Aim: The research compares the fracture resistance of ultra-polyethylene fiber ribbon, fiber-reinforced resin composite EverX posterior, fiber-reinforced flowable resin composite EverX flow, and bulk fill flow posterior restorative material Tetric N-flow. Materials and Methods: 60 caries-free human mandibular molars have been utilized. The teeth have been mounted into acrylic blocks 1mm below the CEJ. Class I cavities, which were deep and wide, had been prepared in each tooth, measuring 4x4 millimeters. Teeth have been categorized randomly into 4 equivalent experimental groups (n=15) regarding restorative material. GI was restored with Ribbond®-Ultra with Tetric N-flow, GII, EverX Posterior, GIII, EverX Flow, and GIV, Tetric N-flow. The teeth have been kept in 20 milliliters of distilled water at 37C for 24 hrs. The restored teeth underwent thermocycling and fracture resistance testing utilizing a universal testing machine (Instron). The fracture resistance of groups has been compared utilizing the one-way ANOVA test also post-hoc test using Tukey's test. Result:  The fiber-reinforced bulk fill resin composite (EverX Posterior) showed the greatest fracture resistance, accompanied by the fiber-reinforced bulk fill flowable resin composite (EverX Flow), and the bulk-fill flowable resin composite (Tetric N-flow). The least fracture resistance was observed within teeth restored with polyethylene fiber ribbon and bulk-fill flowable resin composite (Tetric N-flow). Statistical analysis showed significant variance within the groups, excluding EverX Posterior and EverX Flow. Conclusion: The contemporary fiber-reinforced bulk-fill resin composites are efficient for reinforcing vital teeth against fracture, while utilizing polyethylene fiber ribbon may not hold similar efficacy, regardless of its time-consuming application.