Effect of veneering material and technique on the fracture resistance of porcelain-veneered zirconia crowns

Abstract

Context: Different porcelain veneering materials and techniques are used for the fabrication of porcelain-veneered zirconia crowns. Aim: The aim of this study was to examine the effects of different veneering materials and techniques (layering or over pressing) on the fracture resistance of zirconia-based crowns. Materials and Methods: A prepared molar tooth was scanned using computer-aided design/computer-aided manufacturing technology to create a master metal die. The scanned dies was used to produce forty zirconia copings. The zirconia copings were divided into four groups (n = 10) based on the veneering technique used, as follows: over pressing using Cercon Ceram press (PR1), IPS e.max ZirPress (PR2), layering using IPS e.max Ceram (LR1), and VITAVM9 (LR2). All crowns were cemented using glass-ionomer cement and thermocycled for 3000 cycles, between 5°C and 55°C. They were then loaded using a universal testing machine (3.7-mm ball and 0.5-mm/min crosshead speed) until failure. One-way ANOVA with Bonferroni corrections for multiple comparisons was used for the statistical analyses. Results: The means and standard deviations for failure loads were 1420 ± 54 N, 1797 ± 31 N, 1698 ± 36 N, and 2120 ± 73 N for the PR1, PR2, LR1, and LR2 groups, respectively. The differences in failure loads were statistically significant (P < 0.05) among the different test groups. Failure was predominantly due to adhesive failure in the PR1 and PR2 groups, whereas core fracture occurred more often in the LRI and LR2 groups. Conclusion: The fracture resistance of zirconia-based crowns was affected by the veneering materials and techniques used.