Human beings generally have two sets of teeth, which can be categorized into milk teeth and permanent teeth, usually 20 milk teeth and 28~32 permanent teeth. Milk teeth are the first set of human teeth, which usually begin to erupt 5~6 months after the birth of infants, and end at about 2.5 years old, with the number of milk teeth being 20. Permanent teeth usually begin to erupt around the age of 6 and usually end at the age of 11~12 years old, and the permanent teeth are relatively stable, with their number at 28. It is before or after entering adulthood that the third permanent molar begins to erupt, which is the growth of wisdom teeth. The number of wisdom teeth is usually around 0~4, and not everyone grows them. That’s why permanent teeth are usually in the range of 28 to 32. Whether they are milk teeth or permanent teeth, they need to be protected and any abnormalities should be seen in a timely manner.