Tooth replacement in children is the replacement of milk teeth with permanent teeth, specifically the 20 milk teeth of childhood. Milk teeth often begin to erupt from 6 to 8 months after birth with 5 on each side of the upper and lower dentition. Their names from the midline to the sides are milk mesial incisors, milk lateral incisors, milk cusps, first molar and second molar. Teeth replacement usually begins around the age of 6 when the first permanent molar can erupt behind the second molar. When tooth replacement begins, the 20 milk teeth in the mouth will gradually fall out and the permanent teeth will erupt one after another. Sometimes, when the milk teeth have not yet fallen out and the permanent teeth have already erupted, due to the lack of position, the permanent teeth may erupt in the wrong position, in which case the milk teeth should be extracted in time. If there is any discomfort, it is recommended to consult a doctor in time.