Review Article Bruxism physiology and pathology: an overview for clinicians* G. J. LAVIGNE*, S. KHOURY*, S. ABE*, T. YAMAGUCHI † & K. RAPHAEL ‡ *Faculty of Dentistry, Surgery Department, Pain, Sleep and Trauma Unit, Universite ´ de Montre ´al, Ho ˆ pital du Sacre ´-Coeur de Montre ´al, Montre ´al, Canada, † Department of Temporomandibular Disorders, Hokkaido University, Kita-ku, Sapporo, Japan and ‡ University of Medicine and Dentistry of New Jersey, Newark, NJ, USA SUMMARY Awake bruxism is defined as the aware- ness of jaw clenching. Its prevalence is reported to be 20% among the adult population. Awake brux- ism is mainly associated with nervous tic and reactions to stress. The physiology and pathology of awake bruxism is unknown, although stress and anxiety are considered to be risk factors. During sleep, awareness of tooth grinding (as noted by sleep partner or family members) is reported by 8% of the population. Sleep bruxism is a behaviour that was recently classified as a ‘sleep-related movement disorder’. There is limited evidence to support the role of occlusal factors in the aetiology of sleep bruxism. Recent publications suggest that sleep bruxism is secondary to sleep-related micro-arous- als (defined by a rise in autonomic cardiac and respiratory activity that tends to be repeated 8–14 times per hour of sleep). The putative roles of hereditary (genetic) factors and of upper airway resistance in the genesis of rhythmic masticatory muscle activity and of sleep bruxism are under investigation. Moreover, rhythmic masticatory muscle activity in sleep bruxism peaks in the minutes before rapid eye movement sleep, which suggests that some mechanism related to sleep stage transitions exerts an influence on the motor neurons that facilitate the onset of sleep bruxism. Finally, it remains to be clarified when bruxism, as a behaviour found in an otherwise healthy popu- lation, becomes a disorder, i.e. associated with consequences (e.g. tooth damage, pain and social ⁄ marital conflict) requires intervention by a clinician. KEYWORDS: bruxism, awake, sleep, tooth grinding, movement disorders, pathophysiology, scoring, monitoring Accepted for publication 10 March 2008 Tooth grinding (TG) is an activity of major concern to dentists because of its consequences: tooth destruction, breakage of dental restoration or rehabilitation, exac- erbation of temporomandibular disorders or induction of temporal tension headache and grinding sounds that may interfere with the sleep of family or life partners. The common belief that tooth wear is a specific marker of bruxism is outdated because the cause (bruxism) and the effect (tooth wear) could have occurred months and years before the patient consultation. One of the main challenges for the dentist is to identify whether the patient presents awake or sleep bruxism (SB) according to the patient’s motive for the consultation, i.e. conse- quences, such as tooth damage, pain or complaints of noise. Electronic recordings (muscles, heart, respiration and brain activity) made in a laboratory or home environment are a recognized method for quantifying SB frequency. The specificity of scoring is increased when audio and video signals are collected in parallel because numerous usual oromandibular activities such as chewing, swallowing and sleep talking can be *Based on a lecture given at the JOR Summer School 2007 sponsored by Blackwell Munksgaard and Medotech. ª 2008 The Authors. Journal compilation ª 2008 Blackwell Publishing Ltd doi: 10.1111/j.1365-2842.2008.01881.x Journal of Oral Rehabilitation 2008 35; 476–494