What makes people grind their teeth during sleep?

Bruxism: Grinding of the teeth called brutism is a common sleep disorder called parasomnia. It is related to stress levels generally. Bite devises are typically used to limit the damage to teeth and jaw joint.

Lots of reasons: There are all sorts of reasons for clenching and or grinding. It is my experience that it is a major stress coping mechanism. Regardless of the reason, these habits are very bad for the teeth, mouth and all muscles in the area. I f you suffer from lots of headaches you could be clenching or grinding your teeth.