Q: My child, age 3, grinds his teeth at night. What can we do to prevent him from doing this? What is this doing to his teeth?

A: Grinding teeth, or bruxism, is surprisingly common in children. Nearly one in three children does it at some point, nearly always during sleep.

Nobody knows the cause. There are theories, including teeth not fitting together properly (malocclusion), a problem with the joint of the jaw (temporomandibular joint), anxiety or just habit. The cause may be different in different children.

Luckily, children usually stop by themselves—and there is usually no damage to the teeth. If they grind hard enough for long enough it can wear down the teeth and increase the risk of infections, but this is uncommon.

It’s important, for all sorts of reasons, that you take your child to the dentist regularly. The next time you do, mention your concerns about teeth grinding. If the dentist sees more than the average wear and tear, he or she may prescribe a mouth guard. It’s most likely, though, that nothing will need to be done.

Because bruxism can be associated with stress, be on the lookout for any changes in your child's behavior—and think about whether anything in his life may be worrying or upsetting him (like a new school, new sibling, conflict between parents) and whether there is anything you can do about it. If your child has been having changes in his behavior, and if your efforts to help him aren't making a difference, talk to your pediatrician.