A lump underneath a bad tooth needs to be treated according to its cause, such as inflammatory swelling, cyst, enamel cell tumor, etc. After a clear diagnosis, medication, crown restoration, root canal treatment, surgical treatment, etc. are chosen. 1. Inflammatory swelling: there is a lump underneath the bad teeth may be due to more serious inflammation of dental caries, so the formation of localized swelling. Treatment can follow the medical advice to choose to take anti-infective drugs, such as metronidazole, cefdinir, amoxicillin. Secondly, the caries can be filled, if necessary, can choose to root canal treatment after the crown repair. 2. Cysts: If there is a lump underneath the bad tooth belonging to keratocysts and apical cysts, treatment can be taken according to the size of the cyst. Small cysts can choose root canal treatment, regular observation of cyst changes; large cysts need root canal treatment, then with apical surgery. 3. Enamel cell tumor: enamel cell tumor can also lead to the phenomenon of a pimple under the bad teeth, the treatment can choose to scrape the local, or open the window decompression, prompting the tumor to become smaller. If the invasion to the alveolar bone, you need to extract the local teeth, root canal treatment of the surrounding teeth, and then with the surgical removal of the tumor. There are many reasons why there is a lump underneath the bad teeth, and after the symptoms appear, it is recommended to go to the hospital in time to improve the examination and choose standardized treatment after a clear diagnosis, so that you can’t ignore the symptoms and take them lightly. The above drugs need to be used in a standardized way under the guidance of a doctor.