In 10 mature laboratory-strain rats implanted with gold-gallium dlloy test cylinders and silver amalgam alloy control cylinders, the host tissue response elicited by each alloy contrasted. After being implanted for 6 months, the silver amalgam implants caused mild tissue response, whereas the gold gallium implants caused a severe inflammatory tissue response—fibrosis. In 10 mature laboratory-strain rats implanted with gold-gallium dlloy test cylinders and silver amalgam alloy control cylinders, the host tissue response elicited by each alloy contrasted. After being implanted for 6 months, the silver amalgam implants caused mild tissue response, whereas the gold gallium implants caused a severe inflammatory tissue response—fibrosis.