Under normal circumstances, periodontally healthy teeth after perfect root canal treatment, usually will not appear inflammation, root canal treatment inflammation after the following common situations: 1, the existing medical technology defects, even if the perfect root canal treatment, the doctor did his best to clean up the root canal, but due to the natural complexity of the root canal, some places on the existing medical technology is not 100% clean, or each do root canal treatment However, due to the natural complexity of root canals, there are some areas that cannot be cleaned 100% with current medical technology, or each tooth that undergoes root canal treatment cannot be completely sterile. The root canal structure is complex, some root canals are thin and curved, and the lateral root canals are complicated, which makes it very difficult to clean them. Therefore, in addition to the mechanical preparation of root canal cleaning, the clinic also attaches great importance to root canal disinfection, such as chemical cleaning, laser disinfection, etc., to eliminate the infection in the root canal as much as possible; 2. After root canal treatment, the crown restoration is not timely and perfect, providing a way for bacteria to invade, and crown leakage can lead to root canal infection again.