If a tooth with RCT is symptomatic and has a radiolucency in one of the canals, how should it be treated?

When a tooth that has undergone root canal treatment (RCT) presents with symptoms and a radiolucency in one of the canals, retreating all the canals is the most appropriate course of action. This approach is essential because the presence of symptoms and a radiolucency indicates that there may be ongoing infection or insufficient treatment that could involve multiple canals.

Retreating only the symptomatic canal may not sufficiently address the underlying issue, as there could be untreated or inadequately cleaned canals that contribute to the radiolucency and persistent symptoms. Each canal must be thoroughly evaluated and treated to ensure complete removal of potential pathogens and to adequately fill each space, thus promoting healing and resolution of the symptoms.

Furthermore, filling a canal retroactively or performing vital pulp therapy would not be appropriate in this scenario since retreatment is necessary due to the existing symptoms and radiographic findings. Vital pulp therapy is reserved for teeth where the pulp is still alive and remains asymptomatic, which is not the case here.