Re-treatment, also known as root canal re-treatment, is performed when a previously treated tooth develops new infection or inflammation in the root canal system. This can occur for reasons such as incomplete removal of infected tissue during the initial treatment, the presence of hidden canals that were not treated or new infection introduced to the tooth.

Root canal re-treatment involves reopening the tooth, removing the filling material, cleaning the root canals again and then sealing the tooth to prevent further infection. In some cases, additional procedures such as apical surgery (surgery at the root tip) may be necessary if the infection persists despite re-treatment. This can be very effective but the outcome for re-treatments will be lower than first-time therapy.

In summary, conventional root canal treatment is performed initially to treat infected or damaged pulp, while root canal re-treatment is performed if the initial treatment fails or if new infection develops in a previously treated tooth. Both procedures aim to save the natural tooth and alleviate pain and discomfort associated with pulp infection or damage.