ABSTRACT
Statement of the Problem: Although all-ceramic restorations are broadly used, there is a lack of information concerning how their fit is affected by fabrication procedure and marginal configuration
Purpose: The purpose of this study was to evaluate the marginal fit of zirconia CAD/CAM ceramic crowns before and after porcelain firing. The influence of finish line configuration on the marginal fit was also evaluated
Materials and Method: Twenty standardized zirconia CAD/CAM copings were fabricated for chamfer and shoulder finish line designs [n=10]. The marginal fit of specimens was measured on 18 points, marked on the master metal die by using a digital microscope. After the crowns were finalized by porcelain veneering, the measurements of marginal fit were performed again. The means and standard deviations were calculated and data were analyzed using student's t-test and paired t-test [alpha=0.05]
Results: There were significant differences between marginal fit of chamfer and shoulder finish line groups before and after porcelain firing [p= 0.014 and p= 0.000, respectively]. The marginal gap of copings with shoulder finish line was significantly smaller than those with chamfer configuration [p= 0.000], but there were no significant differences between the two marginal designs, after porcelain firing [p= 0.341]
Conclusion: Porcelain veneering was found to have a statistically significant influence on the marginal fit of zirconia CAD/CAM crowns. Both margin configurations showed marginal gaps that were within a reported clinically acceptable range of marginal discrepancy
ABSTRACT
Statement of the Problem: By introducing the coloring liquids, it is claimed that it is possible to make the color of frameworks fabricated from zirconium oxide extremely close to the natural tooth color.
Purpose: The purpose of this research was to evaluate the effect of two staining techniques on value changing in zirconia crowns.
Materials and Method: Three groups A, B, and C, each containing ten zirconia crowns, were used. The zirconium cores samples were fabricated by a CAD/CAM device. Group A was left uncolored, Groups B was submerged for two minutes in A2 coloring liquid and Group C was stained with brush. Then all cores were sintered and the porcelain was applied by using the layering technique. Ultimately, the crowns color was determined using a spectrophotometer. Their color changing [Delta E] and value changing [Delta L] in relation to A2 color were also assessed. The data were analyzed with one-sample t-test, post-hoc Tukey, and one-way ANOVA tests with significant level set at 0.05
Results: The mean value in all groups was higher than the value obtained from A2 color samples [p= 0.001]. The highest mean value was 78.31 +/- 1.22 belonging to group C [staining with brush] and the lowest mean value was 76.99 +/- 0.65 belonging to group B [submerging]. The results of post-hoc Tukey regarding both Delta E and Delta L variables showed a significant difference between groups A [uncolored] and C [staining with brush] with P Delta E=0.006 and P Delta L=0.039, respectively. A significant difference between group B [submerging technique] and C [staining with brush] were shown when these two variables were compared [P Delta E=0.001, P Delta L=0.015]
Conclusion: Due to the higher value increase in surface staining [brush], it is recommended to use the submerging technique for staining zirconia cores