Abstract
✓ Metal devices currently used as permanent neurosurgical implants have been implanted in dogs for 6 months. The tissue responses corresponded to the known electrochemical characteristics of these metals. Tantalum caused the least reaction, and silver clips (sterling silver) uniformly provoked an inflammatory response. The various stainless steels caused reactions corresponding to the degree of ionization provoked by the tissues. Nonsurgical control materials used for comparison were gold, platinum, glass, and carbon steel.