Root canal therapy involves tightly filling the root canal by removing the infected material from the canal, enlarging and shaping the canal, and giving it sterilization. Root canal therapy is a method used in dentistry to treat diseases such as endodontics and periapical disease. Doctors use professional instruments to clean, shape, disinfect and sterilize the root canals, and then tightly fill the root canals to control infection, prevent the occurrence of apical periodontitis, or promote the healing of existing periapical lesions. Main purpose: to control infection, repair damage, promote healing of periapical lesions, and prevent the occurrence of periapical disease. Applicable people: patients suffering from irreducible pulpitis, pulp necrosis, intradental resorption, apical periodontitis, traumatized teeth, transplanted teeth, re-implanted teeth, and so on. Contraindications: patients with severe periodontal or dental defects that cannot be preserved, and patients who are physically unable to tolerate surgical treatment or who have limited mouth opening. Root canal treatment is recommended to visit an authoritative medical institution for consultation and treatment.