Acceptability of shade differences in metal ceramic crowns

Evaluation of Color Changes in the Vitapan Classical Shade Guide After Disinfection

“…It was found in this study that only the a* coordinate (red and green chroma) registered a significant change at year 3, while the L* and b* coordinates were consistent over years 1, 2, and 3 (Table 1). This concurs with the finding of Douglas and Brewer, 34 who reported that visual perception is more sensitive to objects differing in their red chroma. It is important to note that although the mean values are given in Tables 1, 2, and 3, the median values and the appropriate nonparametric statistical tests were used for statistical analysis; mean values are given for simplification of presentation.…”

“…They also reported that the visual thresholds of color acceptability were significantly lower for metal ceramic crowns differing in their red chroma or, in other words, differing in the a* coordinate (mean 1.1 DE units) compared with those of metal ceramic crowns differing in their yellow chroma, or b* coordinate (mean 2.1 DE units). 34 In this study and after 1440 cycles (1440 minutes) of disinfection, which simulated three years of clinical use, the mean DE for shade guide tabs was 0.62 units, which is almost one-third of that found by Pohjola and others, 26 who also used a spray technique to disinfect shade guide tabs. They found a statistically significant chromametric color change (1.8 DE units) after three years of simulated treatment, but they reported that this color change was not visually observable.…”

Influence of Cement Shade and Water Storage on the Final Color of Leucite-reinforced Ceramics

“…14,[24][25] Prior to each session, the colorimeter used for color measurements (ShadeEye NCC, Shofu Dental) was calibrated against a white working standard according to the manufacturer's recommendations. Because repositioning errors could affect accuracy of the assessments of the specimens, an index for each specimen was prepared and a standardization device was used for the instrument.…”

“…The advantage of this system over the Munsell system (hue, chroma and value) is that CIELab units are evenly spaced in terms of visual perception, so that the spectral readings can be correlated with subjective operations. 10 The color difference (ΔE) between two specimens whose color is expressed in L*, a*, b* coordinates is derived from the following equation: [12][13][14][15][16][17][18][19] …”

“…The benefits of performing color matching under controlled standard illumination have been reported. 14,25 Unfortunately, there are some disadvantages associated with the use of colorimeters. Results from a colorimetric device can be altered, because the standardized illuminating light emitted from the device can be scattered, absorbed, transmitted, reflected and even displaced in a sideways direction as a result of the translucent optical properties of teeth and dental ceramics.…”