IRCT20210501051147N1 IRCT 2022-06-06 Islamic Azad University Evaluation of post-operative pain after three different supplementary irrigation protocol in non-surgical endodontic retreatment cases Clinical evaluation of post-operative pain in patients with single rooted teeth with apical periodontitis requiring non-surgical endodontic retreatment after three different supplementary irrigation protocol 2021-09-23 anticipated 48 Complete https://irct.ir/trial/58700 interventional Randomization: Randomized, Blinding: Single blinded, Placebo: Not used, Assignment: Parallel, Purpose: Prevention, Randomization description: For randomization all the patients assigned to one of the 3experimental groups using computer sourced random table (www.rando m.org) by a person who did not include in the study. Randomization group number and patient serial number was in the dark envelope which was opened prior to the treatment by the operator to identify which patient belonged to which group, Blinding description: Randomization group number and patient serial number was in the dark envelope which was opened prior to the treatment by the operator to identify which patient belonged to which group. Patient were acknowledged about the study and the devices were used but not aware which system was used among the experiment. N/A Post endodontic pain. Intervention 1: Intervention group: passive ultrasonic irrigation, noncutting tip of U-file ultrasonic tips, tip diameter 20 and taper 0.01%, activation for 20 seconds. Intervention 2: Intervention group: gentle file system finishing brushes, up and down movements, activation for 2 minutes. Intervention 3: Intervention group: XP-endo Finisher files, gentle 7-8 millimeter up and down movement, activation for 1 minute. Undecided - It is not yet known if there will be a plan to make this available Justification or reason for indecision in sharing IPD is no more information