Toothache two years after root canal treatment may be caused by incomplete treatment, incomplete removal of infected materials, hidden cracks in the tooth, etc. It can be treated by secondary root canal treatment, medication, extraction of the affected tooth, etc. The details are as follows: 1. Incomplete treatment: Insufficient filling or overfilling of the root canal will result in local inflammatory reaction, leading to toothache, at which time secondary root canal treatment is required. 2. Infected material is not completely removed: the number of root canals in posterior teeth is large, the shape is complex, the infected material may not be completely removed, and it is easy to have toothache after two years of root canal treatment. It is necessary to carry out root canal treatment again and take amoxicillin capsule and ibuprofen extended-release capsule orally for pain relief after the operation. 3. Hidden tooth cracks: after root canal treatment, the tooth is not braced, biting hard food may cause hidden tooth cracks, resulting in toothache, it is recommended to go to the hospital to check the teeth, cracked teeth are serious, can be extracted from the affected tooth. Root canal treatment after two years of toothache, it is recommended to visit the hospital in a timely manner, to clarify the cause of the disease, targeted treatment, to avoid delaying the condition.