Some ideas about electrochemical characterization of dental alloys

Abstract

Extensions and modifications of standard electrochemical techniques, accounting for unique conditions related to biological considerations, have proved useful in attacking some problems related to biocompatibility of the Biomaterial. Some authors have demonstrated that modern electrochemical techniques can be used to clarify some difficult problems in the field of biomaterials. Precious alloys can not be apply for all cases especially such as long range bridges or prostheses. For this reason, Ni-Cr as well as Co-Cr casting alloys have been used for dental application as alternatives to precious alloys. The biocompatibility of Ni-Cr alloys have been questioned because of their corrosive, allergenic, and even mutagenic potentials. The nature of passive films on metals and alloys is the ultimate factor which controls their corrosion behavior. There is little reliable information on the effects of the physical and chemical factors involved in the tissue response to an implant and the associated ionic release on the cellmaterial interaction. Depending of the casting process during the production of a dental prosthesis, these alloys may show different phases, ones may be more stable than other. For this reason, the development of a quick and simple method for determining the corrosion behavior as a control test in the production Biomecánica, 9 (1), 2001, pp. 66-70 67 of a dental prosthesis is of great interest. The purpose of this work was to show some results on the corrosion behavior of two different commercial alloys: Wiron 99 ( Ni-Cr alloy) and Aurolloyd kf (Au alloy). These results were obtained by several electrochemical methods: Open Circuit Potential vs time and Liner Sweep Voltammetry for Wiron 99, and Open Circuit Potential vs time and Cyclic Voltammetry for Aurolloyd kf. In the case of the Ni-Cr alloys, it is concluded that with the combination of both methods, it is possible to know how the corrosion behavior of casting individual dental Ni-Cr alloy prosthesis is, and in the case of Au alloy, it is concluded that the differences in electrochemical behavior strongly depend of surface oxides formed. These results showed that one of the studied combination, Eoc-Rp or Eoc-CV characterization, could be selected as control test after casting of individual prosthesis.