Color characteristics of low-chroma and high-translucence dental resin composites by different measuring modes

The objective of the described research was the evaluation of the effects o f the differences in the color-measuring geometry (SCE, SCI) and the standa rd illuminant on the color and color change after polymerization and thermo cycling of resin composites. White, translucent, and conventional shades of two brands of resin composites were measured before and after polymerizati on and after thermocycling according to the CIE L*a*b* color scale on a ref lection spectrophotometer with SCE and SCI geometry under the standard illu minants A, D65, and C. Under both SCE and SCI modes, the color differences (DeltaE*) of specimens between the values measured under illuminants A and D65 or A and C were larger than those between D65 and C in unpolymerized, p olymerized, and thermocycled conditions. With SCE geometry, DeltaE* after p olymerization of the white shade group was 8.7-9.8 under D65, and was highe r than the conventional shade group (p < 0.05) in both materials. With SCE geometry, DeltaE* between polymerized and thermocycled white, translucent s hade was 4.4-7.1 under D65. With SCI geometry, the results were in general agreement with those of SCE mode. After polymerization, DeltaE* measured un der illuminant A was generally higher than that under D65 or C (p < 0.01). After thermocycling, the color change was different depending on the color- measuring geometry and standard illuminant. (C) 2001 John Wiley & Sons, Inc .