This randomized controlled clinical trial evaluates the effect of different resin composite preheating protocols on pulpal inflammation and postoperative pain. Thirty patients with deep occlusal carious lesions (ICDAS scores 5 and 6) will be randomly assigned to three equal groups (n=10). Group I will receive thermoviscous bulk-fill composite (VisCalor, VOCO) preheated to 65°C and placed as a single 4-mm increment. Group II will receive conventional nanohybrid composite (Ivoclar Vivadent) preheated to 55°C and placed incrementally. Group III (control) will receive the same composite at room temperature (23°C) using incremental placement. Gingival crevicular fluid (GCF) samples will be collected at baseline, immediately post-treatment, and at 7-day follow-up. Tumor necrosis factor-alpha (TNF-α) concentrations will be quantified using ELISA. Postoperative pain will be assessed using the Visual Analog Scale (VAS) at baseline and day 7. The study aims to determine whether different preheating protocols differentially affect pulpal inflammatory status and whether GCF TNF-α correlates with postoperative pain.