Emergence of adult teeth. Panoramic dental X-ray of the mouth of a 12-year-old girl, showing the emergence (eruption) of adult teeth (erupting ones are purple). The adult teeth are permanent teeth that replace the milk teeth of childhood. The permanent teeth start emerging at around 6 years old, and the last milk tooth is lost at around 12 years old. 20 milk teeth are replaced by 32 adult teeth. Here, four unerupted molars (the wisdom teeth, orange) are seen at the back of the mouth. In the lower jaw, two teeth are erupting. Four teeth are erupting in the upper jaw. This child is a twin. See P486/135 for an X-ray of the teeth of her twin sister at the same age, with nearly identical teeth arrangement.