Illuminant effect on the coverage error of a gingiva-colored composite resin shade guide

Dental clinicians face challenges when selecting the proper gingiva-colored composite resin.

The purpose of this study was to evaluate the coverage error (CE) of a gingiva-colored dental composite resin shade guide with regard to the optical characteristics of the attached gingiva of a selected population under 2 different illuminants: Commission Internationale de l'Eclairage (CIE) illuminants A and D65.

The spectral reflectance (SR) values of 12 shade tabs of a gingiva-colored composite resin (Amaris gingiva) were measured at 3 different locations without a backing by using a spectroradiometer and an external light source at wavelengths of 380 to 780 nm at 2-nm intervals. All SR measurements were made using 0-degree observer and 45-degree illumination, with target size 1.1 mm in diameter. The attached gingiva (AG) of 120 participants was measured with the same protocol. CIELab values were calculated from the spectral reflectance values. CEs of the attached gingiva for each of the 120 participants for each of the shade tabs and the 2 illuminants and their combination were determined and averaged. The CIEDE2000 color differences were analyzed by a repeated measures ANOVA (using the maximum likelihood estimation method and the Satterthwaite degrees of freedom method) (α=.001).

The CIEDE2000 color difference for each person's gingiva to the closest match in color to the shade guide was determined separately for CIE illuminants A and D65. CE was calculated as the averages of these color differences and was found to be 4.0 for CIE illuminant D65 and 5.8 for CIE illuminant A.

The tested gingiva-colored shade guide had different CEs under illuminant D65 than under illuminant A and exhibited metamerism. ΔE for both illuminants was greater than the clinically acceptable range reported in the literature.