Influence of TiO2 nanoparticles on the optical properties of resin composites.

Objectives: To determine the influence of titanium dioxide (TiO2) nanoparticle addition on the opalescence, color, translucency and fluorescence of experimental resin composites.

Methods: A light curing resin matrix was made by mixing 60 wt.% Bis-GMA and 40 wt.% TEGDMA. Silane coated glass filler (mean particle size: 1.55 microm) was added in the ratio of 50 wt.% of the resin composites. A fluorescent whitening agent was also added (0.05 wt.%). TiO2 nanoparticles (<40 nm) were added with the concentrations of 0, 0.1, 0.25 and 0.5 wt.%. Reflected and transmitted colors of 1 and 2 mm thick specimens were measured relative to the illuminant D65 with reflection spectrophotometers. Opalescence parameter (OP), color difference (DeltaE*ab), translucency parameter (TP), fluorescence parameter (FL), and fluorescence and opalescence spectra were calculated.

Results: For the 1 mm thick specimens measured with 3 mm x 8 mm rectangular aperture, when the concentration of TiO2 increased from 0% to 0.5%, OP increased from 2.4 to 18.0, TP decreased from 35.4 to 13.1, and fluorescence spectra remained unchanged. Color difference between these specimens was in the range of 3.4-6.6 DeltaE*ab units. OP values were significantly influenced by the thickness of the specimens and the configuration of the spectrophotometers (p<0.05).

Significance: Addition of TiO2 nanoparticles significantly increased the opalescence of resin composites while leaving the fluorescence spectra unchanged; however, it significantly decreased the translucency and also changed the color (p<0.05). Resin composites with 0.1-0.25% TiO2 nanoparticle would simulate the opalescence of human enamel.