## 3 Results
### Color Measurement (L, a, and b Values)
#### 3.1.4 Color Change (\(\Delta\)E, \(\Delta\)L, \(\Delta\)a, and \(\Delta\)b)  
Overall Color Change (\(\Delta\)E)  
Figure 7 shows that all the groups presented a change in color after immersion in saliva and coffee. Regarding color change in crowns after immersion in saliva and at baseline, all groups showed a significant color change; however, it was smaller than the perceptibility threshold PT (1.2) and acceptability threshold AT (2.7). Mean \(\Delta\)E values varied from 1.02 to 0.82. E-max and Celtra crowns showed greater color change compared with Lisi crowns (\(p<0.001\)) (Figure 7A). The color change was not significant after brushing (\(p>0.05\)), and was smaller than PT and AT. Regarding coffee and the baseline color change, Figure 7B shows that all groups showed a significant color change greater than the PT and AT. E-max and Celtra presented a comparable color change (\(p>0.05\)), while Lisi showed lower values (\(p<0.05\)). After brushing, the three crown materials showed a significant color change (\(p<0.05\)); the  
Figure 6: Mean \(\pm\) SD of b values (**A**) at the starting point, following immersion in artificial saliva and following brushing; (**B**) at the starting point, following immersion in coffee and following brushing. The comparison of different crown materials at the same measurement time point is indicated by upper-case letters. The comparison of the same crown material at different measurement time points is indicated by lower-case letters. Figure 7: Mean \(\pm\) SD of \(\Delta\)E values (**A**) between immersion in saliva and the starting point, and between saliva and brushing; (**B**) between immersion in coffee and the starting point, and between coffee and brushing. Different letters denote statistically significant differences. The comparison of different materials at the same measurement time point is indicated by upper-case letters. The comparison of the same material at different measurement time points is indicated by lower-case letters. mean \(\Delta\)E values were 2.51 \(\pm\) 0.64, 2.34 \(\pm\) 0.76, and 2.61 \(\pm\) 0.52 for E-max, Lisi, and Celtra, respectively. All the color changes were below the acceptability threshold (2.7). Lightness Difference (\(\Delta\)L)  
Figure 8A shows that the lightness difference between crowns after immersion in saliva and at the baseline was negative for all three materials. E-max showed significantly lower mean \(\Delta\)L values than Lisi and Celtra (\(p\) < 0.05). All the crowns immersed in saliva presented an increase in the mean \(\Delta\)L values when followed by brushing. Regarding the difference in lightness between immersion in coffee and at baseline, Figure 8B shows that coffee significantly decreased the luminosity for the three crown materials (\(p\) < 0.05). All crowns showed a significant increase in luminosity after brushing (\(p\) < 0.05). Redness-Greenness Difference (\(\Delta\)a)  
Considering the analysis of \(\Delta\)a, Figure 9A shows that Lisi and Celtra crowns presented redness after immersion in saliva and at the baseline, while E-max presented greenness (\(\Delta\)a = -0.4 \(\pm\) 0.14). After immersion in saliva and followed by brushing, all the crown materials showed redness. Regarding the difference in redness-greenness between immersion in coffee and at baseline, Figure 9B shows that E-max and Celtra crowns presented greenness, while Lisi presented redness. Interestingly, E-max showed a significant difference compared to other groups (\(p\) < 0.05). After brushing, E-max showed redness, while Lisi and Celtra presented greenness with a significant difference compared to other groups (\(p\) < 0.05). Figure 8: Mean \(\pm\) SD of \(\Delta\)L values (**A**) between immersion in saliva and the starting point, and between saliva and brushing; (**B**) between immersion in coffee and the starting point, and between coffee and brushing. Different letters denote statistically significant differences. The comparison of different crown materials at the same measurement time point is indicated by upper-case letters.