Mechanical behavior and reinforcement mechanism of nanoparticle cluster fillers in dental resin composites: Simulation and experimental study

In dental resin composites (DRCs), the structure of fillers has a great impact on the mechanical behavior. The purpose of this study is to gain an in-depth understanding of the reinforcement mechanism and mechanical behavior of DRCs with nanoparticle clusters (NCs) fillers, thereby providing a guidance for the optimal design of filler structures for DRCs. This work pioneers the use of discrete element method (DEM) simulations combined with experiments to study the mechanical behavior and reinforcement mechanism of DRCs with NCs fillers. The uniaxial compressive strength (UCS) of NCs-reinforced DRCs have an improvement of 9.58 % and 15.02 % in comparison with nanoparticles (NPs) and microparticles (MPs), respectively, because of the ability of NCs to deflect cracks and absorb stress through gradual fracturing. By using NCs and NPs as co-fillers, the internal defects of DRCs can be reduced, resulting in a further improvement of UCS of DRCs by 6.21 %. Furthermore, the mechanical properties of DRCs can be effectively improved by increasing the strength of NCs or reducing the size of NCs. This study deepens the understanding of relationship between filler structure and mechanical behavior in DRCs at the mesoscale and provides an avenue for the application of DEM simulations in composite materials.