Children’s posterior teeth are replaced between the ages of 9 and 12 years. Children’s posterior alveolar teeth (clinically known as molar teeth) include the first molar and the second molar, there are a total of eight molar teeth; the molar teeth will be replaced by the secondary permanent teeth at the age of 9-12 years old, i.e., the first premolar will replace the eruption of the first molar at the age of 9-10 years old; the second premolar will replace the eruption of the second molar at the age of 10-12 years old. During tooth replacement, children need to chew hard objects more often to help the replacement of teeth, and still need to take good care of their mouths during the tooth replacement period, because the newly erupted teeth are susceptible to caries due to the attack of bacteria and other substances; therefore, they need to check their teeth on a regular basis, and if any problems are found, they should be treated under the guidance of the doctor in a timely manner.