I. SCHULTZ*, B. MELLE, E. LENZ (Dept. Prosthetic Dentistry and Dental Materials Research Erfurt, Friedrich-Schiller- University Jena)
Metals and alloys are the most important materials in prosthodontics. But the corrosion behaviour determines the biocompatibility of these materials. Therefore the corrosion behaviour must be evaluated under simulated biological conditions. For this reason cast samples of five types of dental alloys (14 different alloys) were characterized in this study. Gold- (high and low Au-content) and Palladium-base dental alloys were tested:
Au>75 Pt / Au>75 PtPd / Au<75 AgPd / Au<75 AgCu / Pd Ag
For this purpose anodic polarizations measurements by a computer aided potentiostat were performed in 3 anorganic (0,9% NaC1, pH = 7,4; 0,9% NaCl, pH = 1 and artificial salvia according to DIN 13927) and one organic (Dextrose bacteria food solution) electrolytes by aid of the bioreactor under standard environmental conditions.
The tests show that the corrosion behaviour depends on the quality of the electrolytes, The breakdown potentials in strongly acid sodium chloride solution are lower than in the other electrolytes. It simulates the aggressive conditions of crevice corrosion. In the organic electrolyte the breakdown potentials are about 400 mV higher compared with strongly acid sodium chloride solution. All materials show high passivation by forming biofilms.
It was shown that the corrosion resistance mainly depends on the amount of precious metals (Au+Pt+Pd).