I was asked this today and I haven't been able to come up with a good answer. Kid just brought up writing the tooth fairy letter next time, so now i have to come up with something better than "I don't know!". The things I've found on google aren't going to fly with my child (last week, we read a book about the big bang theory, so "she turns the teeth into stars" not so much). Other things just sound dumb - she grinds teeth into fairy dust? she uses them to build a castle? wtf?). Any other good suggestions?
I KNOW this is a silly question, don't tear me a new one, please!