Color and translucency of A2 shade resin composites after curing, polishing and thermocycling.

This study determined the differences in values and changes of color and translucency of eight brands of A2 shade resin composites after curing, polishing and thermocycling (TC). The color of specimens 10-mm in diameter and 2-mm thick was measured on a reflection spectrophotometer with SCE geometry under D65 illumination over a white and black background. Measurements were obtained before curing, after curing, after polishing and after TC. The color change (deltaE*ab), translucency parameter (TP) and contrast ratio (CR) were then compared. The range of deltaE*ab after curing was 3.8 to 10.2 (average deltaE*ab for the eight composites = 6.4), which was deemed perceptible to the observer. Polishing caused deltaE*ab of 1.9 to 4.5, which was perceptible in five of the eight composites. After 2,000 TC, deltaE*ab was 0.4 to 1.3. TP values tended to increase after curing and decrease after TC (range before curing was 7.1 to 17.2). Changes in TP values after curing were statistically significant in all composites (p<0.05). Changes in CR values were similar to the translucency changes in TP. Though the composite shades were all designated as A2, color coordinates, TP and CR values, changes in color and translucency after curing, polishing and thermocycling varied by brand.