Baltomommie wrote to ask for advice on how to help her preschooler stop grinding his teeth at night. She also wanted to know whether a sealant that dentists apply to children's teeth these days to prevent cavities would help protect his teeth from the wear and tear of grinding.

I sent the question to Shari Kohn, a pediatric dentist at Dentistry for Kids in Hunt Valley and a clinical instructor at the University of Maryland Dental School. She counsels patience.

"Many preschoolers grind their teeth," she wrote in an e-mail. "There are many different theories as to why - nothing has been proven. One theory is that grinding is a subconscious stress release. Another is that it is an inherited trait from a parent who grinds. Many parents tell me that their children started grinding when they started school. We also see grinding commonly in children who have a malocclusion or poor bite alignments who will need braces in the future."

There's not much a parent can do when a child is a preschooler, Kohn says, because night guards are a choking hazard at this age. She says most young kids won't suffer anything more than mild wear on their teeth from grinding, and that can be treated with desensitizing products. Most kids will lose their baby teeth before the wear from grinding becomes more severe; if they're still grinding and causing damage to permanent teeth, they'll probably be old enough to wear a night guard then. Children whose bite alignments are causing grinding can be referred to an orthodontist at that point, too.

Anti-cavity sealants aren't an answer to grinding, Kohn says, because they are designed to fill in grooves and pits of teeth, while grinding affects the cusps of teeth.