Influence of TiO2 nanoparticles on the optical properties of resin composites

Abstract

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 μm) 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 (ΔE*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 × 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 ΔE*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.