If a child’s milk tooth decay is not treated in time, it will develop into pulpitis (commonly known as “dental nerve”) or even periapical inflammation, which usually manifests as pain, gum swelling, percussion pain and loosening of the affected tooth. However, the absence of these symptoms does not mean that the pulp is healthy, as the lack of sensitivity to pain and the lack of clarity about the condition in pediatric patients often leads parents to delay consultation, and severe periapical infection can affect the development and correct position of the permanent tooth germ below. For this type of tooth, a “filling” is not enough, but a root canal treatment is required, usually in 2-3 visits, the cost of which depends on the number of roots. The child may experience mild pain for a few days after each treatment, which is a normal reaction and parents should not worry too much. If the pain is severe and the swelling is obvious, it is necessary to consult the doctor in time for open or anti-inflammatory treatment. Before treatment, deep caries progressed to the pulp cavity and caused pulp infection; After treatment, the filling is complete and constant under the milk molar; The tooth embryo and tooth capsule are intact and not damaged by inflammation.