A tooth with an old root canal might become painful because of an infection in the root, salivary contamination has occurred, the tooth has decayed since the root canal was performed or the tooth has been fractured, according to the American Association of Endodontists. Some root canals last for the rest of the patient's life while others fail within weeks, months or years of treatment.
The most common symptom of a failed root canal is pain in the tooth that does not go away after several days. This usually indicates an infection in the root of the tooth, according to 1800 Dentists, and treatment from a dentist or endodontist is necessary to treat it.
In some cases, root canals can be corrected years after the original treatment was performed. Essentially, the dental professional performs the root canal procedure again, including removing the original post and reshaping the canals from the root of the tooth.
It is not always possible to rescue a tooth in which a root canal is failed. If the root is too damaged, the dentist or endodontist may suggest removing the tooth entirely. While tooth extraction is not the preferred solution for most patients, it might be the only way to eliminate the pain and to protect the surrounding teeth.