Effect of Thickness of Zirconia Core on Marginal Adaptation of All-Ceramic Restorations

Marginal adaptation is important for long-term Successof full-coverage restorations. Thickness of core is one of the important factors influencing the marginal integrity.Thus, the aim of this studywas to evaluate the effect of different thicknesses of zirconia core on marginal adaptation of all-ceramic restorations. In this single blind in vitro study,a standard brass die7 mm in length and 5 mm in diameter was prepared with a classic chamfer finish line with 0.8 mm depthand 10 degrees of wall taper. Copings were made using the CAD / CAM system. We had three groupsof10 samples each.Group 1 with a zirconia thickness of 3.0 mm, group 2 with a thickness of 0.5 mm and group 3 with a thickness of 0.7 mm. Copings were then placed on the die and randomly numbered. The vertical gap in the margin was measured at 10 points using scanning electron microscopy (SEM). Data were collected. The mean and standard deviation values were calculated and ANOVA. was used for the comparison of the three groups. Tukey’s test was also applied. The gap in 0.3,0.5 and 0.7 mm thicknesses of zirconia before porcelain firing was 89.21± 28.90, 79.55 ± 39.32 and 40.813 ± 10.3 µ, respectively.The difference in marginal gap between the three groups was statistically significant (P=0.001).Tukey’s test failed to find a significant difference in marginal gap between 0.3 and 0.5 mm thicknesses(P=0.006).But, the difference between 0.3 and 0.7 mm (P=0.001) and also 0.5 and 0.7mm(P=0.001) was statistically significant. Based on the results, by increasing the thickness of the zirconia core marginal gap decreases in all ceramic restorations.