Outcome of Endodontic Retreatment in One or Two Visits

This study is comparing whether root canal retreatment — redoing a previously failed root canal — works better when completed in one visit versus two visits. Root canal treatment sometimes fails, leaving infection at the tip of the root. When this happens, the tooth needs retreatment. There is ongoing debate about whether a one-visit approach (faster) is as effective as two visits (allowing time for disinfection between appointments). Participants will be followed over time after retreatment to compare success rates between the two approaches. You may be eligible if: - You are between 18 and 75 years old - You need retreatment of a previously failed root canal - You have been diagnosed with apical periodontitis (infection at the root tip) - The affected tooth has one or two roots You may NOT be eligible if: - You have systemic diseases, diabetes, or are immunocompromised - You are pregnant - Your tooth has root resorption, root fracture, or cannot be properly restored Talk to your doctor to see if this trial is right for you.