Abstract. Bruxism is a common masticatory-muscle activity characterized by grinding or clenching of the teeth and by bracing or thrusting of the mandible. Contemporary understanding has shifted away from the historical occlusal model toward a predominantly centrally regulated etiology, and has established sleep bruxism and awake bruxism as distinct circadian phenotypes with differing risk-factor profiles. Although frequently benign, bruxism can contribute to dental attrition, restorative failure, masticatory-muscle pain, and temporomandibular disorders (TMDs). This review summarizes current evidence on the definitions, prevalence, etiology, diagnosis, TMD associations, and management of bruxism relevant to clinical dental practice.
Definitions and Phenotypes
Current international consensus defines bruxism not as a single disorder but as a masticatory-muscle activity with two distinct circadian manifestations. Sleep bruxism is a sleep-related movement behavior characterized by rhythmic masticatory muscle activity, whereas awake bruxism consists of predominantly semi-voluntary clenching and mandibular bracing during wakefulness. In otherwise healthy individuals, consensus frameworks regard bruxism as a behavior rather than a disorder, one that may be a risk factor for, or protective against, various clinical outcomes depending on context. Distinguishing the two phenotypes is clinically important, as they differ in mechanism, associated behaviors, and management.
Prevalence
Systematic review and meta-analytic data indicate a global bruxism prevalence of approximately 22%, with awake bruxism (around 23%) somewhat more prevalent than sleep bruxism (around 21%) in adult populations. Sleep bruxism is notably more common in children and tends to decline with age. Prevalence estimates vary considerably with assessment method, as much of the literature relies on self-report rather than instrumental confirmation.
Etiology
The etiologic model of bruxism has undergone a substantial paradigm shift. Once attributed principally to occlusal interferences, bruxism is now regarded as multifactorial and largely centrally mediated. Sleep bruxism is closely linked to transient sleep microarousals and associated activation of the autonomic nervous system, with a characteristic sequence of autonomic-cardiac and cortical activation preceding rhythmic masticatory muscle activity. Contributing and associated factors include psychosocial variables—particularly stress, anxiety, and depression, which show strong associations with awake bruxism—as well as tobacco, alcohol, and caffeine use, certain medications (notably selective serotonin reuptake inhibitors), and comorbid sleep-related breathing disorders. For a related discussion of airway-associated findings, see our review of sleep-disordered breathing and oral health.
Relationship to Temporomandibular Disorders
The association between bruxism and TMDs is well documented but nuanced. Evidence indicates that bruxism increases the likelihood of TMD signs and symptoms, though the relationship is not strictly causal and is modified by psychological and behavioral factors. Notably, the specific motor behavior appears to matter: sustained clenching and bracing are more closely associated with musculoskeletal complications such as TMD-related myofascial pain, whereas grinding is more strongly linked to dental consequences including attrition and restoration failure. Awake bruxism, in particular, demonstrates significant associations with depression, anxiety, and stress, reinforcing the biopsychosocial framework now applied to both bruxism and TMD.
Diagnosis
Diagnosis is graded by degree of certainty. Possible bruxism rests on self-report or questionnaire; probable bruxism adds clinical examination findings such as masseteric hypertrophy, tooth wear consistent with grinding, linea alba, or tongue indentations; and definite bruxism requires instrumental confirmation, with polysomnography (ideally with audio-video recording) representing the reference standard for sleep bruxism and electromyography-based tools increasingly used for awake bruxism. In routine practice, most diagnoses remain at the possible or probable level, and clinical vigilance for the characteristic signs is essential.
Management
Management is directed at protecting the dentition, relieving symptoms, and addressing modifiable contributors rather than at abolishing the behavior itself, which is often not feasible. An occlusal splint (stabilization appliance) is the mainstay for protecting teeth and restorations from grinding forces and may reduce muscle discomfort, although evidence that splints reduce the underlying muscle activity is limited and their role is chiefly protective. Importantly, occlusal appliances are relatively contraindicated in patients with untreated obstructive sleep apnea, where certain designs may aggravate airway obstruction—underscoring the need to screen for sleep-related breathing disorders. Behavioral strategies, including stress management, sleep-hygiene optimization, biofeedback, and awareness training for awake bruxism, are valuable adjuncts. Pharmacologic and botulinum-toxin approaches have been investigated for refractory or symptomatic cases but warrant judicious, individualized use.
Conclusion
Bruxism is a prevalent, centrally regulated masticatory-muscle behavior with distinct sleep and awake phenotypes and a multifactorial, biopsychosocial etiology. Its relationship to TMDs is real but conditional, mediated by the type of motor activity and by psychological factors. Effective care rests on accurate phenotyping, recognition of characteristic clinical signs, protection of the dentition, screening for comorbid sleep-related breathing disorders, and attention to modifiable behavioral contributors. A patient-oriented companion to this review is available in our guide to teeth grinding and how to protect your smile.
References
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This article is intended for general educational purposes and does not constitute individual medical or dental advice. If you are concerned about teeth grinding or jaw pain, the team at Fridman Family Dental Care in Valencia, CA can help — contact us to schedule an evaluation.
