In vitro comparison of compressive strength of bulk-fill composites and nanohybrid composite

Objectives: The objective of this study is to measure and compare the compressive strength of two bulk-fill posterior composites (Smart dentin replacement or SDR and Filtek bulk fill) with universal nanohybrid composite (Filtek Z 250XT). Materials and methods: In this in vitro study, three different types of posterior composites are used as follows: Group 1 – SDR (Dentsply, Konstanz, Germany); group 2 – Filtek bulk-fill (3M ESPE, St. Paul, MN, USA); group 3 – Filtek Z-250XT (3M ESPE, St. Paul, MN, USA). Ten cylindrical samples of 6 mm height and 4 mm diameter in each group were made using a split brass mold. The composites filled in the brass mold were photopolymerized using light-emitting diode (LED) light-curing unit and the cured samples were stored in water at 37°C for 48 hours before testing. The compressive strength of the stored samples was tested using universal testing machine (Instron 3366, UK) at a cross-head speed of 0.5 mm/minute. The compressive strength was calculated by dividing the maximum load with area of the samples. Results: Results are statistically analyzed using one-way analysis of variance (ANOVA) with Tukey’s post hoc test. Analysis showed that SDR and Filtek bulk-fill have greater compressive strength than Filtek Z-250 (p < 0.05). However, there is no statistical difference between compressive strength of SDR and Filtek bulk-fill composites (p > 0.05).