Most patients are completely unaware that they may be grinding or clenching their teeth. For instance, many people sleep on their sides or stomach, and their teeth go into positions sleeping that they would not ordinarily be in during the day. Nocturnal tooth grinders often place up to 3 to 10 times amount of biting pressure on the teeth in short sporadic periods than they do chewing during the day (usually during the delta phase of sleep). Over time the hard protective enamel covering of the teeth wears off, and the teeth begin to fray and fracture.

The  worn surfaces are prone to decay as the soft dentin becomes exposed. Many of these teeth fracture, especially if silver mercury fillings are present. Some teeth develop root fractures requiring root canals or extraction. Gum recession, tooth mobility, damage to the jaw joint (TMJ), and bone loss can also occur with type of wear.

It is estimated that about 25 to 50% of people cause damage with grinding. There are several types of bite guards that may be used to prevent damage from grinding. They need to be custom made for the patient—and can be hard or soft, thick or thin, or fit either the top or bottom teeth.