There is individual variation in the age of tooth replacement in young children, which usually begins around the age of 5 to 6 years. Human teeth are divided into milk teeth and permanent teeth. Milk teeth erupt around 6 to 8 months of age and grow in at 2 to 3 years of age. Tooth replacement is the process of milk teeth falling out and permanent teeth coming in. Under normal circumstances most children begin to change their teeth around the age of five to six. The earliest teeth to be replaced are the incisors and the incisors on both sides, most of which will be replaced by the age of 9. The premolars and cuspids will be replaced by the age of 8 to 9, and the second molars will start to grow in around the age of 12, and they will all be complete by the age of 15. Between the ages of 18 and 30, the third molar, often referred to as the wisdom tooth, grows in. When young children are replacing their teeth, parents need to pay attention to brushing habits, practicing mouth rinsing, paying attention to the development of teeth, correcting bad habits and so on.