I was told there is pus at the tip of a tooth that had root canal treatment. Does retreatment to save it work well?

Root canal retreatment is known to have a somewhat lower success rate than initial treatment, but it is a worthwhile way to save a natural tooth before resorting to extraction. It involves removing the existing filling material and re-disinfecting the source of inflammation inside the root, usually over 2 to 4 visits. If retreatment cannot resolve it, we consider 1) an apicoectomy, which surgically removes only the inflamed root tip, and 2) extraction followed by an implant if that is still not enough. However, if the root is cracked or bone loss is severe, extraction may be the better choice, so a thorough diagnosis comes first.