Coverage Error of Three Different Shade Guides in a Japanese Population

Objectives: The purposes of this investigation were to determine and to compare the coverage errors (CE's) of three conceptually different shade guides when selecting anterior tooth shades for a Japanese population. The CE's of the following were evaluated: (1) Vita Lumin, (2) Chromascop, (3) Vitapan 3D Master, and (4) the closest shade when all shades of the three shade guides were considered, i.e., the combined method. Methods: The spectral reflectance values of the center 1/9 (1.5 mm diameter) of each shade tab (with a black backing) were measured using a spectroradiometer (PR-750 SpectraScan, Photo Research Inc.) and two external light sources at wavelengths from 380nm to 780nm with a 2.5 nm interval. All spectral reflectance measurements were made using 0 degree observer and 45 degree illumination, and then converted to CIE L*, a* and b* values. The color values of 99 anterior teeth of Japanese subjects were measured with the method of Ishikawa-Nagai S. et al. (IJP, 1994) Using the method of O'Brien WJ et al. for determining CE (IJP, 1991), the minimum CIELAB color differences (Delta E) for each of the subjects’ 99 anterior teeth within each shade guide and within all three guides were determined and averaged. The mean CE's were then statistically analyzed using a Repeated Measures ANOVA. Results: The CE's obtained were: Vita Lumin=9.9(5.6); Chromoscop=11.7(6.2); 3D Master=8.2(5.2); All Three Guides/Combined Method=8.1(5.2). A highly statistically significant difference (p < 0.001) was found among the CE's of the three shade guides and the combined method. Conclusion: Within the limits of this study, the color difference between Japanese subjects' anterior teeth and the closest color-matched shade tab is dependent on the type of shade guide used.