Khaled Q Al Hamad1, Ismaeel I Obaidat1, Nadim Z Baba2. 1. Department of Prosthodontics, Jordan University of Science & Technology, Irbid, Jordan. 2. Advanced Specialty Education Program in Prosthodontics, Loma Linda University, School of Dentistry, Loma Linda, CA.
Abstract
PURPOSE: To investigate the effects of background color on shade reproduction using CAD/CAM zirconia and lithium disilicate ceramics. MATERIALS AND METHODS: A plastic tooth was prepared for an all-ceramic crown and scanned. Tooth-shaped light background dies were manufactured. Full-contour crowns were milled from translucent zirconia (ZT) and low translucency lithium disilicates (E [LT]). Copings from opaque zirconia (Z) and medium opacity lithium disilicate (E[MO]) ceramics were milled and layered with veneering porcelain to full contour. Metal copings were used to produce a dark background. Specimens were divided into 8 groups with 3 variables: background color, ceramic type, and translucency. Crowns were cemented using composite resin cement. Color was measured with a spectrophotometer. Color difference (∆E) was calculated using the CIEDE2000 formula between the specimens and the target shade, A1. Statistical analysis was performed using a nested design 3-way ANOVA and Tukey multiple comparisons. RESULTS: The closest ∆E to target shade was produced by E (LT) (2.13 ± 0.19) on the dark background. This increased significantly to 2.90 ± 0.19 on the light background (p = 0.03). The e.max (MO) groups significantly increased (p = 0.001) to 4.40 ± 0.22 and 4.47 ± 0.4, (p = 1.00) for the dark and light backgrounds, respectively. ∆E for the zirconia groups were higher and ranged from 4.85 ± 0.48 to 5.60 ± 0.48 in the ZT groups (p = 0.04) and 6.5 ± 0.82 to 7.75 ± 0.53 (p = 0.001) for Z groups from dark to light backgrounds. There was an overall lack of chromaticity between the specimens and the target shade A1 CONCLUSIONS: Ceramic color was affected by ceramic type, background, and translucency. Lithium disilicate appeared to be better than zirconia in shade reproduction. Less-opaque materials matched the target shade better, while opaque materials and low translucencies were more suitable for dark backgrounds.
PURPOSE: To investigate the effects of background color on shade reproduction using CAD/CAM zirconia and lithium disilicate ceramics. MATERIALS AND METHODS: A plastic tooth was prepared for an all-ceramic crown and scanned. Tooth-shaped light background dies were manufactured. Full-contour crowns were milled from translucent zirconia (ZT) and low translucency lithium disilicates (E [LT]). Copings from opaque zirconia (Z) and medium opacity lithium disilicate (E[MO]) ceramics were milled and layered with veneering porcelain to full contour. Metal copings were used to produce a dark background. Specimens were divided into 8 groups with 3 variables: background color, ceramic type, and translucency. Crowns were cemented using composite resin cement. Color was measured with a spectrophotometer. Color difference (∆E) was calculated using the CIEDE2000 formula between the specimens and the target shade, A1. Statistical analysis was performed using a nested design 3-way ANOVA and Tukey multiple comparisons. RESULTS: The closest ∆E to target shade was produced by E (LT) (2.13 ± 0.19) on the dark background. This increased significantly to 2.90 ± 0.19 on the light background (p = 0.03). The e.max (MO) groups significantly increased (p = 0.001) to 4.40 ± 0.22 and 4.47 ± 0.4, (p = 1.00) for the dark and light backgrounds, respectively. ∆E for the zirconia groups were higher and ranged from 4.85 ± 0.48 to 5.60 ± 0.48 in the ZT groups (p = 0.04) and 6.5 ± 0.82 to 7.75 ± 0.53 (p = 0.001) for Z groups from dark to light backgrounds. There was an overall lack of chromaticity between the specimens and the target shade A1 CONCLUSIONS: Ceramic color was affected by ceramic type, background, and translucency. Lithium disilicate appeared to be better than zirconia in shade reproduction. Less-opaque materials matched the target shade better, while opaque materials and low translucencies were more suitable for dark backgrounds.