1. During a person’s lifetime, there are two sets of teeth, milk teeth and permanent teeth, which are distinguished according to the time of eruption. There are 20 milk teeth, which begin to erupt between 6 and 8 months after birth, of which the first molar and the second molar are the so-called big teeth of the child, which are located in the right upper jaw, the right lower jaw, the left lower jaw, the left upper jaw, and there are a total of eight of them, which will be lost along with the eruption of permanent teeth. 2. The eruption of permanent teeth usually begins around the age of six, with the first permanent molar erupting behind the second molar. At the age of 6 to 12 years, milk teeth and permanent teeth alternate in the mouth. It is important to note that milk teeth and permanent teeth should be extracted if they overlap. If there is any abnormality, it is recommended to go to a professional medical institution in time.