IRCT20130812014333N266 IRCT 2025-09-30 Islamic Azad University, Khorasgan Branch Comparison of the Effects of Low-Level Laser Therapy at 810 nm and 660 nm in Reducing Pain Evaluation and Comparison of the Effects of Low-Level Laser Therapy at 810 nm and 660 nm in Reducing Pain After Root Canal Treatment of Maxillary and Mandibular Premolar and Molar Teeth with Irreversible Pulpitis and Apical Periodontitis 2025-10-12 anticipated 28 Complete https://irct.ir/trial/86392 interventional Randomization: Randomized, Blinding: Double blinded, Placebo: Not used, Assignment: Parallel, Purpose: Treatment, Randomization description: Simple random method. 28 cards are selected and numbers from 1-28 are inserted on the cards. The cards are placed in an envelope. Two of the design partners take one card out of the envelope each time and announce the card number. Paired numbers are assigned to the intervention group and odd numbers to the control group, Blinding description: In this double-blind study, patients are aware of their participation in the study, but the researcher and participants are unaware of the type of laser. To maintain the two -blind conditions, the laser devices used in appearance and function sound were fully similar to that patients could not detect the type of laser. Disclosure tags and symptoms were hidden on the devices, and each device's settings were made by a technique that was neither associated with patients nor involved in evaluating the results. N/A Symptomatic apical periodontitis. Intervention 1: In the first intervention group, patients will receive a low-power laser with a wavelength of 810 nm in addition to standard endodontic treatment. Intervention 2: In the second intervention group, patients will receive a low-power laser with a wavelength of 660 nm in addition to standard endodontic treatment. No - There is not a plan to make this available Justification or reason for not sharing IPD is There is no further information