Co-Cr PFM Systems: a Comparison of Three Unique Processing Techniques

Objective: The aim of this investigation was to compare the post-sintered microstructure, adhesion and mechanical properties of three unique processing techniques (cast, DentaNEM; CAD/CAM, Remanium star; powder metallurgy, Sintron) used to produce cobalt-chromium restorations but have extremely similar chemical and physical properties.  

Methods: Three groups of 12 metal-porcelain bi-layered specimens were manufactured and adhesion tested with four point bending test. Adhesion energy G was evaluated and compared for cast, CAD/CAM and powder metallurgy produced cobalt-chromium alloy veneered with leucite-based porcelain. Nano-indentation was performed on the bulk and metal-porcelain interface of the alloys to identify the hardness and elastic modulus properties. Microstructural analysis were performed using electron backscatter diffraction.

Results: All three microstructures produced by each processing technique were observably different both in structure and grain size. The average strain energy release rate of the three groups was as follows: cast, 46.16 J/m²; CAD/CAM, 91.24 J/m²; powder metallurgy, 59.03 J/m². Statistical significance (p<.05) were only observed between CAD/CAM to both other groups. Nano-indentation results are listed in Table 1. Significant difference (p<.05) were observed between all elastic modulus and hardness comparisons between bulk and near interface except for the CAD/CAM group. Significant difference (p<.05) was also observed between hardness measurements of all three alloy processing groups.

Conclusion: The three processing technique used in this study showed significant difference in microstructure and mechanical properties. In addition, there appears to be correlation between the hardness and adhesion strength between the alloy and porcelain.