Chronic periapical periodontitis is an inflammatory change around the root tip, secondary to endodontic disease, and is classified as chronic granuloma, chronic abscess, chronic cyst, periapical dense osteitis, and scarring of the periapical area. Clinical diagnostic indexes include: 1. questioning, asking the patient whether there is a history of pain onset, whether there is a history of treatment, and whether there is gum swelling; 2. examination of the dentition, such as whether there is deep caries, exposed pulp, and whether the pulp is vital; 3. percussion, there is no response to the examination of pulp vitality, and there will be percussion discomfort on percussion; 4. asking the patient whether there is pain or discomfort when biting, mainly looking at the gum on whether there is swelling or a fistula; 5, with the help of X-ray film examination, the X-ray film can obviously take the image of the transmissive area around the root tip, indicating that the bone around the root tip has inflammatory stimulation of resorption. To deal with the tooth early, the main treatment is root canal therapy, which completely removes the infection caused in the pulp of the tooth.