It is normal for children to change their teeth at the age of five when systemic diseases are ruled out. The normal time for a child to change teeth is around six years old, that is, at the age of six, the first new tooth will erupt, clinically known as the first permanent molar; girls change teeth a little earlier than boys. However, there are individual differences in the timing of children’s tooth replacement, and it is normal for children to start changing their teeth around the age of five to seven years old when systemic diseases are ruled out. During the period of tooth replacement, children should pay attention to the replacement of milk teeth and permanent teeth, if there is the symptom of retained milk teeth (i.e., double rows of teeth), they should seek medical treatment; in addition, during the period of tooth replacement, they should maintain oral hygiene, brush their teeth morning and night in order to prevent the emergence of dental caries, and have a reasonable diet and increase the chewing of hard objects in order to promote the replacement of normal teeth.