Veneering Techniques and Materials of Zirconia Based Restorations

Aim: The aim of this investigation was to examine the effects of the veneering technique on the fracture resistance, failure pattern, and shade reproducibility of zirconia based crowns. Materials and methods: A prepared tooth was scanned using CAD/CAM technology to fabricate 45 cobalt chromium (CoCr) testing dies. Forty five zirconia copings of 0.5mm uniform thickness were milled and devided according to the veneering technique into 3 groups: layering veneering (LV), overpressing veneering (OV), and digital veneering (DV). A spectrophotometer was used to measure the shade coordinates of an A2 shade tab, as well as the shade coordinates for each specimen. Both the CIE Lab (ΔEab) and the CIE DE2000 (ΔE00) color difference formulas were applied to compare between the shade tab and the study groups . Afterwards, the specimens were thermo-cycled then statically loaded until failure. Failed crowns were inspected and failure patterns were identified. One way ANOVA and multiple comparison bonferroni tests were applied for statistical analysis of the results. Conclusion: LV was superior to other groups in terms of shade reproducibility and fracture resistance.