Effect of surface conditions on the color of dental resin composites

The objectives of this study were to evaluate the effect of surface conditions of dental resin composites on the measured color depending on the measuring geometry (SCE, SCI), and to determine the color difference (DeltaE*) caused by varied surface conditions. Color and surface roughness (Ra) of five brands of resin composites of A2 shade were measured after polymerization and polishing with 600-, 1000-, or 1500-grit SiC paper. Color was measured according to the CIE L*a*b* color scale. DeltaE* between different surface conditions was calculated by the equation DeltaE* = [(DeltaL*)(2) + (Deltaa*)(2) + (Deltab*)(2)](1/2). Before polishing, CIE L* values with the SCE were significantly lower than those measured with the SCI. Before polishing, DeltaE* values depending on the measuring geometry were very high (3.78-5.93). However, those after polishing were lower than 1.61. CIE L* values increased after polishing (p < 0.05) with the SCE; however, they were not changed with the SCI. DeltaE* values between Mylar-covered and 600-grit polished specimens were 4.20-5.99 with the SCE and 0.27-1.46 with the SCI. Measurement with the SCE geometry may result in accurate color determination, which reflects the surface conditions of dental restorative materials. DeltaE* values measured with the SCE between the specimens of different surface conditions were significantly higher than those with the SCI (p < 0.05).