Color Stability of CAD/CAM Ceramics Prepared with Different Surface Finishing Procedures.

PURPOSE: To investigate the color stability of zirconia-reinforced lithium silicate glass-ceramic and lithium disilicate reinforced glass-ceramic, which were prepared with various surface finishing procedures, following 1-week, 2-week, 1-month, and 2-month storage in various beverages, and after the application of polishing paste.

MATERIALS AND METHODS: Lithium disilicate glass-ceramic (IPS e.max CAD HT) and zirconia-reinforced lithium silicate ceramic (Vita Suprinity HT) CAD/CAM blocks were sectioned with a diamond saw (Metkon) under water cooling into 1.5 × 7 × 12 mm dimensions (N = 120). All specimens were polished with silicon carbide paper (600-, 800-, and 1200-grit) under water for 120 seconds. The specimens were prepared using 3 surface finishing procedures: glaze, mechanical polishing, and external staining and glaze in accordance with manufacturers' instructions. Then, each group was divided into 2 storage subgroups, black tea and coffee (n = 10/group). Color values were measured in CIELAB color space with dental spectrophotometer (VITA Easyshade) at the initial stage, and following 1-week, 2-week, 1-month, 2-month storage, and after fine-grit polishing paste application (Proxyt). Color changes (ΔE) were calculated and statistically analyzed using ANOVA followed by Bonferroni corrected post-hoc tests using Number Cruncher Statistical System 2007 (α < 0.05).

RESULTS: For lithium disilicate glass-ceramic, glaze procedure showed statistically lower color change values than mechanical polishing and external staining and glaze surface finishing groups (p < 0.05) following storage in both beverages, whereas for zirconia-reinforced lithium silicate ceramic, glaze procedure showed statistically lower color change values than mechanical polishing, but statistically insignificant values with respect to external staining and glaze group, following storage in both beverages. Lithium disilicate glass-ceramic groups showed statistically lower or statistically insignificant color change values with respect to zirconia-reinforced lithium silicate ceramic groups, except for the external staining and glaze surface finishing group in coffee. Significantly lower discoloration values were obtained following polishing paste application, with respect to 2-month storage in beverages (p < 0.05).

CONCLUSION: Glazing alone led to more color stability with respect to mechanical polishing and external staining and glaze for zirconia-reinforced lithium silicate and lithium disilicate glass-ceramic. Lithium disilicate glass-ceramic showed higher color stability compared to zirconia-reinforced lithium silicate ceramic. Polishing paste resulted in a decrease in discoloration to clinically acceptable values.