The effect of temperature on the viscoelastic properties of nano-hybrid composites

Objectives The purpose of this study was to examine the viscoelastic properties of nanofilled dental composites under both static and dynamic testing and to determine the influence of temperature, medium of storage and storage time. Methods Three nanofilled composites, one packable and one ormocer were tested. The specimens were examined dry at 21 °C and wet at 21, 37 and 50 °C after being stored for 24 h and 1 month under both static and dynamic testing. Shear modulus, elastic modulus, loss tangent, Poissonʹs ratio and other viscoelastic parameters were calculated. Data were analyzed with one-way and two-way analysis of variance (ANOVA) (p = 0.05). Results All materials tested showed a significant decrease in their moduli with the increase of temperature, while the effect of water storage was different among the composites. Grandio was the composite with the highest Youngʹs modulus followed by Filtek P60. Significance Most of the materials tested did not have elastic moduli near to that of dentin, making them less satisfactory in posterior restorations. The materials possessing nano-sized filler particles had different elastic properties among them and this implies that filler size is not the only factor that affects the elastic behavior of dental composites.