The period from the start of eruption of the milk teeth until the eruption of the first permanent tooth is known as the lactation period. The age of the milk tooth period, generally, is between 6 months and 6 years. At this stage, the enamel of milk teeth is thin, the dentin is loose and the mineralization is low, and children naturally like to eat sugar, which accelerates the decay of milk teeth (forming tooth decay and worm teeth) and gradually increases. Tooth decay to a certain extent will stimulate or infect the tooth pulp and cause pain. The methods of prevention and treatment are as follows: 1.Medication: It is applicable to the caries with extensive caries or cavity shape that should not be prepared, the commonly used medicine is 2% sodium fluoride, 75% fluorinated glycerin, repeatedly wipe, the affected teeth for 2-3 minutes, once or twice a week. 2.Filling treatment. Remove the cavity shape by removing the carious lesion, and fill the cavity with suitable oral filling material. Commonly used is glass ion filling material. 3.Open pulp treatment: The tooth with painful history indicates that the pulp has inflammation or necrosis, and the acute pain will be treated by oral surgeon to open pulp and reduce pressure. In short, if children have severe tooth decay pain, they must seek timely medical treatment.