In this study, the researchers will evaluate the effect of three highly biocompatible materials-TheraCal PT (ThPT), Biodentin, and MTA-on postoperative pain in permanent teeth affected by deep caries and symptomatic irreversible pulpitis. Participants: The study will include 51 participants aged between 18 and 45 years who are systemically healthy. Methodology: Pulpotomy Procedure: Pulpotomy will be performed on the lower first molar tooth of each participant. The teeth will be randomly divided into three groups, with 17 participants in each group. Coronal pulp tissue will be removed using a high-speed sterile diamond bur. Hemostasis will be achieved by applying gentle pressure with a cotton pellet soaked in 2.5% NaOCl, and this procedure may be repeated up to three times (totaling 6 minutes) if necessary. Use of Biocompatible Materials: After achieving hemostasis, one of the three biocompatible materials (TheraCal PT, Biodentin, or MTA) will be applied to the canal access. Participants will be prescribed NSAIDs. Pain Assessment: Preoperative Assessment : The pain intensity of participants will be recorded before treatment. Postoperative Assessment : Participants will report their pain intensity at the 6th, 24th, 48th, and 72nd hours and on the 7th day using the Visual Analogue Scale (VAS). Participants will return with their VAS charts for evaluation at the end of one week. Comparative Analysis: The primary outcome will be a comparative evaluation of postoperative pain intensity values among the three different materials used in pulpotomy treatment. This study aims to provide valuable information on the effectiveness of various biocompatible materials in postoperative pain management and to contribute to improving clinical decision-making processes in endodontic treatments.