Root canal treatment is a kind of filling. When there is a deep carious cavity in the crown of a tooth, a fractured tooth, etc. that causes pulpitis or the occurrence of periapical periodontitis, it is necessary to extract the infected and swollen crown pulp and root pulp under local anesthesia, and prepare the root canal into a conical lumen, which is thoroughly rinsed using hydrogen peroxide solution or sodium hypochlorite solution, and then sealed with disinfecting medication, such as calcium hydroxide or camphorated phenol, after drying. After one week, if the tooth has no obvious pain and there is no large amount of exudate in the root canal, root canal filling can be performed. In addition to root canal treatment, fillings can also repair cavities, hidden fissures, and wedge-shaped defects.