Sleep disorders can cause teeth grinding, or bruxism. Other causes of teeth grinding can be caused not just by stress and anxiety, an abnormal bite or teeth that are missing or crooked.
Your dentist can fit you with a mouth guard to protect your teeth during sleep. In some cases, your dentist or physician may recommend taking a muscle relaxant before bedtime. If stress is the cause you need to find a way to relax. Meditation, counseling and exercise can all help reduce stress and anxiety.