The effect of aging on the mechanical properties of nanohybrid composites based on new monomer formulations

Abstract

Nanohybrid resin-based composites (RBCs) containing new types of matrix monomers such as dimer acid-based dimethacrylate or tricyclodecane-urethane are assumed to show decreased water uptake and therefore better resistance to hydrolytic degradation than RBCs using bisphenol A diglycidyl methacrylate (BisGMA) due to their hydropobic nature. Our study aimed to analyze the effect of aging on six nanohybrid RBCs, of which two are using these new types of monomers, with regard to differences in the mechanical properties of the materials. Diametral tensile strength (DTS), Vickers hardness (HV), and creep were measured. Mechanical tests were performed after storing samples for 24h in distilled water, as well as after aging (thermocycling for 5,000 cycles at 5-55°C and storage for 4weeks either in distilled water, artificial saliva, or ethanol). The effect of aging on all test parameters was lower than the effect of the material. This information was provided by a general linear model, showing higher partial η(2) values for the influence factor material than for the factor aging. The influence of aging on the micromechanical properties HV and creep was proven to be more sensitive than on the macromechanical property (DTS). This was also illustrated by lower η(2) values for the variable aging for DTS. An increase of the creep of all materials was observed after storage in alcohol. The use of new types of monomers could not be shown to be a significant advantage to the other examined materials containing BisGMA. Nanohybrid composites can be recommended as universal filling materials, whether based on new or conventional monomers.