A procedure performed on a tooth that has previously had root canal therapy but has failed to heal or has become infected again. The dentist removes the old filling material (gutta-percha), re-cleans the canals, and seals them again.
New decay can expose the old root canal filling to bacteria, or a "hidden canal" might have been missed the first time. Retreatment gives the tooth a second chance.
Typically once or twice. If it fails repeatedly, Apical Resection or Extraction is the next step.
No, it is performed under the same local anesthesia. It just takes longer.