Use of a porcelain color discrimination test to evaluate color difference formulas

Statement of problem: The natural tooth color space reported by a manufacturer may not represent the comprehensive spectrum of natural teeth for all population groups. Purpose: The purpose of this study was to define a natural tooth color space within the Greater Buffalo, New York population and to compare that to the color space determined by a manufacturer. Material and methods: Nine hundred and thirty-three maxillary central incisors (501 patients) were measured with a shade-taking device (Vita Easyshade). For each tooth, L*, a*, b* values, chroma, hue, and the closest shade (Vita 3D-Master) were recorded. A linear regression analysis was performed to determine how well the manufacturer's values predict actual values for L*, a*, and b*. Color differences (ΔE*) between the Buffalo population and the closest shade were also calculated. A 1-sample t test was used to determine whether the color differences seen in the sample were statistically different from the perceptibility threshold, ΔE*=3.7 (a=.05). Results: All 3 attributes of the Buffalo population displayed a broader range than those from the shade guide. However, the regression analysis revealed a significantly positive relationship between the L*, a*, and b* values of the 2 methods (P<.001). The 1-sample t test revealed a significant ΔE* (mean ΔE*=6.15) difference from the perceptibility threshold of ΔE*=3.7 (P<.001). Conclusions: Color differences between the Buffalo population and the shade guide were frequently above published perceptibility thresholds, but within the range of acceptability. The Buffalo population tooth color space encompassed the manufacturer's color space.