Children usually start to change their teeth around the age of 6, i.e., the milk teeth fall out and the permanent teeth erupt in a certain sequence, each lasting no more than 2 months. The teeth that come out when a person is born are milk teeth, and there are 20 of them in total. From the age of 6, milk teeth are gradually replaced by permanent teeth, which are 28 to 32 in total, with some variations between individuals. There is a certain pattern of tooth replacement, generally the front teeth are replaced the earliest, the lower teeth are replaced earlier than the upper teeth, and after the incisors are replaced, the lateral incisors are replaced, followed by the permanent molars. Moreover, at the age of six, a new permanent tooth grows behind the second molar and does not replace any of the teeth, which is called the “six-year-old tooth”. This is an extremely important permanent tooth and should be brushed carefully to prevent decay. During the period of tooth replacement, you need to pay extra attention to your child’s diet to ensure balanced nutrition, eat more vegetables and fruits, and supplement calcium and protein as appropriate. Adopt the habit of brushing in the morning and evening, rinsing after meals to maintain a good oral environment.