Multiaxial strength and stress forming behavior of four light-curable dental composites

The resulting internal stress situation in curing dental composites is still oversimplified due to analytical inaccessibility of local information of state and loading. Similar applies to the strength behavior of cured dental composites. Using recent progress of a finite-element-based curing model, we developed and attempted to benchmark dental composites based on their mechanical behavior and tendency to form internal stress. Additionally, in order to understand the influence of restoration techniques on the mechanical loading, curing simulations were necessary. Three-point flexural strength, compressive strength and diametral tensile strength and the necessary curing parameters were studied for four state-of-the-art dental composites (Tetric EvoCeram, Venus Diamond, EsthetX, Filtek Supreme XT). The investigated composites fracture can be analyzed by the Drucker Prager failure criteria for each composite. The lowest resulting curing stresses were found for Tetric EvoCeram because of its low volumetric shrinkage and a high ratio of initiation phase to dark phase conversion. Venus Diamond showed the best overall mechanical properties because it can withstand tensile as well as compressive stress. In order to draw conclusions on comparisons between several composites, flexural strength tests, volume shrinkage measurements, cavity classifications and general preparation recommendations may still be a suitable way for the simplification of the immense complexity in curing and restoration. Nevertheless, finite-element-based simulations are necessary to include fundamental effects such as stress relaxation by flow and multiaxial strength of the composite.