It is relatively common for endodontitis to still hurt after a root canal. These problems can occur if the root canal was not done very thoroughly. If the pulp is not cleaned out, it means that there is still infected material present in it, and inflammation can easily develop later on. If the root canals are missed, for example, there are often four root canals MB2 in the maxillary six, and two in the mandibular distal center are often missed, and inflammation can occur if the root canals are not thoroughly cleaned. Inflammation can also occur if the root canals are not cleaned thoroughly. If the patient’s body resistance drops or if he/she is tired, inflammation can easily occur. After root canal treatment is done, an apical film will be taken to clarify the situation of root filling and whether it is in place. In many cases, many patients have under or overfilling problems, which may not show up at the time, but after a period of time, pain may occur. If the pain is not relieved after a long period of time, the root canal can only be redone again. Another thing is that the tooth is prone to splitting, because the treated tooth has no neurovascular nutrient supply, and it is easy to become very brittle, so that it is easy to chip off when biting hard things.