When a child’s baby teeth do not fall out and new teeth grow out of the gums, this is called retained milk teeth, and the new teeth are permanent teeth. According to the X-ray film, some of them need to be surgically extracted, while others can be removed on their own. Retained milk teeth refers to the phenomenon that the inherited permanent teeth have already erupted, or have semi-erupted, but the milk teeth have not been removed in time, usually due to abnormal root resorption of milk teeth, permanent teeth eruption obstacles and other factors. For children with retained milk teeth, if the permanent teeth have already erupted, but the milk teeth are not loosened for the time being, or the position of the permanent teeth is deviated, in this case, surgical extraction treatment is needed. If the child’s permanent teeth are already surrounded by obvious redness, swelling, pain and other infectious tendencies, it is also necessary to remove the milk teeth in time. For children whose permanent teeth have already erupted, with no obvious deviation in position and direction, and whose milk teeth are loose, it is not recommended to remove them surgically, but to observe their sustainability and wait for them to fall out on their own. For children with retained milk teeth, the specific measures to be taken need to listen to the advice of a professional dentist. In daily life, pay attention to maintain oral hygiene.