Papers by Author: Rogério Albuquerque Marques

Abstract: - Ferromagnetic stainless steels (SS) produced by powder metallurgy (PM) techniques have been investigated as potential candidates for dental prosthesis applications in replacement of magnetic attachments made of noble and expensive alloys. Two SS were investigated: SS 17-4 PH produced by powder injection (PIM) and SS PM2000 obtained by mechanical alloying. In vitro cytotoxicity analysis of the two SS showed no cytotoxic effects. The magnetic retention force of both tested SS was also evaluated and they were comparable to noble commercially available material that is in use at the moment. The corrosion resistance of both SS was evaluated by electrochemical techniques in sodium phosphate buffer solution (PBS) at 37°C. The AISI 316L SS was also tested under the same conditions for comparison reasons. SS samples tested showed passive behaviour in the electrolyte, but they also presented susceptibility to pitting. The best pitting resistance was associated to the PM2000 whereas the 17-4PH PIM showed the highest pitting susceptibility among the tested steels. The results pointed out that the PM2000 SS might be considered a potential candidate for substitution of high cost magnetic alloys used in dental prosthesis.

Abstract: The corrosion resistance of 17-4PH stainless steel obtained by powder injection molding (PIM) was investigated in a phosphate buffer solution (PBS) that simulates physiological solution and compared with that of 17-4PH steel obtained by conventional metallurgy. The corrosion resistance was investigated by electrochemical techniques for different immersion times. The cytotoxicity of both types of 17-4PH steel was also investigated using a minimum Eagle’s medium (MEM). The MEM solution is a type of cell culture medium, which simulates physiological fluids. The cytotoxicity assay was carried out by neutral red uptake methodology utilizing NCTC L929 cell line from ATCC bank and none of the steels showed cytotoxic effects. The resulting extracts obtained by immersion of the steel samples in MEM were analyzed by neutron activation analysis and the results indicated liberation of chromium and cobalt as corrosion products but in very low amounts. The electrochemical evaluation of both steels indicated that they are passive in PBS but presented susceptibility to pitting. The 17-4PH PIM steel was slightly more susceptible to pitting than that fabricated by conventional metallurgy due to its inherent porosity.