Translucency, opalescence and light transmission characteristics of light-cured resin composites

To evaluate the translucency, opalescence and light transmission characteristics of resin composites with different thicknesses.

Disks of three resin composites (Estelite∑, Beautifil II, Clearfil Majesty) of A2 shade were prepared in diameter of 10mm with various thicknesses (0.5mm, 1.0mm and 2.0mm). Color was measured according to CIELAB color scale on a reflection spectrophotometer and a color haze meter, and translucency parameter (TP) and opalescence parameter (OP) were calculated. Using the distribution graphs of transmitted light intensity on a goniophotometer, diffusion factor (DF) as an indicator for a diffuse transmission property and peak gain (G0) for a straight-line transmission property were calculated.

The TP and G0 values significantly decreased in the order: 0.5mm>1.0mm>2.0mm thickness (p<0.05). The OP value increased as the thickness of resin composite increased from 1.0mm to 2.0mm (p<0.05), while was similar for the 0.5mm- and 1.0mm-thick groups. The DF value increased from 0.5mm to 1.0mm, but was similar for the 1.0mm- and 2.0mm-thick groups. There was a significant correlation between TP and DF (R(2)=0.96, p<0.001). On the other hand, there was a weak correlation between OP and DF (R(2)=0.21, p<0.005), however within the values of the 0.5mm-thick group, OP was highly correlated with DF (R(2)=0.84, p<0.001).

At the 0.5mm thickness, the translucency (TP) and opalescence (OP) of resin composites had a significant correlation with a diffuse transmission property (DF). When more than 1.0mm thickness of resin composites, translucency and opalescence were influenced by the thickness, in which translucency significantly decreased and opalescence significantly increased.