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Corrosion in a neutral artificial saliva of metallic alloys used for frameworks strengthening fixed partial dentures

Pascal De March, Patrice Berthod

The frameworks supporting the ceramic part of a fixed dental prosthesis are composed of the assemblage of alloys of different natures for soldering reasons. Post-solder joints, and eventually the extremities of parent alloy parts, are exposed to the buccalmilieu and can suffer individual or galvanic corrosion. Eight types of parent alloys and four types of solder alloys were immersed in a pH=7.4 artificial saliva (Afnor norm) and their corrosion behaviours were characterized by the measurement of their potential and linear polarization according to the Stern-Geary method. Open circuit potentials are high (0mV/NHE) to very high (+300mV/NHE) due to the immunity of the noblest elements or to the passivation of the others. Polarization resistances are high (several tens k.cm²) or very high (more than 1M.cm²), and consequently corrosion currents very low (levels: 1A/ cm² down to 10A/cm²). Galvanic currents are not attended between parent and post-solder alloys in most cases since the Eocp are close to one another. However there are three assemblages which can potentially lead to low galvanic currents.