Effect of Nanofiller Loading on Cure Efficiency and Potential Color Change of Model Composites

Objectives To evaluate the effect of nanofiller loading on cure efficiency and potential color change of experimental composites. Materials and Methods Four different polymeric materials were produced using the same organic matrix blend. To this matrix, different amounts of 0.05 μm fumed silica filler were added: no filler, 13, 52, and 65wt%. Fourier transform infrared spectroscopy was used to evaluate the degree of conversion (DC) for each composite using near-IR analysis, and spectrophotometry according to CIELab chromatic space was used to evaluate the color change.To induce color change, composites were artificially aged with exposure to cycles of UV-B light for 300 hours. Trasmission electron microscopy was used to illustrate nanoffiler aglomeration in the resin matrix. Data were analyzed using correlation analysis (α = 0.05). Results There was an excellent inverse linear correlation between filler wt% and either DC or color change. Greater changes to red (+Δa) and yellow (+Δb) were observed as the filler wt% increased. Conclusions A higher percentage of nano-sized filler particles in dental resin composites directly affects their cure efficiency and potential for color change. Clinical Significance The increase in filler particle loading negatively affected monomer conversion and color stability of resin-based composites. As reduced filler loading results in poorer mechanical properties, to enhance color stability, resin-based composites should be formulated by making the refractive index of the polymeric matrix more closely match that of the filler throughout the polymerization process.