalis, to adapt by increasing muscle size and strength. Several reports indicate that men tend to exhibit more severe sleep bruxism than women. Smardz and colleagues reported significantly higher rhythmic masticatory muscle activity frequency and bruxism episode index in men with sleep bruxism than in women ( 20 ). Experimental evidence suggests that long-standing bruxism is associated with increased masseter cross-sectional area, particularly in men ( 21 ). In an ultrasound study comparing masseter thickness in individuals with temporomandibular disorders with and without sleep bruxism, Lee Y-H and colleagues found significantly greater masseter thickness during clenching in the sleep bruxism group ( 19 ). In our electromyography recordings, the sleep bruxism group showed bruxism episode index values of 7.1–13.9, substantially above the diagnostic threshold of 5.5. In this study, maximum bite force was measured during wakefulness, whereas the percentage of maximum voluntary contraction was normalized to a standardized pre-sleep baseline maximum voluntary contraction; the correspondence between these two “maximum” measures was not assessed. Importantly, the percentage of maximum voluntary contraction reflects the relative amplitude of sleep-related muscle bursts rather than absolute bite force during sleep, and a higher value should not be interpreted as a higher nocturnal peak force. The absence of a between-group difference in percentage of maximum voluntary contraction therefore indicates similar average relative burst intensity in the sleep bruxism and control groups. However, the higher bruxism episode index in the sleep bruxism group implies greater event frequency and cumulative contraction time, which may translate into higher cumulative loading on teeth, masticatory muscles, and the temporomandibular joint. One proposed mechanism is a “training effect”, whereby repetitive bruxism activity strengthens the masseter and temporalis muscles, increasing both force-generating capacity and muscle thickness. Clinically, the prevalence of masseter hypertrophy has been reported to be approximately 15-fold higher in individuals with bruxism than in those without ( 22 ). In individuals with bruxism, increased bite force in the incisor–premolar regions may result from three interacting mechanisms: repetitive bruxism activity producing a “training effect” that promotes masseter hypertrophy; eccentric bruxism movements (protrusive or lateral sliding) concentrating contacts and loads on anterior and premolar teeth to reduce temporomandibular joint loading, while molars are often discluded or carry less load; and during sleep, reduced inhibitory protective reflexes mediated by periodontal mechanoreceptors, particularly sensitive in the anterior region, may raise the physiological force threshold. Consequently, force in these regions may increase and include a greater shear component. Although sleep bruxism can include tonic contractions (vertical clenching), the characteristic pattern is often eccentric with lateral and protrusive movements, which commonly disclude the molars. Therefore, force generated by hypertrophic muscles may not be transmitted as pure axial compressive loading on the first molars, as occurs during maximal voluntary clenching, but rather as non-axial sliding forces. In addition, periodontal mechanoreceptors around molars are less sensitive to force changes than those around incisors ( 23 ), resulting in a higher threshold for triggering inhibitory protective reflexes and potentially less variation in reflex inhibition during sleep. In non-bruxism populations, maximum bite force is typically greatest in the molar region and decreases toward the anterior teeth. Mei and colleagues measured single-tooth bite force in 179 individuals without detected sleep bruxism and reported that force at the first molar was approximately 1.4 times that at the premolars and 3.2 times that at the incisors ( 24 ). In our study, there was no between-group difference in this regional distribution pattern. Thus, although maximum bite force at the premolar and incisor regions was higher in the sleep bruxism group than in controls, the overall distribution of bite force along the dental arch remained similar, following the typical gradient from molars to incisors in both men and women. Strengths and limitations Strengths of this study include the use of a validated, portable EMG device for multi-night home recordings, the combination of subjective (history, symptoms) and objective (clinical signs, EMG) criteria to diagnose SB, and the measurement of bite force at multiple tooth sites with an adequate sample size. We did not perform a full polysomnography (although our EMG device correlates well with PSG), and we did not assess awake bruxism, which could also influence muscle development. Clinical implications Sleep bruxism may increase both masticatory loading magnitude and cumulative loading time, which can contribute to tooth wear and increase the risk of restorative and technical complications (e.g., tooth cracks, ceramic chipping, and prosthesis fracture) in the absence of protective measures ( 25 ). Quantifying bite force and nocturnal muscle activity indices (e.g., maximum bite force and percentage of maximum voluntary contraction) may help identify patients at higher functional risk and inform restorative planning, including material selection, occlusal scheme, and the need for protective appliances ( 26 ). In addition, repeated measurements over time can support clinical monitoring and treatment evaluation (e.g., occlusal splints, occlusal adjustment, or behavioral interventions), where reductions in force-related metrics may indicate a favorable response, whereas increases may prompt reassessment for recurrence or occlusal instability ( 27 ). Conclusions Adults with sleep bruxism exhibited higher maximum bite force at the premolar and incisor regions, whereas first molar bite force did not differ from controls. Despite these site-specific increases, the overall bite force distribution along the dental arch remained unchanged, following the typical gradient from molars to incisors. Multi-night, at-home surface electromyography provides objective support for case identification and may be considered a useful adjunct in the diagnostic work-up of patients with suspected sleep bruxism. Abbreviations - AASM American Academy of Sleep Medicine - BEI Bruxism episode index - BFM-F4 Digital occlusal force gauge (strain-gauge bite force device) - DC/TMD Diagnostic Criteria for Temporomandibular Disorders - EMG Electromyography - FLA-500-SD Single-channel wearable electromyography device (masseter) - ICSD-3 International Classification of Sleep Disorders, 3rd edition - ICSD-3-TR International Classification of Sleep Disorders, 3rd edition, Text Revision - IQR Interquartile range - MBF Maximum bite force - MVC Maximum voluntary contraction - %MVC Percentage of maximum voluntary contraction - PSG Polysomnography - SB Sleep bruxism - SD Standard deviation - sEMG Surface electromyography - SPSS Statistical Package for the Social Sciences - TMD Temporomandibular disorder(s) Declarations Ethics approval and consent to participate The study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of University of Medicine and Pharmacy at Ho Chi Minh City (No. 1699/HĐĐĐ-ĐHYD; July 19, 2024). Written informed consent was obtained from all participants prior to enrollment. Consent for publication: Not applicable Competing interest The authors have no conflicts of interest to declare. All co-authors have seen and agree with the contents of the manuscript, and there is no financial interest to report. We certify that the submission is original work and is not under review at any other publication. Funding No funding was received for conducting this study. Author Contribution O.N.-N.H. and X.V.T conceived and designed the study. O.N.-N.H. and A.N.H.Q. conducted participant recruitment, clinical examinations, and data collection. N.N.G.K. performed the statistical analysis and contributed to data interpretation. O.N.-N.H. drafted the manuscript. X.V.T and A.N.H.Q. critically revised the manuscript for important intellectual content. All authors reviewed and approved the final manuscript. 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Relationship between sleep bruxism and masticatory performance in healthy adults: A cross-sectional study. J Prosthet Dent. 2025. Thayer MLT, Ali R. The dental demolition derby: bruxism and its impact - part 3: repair and reconstruction. Br Dent J. 2022;232(11):775–82. Schmitter M, Bömicke W, Behnisch R, Lorenzo Bermejo J, Waldecker M, Rammelsberg P et al. Ceramic Crowns and Sleep Bruxism: First Results from a Randomized Trial. J Clin Med. 2022;12(1). Shoji Y, Yusof M, Idris RIB, Mitrirattanakul S. Bite force of patients with tooth pain. Clin Exp Dent Res. 2022;8(5):1213–7. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 08 Apr, 2026 Reviews received at journal 05 Apr, 2026 Reviews received at journal 29 Mar, 2026 Reviewers agreed at journal 25 Mar, 2026 Reviewers agreed at journal 21 Mar, 2026 Reviewers invited by journal 19 Mar, 2026 Editor invited by journal 20 Feb, 2026 Editor assigned by journal 18 Feb, 2026 Submission checks completed at journal 18 Feb, 2026 First submitted to journal 15 Feb, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8889308","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":610101810,"identity":"ada5257e-afe1-49db-9c75-0e9bff78b38f","order_by":0,"name":"Oanh Nguyen-Ngoc Hoang","email":"","orcid":"","institution":"University of Medicine and Pharmacy at Ho Chi Minh","correspondingAuthor":false,"prefix":"","firstName":"Oanh","middleName":"Nguyen-Ngoc","lastName":"Hoang","suffix":""},{"id":610101812,"identity":"04acc138-b628-415f-93df-99a0304a68e9","order_by":1,"name":"Xuan Vinh TRAN","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3UlEQVRIie3SMQrCMBSA4aeB55I2a4KgV1ACvY90cHFzERQRCh31AvUOHqESqEvBVdDBKjh1cBKnYgouLm3cBPMvb8lHeCQANtsvRgCB6okAjTNAbE44AiE9MwJvojFyI9LbOck5n5zmLtsnUzo7dRiQ7HKoIsod9qP0xpH7eKTJTYoFSjmqICKgXtsJlSZEE1SDTUyxXU8KTZjCMS0MCCMlWWgCPhJ9nRkRUaJEyH0p1kslRVCzC7LU4/lMse5qm93zh+qwVpBdq8hHzfIb6Mf9osbzm9M2m832N70AeCFCVmyLwrsAAAAASUVORK5CYII=","orcid":"","institution":"University of Medicine and Pharmacy at Ho Chi Minh","correspondingAuthor":true,"prefix":"","firstName":"Xuan","middleName":"Vinh","lastName":"TRAN","suffix":""},{"id":610101814,"identity":"ba55475e-f85c-4f68-b66d-3ce04d9b9326","order_by":2,"name":"Anh Nguyen Ho Quynh","email":"","orcid":"","institution":"University of Medicine and Pharmacy at Ho Chi Minh","correspondingAuthor":false,"prefix":"","firstName":"Anh","middleName":"Nguyen Ho","lastName":"Quynh","suffix":""},{"id":610101815,"identity":"3bfafe2d-cc23-4c3d-b958-9665ed818d1e","order_by":3,"name":"Ngan Nguyen Gia Kieu","email":"","orcid":"","institution":"University of Medicine and Pharmacy, Hue University","correspondingAuthor":false,"prefix":"","firstName":"Ngan","middleName":"Nguyen Gia","lastName":"Kieu","suffix":""}],"badges":[],"createdAt":"2026-02-16 03:23:28","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8889308/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8889308/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":105297170,"identity":"e60bf50a-711a-4617-a217-74319522331a","added_by":"auto","created_at":"2026-03-24 13:17:55","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":813696,"visible":true,"origin":"","legend":"\u003cp\u003eThe sleep bruxism questionnaire adapted from the criteria described by the American Academy of Sleep Medicine (10)\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8889308/v1/fa4b301f64e4260d28aaa5db.jpeg"},{"id":105297186,"identity":"eefd9e41-9a1f-4f8b-9ad8-68c39a594655","added_by":"auto","created_at":"2026-03-24 13:18:00","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1705007,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8889308/v1/d21d6c82-9fbf-4322-892b-7ee8b832d9c9.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Sleep bruxism, bite force, morning symptoms, and home electromyography: a cross-sectional study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eBruxism is considered common and may have a substantial impact on oral health. This activity can occur both during sleep and while awake (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). In individuals with bruxism, clinical manifestations may involve multiple components of the masticatory system: teeth (occlusal wear, cracks or fractures, hypersensitivity, mobility), muscles (hyperactivity, pain or fatigue, hypertrophy), and the temporomandibular joint (intra-articular disorders, changes in joint tissues, disc displacement). These consequences are largely attributed to prolonged and repetitive muscle contraction that exceeds physiological tolerance, resulting in cumulative tissue damage over time (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\n\u003cp\u003eCurrent evidence regarding maximum bite force in patients with sleep bruxism remains limited. Todic and colleagues suggested that bruxism increases maximum bite force and proposed maximum bite force as a potential indicator for diagnosis and for understanding the pathophysiology of this parafunctional activity (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). Helkimo and Ingervall reported that maximum bite force increased only in the incisor region, whereas Cosme and colleagues (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e) concluded that bruxism does not affect maximum bite force (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). Other authors have reported a 54.5% increase in maximum bite force among individuals with bruxism (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e). To date, conclusions about the effect of bruxism on maximum bite force remain inconsistent. Such discrepancies may reflect differences in diagnostic criteria, study design, sample characteristics (sex, tooth loss, temporomandibular disorders), or the measurement site and method.\u003c/p\u003e\n\u003cp\u003eIn clinical practice, bruxism diagnosis is still largely based on questionnaires, history taking, and clinical signs. However, these approaches lack objectivity and have limited diagnostic\u003c/p\u003e\n\u003cp\u003evalue (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). In 2023, the American Academy of Sleep Medicine, through successive revisions of the International Classification of Sleep Disorders, issued clinical diagnostic criteria for sleep bruxism that have been widely used in research as a screening tool. In parallel, advances in surface electromyography have enabled more objective assessment. Yamaguchi T. and colleagues introduced the FLA-500-SD surface electromyography device, which allows accurate multi-night, at-home recording of masseter activity and supports clinical identification of sleep bruxism (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). Surface electromyography does more than classify sleep bruxism: it quantifies masticatory muscle activation during sleep, thereby contextualizing maximum bite force findings. These data link functional measurements to underlying muscle activity rather than symptoms alone.\u003c/p\u003e\n\u003cp\u003eIf maximum bite force truly changes in individuals with bruxism, measuring this parameter could become a useful quantitative tool for diagnosis and risk stratification (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n\u003cp\u003eThis study aimed to assess awakening masticatory symptoms using a questionnaire aligned with the American Academy of Sleep Medicine framework, compare site-specific maximum bite force between adults with and without sleep bruxism identified using at-home surface electromyography, and evaluate between-group differences in electromyography indices, including the bruxism episode index and the percentage of maximum voluntary contraction.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003eStudy design and participant recruitment\u003c/h2\u003e\n \u003cp\u003eThis study aimed to compare site-specific maximum bite force and awakening masticatory symptoms between adults with and without sleep bruxism, and to examine electromyography indices across groups. This cross-sectional study was conducted at the Dental Speciality Clinic, University of Medicine and Pharmacy at Ho Chi Minh City. Participants were recruited by convenience sampling from adults attending the dental clinic for routine dental care during the study period; recruitment was not restricted to individuals presenting with suspected bruxism. Eligible participants were adults aged 18\u0026ndash;45 years with full natural dentition in both arches (28 teeth excluding third molars), a bilateral Angle Class I molar relationship, and no severe systemic disease, regardless of sleep bruxism status. Exclusion criteria included anterior or posterior crossbite; history of maxillofacial trauma or surgery; fixed prostheses or restorations on the functional surfaces of first molars, premolars, or incisal edges; active dental pathology such as pulpitis, periapical or periodontal disease; and use of medications affecting neuromuscular activity, such as analgesics, anxiolytics, antidepressants, or antipsychotics. Participants were also excluded if they had a pain-related temporomandibular disorder (according to DC/TMD classification) with moderate to severe pain lasting at least three months or were undergoing treatment for TMD, orthodontic therapy, or bruxism. All participants underwent clinical screening and diagnostic procedures, including surface electromyographic monitoring, as part of the study protocol.\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003eSample size\u003c/h3\u003e\n\u003cp\u003eAn a priori sample size calculation was performed to compare two independent means with equal group allocation. Parameter estimates were derived from a previous study by Dıra\u0026ccedil;oğlu and colleagues in which maximum bite force was measured at the incisor region. Assuming a two-sided significance level of 0.05 and 80% power (\u0026beta;\u0026thinsp;=\u0026thinsp;0.20), with expected mean (standard deviation) values of 105.1 (34.2) and 81.3 (31.0), the minimum required sample size was 30 participants per group (total n\u0026thinsp;=\u0026thinsp;60). This target sample size was therefore adopted for recruitment and group comparisons in the present study.\u003c/p\u003e\n\u003ch3\u003eGroup allocation based on sleep bruxism status\u003c/h3\u003e\n\u003cp\u003eParticipants were classified into two groups, those with SB and those without, based on a three-step diagnostic process integrating subjective, clinical, and instrumental criteria in accordance with the International Classification of Sleep Disorders (ICSD-3-TR, 2023).\u003c/p\u003e\n\u003ch3\u003e\u0026bull; Step 1: History-based screening using a structured questionnaire\u003c/h3\u003e\n\u003cp\u003eAll participants completed a standardized SB Questionnaire (Fig. \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) adapted from the criteria described by the American Academy of Sleep Medicine and validated through previous literature (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). A participant fulfilled this criterion if they answered \u0026ldquo;Yes\u0026rdquo; to item 1 (self- or bed partner-reported grinding/clenching noises) or item 2 (awareness of abnormal tooth wear), and \u0026ldquo;Yes\u0026rdquo; to at least one of the listed morning symptoms (e.g., jaw stiffness, clenching sensation, headache, limited mouth opening, joint clicking). Participants satisfying these conditions were considered positive for the history-based criterion (A).\u003c/p\u003e\n\u003ch3\u003e\u0026bull; Step 2: Clinical examination for suspected bruxism-related tooth wear\u003c/h3\u003e\n\u003cp\u003eA calibrated dental specialist conducted a comprehensive examination of all tooth surfaces to identify patterns of occlusal wear indicative of SB. Participants were deemed to fulfill the clinical criterion (B) if at least one pair of opposing teeth exhibited wear facets that were flat, glossy, sharply demarcated, and demonstrated interlocking morphology characteristic of bruxism-related attrition.\u003c/p\u003e\n\u003ch3\u003e\u0026bull;\u0026nbsp;\u003cstrong\u003eStep 3: Instrumental confirmation using home surface electromyography\u003c/strong\u003e\u003c/h3\u003e\n\u003cp\u003eParticipants were instructed to wear the FLA-500-SD surface electromyography (sEMG) device at home for three consecutive nights. The first night served as an adaptation period during which the device was worn without activation, allowing subjects to become accustomed to its presence. On the following two nights, the device was activated to record jaw muscle activity. A bruxism episode index of \u0026ge;\u0026thinsp;5.5 episodes/hour (averaged across the two recorded nights) was used as the instrumental criterion, based on prior validation studies for this device. Meeting this threshold constituted the instrumental diagnostic criterion (C).\u003c/p\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003eFinal classification\u003c/h2\u003e\n \u003cp\u003eParticipants who met all three diagnostic criteria: subjective report (A), clinical signs (B), and instrumental confirmation via EMG (C), were classified into the SB group. Conversely, those who did not meet any of the three criteria were assigned to the control (non-SB) group. Individuals who satisfied only one or two criteria were considered diagnostically inconclusive and were therefore excluded from further analysis to maintain the diagnostic specificity of the comparison groups.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eMaximum bite force measurement\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eParticipants were seated upright with the head in a natural position, facing forward, and feet flat on the floor. Maximum bite force (MBF) was measured within one week of EMG recording using a custom-built digital strain-gauge occlusal force gauge (BFM 4th generation, Vietnam) (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). Measurements were taken bilaterally at three sites: first molars, premolars, and central incisors. At each site, participants were instructed to bite maximally for 3 seconds. Three trials were performed per site, with a 2-minute rest between measurements to minimize muscle fatigue. For each tooth region, the highest of three trials was recorded for each side, and the final value used for analysis was the mean of the left and right maxima (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003eData analysis\u003c/h2\u003e\n \u003cp\u003eData were analyzed using SPSS 26. Normality was assessed with the Shapiro-Wilk test. Continuous variables (MBF and EMG indices) are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation or median (interquartile range) where appropriate. Categorical variables are shown as frequencies and percentages. Intergroup comparisons of MBF and BEI were made using independent-samples \u003cem\u003et\u003c/em\u003e-tests or Mann-Whitney \u003cem\u003eU\u003c/em\u003e-tests. Sex-stratified differences were analyzed similarly. Chi-square or Fisher\u0026rsquo;s exact tests compared symptom frequencies. A significance level of 0.05 was adopted.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003eParticipant characteristics\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA total of 60 subjects (30 SB, 30 controls) completed the study (Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The SB group had a median age of 23.0 years (range 19\u0026ndash;43) and included 14 men and 16 women; controls had a median age of 25.0 years (19\u0026ndash;44) with 13 men and 17 women. The age and sex distributions did not differ significantly (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003cbr\u003e\u003c/div\u003e\u0026nbsp;\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eDemographic characteristics and self-reported awareness of sleep bruxism\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"4\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eCharacteristic\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eSB group (n\u0026thinsp;=\u0026thinsp;30)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eControl group (n\u0026thinsp;=\u0026thinsp;30)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003ep-value\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eAge (years), median (range)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e23 (19\u0026ndash;43)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e25 (19\u0026ndash;44)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eMale, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e14 (46.7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e13 (43.3%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eFemale, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e16 (53.3%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e17 (56.7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eSelf-aware\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e8 (26.7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e3 (10.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eNot self-aware\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e22 (73.3%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e27 (90.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u003cem\u003e\u0026nbsp;Self-awareness was defined as a \u0026ldquo;Yes\u0026rdquo; response indicating that the participant personally noticed sleep-related grinding or clenching; participants without personal awareness were classified as not self-aware, regardless of bed-partner report\u003c/em\u003e\u003c/p\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003eMorning masticatory symptoms\u003c/h2\u003e\n \u003cp\u003eMorning masticatory symptoms were more common in the sleep bruxism group (Table \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Fatigue or pain on awakening (93.3% vs 20.0%) and clenching sensation/oral soreness on awakening (50.0% vs 6.7%) were both significantly higher in participants with sleep bruxism than in controls (both p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). No between-group differences were observed for temporal headache, difficulty opening the mouth, jaw tension relieved by mandibular movement, or temporomandibular joint clicking (all p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003cbr\u003e\u003c/div\u003e\u0026nbsp;\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eFrequency of morning masticatory symptoms\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"4\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eSymptom\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eSleep bruxism\u003c/p\u003e\n \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;30)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;30)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003ep-value\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eJaw feels sore or stiff on awakening\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e28 (93.3%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e6 (20.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;0.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eUpper and lower teeth tightly together (clenching) or mouth hurts on awakening\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e15 (50.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e2 (6.7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;0.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eForehead feels tense on awakening\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e12 (40.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e8 (26.7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e0.411\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eTrouble opening the mouth wide on awakening\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e3 (10.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e0 (0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e0.237\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eJaw feels tense on awakening and tension decreases after moving the lower jaw\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e2 (6.7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e0 (0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e0.492\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eClicking sound/feeling in the jaw on awakening that goes away afterwards\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e10 (33.3%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e8 (26.7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e0.778\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cem\u003eValues are n (%). P values were calculated using the chi-square test or Fisher\u0026rsquo;s exact test, as appropriate (Fisher\u0026rsquo;s exact test was used when expected cell counts were \u0026lt;\u0026thinsp;5).\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eMaximum bite force\u003c/strong\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003cp\u003eMean maximum bite force values are shown in Table \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Compared with controls, participants with sleep bruxism had higher maximum bite force at the premolar (495.3\u0026thinsp;\u0026plusmn;\u0026thinsp;79.5 N vs 447.6\u0026thinsp;\u0026plusmn;\u0026thinsp;63.5 N; p\u0026thinsp;=\u0026thinsp;0.002) and incisor regions (268.7\u0026thinsp;\u0026plusmn;\u0026thinsp;41.1 N vs 235.6\u0026thinsp;\u0026plusmn;\u0026thinsp;41.2 N; p\u0026thinsp;=\u0026thinsp;0.003), whereas no difference was observed at the first molar site (597.6\u0026thinsp;\u0026plusmn;\u0026thinsp;61.2 N vs 574.9\u0026thinsp;\u0026plusmn;\u0026thinsp;77.3 N; p\u0026thinsp;=\u0026thinsp;0.21). Sex-stratified analyses showed the same pattern in men and women (premolar and incisor: all p\u0026thinsp;\u0026lt;\u0026thinsp;0.05; molar: p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Across groups and sites, men exhibited higher maximum bite force than women (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Bite force ratios across dental regions (molar/premolar, molar/incisor, and premolar/incisor) did not differ between groups (all p\u0026thinsp;\u0026gt;\u0026thinsp;0.4), indicating similar relative force distribution along the arch.\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eValues are mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD. p values were calculated using the independent-samples t-test.\u003c/em\u003e\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003cbr\u003e\u003c/div\u003e\u0026nbsp;\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eMaximum bite force (MBF) by site and group\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"4\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eTooth region\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eSleep bruxism (n\u0026thinsp;=\u0026thinsp;30)\u003c/p\u003e\n \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD (N)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eControl (n\u0026thinsp;=\u0026thinsp;30)\u003c/p\u003e\n \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD (N)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003ep-value\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eFirst molars\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e\n \u003cp\u003e597.6\u0026thinsp;\u0026plusmn;\u0026thinsp;61.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e\n \u003cp\u003e574.9\u0026thinsp;\u0026plusmn;\u0026thinsp;77.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e0.210\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003ePremolars\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e\n \u003cp\u003e495.3\u0026thinsp;\u0026plusmn;\u0026thinsp;79.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e\n \u003cp\u003e447.6\u0026thinsp;\u0026plusmn;\u0026thinsp;63.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.002\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eCentral incisors\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e\n \u003cp\u003e268.7\u0026thinsp;\u0026plusmn;\u0026thinsp;41.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e\n \u003cp\u003e235.6\u0026thinsp;\u0026plusmn;\u0026thinsp;41.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.003\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003eElectromyography results\u003c/h2\u003e\n \u003cp\u003eThe SB group exhibited a significantly higher bruxism episode index (BEI), averaging 10.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.4 episodes/hour compared to 3.2\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5 in controls (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), confirming increased nocturnal muscle activity (Table \u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). In contrast, the average percentage of maximum voluntary contraction (%MVC) did not differ significantly between groups (20.9% \u0026plusmn; 13.0% in SB vs. 19.7% \u0026plusmn; 13.7% in controls; p\u0026thinsp;=\u0026thinsp;0.72), suggesting comparable contraction intensity during episodes.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003cbr\u003e\u003c/div\u003e\u0026nbsp;\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eElectromyographic indices\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"4\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eParameter\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eSB group\u003c/p\u003e\n \u003cp\u003e(Mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eControl group\u003c/p\u003e\n \u003cp\u003e(Mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003ep-value\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eBruxism Episode Index (BEI)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e\n \u003cp\u003e10.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e\n \u003cp\u003e3.2\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;0.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e% MVC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e\n \u003cp\u003e20.9\u0026thinsp;\u0026plusmn;\u0026thinsp;13.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e\n \u003cp\u003e19.7\u0026thinsp;\u0026plusmn;\u0026thinsp;13.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e0.72\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003cp\u003ea: two sample t-tests in comparison between SB group and control group\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study applied a multimodal diagnostic approach to sleep bruxism, integrating both subjective and objective assessments: (i) a structured history-based questionnaire, (ii) clinical examination for tooth wear, and (iii) recording of masticatory muscle activity using the FLA-500-SD electromyography device. The FLA-500-SD is a portable single-channel electromyography system positioned over the masseter muscle, enabling multi-night, at-home recording during sleep. Previous studies have reported high sensitivity and specificity compared with audio\u0026ndash;video polysomnography, particularly when using a calibrated bruxism episode index threshold (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). In the present study, participants wore the device for three consecutive nights; the first night was an adaptation night without recording to facilitate habituation and minimize behavioral changes when first using the device. Multi-night recording in a familiar sleep environment may reduce the \u0026ldquo;first-night effect\u0026rdquo; commonly observed with audio\u0026ndash;video polysomnography and may better reflect sleep bruxism frequency under real-world conditions (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e). This is consistent with findings reported by Sakuma and colleagues, who noted stable device performance both in the laboratory and at home compared with polysomnography (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e). Overall, given its feasibility for research and its ability to provide quantitative indices (e.g., bruxism episode index and percentage of maximum voluntary contraction) that characterize the intensity and patterns of masticatory muscle activity, the FLA-500-SD appears suitable for supporting the identification and monitoring of sleep bruxism.\u003c/p\u003e\n\u003cp\u003eSeveral previous studies have suggested that diagnosing sleep bruxism using questionnaires and clinical examination based on ICSD-3 criteria has limited accuracy; when compared with single-channel electromyography, this approach yielded a sensitivity of 63.2% and specificity of 72.7% (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e). These findings indicate a substantial risk of missed sleep bruxism cases when relying on clinical assessment alone (\u003cspan additionalcitationids=\"CR16\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e). In our study, the ICSD-3-based classification was broadly consistent with the electromyography-based diagnosis, although 73.3% of participants did not self-report awareness of bruxism and therefore met only the remaining two questionnaire criteria.\u003c/p\u003e\n\u003cp\u003eThe questionnaire proposed by Yunisa and colleagues has a notable advantage in its two-stage screening structure: it is easy to administer yet includes a threshold that may reduce false positives compared with single-item screening. Specifically, participants are classified as suspected sleep bruxism when they respond \u0026ldquo;Yes\u0026rdquo; to Question 1 or Question 2 (night-time grinding/clenching or perceived abnormal tooth wear) and report at least one morning symptom in Question 3 (e.g., jaw pain or stiffness, forehead tension, difficulty opening the mouth, jaw tension relieved by moving the mandible, or joint clicking) (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). Compared with the American Academy of Sleep Medicine screening questions, which include only two brief items for sleep bruxism (morning jaw pain and sleep grinding), the Yunisa questionnaire broadens the symptom spectrum while retaining a simple yes/no format suitable for large-scale surveys. In the present study, symptoms on awakening such as jaw pain/fatigue (93.3%) and a clenching sensation (50.0%) were more frequent in the sleep bruxism group than in controls, with statistically significant differences. These symptoms may reflect repeated masticatory muscle contractions during sleep and have high screening value, whereas symptoms such as temporal pain or jaw stiffness appear less specific. In addition, we observed occlusal wear patterns suspected to be related to bruxism.\u003c/p\u003e\n\u003cp\u003eMaximum bite force followed the expected anteroposterior gradient, with the highest values at the first molar region and progressively lower values at the premolar and incisor regions in both sexes. When comparing groups, sleep bruxism was associated with higher maximum bite force at the premolar and incisor regions, whereas molar values were comparable to those of controls. This site-specific pattern aligns with prior reports showing no between-group difference when bite force was assessed only at the first molar, as in studies by Calderon and by Chrcanovic and colleagues (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e), and anterior differences without posterior changes as reported by Helkimo and Ingervall (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). Importantly, those earlier studies relied on questionnaires and clinical signs to define bruxism (probable bruxism), whereas our classification incorporated multi-night, at-home surface electromyography, supporting a definite bruxism diagnosis. Using an instrumental criterion may reduce exposure misclassification and improve the internal validity of site-specific bite force comparisons across groups.\u003c/p\u003e\n\u003cp\u003eBruxism involves involuntary masticatory muscle contraction that occurs during sleep (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e). Repeated occlusal loading associated with bruxism may lead the masticatory muscles, particularly the masseter and temporalis, to adapt by increasing muscle size and strength. Several reports indicate that men tend to exhibit more severe sleep bruxism than women. Smardz and colleagues reported significantly higher rhythmic masticatory muscle activity frequency and bruxism episode index in men with sleep bruxism than in women (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e). Experimental evidence suggests that long-standing bruxism is associated with increased masseter cross-sectional area, particularly in men (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e). In an ultrasound study comparing masseter thickness in individuals with temporomandibular disorders with and without sleep bruxism, Lee Y-H and colleagues found significantly greater masseter thickness during clenching in the sleep bruxism group (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e). In our electromyography recordings, the sleep bruxism group showed bruxism episode index values of 7.1\u0026ndash;13.9, substantially above the diagnostic threshold of 5.5. In this study, maximum bite force was measured during wakefulness, whereas the percentage of maximum voluntary contraction was normalized to a standardized pre-sleep baseline maximum voluntary contraction; the correspondence between these two \u0026ldquo;maximum\u0026rdquo; measures was not assessed. Importantly, the percentage of maximum voluntary contraction reflects the relative amplitude of sleep-related muscle bursts rather than absolute bite force during sleep, and a higher value should not be interpreted as a higher nocturnal peak force. The absence of a between-group difference in percentage of maximum voluntary contraction therefore indicates similar average relative burst intensity in the sleep bruxism and control groups. However, the higher bruxism episode index in the sleep bruxism group implies greater event frequency and cumulative contraction time, which may translate into higher cumulative loading on teeth, masticatory muscles, and the temporomandibular joint. One proposed mechanism is a \u0026ldquo;training effect\u0026rdquo;, whereby repetitive bruxism activity strengthens the masseter and temporalis muscles, increasing both force-generating capacity and muscle thickness. Clinically, the prevalence of masseter hypertrophy has been reported to be approximately 15-fold higher in individuals with bruxism than in those without (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e).\u003c/p\u003e\n\u003cp\u003eIn individuals with bruxism, increased bite force in the incisor\u0026ndash;premolar regions may result from three interacting mechanisms: repetitive bruxism activity producing a \u0026ldquo;training effect\u0026rdquo; that promotes masseter hypertrophy; eccentric bruxism movements (protrusive or lateral sliding) concentrating contacts and loads on anterior and premolar teeth to reduce temporomandibular joint loading, while molars are often discluded or carry less load; and during sleep, reduced inhibitory protective reflexes mediated by periodontal mechanoreceptors, particularly sensitive in the anterior region, may raise the physiological force threshold. Consequently, force in these regions may increase and include a greater shear component. Although sleep bruxism can include tonic contractions (vertical clenching), the characteristic pattern is often eccentric with lateral and protrusive movements, which commonly disclude the molars. Therefore, force generated by hypertrophic muscles may not be transmitted as pure axial compressive loading on the first molars, as occurs during maximal voluntary clenching, but rather as non-axial sliding forces. In addition, periodontal mechanoreceptors around molars are less sensitive to force changes than those around incisors (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e), resulting in a higher threshold for triggering inhibitory protective reflexes and potentially less variation in reflex inhibition during sleep.\u003c/p\u003e\n\u003cp\u003eIn non-bruxism populations, maximum bite force is typically greatest in the molar region and decreases toward the anterior teeth. Mei and colleagues measured single-tooth bite force in 179 individuals without detected sleep bruxism and reported that force at the first molar was approximately 1.4 times that at the premolars and 3.2 times that at the incisors (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e). In our study, there was no between-group difference in this regional distribution pattern. Thus, although maximum bite force at the premolar and incisor regions was higher in the sleep bruxism group than in controls, the overall distribution of bite force along the dental arch remained similar, following the typical gradient from molars to incisors in both men and women.\u003c/p\u003e\n\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\n \u003ch2\u003eStrengths and limitations\u003c/h2\u003e\n \u003cp\u003eStrengths of this study include the use of a validated, portable EMG device for multi-night home recordings, the combination of subjective (history, symptoms) and objective (clinical signs, EMG) criteria to diagnose SB, and the measurement of bite force at multiple tooth sites with an adequate sample size. We did not perform a full polysomnography (although our EMG device correlates well with PSG), and we did not assess awake bruxism, which could also influence muscle development.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\n \u003ch2\u003eClinical implications\u003c/h2\u003e\n \u003cp\u003eSleep bruxism may increase both masticatory loading magnitude and cumulative loading time, which can contribute to tooth wear and increase the risk of restorative and technical complications (e.g., tooth cracks, ceramic chipping, and prosthesis fracture) in the absence of protective measures (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e). Quantifying bite force and nocturnal muscle activity indices (e.g., maximum bite force and percentage of maximum voluntary contraction) may help identify patients at higher functional risk and inform restorative planning, including material selection, occlusal scheme, and the need for protective appliances (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e). In addition, repeated measurements over time can support clinical monitoring and treatment evaluation (e.g., occlusal splints, occlusal adjustment, or behavioral interventions), where reductions in force-related metrics may indicate a favorable response, whereas increases may prompt reassessment for recurrence or occlusal instability (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eAdults with sleep bruxism exhibited higher maximum bite force at the premolar and incisor regions, whereas first molar bite force did not differ from controls. Despite these site-specific increases, the overall bite force distribution along the dental arch remained unchanged, following the typical gradient from molars to incisors. Multi-night, at-home surface electromyography provides objective support for case identification and may be considered a useful adjunct in the diagnostic work-up of patients with suspected sleep bruxism.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003eAASM\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eAmerican Academy of Sleep Medicine\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003eBEI\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eBruxism episode index\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003eBFM-F4\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eDigital occlusal force gauge (strain-gauge bite force device)\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003eDC/TMD\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eDiagnostic Criteria for Temporomandibular Disorders\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003eEMG\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eElectromyography\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003eFLA-500-SD\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSingle-channel wearable electromyography device (masseter)\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003eICSD-3\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eInternational Classification of Sleep Disorders, 3rd edition\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003eICSD-3-TR\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eInternational Classification of Sleep Disorders, 3rd edition, Text Revision\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003eIQR\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eInterquartile range\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003eMBF\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMaximum bite force\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003eMVC\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMaximum voluntary contraction\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003e%MVC\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ePercentage of maximum voluntary contraction\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003ePSG\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ePolysomnography\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003eSB\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSleep bruxism\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003eSD\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eStandard deviation\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003esEMG\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSurface electromyography\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003eSPSS\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eStatistical Package for the Social Sciences\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e- \u003cb\u003eTMD\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eTemporomandibular disorder(s)\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":" \u003cp\u003e \u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e \u003cp\u003e The study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of University of Medicine and Pharmacy at Ho Chi Minh City (No. 1699/HĐĐĐ-ĐHYD; July 19, 2024). Written informed consent was obtained from all participants prior to enrollment.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication:\u003c/strong\u003e \u003cp\u003eNot applicable\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eCompeting interest\u003c/h2\u003e \u003cp\u003eThe authors have no conflicts of interest to declare. All co-authors have seen and agree with the contents of the manuscript, and there is no financial interest to report. We certify that the submission is original work and is not under review at any other publication.\u003c/p\u003e \u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eNo funding was received for conducting this study.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eO.N.-N.H. and X.V.T conceived and designed the study. O.N.-N.H. and A.N.H.Q. conducted participant recruitment, clinical examinations, and data collection. N.N.G.K. performed the statistical analysis and contributed to data interpretation. O.N.-N.H. drafted the manuscript. X.V.T and A.N.H.Q. critically revised the manuscript for important intellectual content. All authors reviewed and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgements:\u003c/h2\u003e \u003cp\u003eNot applicable\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request, in accordance with the participants\u0026rsquo; informed consent and confidentiality requirements.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eLobbezoo F, Ahlberg J, Glaros AG, Kato T, Koyano K, Lavigne GJ, et al. Bruxism defined and graded: an international consensus. J Oral Rehabil. 2013;40(1):2\u0026ndash;4.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBader G, Lavigne G. Sleep bruxism; an overview of an oromandibular sleep movement disorder. REVIEW ARTICLE. Sleep Med Rev. 2000;4(1):27\u0026ndash;43.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTodic J, Mitic A, Lazic D, Radosavljevic R, Staletovic M. Effects of bruxism on the maximum bite force. Vojnosanit Pregl. 2016;74:165.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCosme DC, Baldisserotto SM, Canabarro Sde A, Shinkai RS. Bruxism and voluntary maximal bite force in young dentate adults. Int J Prosthodont. 2005;18(4):328\u0026ndash;32.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHelkimo E, Ingervall B. Bite force and functional state of the masticatory system in young men. Swed Dent J. 1978;2(5):167\u0026ndash;75.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNishigawa K, Bando E, Nakano M. Quantitative study of bite force during sleep associated bruxism. J Oral Rehabil. 2001;28(5):485\u0026ndash;91.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStuginski-Barbosa J, Porporatti AL, Costa YM, Svensson P, Conti PC. Diagnostic validity of the use of a portable single-channel electromyography device for sleep bruxism. Sleep Breath. 2016;20(2):695\u0026ndash;702.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMaeda M, Yamaguchi T, Mikami S, Yachida W, Saito T, Sakuma T, et al. Validity of single-channel masseteric electromyography by using an ultraminiature wearable electromyographic device for diagnosis of sleep bruxism. J Prosthodont Res. 2020;64(1):90\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYamaguchi T, Mikami S, Saito M, Okada K, Gotouda A. A newly developed ultraminiature wearable electromyogram system useful for analyses of masseteric activity during the whole day. J Prosthodont Res. 2018;62(1):110\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYunisa F, Kurniasih I, Putri VD, Biddinika MK. Early identification of sleep bruxism among dental students: an observational study. Majalah Kedokteran Gigi Indonesia. 2024.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNguyen AH, Nguyen ON, Nguyen DL, Ho TS, Pham KD, Nguyen KD, et al. Digital analysis of the relationship between maximum bite force and 3-dimensional arrangement of mandibular first molars. J Clin Exp Dent. 2024;16(12):e1468\u0026ndash;74.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHasegawa Y, Lavigne G, Rompr\u0026eacute; P, Kato T, Urade M, Huynh N. Is there a first night effect on sleep bruxism? A sleep laboratory study. J Clin Sleep Med. 2013;9(11):1139\u0026ndash;45.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMiettinen T, Myllymaa K, Hukkanen T, T\u0026ouml;yr\u0026auml;s J, Sipil\u0026auml; K, Myllymaa S. Home Polysomnography Reveals a First-Night Effect in Patients With Low Sleep Bruxism Activity. J Clin Sleep Med. 2018;14(8):1377\u0026ndash;86.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSakuma T, Yamaguchi T, Maeda M, Saito T, Nakamura H, Mikami S, et al. Comparison of the occurrence of sleep bruxism under accustomed conditions at home and under polysomnography conditions in a sleep laboratory. J Prosthodontic Res. 2022;66(4):630\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMikami S, Yamaguchi T, Saito M, Nakajima T, Maeda M, Gotouda A. Validity of clinical diagnostic criteria for sleep bruxism by comparison with a reference standard using masseteric electromyogram obtained with an ultraminiature electromyographic device. Sleep Biol Rhythms. 2022;20(2):297\u0026ndash;308.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCasett E, R\u0026eacute;us JC, Stuginski-Barbosa J, Porporatti AL, Carra MC, Peres MA, et al. Validity of different tools to assess sleep bruxism: a meta-analysis. J Oral Rehabil. 2017;44(9):722\u0026ndash;34.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStuginski-Barbosa J, Porporatti AL, Costa YM, Svensson P, Conti PC. Agreement of the International Classification of Sleep Disorders Criteria with polysomnography for sleep bruxism diagnosis: A preliminary study. J Prosthet Dent. 2017;117(1):61\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChrcanovic BR, Bergengren T, Stanisic N, Sohrabi S, Larsson C, Svensson P, et al. Relationship between bite force, bruxism, and fractures of teeth and dental restorations. Sci Rep. 2025;15(1):22752.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLee Y-H, Chun Y-H, Bae H, Lee J-W, Kim H-J. Comparison of ultrasonography-based masticatory muscle thickness between temporomandibular disorders bruxers and temporomandibular disorders non-bruxers. Sci Rep. 2024;14(1):6923.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSmardz J, Wieckiewicz M, Gac P, Poreba R, Wojakowska A, Mazur G, et al. Influence of age and gender on sleep bruxism and snoring in non-apneic snoring patients: A polysomnographic study. J Sleep Res. 2021;30(3):e13178.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJason S, Christian S, Maria M, Torsten M, Olaf B, Stavros K, et al. Influence of gender and bruxism on the masseter muscle: A population-based magnetic resonance imaging study. Am J Orthod Dentofac Orthop. 2025;167(1):80\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePopescu A, Vlăduțu D-E, Ionescu M, T\u0026acirc;rtea D, Popescu S, Mercuț V. The Role of Occlusal Appliances in Reducing Masseter Electromyographic Activity in Bruxism. J Clin Med. 2024;13:7218.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTrulsson M. Sensory-motor function of human periodontal mechanoreceptors. J Oral Rehabil. 2006;33(4):262\u0026ndash;73.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMireia U-B, Carla Z-O, Laura K-R, Bernat R-L, Jordi M-G. Relationship between sleep bruxism and masticatory performance in healthy adults: A cross-sectional study. J Prosthet Dent. 2025.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eThayer MLT, Ali R. The dental demolition derby: bruxism and its impact - part 3: repair and reconstruction. Br Dent J. 2022;232(11):775\u0026ndash;82.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchmitter M, B\u0026ouml;micke W, Behnisch R, Lorenzo Bermejo J, Waldecker M, Rammelsberg P et al. Ceramic Crowns and Sleep Bruxism: First Results from a Randomized Trial. J Clin Med. 2022;12(1).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShoji Y, Yusof M, Idris RIB, Mitrirattanakul S. Bite force of patients with tooth pain. Clin Exp Dent Res. 2022;8(5):1213\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"sleep bruxism, maximum bite force, electromyography, masticatory symptoms, parafunctional habits","lastPublishedDoi":"10.21203/rs.3.rs-8889308/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8889308/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eSleep bruxism is a common parafunctional activity marked by involuntary tooth grinding or clenching during sleep and has been linked to tooth wear, masticatory muscle discomfort, and temporomandibular joint loading. However, its association with maximum bite force and awakening masticatory symptoms remains unclear. This study aimed to compare maximum bite force and morning masticatory symptoms between adults with and without sleep bruxism using a combined clinical assessment and multi-night, at-home surface electromyography monitoring.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis cross-sectional study enrolled 60 adults aged 18\u0026ndash;45 years (30 with sleep bruxism and 30 controls). Sleep bruxism was identified using a multimodal approach that combined self-report, clinical signs, and three nights of at-home single-channel surface electromyography recorded over the masseter muscle with the FLA-500-SD device (GC Corporation, Japan), in accordance with the American Academy of Sleep Medicine criteria. Participants completed a structured questionnaire on awakening masticatory symptoms and underwent a standardized assessment of occlusal wear. Maximum bite force was measured bilaterally at the first molar, second premolar, and central incisor regions using a digital occlusal force gauge (BFM, 4th generation, Vietnam). Three measurements were conducted per site, and the highest value was used for analysis. Electromyography outcomes included the bruxism episode index and the percentage of maximum voluntary contraction. Between-group differences were evaluated using the independent-samples t-test or the Mann-Whitney U test, with a two-sided significance level of 0.05.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eParticipants with sleep bruxism reported more frequent awakening symptoms, including jaw stiffness, jaw fatigue, and temporal headache (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Maximum bite force at the molar region did not differ between groups, whereas values at the premolar and incisor regions were higher in the sleep bruxism group (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Across all tooth regions, men showed higher maximum bite force than women (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eAdults with sleep bruxism showed higher anterior bite force and more frequent awakening masticatory symptoms than controls, while molar bite force did not differ. However, awakening symptoms alone are insufficient for identifying sleep bruxism. A multimodal approach that integrates clinical assessment with instrumental measures, such as electromyography, may improve diagnostic accuracy.\u003c/p\u003e\u003ch2\u003eTrial registration\u003c/h2\u003e \u003cp\u003eNot applicable.\u003c/p\u003e","manuscriptTitle":"Sleep bruxism, bite force, morning symptoms, and home electromyography: a cross-sectional study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-24 13:17:50","doi":"10.21203/rs.3.rs-8889308/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-04-08T10:39:09+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-05T14:45:34+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-29T13:10:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"108686653056898425249487905661690838890","date":"2026-03-25T13:00:18+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"52028037786648160444935561505496158946","date":"2026-03-21T07:29:31+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-19T07:12:51+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-02-20T10:36:06+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-19T03:08:28+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-19T03:07:22+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Oral Health","date":"2026-02-16T03:17:51+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"246e7db2-2e10-40c4-af21-d4d8a381f706","owner":[],"postedDate":"March 24th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2026-05-13T10:42:46+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-24 13:17:50","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8889308","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8889308","identity":"rs-8889308","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}