Bruxism is a chronic clenching of the jaws and grinding of the teeth. Bruxism is relatively common, especially in children under 5. In older children and adults, bruxism often occurs in people ranging from the late teens to 40s, or those who are under excessive stress or who have certain personality types. Teeth grinding, or bruxing, appears to decrease in most people as they age.

Bruxism occurs when a person tightly clamps the top and bottom teeth together. It is particularly likely to involve the back teeth. In addition, many people who clench their teeth also grind them in a sideways, back-and-forth movement. Both clenching and grinding put pressure on the muscles, tissues and other structures surrounding the jaw. This may cause pain, wearing down of the tooth enamel and other symptoms.

Bruxism tends to occur most often during deep sleep, particularly in the early part of the night. Many patients are not aware that they clench or grind their teeth overnight. In addition, bruxing may occur during waking moments when a person feels particularly stressed or anxious. For reasons that are not completely understood, people tend to grind their teeth with less frequency as they get older.

The exact cause of bruxism remains unknown, but it tends to occur more often in those whose top and bottom teeth are not aligned properly (malocclusion). Stress also is suspected as a major contributor to bruxism. People who experience high levels of nervous tension (e.g., anger, pain, frustration) are more likely to brux, as are people who have an aggressive, anxious or very competitive nature.