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 (Delta E) were calculated. The data were analyzed with a 3-way ANOVA (tooth abutment color, ceramic thickness, and luting agent) and Tukey's HSD test (alpha=.05), which evaluated within-group effects of the tooth abutment color to the Delta E at each ceramic thickness. Results. The Delta E 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 Delta E values relative to other variables tested. An increase in ceramic thickness resulted in a significant decrease in Delta E values (P<.01). The Delta E 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. Prosthet Dent 2011;105:83-90)