Abstract
We studied the conditions of dynamic extraction in cytotoxicity testing of metallic biomaterials. Extraction was performed by gyrating specimens weighing 1.5 g and 2.0 g on alumina or zirconia balls for 1, 3 and 5 days at 200 rpm and 240 rpm. Extracts and filtrates were exposed to L-929 cells and cell viability after 72 hours was determined by neutral red assay. There was no significant difference in cell viability between extracts from specimens of different weights. Increasing the gyrating speed and extraction time resulted in a decrease in cell viability. Cell viability after extraction on alumina balls was lower than that after extraction on zirconia balls. By gyrating specimens on alumina balls at 240 rpm, ten types of metals were classified into four groups according to the effect of the extraction on cell viability. In these four groups, cell viability was decreased in the following order; a group that included titanium and Ti-6 Al-4 V alloy: a group that included cobalt-chromium alloy, nickel-titanium alloy, and 316L stainless steel; a group that included Type IV gold alloy and gold-silver-palladium alloy; and a group that included nickel-chromium alloy, siver-indium alloy, and silver-tin alloy. Cell viability after exposure to filtrates was greater than that after exposure to extracts. After gyrating specimens on alumina balls for 5 days at 240 rpm, copper was selectively dissolved in the filtrates from Type IV gold alloy and gold-silver-palladium alloy. Zinc was dissolved from silver-indium alloy and silver-tin alloy. Nickel was dissolved from nickel-chromium alloy, nickel-titanium alloy, and 316L stainless steel and cobalt from cobalt-chromium alloy. Dissolution from titanium and Ti-6 Al-4 V alloy was not recognized. The most efficient dynamic extraction condition for testing of cytotoxicity was found to include specimens weighing 1.5 g and extraction by gyrating on alumina balls at 240 rpm. These results might offer the potential to simulate the behavior of metallic biomaterials in vitro.
