Nocturnal bruxism occurs in 5% to 20% of adults and in 30% of children in the age group of five and six years.
True incidence and prevalence rates of bruxism are not known as over 80% of all bruxers may be unaware of the habit or be ashamed to admit it, hence they may dismiss any evidence of self-destructive behavior.
Information about the incidence of bruxism in both genders is still ambiguous. What is known is that bruxism is uncommon after the age of forty and the risk factors for bruxism diminish with age.
Clenching or grinding of teeth is common among three out of every ten children. The highest prevelance is seen in those below five years.
It is particularly common in children with cerebral palsy or severe mental retardation. Bruxism is extremely rare in children after the eruption of the permanent teeth (secondary dentition).