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- Bruxism is defined as habitual nonfunctional forceful contact of teeth, which is involuntary. These movements can include excessive grinding, clenching, or rubbing of teeth.
- Other nonfunctional (or “parafunctional”) oral habits include movements not involved with normal chewing, swallowing, or speaking, such as chewing pencils, nails, cheek, or lip.
- Sleep bruxism should be distinguished from daytime awake bruxism.
- Awake bruxism is rare with little or no audible sound during clenching, compared to the loud grinding sound commonly occurring in sleep bruxism.
- May occur throughout life but frequently tends to peak in early childhood, then decreases with age
- Infants have been known to grind their teeth during the eruption of primary teeth.
- May be temporarily or intermittently present, which makes diagnosis difficult
- Recent systematic review of literature reported no gender differences in prevalence. Previous studies suggested girls may be more affected than boys.
- Some studies support higher incidence in children with developmental disabilities, Down syndrome, sleep disorders, and autism.
- No genetic mechanism has been explained. Based on self-reports, 20–50% of children with sleep bruxism have an immediate family member who experienced bruxism as a child.
In children, prevalence in the literature is highly variable with a range of 4–40%. Prevalence decreases with increasing age. Sleep bruxism progressively diminishes around 9–10 years of age.
The exact cause is not known. It is likely to be a multifactorial process including pathophysiologic, psychologic, or morphologic factors.
- Awake bruxism is more commonly associated with psychosocial factors and psychopathologic symptoms.
- Dental factors (current evidence suggests that they play a small role, only ∼10% of cases)
- Occlusal interferences, including malocclusions, in which teeth do not interdigitate smoothly
- High dental restorations (e.g., fillings or crowns)
- Intraoral irritation (e.g., sharp tooth cusp)
- Psychological factors
- Nervous tension (related to stress, anger, and aggression)
- Personality disorders
- Posttraumatic stress disorder
- Common systemic factors
- Moving between levels of sleep
- Sleep-disordered breathing
- Snoring and sleep apnea
- Tonsil/adenoid hypertrophy
- Neurodevelopmental disorders (e.g., cerebral palsy)
- Brain injury
- Other possible factors
- Nasal obstruction
- Exposure to secondhand smoke
- Medications (amphetamines, antidepressants—particularly serotonin reuptake inhibitors)