OVERVIEW OF SLEEP BRUXISM, SLEEP DISORDERED BREATHING, AND TEMPOROMANDIBULAR DISORDERS
Sleep bruxism (SB) is defined as a stereotyped movement disorder characterized by rhythmic masticatory muscle activity (RMMA) associated with tooth grinding (TG) and occasional tooth clenching.1 The definition of bruxism was recently reviewed by an international group of experts,2 and this updated definition has been adopted for the International Classification of Sleep Disorders-3, to be published online in 2013. This consensus work: (1) recognized that bruxism has two distinct circadian manifestations: sleep (indicated as sleep bruxism) or wakefulness (indicated as awake bruxism) and (2) reinforced that SB is a repetitive jaw-muscle activity characterized by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible. The prevalence of self-reports of tooth grinding to assess SB is about 8%. The gold standard for diagnosis of SB is a polysomnogram (PSG), and a one-night study is considered adequate for the diagnosis of moderate to high frequency SB. In some cases of low RMMA frequency, a second night study may be necessary to confirm the findings of the first night. A recent study involving 1,042 subjects who completed a questionnaire and underwent a PSG found that, based on the questionnaire alone, the prevalence was 12.5%. With the use of PSG alone regardless of the subjects report, the prevalence was 7.4%. The prevalence of SB when the questionnaire was combined with polysomnographic recording was 5.5%.
Interest in SB has gained more attention due to a shift in the modern day employment environment and its putative recent association to sleep disorders such as insomnia and SDB. The word night or nocturnal as it relates to bruxism should no longer be used, since many workers sleep during the daytime due to flexible work schedules. Therefore, SB can occur anytime during a 24-h cycle. SB can be divided into two distinct catego- ries. They are: (1) primary or idiopathic SB, which is without an identifiable cause or any associated sociopsychological or medical problem; and (2) secondary SB, which is related to sociopsychological and/or medical conditions (e.g., movement or sleep disorder, neurologic or psychiatric condition, drug/ chemical related). Practitioners must be aware that SB may occur concomitantly with many other sleep disorders such as insomnia, sleep epilepsy, REM behavior disorder (RBD), and SDB.
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