This is a serious situation. It's possible your child is grinding/gnashing her teeth at night. This is actually a common thing for children to do, but it may be that she's overdoing it. Eventually this grinding/clenching problem can lead to TMJ Disorder...you DON'T want that. Does your daughter see the dentist on a regular basis? The dentist should be able to detect tooth fractures and may recommend a night guard for your daughter to wear at night. These work for some people....not all. There may be a dietary deficiency also that's causing this. I'd check into this as soon as you can.