Bruxism is an unconcious clenching and/or grinding of the teeth, most commonly during the night. Very present in children, it tends to become a pathological condition beyond a certain age, or rather in adulthood. The teeth undergo constant stress and tend to erode due to the friction between them. No less important is the tendency during the day to clench the teeth. The latter differs from bruxism because the eccentric component of the movement is less present. Bruxism and clenching, in patients with certain occlusal situations, are often one of the causes of the onset of pain in the TMJ.