Browsing by Author "Johnston, William M."

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    Color Stainability of CAD/CAM and Nanocomposite Resin Materials
    (2016) Acar, Ozlem; Yilmaz, Burak; Altintas, Subutay Han; Chandrasekaran, Indumathi; Johnston, William M.; 26386483
    Statement of problem. The color stainability of recently introduced computer-assisted design/computer-assisted manufacturing (CAD/CAM) hybrid ceramic and resin nanoceramic is unknown. Purpose. The purpose of this in vitro study was to compare the effect of coffee staining on the color of 3 different CAD/CAM restorative materials and a nanocomposite resin. Material and methods. Specimens from a hybrid dental ceramic (VITA Enamic), a resin nanoceramic (Lava Ultimate), a lithium disilicate glass ceramic (IPS e.max CAD), and a nanocomposite resin (Filtek Supreme Ultra Universal) were evaluated for color change due to thermocycling in coffee (n=5). Specimens 0.5 to 0.7 mm and 1 to 1.2 mm in thickness were thermocycled for 5000 cycles. CIEDE2000 color differences (Delta E-00) due to thermocycling in coffee were calculated using the color coordinates obtained from a spectroradiometer. ANCOVA was used to analyze the color differences among the materials with thickness as the covariate. Significant differences at average thickness were analyzed with the Tukey-Kramer test. Results. For color difference due to staining, thickness was a significant covariate (P<.001). Regarding the analysis of color differences, every pair of the tested materials was significantly different (P<.001). Least squares means of color differences (Delta E-00) at mean thickness were 4.34 for the nanohybrid composite resin, 3.66 for the resin nanoceramic, 1.35 for the hybrid ceramic, and 0.43 for the lithium disilicate ceramic. Conclusion. When exposed to hot and cold coffee, the color change was beyond clinical acceptability for the tested resin nanoceramic and nanocomposite resin materials. The average color change of the hybrid ceramic was clinically perceivable over the tested thickness values. The color change of lithium disilicate ceramic was not clinically perceivable at any tested thickness.
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    Effect of Metal Opaquer on The Final Color of 3 Ceramic Crown Types on 3 Abutment Configurations
    (2018) Arif, Rabia; Yilmaz, Burak; Mortazavi, Aras; Ozcelik, Tuncer B.; Johnston, William M.; 29724553
    Statement of problem. The effect of a recently introduced metal opaquer when used to mask the color of a titanium abutment under ceramic crown systems is unknown. Purpose. The purpose of this study was to compare the color coordinates of 3 ceramic crown types-characterized monolithic lithium disilicate (LDC) (IPS e.max; Ivoclar Vivadent AG), layered lithium disilicate (LDL) (IPS e.max; Ivoclar Vivadent AG), and layered zirconia (ZL) (H.C. Starck)-on 3 abutment configurations, nonopaqued titanium (Ti), resin opaqued titanium (Op), and zirconia (Zir). In addition, the color differences (CIEDE2000) were evaluated among the 3 crown types on 3 different abutment substrates. Material and methods. Ten Ti disks (10x1 mm) were fabricated with computer-aided design and computer-aided manufacturing (CAD-CAM) to represent the Ti abutments. Five Ti specimens were opaqued (Op) (whiteMetal Opaquer wMO; Blue Sky Bio), and 5 were not opaqued (Ti). Ten zirconia disks were fabricated with CAD-CAM and sintered (10x1.2 mm). Five disks were used as backings to represent Zir abutments, and 5 disks were layered with 1 mm of porcelain (131, IPS e.Max Ceram; Ivoclar Vivadent AG) to represent layered zirconia crowns (ZL). Ten lithium disilicate plates (14x14x1.2 mm) were sectioned from CAD blocks (B1 IPS e.Max CAD; Ivoclar Vivadent AG). Five plates were layered with the same porcelain (B1, 1 mm), and 5 plates were surface characterized and glazed. An LDL crown on a Zir abutment configuration was used as the control. The 3 simulated crown types (n=5) were optically connected to each of the 3 abutment types, and the color of the 9 groups was measured using a spectroradiometer. Measured data were reported in CIELab coordinates. CIELab data were used to calculate color differences between the control and the 8 experimental groups. Color data were summarized for each group, and analyzed by repeated-measures ANOVA. For pairwise comparisons, a Bonferroni correction of t tests was used, and for interpretive analysis of resulting color difference data, a 1-way ANOVA and subsequent Tukey testing for pairwise comparisons were used. Results. The statistical significance of the analysis of color coordinates was found to be P <=.002. Although 3-way interaction was not found to be significant (P=.335), all three 2-way interactions of the main effects were found to be significant (P <=.002). All crown types on the Zir abutment revealed color differences from the control group. The color differences of the crown types on the Op and Zir abutment configurations compared with the control (LDL/Zir) were not (P>.05) statistically different. Conclusions. Colors of tested crown systems on Ti backing were each unacceptably different from the control group. Colors of these systems on zirconia backing were not perceivably different. Use of opaquer on titanium backing resulted in a small color difference from the control group (P>.05) for each crown system, demonstrating that it may be used to prevent the unfavorable metal show-through that can influence the final color of all ceramic crown systems tested.