Evaluation of Staining-Beverage on the Color-Stability of Lithium-Disilicate CAD/CAM Materials

Objectives: The aim of this study was to compare the color stability of lithium disilicate and lithium disilicate-strengthened aluminosilicate glass ceramics following exposure to an acidic staining beverage.
Methods: Lithium disilicate glass-ceramic (LS-IPS e.max CAD) and lithium disilicate-strengthened aluminosilicate glass-ceramic (LA-N!ce) blocks were sectioned to obtain 20 specimens. The LS specimens were sintered and glaze-fired. Since LA is in its fully crystallized form, these specimens were fired for glazing only. The color measurements of all specimens were performed using a spectrophotometer after the glaze processes. Then, the specimens were allocated into 2 groups according to the immersion protocol; half of each ceramic type was immersed in a staining acidic beverage (Coca-Cola) for 12 days, while the other half was stored in distilled water as the control group (n=10). The colors of the specimens were re-measured and the color change was calculated based on the ΔE00 formula using L*, a*, and b* values obtained at the baseline and after immersion. The statistical analysis of the obtained data was performed using the Mann-Whitney U test (α=0.05).
Results: The mean ΔE values for control groups of LS and LA were 0.85±0.69 and 1.78±1.26, respectively. The mean ΔE values for LS and LA after immersion in the acidic beverage were 2.49±1.62 and 3.82±1.93, respectively. All intra-and inter-group comparisons were statistically different except for LS-LA comparison after immersion in the acidic beverage.
Conclusions: Both types of ceramics showed significant discoloration after exposure to the acidic beverage. Since ΔE value exceeding 3.7 represents a color change perceptible to the human eye, the color change in the lithium disilicate-strengthened aluminosilicate glass-ceramic after exposure to the acidic staining beverage can be considered visually detectable.