Hi
My Lucy is definitely too young to have teeth falling out yet (she is only 18 months old!), but your question reminded me of my husband - NONE of his baby teeth fell out naturally. The adult teeth would start growing behind the baby teeth, but the baby teeth just wouldn't fall out. So he had to have each and every one of his baby teeth extracted by a dentist.
So, when Lucy's baby teeth do begin to drop out (hopefully by themselves), I will take a big sigh of relief - I hope that she doesn;t get her father's teeth genetics!
Alice