The effects of different opacifiers on the translucency of experimental dental composite resins

The aim of this study was to evaluate the effects of different opacifiers on the translucency of experimental dental composite-resins.

Three metal oxides that are used as opacifiers were tested in this study: titanium oxide (TiO₂), aluminium oxide (Al₂O₃) and zirconium oxide (ZrO₂). Experimental composite-resins were fabricated containing 25wt.% urethane dimethacrylate (UDMA)-based resin matrix and 75% total filler including different concentrations of metal oxides (0, 0.25, 0.5, 0.75 and 1wt.%) blended into silane treated barium-silicate filler. The specimens (15.5mm diameter and 1mm thickness) were light-cured and tested in the transmittance mode using a UV/VIS spectrophotometer at wavelengths from 380 to 700nm under a standard illuminant D65. The color differences (ΔE* ab) between different concentrations of opacifiers were also measured in transmittance mode based on their Lab values.

Statistical analysis by ANOVA and Tukey's test showed a significant decrease (p<0.05) in light transmittance with the addition of opacifiers to the experimental composite-resins. There was a linear correlation between different concentrations of TiO₂ and Al₂O₃ and total transmittance. Total transmittance was also found to be wavelength dependent. The color differences for the concentrations of 0-1wt.% of the opacifiers were above 1 ΔE* unit, with Al₂O₃ showing the smallest color shift.

The type and the amount of the opacifiers used in this study had a significant effect on the translucency of the experimental UDMA-based dental composite resins. The most effective opacifier was TiO₂, followed by ZrO₂ and Al₂O₃ in decreasing order, respectively.