Influence of Filler Load on Microhardness of Bis-GMA, UDMA and Bis-EMA-based Experimental Resin Composites

Objectives: The objective of this study was to evaluate the influence of 3 different filler loads on surface microhardness of Bis-GMA, UDMA and Bis-EMA-based experimental resin composites.
Methods: The organic matrix of experimental composites was prepared in a base monomer and co-monomer ratio of 60:40mol%. The base monomers used were Bis-GMA, UDMA and Bis-EMA with TEGDMA used as a co-monomer. The filler content constituted of silanated barium-glass fillers and Ox-50 silica fillers (90wt% and 10wt% respectively). Three different filler load:organic matrix ratio were used for each of the 3 base monomers: Low filled (50:50wt%), Medium filled (60:40wt%) and High filled (70:30wt%), to create a total of 9 experimental resin composites. Disk-shape molds (2mm thickness and 6mm diameter) were filled with the experimental resin composites (n=2). Top and bottom surfaces were covered with a Mylar strip and photoactivated on the top surface for 40s at 560mW/cm² irradiance with a light-curing unit. Samples were stored in dry, at room temperature and blocked from ambient light for 24h. Surface microhardness was measured with a microhardness tester using a Knoop diamond indenter under a 50g load with a dwell time of 10s. Three indentations were performed on each sample with a minimum of 1mm of distance between each indentation. For each base monomer, a One-Way ANOVA followed by a Tukey post-hoc test was performed to observe differences between the three filler loads.
Results: See Table 1.
Conclusions: Bis-EMA-based experimental composites benefitted from the increase in filler load, showing a progressive significant increment of surface microhardness from the lowest to the highest filler load evaluated.