Could digital imaging be an alternative for digital colorimeters?

Abstract

This study evaluated the colour parameters of composite and ceramic shade guides determined using a colorimeter and digital imaging method with illuminants at different colour temperatures. Two different resin composite shade guides, namely Charisma (Heraeus Kulzer) and Premise (Kerr Corporation), and two different ceramic shade guides, Vita Lumin Vacuum (VITA Zahnfabrik) and Noritake (Noritake Co.), were evaluated at three different colour temperatures (2,700 K, 2,700-6,500 K, and 6500 K) of illuminants. Ten shade tabs were selected (A1, A2, A3, A3,5, A4, B1, B2, B3, C2 and C3) from each shade guide. CIE Lab values were obtained using digital imaging and a colorimeter (ShadeEye NCC Dental Chroma Meter, Shofu Inc.). The data were analysed using two-way ANOVA, and Pearson's correlation. While mean L* values of both composite and ceramic shade guides were not affected from the colour temperature, L* values obtained with the colorimeter showed significantly lower values than those of the digital imaging (p<0.01). At combined 2,700-6500 K colour temperature, the means of a* values obtained from colorimeter and digital imaging did not show significant differences (p>0.05). For both composite and ceramic shade guides, L* and b* values obtained from colorimeter and digital imaging method presented a high level of correlation. High-level correlations were also acquired for a* values in all shade guides except for the Charisma composite shade guide. Digital imaging method could be an alternative for the colorimeters unless the proper objectcamera distance, digital camera settings and suitable illumination conditions could be supplied. However, variations in shade guides, especially for composites, may affect the correlation.

Relative Translucency of a Multilayered Ultratranslucent Zirconia Material

“…This method has been used to assess ΔE with established accuracy. 20,21,24,33,37 While ΔE which corresponds to differences in color perception with specimens positioned on the same background is computed according to the formula:…”

“…This method has been used in various investigations to assess differences in color perception between teeth, 19 shade guides, 20,21 and observers. 22,23 Moreover, image analysis is applied in shade matching, [24][25][26] communication between dentists and laboratory technicians, 27,28 diagnosis of gingival inflammation, [29][30][31] oral lesions detection, 32 and evaluation of bleaching results.…”

Effects of surface-finishing protocols on the roughness, color change, and translucency of different ceramic systems

“…22,25,26,28,30 ∆E> 3.5 has been accepted as a clinically unacceptable color difference. 28,35,36 The aim of this study was not to achieve the shade match but to evaluate the ∆E values in comparison with the corresponding VITA shade tab (A2) considering the limitations of the specimen preparation protocols used in this study. Almost all ∆E values were higher than 3.5, except for LITV ceramic system (3.05 ±0.60) subjected to the AG method.…”

“…While subjective and qualitative methods, i.e., shade guides and photographic methods lead to unpredictable results, electronic intraoral devices such as colorimeters and spectrophometers can objectively detect color differences. 18,[34][35][36] These high-precision devices can metrically deliver consistent results using the CIE (Commision International de l'Eclairage [illumination]) L* a*b* system. 37,38 In the widely-recognized CIE L*a*b* color system, the location of the particular shade in the color space is defined by 3 coordinates, L*a*b*, where L*describes a color due to the lightness of the object being assessed, a* values are the chromaticity coordinates in the red-green axis, and b* in the yellow-blue axis.…”

A Study on Possibility of Clinical Application for Color Measurements of Shade Guides Using an Intraoral Digital Scanner

“…Obvious differences in L*a*b* values may originate from the variations in light reflection/detection system or dissimilar software algorithms of color image processing between two instruments . Even with a certain degree of linear relationship, non‐harmonious results of some color values were found in the previous studies due to the dissimilar reflectance of light in the analytic systems . Variations in light sources between the digital scanner (LED and a fluorescent lamp) and colorimeter (Xenon lamp) could also interfere with the verification of the digital scan image analysis versus colorimeter in this study …”