Kai Chun Li1, LeYing Tran2, David J Prior3, J Neil Waddell2, Michael V Swain4. 1. Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand. Electronic address: lika6144@gmail.com. 2. Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand. 3. Department of Geology, University of Otago, Dunedin, New Zealand. 4. Bioclinical Sciences, Faculty of Dentistry, Kuwait University, Kuwait.
Abstract
OBJECTIVE: The objective of the present study was to determine the hardness and adhesion strength at the porcelain to alloy interface. METHODS: 15 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. RESULTS: The 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. SIGNIFICANCE: The 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. Copyright Â
OBJECTIVE: The objective of the present study was to determine the hardness and adhesion strength at the porcelain to alloy interface. METHODS: 15 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. RESULTS: The 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. SIGNIFICANCE: The 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. Copyright Â