Keywords: عامل ضد التهابی غیر استروئیدی; Endodontics; analgesics; pain; flare-ups; randomized controlled trials; AB; Attrition bias; DM; Double masked; LSS; Low sample size; NSAID; Nonsteroidal anti-inflammatory agent; NSET; Nonsurgical endodontic treatment; PA; Periapical; RCT; Randomized contr