Development of the Teeth Age 13 This series of pages show the annual development of teeth in the mouth and jaws from childhood to young adult. A beautiful 13 year-old smile This is an example of what is developing inside the mouth of a typical 13 year-old child. All of the permanent teeth, except for the 3rd molars (wisdom teeth), have erupted and are in occlusion except for the second molars. Spaces are closed and root formation is essentially complete for all erupted teeth. The 3rd molars are developing and will erupt, on average, around years 18-21. Next