Bruxism into three groups, namely central or pathophysiological factors, psychosocial factors and peripheral factors. The World Health Organization's International Classification of Diseases 10th revision does not have an entry called bruxism, instead listing "tooth grinding" under somatoform disorders. To describe bruxism as a purely somatoform disorder does not reflect the mainstream, modern view of this condition (see causes). The ICSD-R described three different severities of sleep bruxism, defining mild as occurring less than nightly, with no damage to teeth or psychosocial impairment; moderate as occurring nightly, with mild impairment of psychosocial functioning; and severe as occurring nightly, and with damage to
Bruxism a link between episodes of sleep bruxism and a supine sleeping position (lying face up). Disturbance of the dopaminergic system in the central nervous system has also been suggested to be involved in the etiology of bruxism. Evidence for this comes from observations of the modifying effect of medications which alter dopamine release on bruxing activity, such as levodopa, amphetamines or nicotine. Nicotine stimulates release of dopamine, which is postulated to explain why bruxism is twice as common in smokers compared to non-smokers. Many studies have reported significant psychosocial risk factors for bruxism, particularly a stressful lifestyle, and this evidence