Esthetic restorative material shade changes due to photopolymerization

This study sought to measure color values (before and after photopolymerization) and variations of A1 shade polymeric dental restorative materials. The L*a*b* values of polymeric dental restorative material disks were measured by a spectrophotometer with the specular component excluded (SCE) geometry under D65 illumination over a standardized white background before and after photopolymerization. Color differences (DeltaE*ab) due to polymerization were calculated using the CIE Lab color-difference formula. DeltaE*ab indicates differences between two colors in the L*a*b* color space. In this system, L*, a*, and b* indicate lightness, red-green, and yellow-blue, respectively. Color differences (DeltaE*ab) were calculated by the equation DeltaE*ab = [(DeltaL*)2 + (Deltaa*)2 + (Deltab*)2]1/2. Eight resin composites, three flowable resin composites (FRCs), and two resin-modified glass ionomers (RMGIs) were utilized; L*a*b* and DeltaE*ab values of the test groups were analyzed using ANOVA and Newman-Keuls multiple comparison tests. DeltaE*ab values before and after photopolymerization ranged from 3.01-17.76. All RMGI and two FRC materials displayed greater color changes than the resin composites (p < 0.05). Photopolymerization produced measurable increases and decreases in lightness. Yellow-blue (b*) values decreased in all test groups after polymerization, while most red-green (a*) values increased. Color differences between polymerized A1 shade materials ranged from 0.76-25.41 DeltaE*ab. The color difference between the test materials and a widely used tooth shade guide (the Vita Lumin) was averaged at 12.66 DeltaE*ab.