Résumé
Recent clinical results for Zirconia all-ceramic restorations have revealed that the fracture rate 6-15% of the Zirconia framework is so low and the core of Zirconia has high stability. However, chipping-off fractures of porcelain are the most common reason for failures of Zirconia in the fixed partial dentures
Objectives: The purpose of this study was to compare the shear bond strength [SBS] of porcelain in the porcelain fused to metal and all-ceramic crowns with Zirconia core
Materials and Methods: Two groups were selected: porcelain fused to metal [PFM] and porcelain fused to Zirconia [PFZ] [n = 30].In the PFM group, a wax model [10 × 10 × 10mm]was used to cast metal base [Ni_Cr alloy]. In the PFZ group, an acrylic cubic model [10 × 10 × 10mm] was made as Zirconia model for scanning.15 cubic Zirconia samples were milled by CAD-CAM. The procedure of porcelain veneering was conducted by the conventional layering technique up to 2 mm thickness [2.5 × 2.5 × 2 mm]. All specimens were stored in water for 48 hrs. Thermal cycling was conducted for 20000 cycles between 55[degree sign]C and 5[degree sign]C alternatively for 30s.All samples were mounted in acrylic resin and the SBS test was performed, using a universal testing machine. The analysis of data was performed at a significance level of 0.05 using Kolmogorov-Smirnov and Mann-Whitney U-test
Results: Mean of SBS in PFM and PFZ was 24.57 and 20.88, respectively. The results of Mann-Whitney test showed that there was no statistically significant difference between the two groups of porcelain fused to metal and Zirconia in item shear bond strength [p = 0.455]
Conclusions: There was no significant difference between the two groups of PFM and PFZ in the item SBS