Orofacial Pain/Temporomandibular Disorders in Relation to Sleep Bruxism and Breathing Disorders
Among chronic orofacial pain conditions, temporomandibular disorders (TMDs) are the most common. The etiology of TMD is multifactorial. The role of sleep-disordered breathing (SDB) and sleep bruxism (SB) in the initiation and persistence of TMD pain is poorly understood but of considerable interest to dental clinicians who treat these patients. Evidence for SDB as a causal risk factor for TMD is limited at present to a few cross-sectional studies reporting higher prevalence of SDB or suspected SDB in patients with TMDs, and higher prevalence of TMDs among patients with SDB. Laboratory-based measures of sleep respiration indicate that respiratory effort–related arousals during sleep are more frequent in women with TMD than in control subjects. The prevalence of SDB also is greater in patients with fibromyalgia syndrome, a chronic pain condition commonly comorbid with TMD. One population-based prospective cohort study found that signs and symptoms of SDB predict incident TMD. However, the premise that SDB leads in a dominant sequence to SB, and eventually to TMD, is not supported by current scientific evidence. A complex set of interrelationships may explain an association between SDB and TMD. Proposed mechanisms include elevated background levels of activity in the masticatory muscles during sleep or wakefulness, intermittent hypoxia during sleep, altered autonomic nervous system function, oxidative stress, and inflammation. Moreover, recent studies suggest that phenotyping patients with SDB and patients with TMD may elucidate relationships that have been obscured in previous studies that did not recognize possible differences among patients.
