Do you have tenderness or pain in your jaw muscles? Are your teeth worn down, fractured or chipped? If so, you may have bruxism, a condition in which a person grinds their teeth involuntarily while not chewing. The teeth grind or rub together as the jaw moves forcefully either from side to side or back and forth. Often, the person is not aware that they are doing it. While it can happen during the day, bruxism typically takes place while you are asleep. Sleep bruxism is generally more severe due to the force applied during episodes, which can cause serious problems for the teeth and jaw.