Why do people grind their teeth when they asleep?

Bruxism: Grinding your teeth is a mechanism to react to stress in your life. There is family history of grinding (genetic codes) as well as environmental factors that contribute. All you can do is have a bite coverage appliance made to stop further damage to your teeth. Even a complete lifestyle change to remove stresses from your life may not stop the grinding habit.

It's complicated...: This is an area of debate in dentistry. There are several theories - like grinding is a reaction to stress. Other theories are that the teeth are not contacting properly due to the tooth anatomy, jaw joint, or jaw muscles. A fairly new idea is that people with sleep apnea may clench their jaws in a forward posture to open their airway.

Parafunctional habit: Like grinding or bruxism is also found in children with ear infection. Some anti- depressant drugs can also cause it.