Fracture Resistance and Surface Hardness of Different Posterior Proximal Tooth-Colored Restorations

Objectives: This study aimed to compare fracture resistance (FR) and surface micro-hardness (SH) of teeth restored using both conventional and bulk-fill resin composites (RCs). Materials and methods: One conventional RC and four bulk-fill RCs were used. For FR test, 75 healthy molars had proximal boxes made in them, and they were split into 5 groups at random (n=15). Each group was restored with one of these RCs following manufacturers’ instructions. All the specimens were finished, polished, and aged by 500 cycles of thermo-cycling before testing. By applying compressive force until fracture, FR was measured in Newton (N) using Instron Testing Machine (ITM). For SH test, 75 cylindrical discs were made by using Teflon mold (5 X 2 mm) between 2 glass slabs, finished, polished, and divided into 5 groups as before. Discs were subjected to 500 cycles of thermo-cycling and evaluated by Vickers Hardness Testing Machine (VHTM). Results: One-way ANOVA showed significant differences in FR and SH among all the different restorative materials. Conclusions: The conventional and bulk-fill RCs have incomparable FR and SH due to the differences in compositions.