Effect of abutment tooth color, cement color, and ceramic thickness on the resulting optical color of a CAD/CAM glass-ceramic lithium disilicate-reinforced crown.

STATEMENT OF PROBLEM: A dark-colored prepared abutment tooth may negatively affect the esthetic outcome of a ceramic restoration if the tooth is restored using translucent enamel-like ceramic materials.

PURPOSE: The purpose of this study was to evaluate the cumulative effect that the tooth abutment color, cement color, and ceramic thickness have on the resulting optical color of a CAD/CAM glass-ceramic lithium disilicate-reinforced crown.

MATERIAL AND METHODS: A CAD/CAM glass-ceramic lithium disilicate-reinforced monolithic crown (IPS e.max CAD LT) was fabricated. Three possible crown restoration variables were tested in vitro. The procedure examined 4 prepared abutment tooth colors (light, medium light, medium dark, and dark), 2 cement (Variolink II) colors (translucent and opaque), and 4 ceramic thickness values (1.0 mm, 1.5 mm, 2.0 mm, and 2.5 mm). The color of each combination was measured using a spectrophotometer, and the average values of the color difference (ΔE) were calculated. The data were analyzed with a 3-way ANOVA (tooth abutment color, ceramic thickness, and luting agent) and Tukey's HSD test (α=.05), which evaluated within-group effects of the tooth abutment color to the ΔE at each ceramic thickness.

RESULTS: The ΔE values of a CAD/CAM glass-ceramic lithium disilicate-reinforced crown were significantly influenced by the tooth abutment color (P<.001), cement color (P<.001), and ceramic thickness (P<.001). Significant interactions were present among these 3 variables (P<.001). A dark-colored abutment tooth demonstrated the greatest ΔE values relative to other variables tested. An increase in ceramic thickness resulted in a significant decrease in ΔE values (P<.01). The ΔE values were slightly decreased when the crowns were cemented using the opaque cement.

CONCLUSIONS: This study demonstrated that underlying tooth abutment color, cement color, and ceramic thickness all influence the resulting optical color of CAD/CAM glass-ceramic lithium disilicate-reinforced restorations.