In vitro element release and biological aspects of base-metal alloys for metal-ceramic applications

Objective: The aims of this study were to investigate the release of element from, and the biological response in vitro to, cobalt-chromium alloys and other base-metal alloys used for the fabrication of metal-ceramic restorations. Material and methods: Eighteen different alloys were investigated. Nine cobalt-chromium alloys, three nickel-chromium alloys, two cobalt-chromium-iron alloys, one palladium-silver alloy, one high-noble gold alloy, titanium grade II and one type III copper-aluminium alloy. Pure copper served as positive control. The specimens were prepared according to the ISO standards for biological and corrosion testing. Passive leaching of elements was measured by using Inductively Coupled Plasma - Mass Spectrometry (ICP-MS) after incubation in cell culture media, MEM, for 3 days. Corrosion testing was carried out in 0.9% sodium chloride (NaCl) and 1% lactic acid for 7 days, and the element release was measured by Inductively Coupled Plasma - Optical Emission Spectroscopy (ICP-OES). The biological response from the extract solutions was measured though MTT cytotoxicity testing and the Hen's egg test-chorio-allantoic membrane (HET-CAM) technique for irritationt. Results: The corrosion test showed similar element release from base-metal alloys compared to noble alloys such as gold. Apart from the high-copper alloy, all alloys expressed low element release in the immersion test, no cytotoxic effect in the MTT test, and were rated non-irritant in the HET-CAM test. Conclusions: Minimal biological response was observed for all the alloys tested, with the exception of the high-copper alloy.