Correlations between Color Differences Based on Three Color-Difference Formulas Using Dental Shade Guide Tabs

Purpose: The purpose of this study was to determine the correlation among color-difference values based on three formulas between shade tab pairs from two shade guides [Vita Lumin (VITA) and Chromascop (CHRO)]. Materials and Methods: The color of shade tabs was measured relative to the standard illuminant D(65) under the 8 degrees standard observer function, and distributions for CIE L*, a*, and b* values were compared. One hundred and twenty shade pairs from VITA and 190 shade pairs from CHRO were used to calculate color differences using CIELAB, DIN99, and CIEDE2000 formulas (Delta E*(ab), Delta E(99), and Delta E(00), respectively). A paired t-test was used to determine the difference between each pair of the three color-difference values (alpha = 0.01). Regression analysis was used to determine the correlations between the color differences (alpha = 0.01). Results: For both shade guides, there were significant differences between Delta E*(ab) and Delta E(00), (Delta)E*(ab) and Delta E(99), and Delta E(99) and Delta E(00) (p < 0.01). Delta E*(ab) and Delta E(00), and Delta E*(ab) and Delta E(99) were strongly correlated (r(2) = 0.90 to 0.94, p < 0.05). Although a simplified a* rescaling function of the CIE a* axis has been added in the CIEDE2000 formula, the influence of the opposite signs in the a* value were found to be irrelevant to the Delta E(00) value. Conclusion: Delta E*(ab), Delta E(99), and Delta E(00) can be used interchangeably for the evaluation of color difference of shade tabs.