A randomized clinical trial to assess the efficacy of modified triple antibiotic paste and calcium hydroxide paste when used as an intracanal medication on postoperative pain in patients with symptomatic root canal treatment failure. Fifty participants diagnosed with symptomatic root canal treatment failure in anterior and premolar teeth were randomly assigned into two equal groups, according to intracanal medication used, either modified triple antibiotic paste (MTAP) or calcium hydroxide (CH).Root canal treatment was performed in two visits. During the first visit, access cavity, rubber dam application, removal of old root canal filling using ProTaper retreatment files, working length determination, chemo mechanical preparation with ProTaper universal rotary system and irrigation using 2.5% NaOCl were carried out. Application of intracanal medication then followed as randomly assigned. In the second visit, after one week, access cavity was re-opened, intracanal medication was removed using 20% citric acid and saline irrigation, and obturation was performed using cold lateral compaction technique with protaper gutta percha cones and resin sealer. Post operative pain was recorded using a numerical rating scale (NRS) at different follow up periods; at diagnosis, 6, 12, 24 and 48 hours.Results revealed that:1. There was no statistically significant difference in postoperative pain between the two groups regarding age, gender, tooth type and number of roots.