The treatment for tooth decay in a four year old is determined on a case-by-case basis. Minor cavities can be relieved by removing necrotic tissue and then filling treatment; more serious cavities can be relieved by root canal treatment. 1. Minor tooth decay: If the tooth decay of a four-year-old child is not serious and is only accompanied by localized tooth damage, parents are advised to take their children to the dentist in time to remove the necrotic tissue from the diseased part of the tooth in a timely manner, do a good job of disinfecting the tooth, and follow the doctor’s instructions when changing the medication on a regular basis, and then carry out the filling treatment, so that the child’s symptoms can be improved as soon as possible. 2. More serious cavities: if the lesion site is damaged to the gums, periodontal, leading to infection foci, root canal treatment is needed, and assisted by anti-infection treatment, such as oral amoxicillin capsules to control interstitial infections, to completely improve the symptoms of discomfort. When the child grows up to about 6~7 years old, the decayed teeth will be gradually replaced by permanent teeth, and the discomfort symptoms will disappear gradually. Parents are advised to take better care of their children’s mouths and develop good living habits to help reduce the incidence of tooth decay. If there is any discomfort, it is recommended to consult a doctor in time. Use medication under the guidance of a physician.