“…Copper and silver are unacceptable as stimulating electrodes, as these metals cause tissue necrosis even in the absence of current (Fisher et al, 1961;Dymond et al, 1970;Sawyer and Srinivasan, 1974;Stensaas and Stensaas, 1978;Babb and Kupfer, 1984). Nickel-titanium shape memory alloys have good biocompatibility response (Ryhanen et al, 1998), up to a nickel content of 50% (Bogdanski et al, 2002).…”