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.
BACKGROUND
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.


OBJECTIVE
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.


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.
Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, Wash., USA. yada@koiscenter.com
Yada
Y
Chaiyabutr
John C
JC
Kois
Dene
D
Lebeau
Gary
G
Nunokawa
D000704:Analysis of Variance; D003116:Color; D003124:Colorimetry; D017076:Computer-Aided Design; D003442:Crowns; D000044:Dental Abutments; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D006801:Humans; D018020:Lithium Compounds; D055620:Optical Phenomena; D017797:Prosthesis Coloring; D019279:Resin Cements
C520133:IPS e.max CAD LT; D018020:Lithium Compounds; D019279:Resin Cements; D003776:Dental Porcelain; C103502:Variolink