Changes in color and color parameters of dental resin composites after polymerization

The objectives were to measure the color change of varied shades of dental resin composites after polymerization, and to determine the correlation among the polymerization color change and the changes in color parameters after polymerization.

Eight light-curing resin composites, a total of 41 shades, were studied. Color of specimens (1 mm in thickness) was measured on a reflection spectrophotometer before and after polymerization over a white background. Changes in color (Delta E*(ab)), and color parameters (Delta L*, Delta C*(ab), Delta a*, and Delta b*: value after polymerization - value before polymerization) were calculated.

The range of changes in each shade of resin composites was 1.1-7.9 for color (Delta E*(ab)), -7.5 to 2.3 for Delta L*, -6.8 to 3.1 for Delta C*(ab), -0.9 to 1.2 for Delta a*, and -6.8 to 3.1 for Delta b*. Delta E*(ab), Delta L*, Delta C*(ab), Delta a*, and Delta b* were influenced by the brand and shade of resin composites, and there was a significant interaction between two independent variables (p < 0.05). On the basis of the multiple regression analysis, in which Delta E*(ab) after polymerization was set as a dependent variable and Delta L*, Delta C*(ab), Delta a* and Delta b* as independent variables, multiple correlation coefficient (r) was 0.842 and the included predictors were Delta L* [standardized partial correlation coefficient (beta) = -0.760] and Delta C*(ab) (beta = -0.715). This result indicated that the polymerization changes in color and color parameters were varied by the brand and shade of resin composites, and the polymerization color change was caused by the changes in lightness and chroma with the similar power of influence.