Kids normally begin losing their primary teeth from around 6 years old. From 6-12 years, children have a mixture of adult and primary teeth. By about 12 years, many children have all their adult teeth except for the 3rd molars ( knowledge teeth). There are 32 grown-up teeth. If your child's baby teeth came late, the adult teeth will probably be late too. If you're concerned concerning kids dentist as well as your kid's teeth advancement, see your dental expert.