Novel nano-particles as fillers for an experimental resin-based restorative material

The purpose of this study is to compare the properties of two experimental materials, nano-material (Nano) and Microhybrid, and two trade products, Clearfil AP-X and Filtek Supreme XT. The flexural strength and modulus after 24 h water storage and 5000 thermocycles, water sorption, solubility and X-ray opacity were determined according to ISO 4049. The volumetric behavior (ΔV) after curing and after water storage was investigated with the Archimedes principle. ANOVA was calculated with p < 0.05. Clearfil AP-X showed the highest flexural strength (154 ± 14 MPa) and flexural modulus (11,600 ± 550 MPa) prior to and after thermocycling (117 ± 14 MPa and 13,000 ± 300 MPa). The flexural strength of all materials decreased after thermocycling, but the flexural modulus decreased only for Filtek Supreme XT. After thermocycling, there were no significant differences in flexural strength and modulus between Filtek Supreme XT, Microhybrid and Nano. Clearfil AP-X had the lowest water sorption (22 ± 1.1 μg mm−3) and Nano had the highest water sorption (82 ± 2.6 μg mm−3) and solubility (27 ± 2.9 μg mm−3) of all the materials. No significant differences occurred between the solubility of Clearfil AP-X, Filtek Supreme XT and Microhybrid. Microhybrid and Nano provided the highest X-ray opacity. Owing to the lower filler content, Nano showed higher shrinkage than the commercial materials. Nano had the highest expansion after water storage. After thermocycling, Nano performed as well as Filtek Supreme XT for flexural strength, even better for X-ray opacity but significantly worse for flexural modulus, water sorption and solubility. The performances of microhybrids were superior to those of the nano-materials.