Mr. Li, a patient in Henan, was recently treated at a local hospital for a painful maxillary molar and was told by his doctor to undergo root canal treatment (commonly known as nerve extraction), but he was worried that the local treatment would not be effective and went to the Union Hospital of Tongji Medical College of Huazhong University of Science and Technology. So why does a toothache need root canal treatment and what is the treatment procedure? In clinical practice, there are many causes of toothache, but the most important is the inflammation of the pulp (commonly known as the dental nerve) and the tissues around the root tip of the tooth. Currently, root canal therapy is the treatment of choice for pulp and apical infections. Root canal treatment is to completely remove the infected material from the pulp and around the root tip, and disinfect the nerve canal before filling the nerve canal tightly with materials that are not harmful to the body and repairing the defective tooth to restore the chewing function. Root canal treatment is more complicated and includes treatment procedures such as pulp opening, root canal preparation, root canal disinfection and root canal filling. Patients usually need to visit the hospital several times, which takes a lot of time and effort, and for out-of-town patients like Mr. Li, it is difficult to complete the treatment. For this reason, Mr. Li asked: Can root canal treatment be completed in one visit? In order to facilitate the patient’s visit, our department summarized the experience of domestic and foreign root canal treatment and carried out one-time root canal treatment, which greatly facilitated the patient’s treatment and completed the root canal treatment in one visit, without the need for follow-up. So is all patients who come to the hospital suitable for one-time root canal treatment? The answer is no, not all patients with pulpal or apical inflammation are suitable for one-time root canal treatment, some patients are not suitable for one-time root canal treatment during acute suppurative inflammation such as acute periapical abscess, when the affected tooth has severe percussion pain, or when there is a lot of fluid exuding from the root canal and cannot be dried immediately. In addition, one-time root canal treatment is not suitable for old and weak people or those who cannot tolerate long time operation, as well as those with extremely curved, calcified or obstructed root canals. It requires accurate measurement of the root canal length, as well as the availability of instruments and equipment, such as a nickel-titanium preparation instrument, a rubberized waterproof barrier, and the appropriate supplies.