In our daily work in the dental department, a large percentage of patients need root canal treatment. Many times I hear patients ask: “Doctor, I have already treated this tooth twice, how many more times do I need to finish it?” Some patients ask, “Doctor, it’s been a week since my tooth was treated, but why does it still hurt?” . In fact, patients ask this question because they do not fully understand the complexity and limitations of root canal treatment. It is true that root canal therapy has a wide range of applications and is very effective in most cases, but it is not a panacea. The following is an introduction to some of the more common concerns. How many root canals are needed? According to the traditional root canal treatment trilogy (i.e. root canal preparation, root canal disinfection and root canal filling), three root canal treatments are usually required. However, this is only a theoretical situation, but in practice it varies from patient to patient, from tooth to tooth, and from doctor to doctor depending on their skill level. Modern endodontic techniques have evolved by leaps and bounds, and some root canals can even be completed in one visit. However, it is necessary to consider whether the patient is able to tolerate this technique, because the one-time operation is relatively long and causes relatively more discomfort to the patient, and whether the patient’s cooperation is sufficient, which requires the discretion of the doctor. For anterior and posterior teeth, there is a difference in the difficulty of root canal treatment, the more backward the tooth is, the more difficult it is. The length, narrowness, curvature, etc. of the root will also have an impact on the number of root canal operations. Again, technical details are a factor that cannot be ignored. Second, why is there sometimes a period of pain after root canal treatment? During and after root canal treatment, there may be some minor painful discomfort. In most cases, it is a normal reaction of the body to the treatment process and is not a cause for concern, and usually recovers on its own. In some cases, relatively severe pain may be caused by the irritation of the sealant or by the inflammation of the root itself, which is provoked during the treatment process and can be resolved with appropriate symptomatic treatment. However, if there is a long-lasting pain that cannot be reduced, attention must be drawn to it. How long do I need to observe after root canal treatment? Most of the teeth after root canal treatment require crown restoration (i.e., crowning). Before crown restoration, the tooth needs to be observed for a period of time to eliminate adverse reactions and determine the healing of inflammation and make an assessment of the efficacy. For patients with no apical inflammation and very mild postoperative reactions, they may only need to be observed for 2-3 weeks before proceeding to the next step of treatment; however, for patients with very significant apical inflammation, they should be observed for at least 3 months. Some patients may feel that 3 months is too long, but in fact, the World Health Organization (WHO) has set the observation period at 2 years after surgery. Because even a very good root canal treatment has the same possibility of failure, observation is very necessary. Fourth, what conditions are not suitable for root canal treatment? If the patient is not in good physical condition to tolerate such a complicated treatment process, then root canal treatment will naturally not be carried out and some other means can only be used to preserve the affected tooth. Sometimes the condition of the tooth is too poor, such as the inflammation is too extensive, the tooth is significantly loose, the tooth is deeply split, and the tooth is in an abnormal position that prevents it from functioning, then there is no point in doing root canal treatment for these teeth, and it is generally not recommended to preserve them. Root canal treatment is also generally not performed during pregnancy, and if treatment is necessary, it is usually only symptomatic during the 4th-6th months of pregnancy, and then complete treatment is performed after the pregnancy is over. Some children’s teeth are still underdeveloped and if they are damaged during this time other treatments may be used to encourage root development before root canal treatment is performed. The above is a brief list of some of the problems that we often face in root canal treatment, but this is only a general situation. Please criticize and correct any inadequacies.