నైరూప్య

Electrochemical behaviour in corrosion and galvanic corrosion of several alloys used in fixed partial dentures when immersed in a Fusayama saliva

Pascal De March, Patrice Berthod

The framework which supports ceramic in fixed partial denture generally includes several dental alloys in electrical contact (post-solder alloy in the joint between two pieces of a same parent alloy). In service, some parts of the framework can be exposed to saliva and then to individual or galvanic corrosion, with possible detrimental consequences for their mechanical resistance on long times. Eight parent alloys and four post-solder alloys were prepared as electrodes and tested in an aerated Fusayama-type artificial saliva. Electrochemical techniqueswere applied first to specify the individual behaviour of all alloys (follow-up of corrosion potential, determination of polarization resistance, Tafel experiment and calculations), and second to study the galvanic behaviour of each parent alloy coupled with its usual post-solder during four hours. Corrosion potentials were generally very high and corresponded to the immunity domains of the noblest elements or to the passive state for the other elements, excepted other elements fortunately present in low quantities in the alloys. Polarization resistance were high or very high. Tafel experiments allowed verifying that corrosion currents were also very low. Because of different individual behaviours a galvanic current may exist between coupled parent alloy and post-solder alloy.