Defining a natural tooth color space based on a three-dimensional shade system
Yuan, Judy Chia-Chun
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The natural tooth color space reported by a commercial company may not represent the comprehensive spectrum of natural teeth for all population groups. 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 commercial company. 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, and a 1-sample t -test was used to determine whether the color differences seen in the Buffalo population were statistically different from the perceptibility threshold, ΔE* = 3.7. A significance level of .05 was used for all tests. 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*, b* values of the 2 methods (p<0.001). A 1-sample t -test revealed a significant ΔE* (mean ΔE* = 6.15) difference from the perceptibility threshold of ΔE* = 3.7 (p<0.001). 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. Compensating for spatial differences may likely expand the options of shade selection for all populations. With the possible expansion of the natural tooth color space, this new generation of shade guides could bring clinicians closer to reliable shade selection and predictable definitive color matches in dentistry.