Root canal therapy is currently a major clinical treatment for pulpitis and periapical periodontitis. It is important to go to a regular hospital for root canal treatment, which has no side effects after the procedure. However, no treatment has a 100% success rate, and the same is true for root canal treatment. The success rate of root canal treatment is about 90%, and about 10% of patients will experience tooth pain or inability to bite down on hard objects after root canal treatment. After root canal treatment, the tooth is deprived of blood flow and nerve nourishment, the tooth tissue becomes brittle and cannot withstand heavy biting forces, which may cause tooth fracture. Therefore, after root canal treatment, the tooth still needs to be protected by a crown, such as a porcelain crown or all-porcelain crown, to prevent the tooth from fracturing. If there is severe pain after root canal treatment, it may be due to pulpitis caused by the residual pulp nerve not being completely removed, and a new root canal treatment is needed in this case. If there is swelling and painful discomfort in the apical region of the tooth for a long time after root canal treatment, it means that the periapical inflammation has not been able to be completely eliminated, in which case apical surgery is recommended for treatment.