A four-week-old baby with cavities indicates a situation of tooth decay. Some parents may think that the child’s milk teeth will fall out sooner or later, and even if there are cavities, they do not need to be treated, which is incorrect, and if they do not pay attention to it, it will easily affect the chewing function and even jaw bone development. If a cavity is found, parents should take their children to a dental hospital in time to terminate the cavity’s continued development and be given appropriate treatment by a professional dentist according to the situation. If it has not progressed to the dentin, the cavity needs to be removed by the dentist with a dental drill to remove the decayed tooth tissue, and the tooth can be subsequently filled with composite resin, glass ionomer or a mixture of the two. When the child’s tooth decay has been more serious, exposing the nerve of the tooth or causing pulp disease or periapical disease, and there are already symptoms of pain and swelling, parents should promptly take the child to the dental hospital to remove the pulp after local anesthesia, disinfect the root canal and complete the root canal treatment. If the caries has been very serious, parents should take the child to the hospital to extract the baby teeth and wait for the replacement of permanent teeth, the back teeth also need to install the gap retainer after the extraction. After the treatment, parents should correctly guide the child to develop good oral hygiene, eat less sweets, rinse the mouth in time after meals, insist on brushing the teeth in the morning and evening, and can use fluoride toothpaste for the child, but the amount of toothpaste should be controlled in the range of the size of a soybean, and take the baby to the hospital for dental examination regularly to prevent the recurrence of tooth decay.