text: The last one is usually lost around the age of 12 - 13 years.  But keep in mind that occasionally a person will have an adult tooth that doesn't develop, therefore, the baby tooth remains in the mouth.  Take the child to the dentist if they are over 13 and still have any baby teeth to ensure their adult teeth have developed and will erupt properly.  (although your child should be going to the dentist every 6 months for cleanings and exams anyway)