Development of mechanical properties in dental resin composite: Effect of filler size and filler aggregation state

摘要

The aim of this work was to study the effect of filler size and filler aggregation state on the mechanical properties of dental resin composites evaluated at filler loadings between 20 wt% and up to 76.5 wt%. Non-aggregated silica nanoparticles (SiNPMPS) (80 nm), doughnut-shaped silica nanoclusters obtained by spray drying (SDSiNPMPS) (3.5 mu m) and amorphous barium-alumina borosilicate microparticles (BaAlBoSi(MPS)) (1.0 mu m), functionalized by 3-methacryloxypropyl trimethoxysilane (MPS), were the fillers incorporated into resin matrix dental composites composed of triethylene glycoldimethacrylate (TEGDMA), urethane dimethylacrylate (UDMA), bisphenol A polyethylene glycol diether dimethacrylate (Bis EMA), and bisphenol A glycidyl methacrylate (BisGMA) (0.3:0.7:1:1 weight ratio, respectively). The mechanical properties developed in the resin composites were correlated with the formation of percolated-like particle networks, as observed by scanning electron microscopy (SEM), and volume fraction percolation thresholds (phi(c)) calculated from a percolation model. Resin composites with non-aggregated SiNPMPS showed an apparent percolation threshold phi(c) = 0.15 (i.e. 27 wt%); above this filler concentration and up to a volume fraction of particles (phi(p)) of 0.24 (i.e. 40 wt%) there was an increase in the flexural modulus and the compressive strength of the resin composite. However, a further increase in filler concentration diminished all its mechanical properties due to a decrease in the particle-matrix adhesion strength, demonstrated by the increase in surface roughness and fracture steps as observed by SEM images. On the other hand, a resin composite filled with doughnut-shaped silica nanoclusters (SDSiNPMAS) showed an apparent percolation threshold phi(c) = 0.41 (i.e. 60 wt%); increasing filler loading over this concentration generated an improvement in its mechanical properties, except the flexural strength also due to a decrease in the particle-matrix adhesio