Not all retained milk teeth need to be extracted, and it is recommended that they be extracted at the appropriate time under the guidance of a doctor. If the doctor determines that a retained baby tooth needs to be extracted, it must be removed as soon as possible, and the sooner it is removed, the better. There are two main types of retained baby teeth: 1. Baby teeth that have already erupted and have not been removed on time. Usually the baby teeth occupy the normal position for the eruption of permanent teeth, and most of the permanent teeth erupt on the lingual side of the baby teeth, showing a double row of teeth. In this case, the baby teeth must be extracted as soon as possible, otherwise they will be prone to symptoms such as backbite and misalignment of teeth. 2. Baby teeth that have not erupted and are retained in the permanent tooth row. Most of them are caused by congenitally missing permanent tooth germ, in this case, the milk teeth can be left untreated, and we should actively prevent the occurrence of milk tooth caries and delay the time of milk tooth loss as much as possible. It is recommended to actively seek medical examination if there is retained milk teeth. If the teeth need to be extracted as soon as possible to avoid abnormal position of permanent teeth. Parents should also warn their children not to lick the permanent teeth with tongue or break the ectopic eruption with their hands to avoid forming bad oral habits that may adversely affect the establishment of the occlusal relationship.