Corrosion stability of a new dental alloy for restorative metal-polymer works

Abstract

With the aim to increase the corrosion resistance of the dental silver-palladium alloys, a new dental Ag-20Pd-5Au-1.5Ti alloy was elaborated; titanium, the new element introduced in the composition of this alloy is very resistant to corrosion and has favourable effects on its resistance. The behaviour of the new Ag-20Pd-5Au-1.5Ti alloy in Carter-Brugirard artificial saliva un-doped and doped with 0.05M NaF of different pH values (to simulate the extreme conditions that can appear in oral cavity for long term working periods) and Ringer-Brown solution (that reproduce "in vitro" the human fluid) is studied in this paper. The electrochemical techniques of the potentiodynamic and linear polarization and electrochemical impedance spectroscopy were used. Also, the open circuit potentials and corresponding open circuit potential gradients (due to the saliva pH and content non-uniformities) variations versus the exposure time (5000 h) were registered. Both in Carter-Brugirard saliva and Ringer-Brown solution, the new dental Ag-20Pd-5Au-1.5Ti alloy exhibited a passive metal behaviour with electropositive corrosion potentials, relative large passive potential ranges and low passive current densities. From EIS data, an electric equivalent circuit with two time constants was modelled: the first time constant represents the passive film and the second constant illustrates the charge transfer reactions through this passive layer.