Children usually need to replace 20 teeth and need to pay more attention to personal care during tooth replacement. Usually, children will start to change their teeth at the age of 6 years old, and with the eruption of permanent teeth from milk teeth until the age of 12~13 years old, all milk teeth will be replaced by permanent teeth, and generally need to replace 20 teeth. At the age of 12~14 years old, children will also grow the 2nd molar after the first molar, and as they grow older, until after the age of 18 years old, they can also grow the 3rd molar, but some patients do not have the 3rd molar. Meanwhile, during the period of tooth replacement, parents need to urge their children to brush their teeth and rinse their mouths appropriately after eating, so as to ensure oral hygiene. The child also needs to actively regulate the diet, appropriate consumption of certain hardness, high dietary fiber food, such as carrots, corn, etc., can promote the timely loss of milk teeth. The child can also speed up the facial blood circulation through chewing action, and promote the development of the dental bed, facial bone and jawbone. Parents are advised to correct the baby’s bad habits and observe the growth of baby’s milk teeth and permanent teeth during the tooth replacement period, which usually takes 20 teeth.