Bruxism is an excessive clenching or grinding of the teeth that is not a part of normal chewing movements. It can lead to excessive wear on the teeth and may cause permanent damage to the teeth and the jaw joints. Excessive clenching and grinding are not normal, healthy actions of the jaws. In some adults and children, clenching and grinding may occur during the day or at night. They typically have no conscious control over this excessive clenching and grinding, particularly when it occurs during sleep.

The temporalis and masseter muscles bring the jaws together. Slight relaxation of the jaw muscles will prevent chronic muscular facial pain with tension headaches, caused by the intense muscle contraction.