Losing teeth at age 12 is normal if they are milk teeth, but not normal if they have been replaced (permanent teeth). Children usually start to lose milk teeth at the age of 6-8 years old; at the age of 9-10 years old, the first milk molar starts to fall out and the first premolar starts to erupt; at the age of 10-11 years old, the milk cusp starts to fall out and the second premolar and cusp start to erupt; at the age of 11-12 years old, the second milk molar starts to fall out and the second molar starts to erupt from the distal center of the first permanent molar. Children’s tooth loss indicates that the milk teeth have not been completely removed. Generally, after the age of 14 weeks, the permanent teeth will all grow in, and there will not be any further tooth loss, but there will be a small number of children with delayed milk tooth loss. In general, children should avoid licking their teeth with their tongues during the tooth replacement period to prevent the teeth from sticking out or having a bad bite. At the same time, it is important to pay more attention to the eruption of teeth, if there is a double layer of teeth, it may have an impact on the development of the jawbone, and should be corrected in a timely manner.