Porcelain bonding to novel Co–Cr alloys: Influence of interfacial reactions on phase stability, plasticity and adhesion

Publication date: Available online 23 September 2016
Source:Dental Materials
Author(s): Kai Chun Li, LeYing Tran, David J. Prior, J. Neil Waddell, Michael V. Swain
ObjectiveThe objective of the present study was to determine the hardness and adhesion strength at the porcelain to alloy interface.Methods15 bi-layer porcelain veneered Co–Cr specimens of each alloy group [cast, powder metallurgy (PM), CAD/CAM(CC)] were manufactured. 12 bi-layered specimens were tested using four-point bend strain energy release rate adhesion test. One before and after porcelain firing specimen of each alloy group were nano-indented at the bulk and metal-porcelain interface to determine the mechanical properties. Electron backscatter diffraction was used to determine the microstructure and phase of the indented areas.ResultsThe results obtained from the four-point bend strain energy release rate test indicated highest adhesion energy of 92.15J/m² observed in the CC produced Co–Cr alloy. This was followed by the PM alloy with an adhesion energy of 62.24J/m² and cast alloy with an adhesion energy of 42.83J/m². All comparisons of adhesion energy between the three alloys were found to be statistically significant (p<.05). Nano-indentation test indicated higher hardness values of 4.6–6.1GPa at the metal-porcelain interface compared to the bulk, which had hardness values of 3.1–3.9GPa.SignificanceThe adhesion of the alloy to porcelain was found to be inversely related to the hardness of the interfacial layer at the alloy surface. Lower interfacial hardness was found to be accompanied with higher adhesion energy due to the additional plastic energy consumed during crack propagation along the more ductile interface region of the alloy.



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