When a child’s milk tooth does not fall out and another one grows inside, an oral examination can be conducted, and the whole mouth surface tomography film can be taken and treated separately, as follows: 1, supernumerary teeth: if the new teeth are supernumerary teeth, they can be extracted under local anesthesia to prevent hindering the smooth eruption of the permanent teeth. 2, self-exfoliation: the newborn permanent teeth have just broken through the mucous membrane of the oral cavity, and are far away from the milk teeth, and the X-radiographs show that the roots of the milk teeth are longer and have not yet been absorbed, so the child can chew more food with firm texture to speed up the absorption of the roots. You can let the child chew more tough food, accelerate the root resorption of the milk teeth, and wait for its own fall.3, chronic apical periodontitis: milk teeth form deeper caries or cryptic fissure, triggered by chronic apical periodontitis to form the root bone adhesion, you can extract the retained milk teeth under local anesthesia, and induce the permanent teeth to move to the normal position.