The effect of thickness and cement shade on the color match of different CAD-CAM glass-ceramic materials
Shade reproducibility of different glass-ceramics
Keywords:CAD-CAM, cement color, color difference, leucite, lithium disilicate, spectrophotometer
Aim: This study aimed to assess the impact of the type and thickness of the ceramic and cement color on the targeted shade of glass-ceramics with various chemical compositions.
Methodology: Thirty ceramic specimens were prepared from leucite-reinforced (GC Initial LRF, GC Group) and lithium-disilicate (IPS e.max CAD, EM Group) materials in three different thicknesses (0.5 mm, 0.7 mm, and 1 mm). Four 4-mm-thick substrates were then made from A3-shaded composite resin material to mimic tooth structure and be utilized for cement application. Four shades (Variolink II: transparent, white, yellow, and bleach) of 0.2-mm-thick resin cement were polymerized over these substrates. Next, the specimens were placed over these substrates, and color measurements were applied with a spectrophotometer (VITA Easyshade V) leading to 24 group combinations (n=5). The color difference (∆E) readings were obtained in the spectrophotometer's reference shade verification mode by selecting the A2 shade standard. Three-way mixed ANOVA, Tukey HSD, and Bonferroni tests were used for statistical analysis (α=0.05).
Results: The main effects of material, cement, and thickness were found to be statistically significant (p < 0.05), as were the interactions of cement×material, cement×thickness, and material×thickness (p < 0.05). However, the material×cement×thickness interaction was not found to be statistically significant (p = 0.568). Regardless of thickness or cement shade, the GC group had a lower mean ∆E value than that of the EM group (p < 0.05). Lower ∆E values were achieved in both materials with a thickness of 1 mm and bleach-shaded cement (p < 0.05). The materials with the greatest mean ∆E values were those with the thickness of 0.5 mm and the transparent shade cement combination (p < 0.05).
Conclusion: The thickness and shade of the cement used influenced the final color of the glass-ceramic materials with the same shade and translucency but diverse chemical compositions. When compared to the lithium disilicate glass-ceramic material, the leucite-reinforced feldspathic glass-ceramic material displayed lower color difference values and a better color match with the targeted shade.
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