Extensive Assessment of the Physical, Mechanical, and Adhesion Behavior of a Low-viscosity Bulk Fill Composite and a Traditional Resin Composite in Tooth Cavities.

OBJECTIVES: To compare the degree of conversion (DC), depth of polymerization (DP), shrinkage stress (SS), flexural strength (FS), elastic modulus (EM), and bond strength (BS) of a low-viscosity bulk fill resin composite and a paste-like traditional composite. METHODS: Tetric Evo-Flow Bulk Fill (TBF) and Empress Direct (ED; Ivoclar Vivadent) composites were used. DC (%) and FS/EM (MPa/GPa) were evaluated in bar specimens (7x2x1 mm; n=10) using Fourier-transform infrared spectroscopy and a three-point bending test in a universal testing machine (UTM), respectively. For DP and BS tests, conical cavities (n=10) were prepared in bovine dentin and restored with the composites. DP was analyzed by calculating the bottom-to-top surface microhardness ratio (BTHR), and BS (MPa) was determined by push-out testing in the UTM. SS (MPa) was measured for one increment of TBF and two increments of ED in a UTM attached to an extensometer (n=5). Data were analyzed using Student t-test and analysis of variance (alpha=0.05). RESULTS: TBF presented higher values than ED for DC (85.7+/-6.6% vs 54.2+/-4.9%) and BS (0.95+/-0.70 MPa vs 0.35+/-0.15 MPa). TBF values were lower than ED values for FS (76.6+/-16.8 MPa vs 144.9+/-24.1 MPa) and maximum SS (0.77+/-0.07 MPa vs 1.07+/-0.15 MPa). TBF and ED values were similar for BTHR (0.83+/-0.16 vs 0.84+/-0.08) and EM (11.5+/-2.8 GPa vs 12.5+/-2.6 GPa). CONCLUSIONS: The physical and mechanical properties of TBF, a bulk fill resin composite, were similar or superior to those of ED, a conventional composite, with the exception of FS measurements.