Temporal relationship between sleep-time masseter muscle activity and apnea-hypopnea events: A pilot study

Sleep bruxism: The past, the present, and the future-evolution of a concept

BACKGROUND

The concept of sleep bruxism (SB) has evolved exponentially over the past several decades. Many theories and hypotheses have been proposed as to the definition, pathophysiology, and management of SB, from the early 1960s through the present. The role of peripheral factors, such as dental occlusion, in the pathogenesis of SB has been discarded.

TYPES OF STUDIES REVIEWED

The authors searched several electronic databases (ie, PubMed, Google Scholar, Web of Science, Embase, and Ovid MEDLINE) for studies on bruxism. The search was conducted from January 1961 through May 2023 and yielded 4,612 articles, of which 312 were selected for comprehensive review after eliminating duplicates and nonfocused articles.

RESULTS

There has been an evident progressive shift from the role of peripheral factors, such as dental occlusion, to more central factors, such as the involvement of a central pattern generator as well as the autonomic nervous system, in the genesis of bruxing movements. There is continued robust interest in the dental community to elucidate the contributing factors involved in SB.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

The neurophysiology of SB appears to be leaning more toward central rather than peripheral factors. There is increasing evidence of the role of the autonomic nervous system, genetics, and comorbidities in the genesis of SB. The scientific literature seems to refute the role of dental occlusion in the causation of bruxing movements. As per the literature, there has been a paradigm shift in the definition and genesis of SB and its possible dental implications and management, which also highlights the need for succinct scientific studies in this regard.

Sleep bruxism and associated physiological events in children with obstructive sleep apnea: a polysomnographic study

STUDY OBJECTIVES

The aim of this study was to evaluate the physiological events associated with sleep bruxism (Sleep Bruxism [SB]; presence of mandibular movement activity) and the control window (4 minutes prior to SB event, where no mandibular movement activity was detected) in a polysomnography study in children with mild sleep apnea.

METHODS

Polysomnography data from children aged 4 to 9 years old diagnosed with mild sleep apnea were analyzed by 2 trained examiners. The mandibular movement activity (bruxism event; SB) was classified into phasic and tonic. The control window was selected 4 minutes prior to the SB event. All physiological events were recorded in both bruxism and control windows, including sleep phase (N1, N2, N3, and rapid eye movement), arousal, leg movements, tachycardia, bradycardia, oxygen desaturation, and number of obstructive and central sleep apnea events. The moment in which those phenomena occurred when associated with SB was also analyzed (before/after). Data were analyzed using 95% confidence intervals (α = 5%).

RESULTS

A total of 661 mandibular movements were analyzed and classified as tonic (n = 372) or phasic (n = 289). The mean apnea-hypopnea index was 1.99 (SD = 1.27) events/h. The frequency of leg movements, microarousal, and tachycardia was increased in SB events when compared with the control window (P < .05). There was an increase in bradycardia frequency in the control window when compared with SB (in both tonic and phasic events). The frequency of obstructive and central apnea during SB was lower when compared with the other physiological phenomena.

CONCLUSIONS

There is a difference in the physiological parameters evaluated in children with mild sleep apnea when comparing the 2 windows (SB and control). Sleep bruxism is associated with other physiological phenomena, such as leg movements, tachycardia, and microarousal. The use of a control window (where no mandibular activity was detected) was representative since it did not show activation of the sympathetic nervous system.

CITATION

Bonacina CF, Soster LMSFA, Bueno C, et al. Sleep bruxism and associated physiological events in children with obstructive sleep apnea: a polysomnographic study. J Clin Sleep Med. 2024;20(4):565-573.

Sleep architecture as a candidate for phenotyping sleep bruxism: A narrative physiological review

BACKGROUND

Sleep bruxism (SB), an oral behaviour in otherwise healthy individuals, is characterised by frequent rhythmic masticatory muscle activity (RMMA) during sleep. RMMA/SB episodes occur over various sleep stages (N1-N3 and rapid eye movement (REM)), sleep cycles (non-REM to REM), and frequently with microarousals. It currently remains unclear whether these characteristics of sleep architecture are phenotype candidates for the genesis of RMMA/SB.

OBJECTIVES

This narrative review investigated the relationship between sleep architecture and the occurrence of RMMA as a SB phenotype candidate.

METHODS

PubMed research was performed using keywords related to RMMA/SB and sleep architecture.

RESULTS

In non-SB and SB healthy individuals, RMMA episodes were most frequent in the light non-REM sleep stages N1 and N2, particularly during the ascending phase of sleep cycles. The onset of RMMA/SB episodes in healthy individuals was preceded by a physiological arousal sequence of autonomic cardiovascular to cortical activation. It was not possible to extract a consistent sleep architecture pattern in the presence of sleep comorbidities. The lack of standardisation and variability between subject complexified the search for specific sleep architecture phenotype(s).

CONCLUSION

In otherwise healthy individuals, the genesis of RMMA/SB episodes is largely affected by oscillations in the sleep stage and cycle as well as the occurrence of microarousal. Furthermore, a specific sleep architecture pattern cannot be confirmed in the presence of sleep comorbidity. Further studies are needed to delineate sleep architecture phenotype candidate(s) that contribute to the more accurate diagnosis of SB and treatment approaches using standardised and innovative methodologies.

Awake bruxism in temporomandibular disorders patients referred to tertiary care: A retrospective study on its assessment and TMD management

BACKGROUND

Bruxism is defined as a repetitive jaw-muscle activity characterised by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible. Bruxism can occur during sleep (sleep bruxism, SB) or during wakefulness (awake bruxism, AB). To date, the effect of AB on the purported negative consequences of bruxism has remained unclear.

OBJECTIVES

The assessment of AB, its relation to temporomandibular disorders (TMD) treatment modalities, and their possible outcomes were investigated among TMD patients resistant to treatment in primary care and referred to a tertiary care clinic.

METHODS

The records of 115 patients were studied. Patients were referred to the Head and Neck Centre, Department of Oral and Maxillofacial Diseases, Helsinki University Central Hospital, for TMD treatment between 2017 and 2020. The data derived from the eligible patients' records included the following: background data (age and sex), referral data (reason and previous treatment), medical background (somatic and psychiatric), clinical and possible radiological diagnoses at a tertiary care clinic, treatment modalities for masticatory muscle myalgia, bruxism assessment, its possible treatment modalities and their outcomes, and overall management outcome. We analysed the outcomes of single treatment modalities and combined groups of modalities. For the demographic data, the Chi-squared test and Fischer's Exact test were used to determine the associations between the categorical variables. A Sankey-diagram was used to describe the flow of treatment.

RESULTS

Temporomandibular joint-pain-dysfunction syndrome (K07.60) was the most frequent single reason to refer a patient to tertiary care (17.4%). At referral, men had myalgia (M79.1) significantly more often (p = .034) than women. Similarly, men had depression (p = .002) more often and other psychiatric diagnoses (p = .034). At tertiary care, the presence of AB was assessed in 53.9%, and self-reported AB was recorded in 48.7%. In patients with possible AB, those who were prescribed neuropathic pain medication showed significantly less improvement in symptoms (p = .021) than those who underwent splint therapy (p = .009). Overall, half of the patients showed overall improvement in their TMD symptoms from the treatment combinations.

CONCLUSION

Despite several treatment modalities, only half of the patients showed improvement in their symptoms in the present study. A standardised assessment method encompassing all factors contributing to bruxism behaviours and their consequences is suggested.

Research routes on awake bruxism metrics: Implications of the updated bruxism definition and evaluation strategies

BACKGROUND

With time, due to the poor knowledge on it epidemiology, the need to focus on awake bruxism as a complement of sleep studies emerged.

OBJECTIVE

In line with a similar recent proposal for sleep bruxism (SB), defining clinically oriented research routes to implement knowledge on awake bruxism (AB) metrics is important for an enhanced comprehension of the full bruxism spectrum, that is better assessment and more efficient management.

METHODS

We summarised current strategies for AB assessment and proposed a research route for improving its metrics.

RESULTS

Most of the literature focuses on bruxism in general or SB in particular, whilst knowledge on AB is generally fragmental. Assessment can be based on non-instrumental or instrumental approaches. The former include self-report (questionnaires, oral history) and clinical examination, whilst the latter include electromyography (EMG) of jaw muscles during wakefulness as well as the technology-enhanced ecological momentary assesment (EMA). Phenotyping of different AB activities should be the target of a research task force. In the absence of available data on the frequency and intensity of wake-time bruxism-type masticatory muscle activity, any speculation about the identification of thresholds and criteria to identify bruxers is premature. Research routes in the field must focus on the improvement of data reliability and validity.

CONCLUSIONS

Probing deeper into the study of AB metrics is a fundamental step to assist clinicians in preventing and managing the putative consequences at the individual level. The present manuscript proposes some possible research routes to advance current knowledge. At different levels, instrumentally based and subject-based information must be gathered in a universally accepted standardised approach.

The development of the Standardised Tool for the Assessment of Bruxism (STAB): An international road map

This paper summarises the background reasoning and work that led to the selection of the items included in the Standardised Tool for the Assessment of Bruxism (STAB), also introducing the list of items. The instrument is currently being tested for face validity and on-field comprehension. The underlying premise is that the different motor activities included in the bruxism spectrum (e.g. clenching vs. grinding, with or without teeth contact) potentially need to be discriminated from each other, based on their purportedly different aetiology, comorbidities and potential consequences. Focus should be on a valid impression of the activities' frequency, intensity and duration. The methods that can be used for the above purposes can be grouped into strategies that collect information from the patient's history (subject-based), from the clinical assessment performed by an examiner (clinically based) or from the use of instruments to measure certain outcomes (instrumentally based). The three strategies can apply to all aspects of bruxism (i.e. status, comorbid conditions, aetiology and consequences). The STAB will help gathering information on many aspects, factors and conditions that are currently poorly investigated in the field of bruxism. To this purpose, it is divided into two axes. Axis A includes the self-reported information on bruxism status and potential consequences (subject-based report) together with the clinical (examiner report) and instrumental assessment (technology report). Axis B includes the self-reported information (subject-based report) on factors and conditions that may have an etiological or comorbid role for bruxism. This comprehensive multidimensional assessment system will allow building predictive model for clinical and research purposes.

Sleep Bruxism and Orofacial Pain in Patients with Sleep Disorders: A Controlled Cohort Study

BACKGROUND

The gold standard for the diagnosis of sleep bruxism (SB) is laboratory polysomnography (L-PSG) recording. However, many clinicians still define SB using patients' self-assessment and/or clinical tooth wear (TW). The purpose of this cross-sectional controlled study was to compare the prevalence of TW, head-neck muscles sensitivity and Temporomandibular Disorders (TMD) between SB and non-SB patients diagnosed with L-PSG in a cohort of patient with sleep disorders (SD).

METHODS

102 adult subjects with suspected SD underwent L-PSG recording to assess the presence of sleep disorder and SB. TW was clinically analyzed using TWES 2.0. The pressure pain threshold (PPT) of masticatory muscles were assessed using a Fisher algometer. Diagnostic criteria for TMD (DC/TMD) were used to evaluate the presence of TMD. SB self-assessment questionnaires were administered. TWES score, PPT, TMD prevalence and questionnaire results were compared between SB and non-SB patients.

RESULTS

22 SB patients and 66 non-SB patients with SD were included. No significant differences emerged between groups in regards to TW, the PPT values, or SB's self-assessment questionnaires as well the prevalence of TMD.

CONCLUSION

in a SD population, TW is not pathognomonic of active SB and SB self-assessment is not reliable. There seems to be no correlation between SB, TMD and head/neck muscle sensitivity.

Temporomandibular Disorders Within the Context of Sleep Disorders

This paper provided an overview of the knowledge on the relationship between temporomandibular disorders (TMDs) and the main sleep conditions and disorders of dental interest, namely, sleep bruxism (SB), sleep apnea, and gastroesophageal reflux disease (GERD). It emerged that although the topic of SB as a possible detrimental factor for the stomatognathic structures has been the most studied, evidence is growing that SB, obstructive sleep apnea, and GERD, all belong to a circle of mutually interacting sleep disorders and conditions that, in turn, may be associated with TMDs. The pathophysiology of the cause-and-effect relationships, if existing, has to be elucidated yet.

Current Knowledge and Future Perspectives on Awake Bruxism Assessment: Expert Consensus Recommendations

Awake bruxism (AB) is differentiated from sleep bruxism (SB) by the differences in etiology, comorbidities, and consequences related to the different spectrum of muscle activities exerted in relation to the different circadian manifestations. Furthermore, less literature data are available on AB than on SB. The introduction of ecological momentary assessment (EMA) strategies has allowed for collecting valuable data on the frequency of the different activities reported by an individual in his/her natural environment. This strategy has been further improved with the recent use of smartphone technologies. Recent studies have described an average frequency of AB behaviors, within the range of 23–40% for otherwise healthy young adults. An association between AB and some psychological traits has emerged, and the findings have indicated that patients with musculoskeletal symptoms (e.g., temporomandibular joint and/or muscle pain, muscle stiffness, and fatigue) report higher AB frequencies. Preliminary data suggest that muscle bracing and teeth contact are the most commonly reported behaviors, while teeth clenching is much less frequently reported than commonly believed previously. Report of teeth grinding during wakefulness is almost absent. This paper has critically reviewed the currently available approaches for the assessment of AB. In addition, some future perspectives and suggestions for further research have been provided.