The clinical acceptance of dental nickel-chrome alloys

Replacing gold alloys by non-precious ones could save more than 500 million DM per year in German dentistry. However, there are many technical and biological considerations which have to be resolved in evaluating the clinical suitability of non-precious metal alloys. Techniques (e.g. investing, casting, porcelain application) and materials, developed over decades for processing gold alloys, have to be modified in order to achieve complete, sound castings, showing accurate fit and good ceramic-metal bonding. During the 5 years of our clinical studies, no case of localized or generalized tissue reaction due to Ni-Cr alloys was found. The five patients known to suffer from nickel allergy did not show any reaction to Ni-Cr test plates. Although several Ni-Cr alloys are routinely and successfully used in our clinic for single crowns and small bridges as well as for appliances used in complete oral rehabilitation, it should not be assumed that all Ni-Cr based alloys commercially available are equally suitable. There are two main reasons for this: (1) The Ni-Cr alloys comprise a large group; individual alloys exhibit greatly varied composition, microstructure, physical properties and corrosion behaviour. (2) Standards (specifications) by which non-precious metal alloys could be tested, with special regard to their biocompatibility, are lacking. Empirically, some Ni-Cr alloys have turned out to be useful in prosthodontics but further progress will depend upon the development of suitable standards. These are needed urgently.