Adult humans have 32 permanent teeth, while children have 20 primary teeth, also known as baby teeth or deciduous teeth. The 20 deciduous teeth develop between the ages of 6 months and 24 months, and this set of baby teeth begins to fall out at about age 6.
Baby teeth typically fall out in the same order that they grow in. The first 20 permanent teeth replace the baby teeth soon after the deciduous teeth fall out. One set of permanent molars grows in at about age 6, and a second set develops at about age 12. The final set of molars, called wisdom teeth, grow in between the ages of 17 and 21. Many people have their wisdom teeth removed by a dentist and end up with just 28 adult teeth as a result.