Root canal treatment, commonly known as nerve extraction and root poisoning, is a procedure in which the dentist opens the diseased tooth, removes the inflamed and necrotic pulp tissue from the tooth with various instruments, disinfects and cleans the pulp cavity (including the pulp cavity wall), and finally seals the pulp cavity tightly with dental cement and other materials. The endodontic treatment is not always completed in one visit, but is often carried out step by step according to the clinical examination of the patient, and is generally completed in 2-4 visits. During or after the root canal treatment, there may be a short period of discomfort, including swelling, stuffiness or slight pain, which is normal. The discomfort will usually subside after three days and normal sensation will return. If, after three days of root canal treatment, there is still discomfort or abnormal pain, the patient should contact the treating physician for further treatment adjustment; 4. After root canal treatment, the dentist will usually instruct the patient to perform a re-examination within a certain date, and the patient should strictly follow the physician’s regulations for regular checkups; 5. In some patients with chronic periapical inflammation, the apical inflammation of the lesion at the time of treatment is in resting state, or have just had a tendency to have an acute attack, with no obvious self-conscious symptoms and only slight percussion pain at the time of consultation. If the patient has low resistance and does not take anti-inflammatory drugs in time after treatment, acute inflammation will occur and pain will be felt. If the patient’s resistance is strong and he takes anti-inflammatory drugs in time after treatment, and does not overexert himself, then, in general, the pain will not be caused, and he can go to the hospital in time to do open drainage and local physical therapy with oral anti-inflammatory drugs, and he will recover soon; 6. Tooth fracture, prolong the life of the tooth.