A few years after the root canal treatment the tooth hurts again need to identify the cause of the disease and treat it, such as performing a secondary treatment of the root canal. Usually, root canals are used to treat chronic pulpitis, acute pulpitis, and pulp necrosis. The tooth is usually not in significant pain after root canal treatment, but there is no guarantee that the tooth will not be in pain after root canal treatment. If there is inflammation in the gums of that tooth, for example, the acute stage of periodontitis may cause symptoms of toothache after root canal treatment. Also, if the root canal is not very thorough, the tooth may be painful again after several years of root canal treatment, thus requiring the need to go through a secondary root canal. When a toothache occurs, you should visit a dental clinic immediately to clarify the cause of the problem and then treat it correctly under the guidance of a doctor.