Root canal treatment is a process of removing the infected material from the root canal and tightly filling the root canal to isolate the bacteria from entering and reinfecting it, preventing the apical inflammation from producing lesions or promoting the healing of the original lesions. Root canal treatment is one of the most thorough treatments for pulpitis, periapical inflammation, etc. The common reasons for this are: 1. Filling materials: Nowadays, there are more and more root canal filling materials, and for different human characteristics, each material produces The effect is also different. Before the root canal treatment, the doctor should first conduct a comprehensive examination of the patient to understand in a timely manner some of the patient’s allergic reactions and so on. In this way, when choosing the root canal filling material, you can avoid choosing the material to which the patient has an allergic reaction, and, this can not only improve the success rate of root canal treatment, but also reduce the pain of the patient. 2, oral problems: that is to say, before the root canal treatment, oral diseases still exist, simply did not get an effective eradication treatment. Because in the treatment, may be due to improper operation of the doctor, resulting in disease bacteria are not well removed. After the root canal treatment, instead, the bacteria spread everywhere, so that is why the severe pain is produced. 3.Improper operation: In many cases where the tooth is still painful after root canal treatment, some of them are caused by the failure of root canal treatment due to the lack of professional skills of the doctor. For example, it is common that after the root canal treatment, the length of the root canal is not the same, and the friction with the real tooth tissue part occurs regularly, which leads to some inflammation. This can also cause bacteria to develop, leading to complete failure of the root canal treatment and the need to redo it again. Toothache after root canal treatment can usually be relieved by taking anti-inflammatory or painkilling medication, and local swelling and pain should be informed to the doctor for treatment. It is also reminded that root canal treatment must be done in a regular hospital so as to avoid reducing the occurrence of toothache after root canal treatment.