Case report: ionisation tendency of a base metal alloy in the oral environment.

A biological interaction between the oral tissues and base metal alloys may result in corrosion and trace metal ion release, if the materials are not inert in the body. The reactions caused by such an alloy, a nickel-chrome alloy, were established on a woman patient who exhibited dark coloured band-like marks on the gingival tissues adjacent to her metal-ceramic crowns. These crowns were replaced by full ceramic crowns and the old restorations were analysed. The affected gingivae were removed, histopathological, patch and systemic tests were also performed. The results throw doubt on the biocompatibility of this alloy.