Ozyurek T, et al. - This study was carried out with an aim of comparing the fracture strengths of mandibular molar teeth prepared using traditional endodontic cavity (TEC) and conservative endodontic cavity (CEC) methods and restored using SDR (Dentsply Caulk, Milford, DE) and EverX Posterior (GC Dental, Tokyo, Japan) base composite materials. Findings suggested that compared with TEC preparation, CEC preparation did not increase the fracture strength of teeth with class II cavities. The teeth restored with the SDR bulk-fill composite demonstrated higher fracture strength vs teeth restored with EverX Posterior.