Teeth grinding or bruxism is a medical condition in which a person automatically clenches his or her teeth usually while asleep. Bruxism is due to clenching of the teeth other than in chewing and is associated with forceful lateral or protrusive jaw movements. This results in grinding or rubbing the teeth together. Teeth grinding or bruxism, is not only a habit. In fact it is a condition. Doctors believe that bruxism is caused by a number of factors.