Gum decay at the root of the tooth may be caused by apical periodontitis, gingivitis, periodontal abscess, etc. The patient can incise and drain the pus, rinse with medication, and carry out root canal treatment to alleviate the symptoms. 1. Periapical inflammation: often secondary to endodontic disease, patients have toothache, biting pain, gum abscess and other symptoms, inflammation may lead to severe gum ulceration and swelling. For patients with purulent lesions, the first step is to incise and drain the pus or open the pulp, in addition, patients usually have to undergo root canal therapy to control the infection as well as repair the defect. 2. Gingivitis: a kind of inflammation limited only to the gum tissue, patients often have bleeding gums, pain, etc., local redness and swelling. When inflammation persists, gum decay may occur. Patients should thoroughly remove plaque and tartar, which can be accompanied by a 1% to 3% hydrogen peroxide solution rinse. Surgical treatment, such as gingivectomy and gingivoplasty, is required if necessary. 3. Periodontal abscess: It is a limited purulent inflammation in the periodontal pocket or deep periodontal connective tissue, patients may have symptoms such as red and swollen gums, loose teeth, etc. Some patients may have pus breakthrough and outflow. In the early stage of abscess formation, tartar should be removed, periodontal pockets should be flushed, and if there is pus formation, incision and drainage is required, and the pus cavity should be flushed with saline. In addition to the above factors, it may also be caused by other reasons, and it is recommended to seek timely medical treatment for standardized treatment.