BIOCOMPATIBILITY AND SENSITIZATION TO NICKEL RELATED CORROSION PROCESS OF Ni-Cr DENTAL METAL ALLOYS

A high interest of today dentistry is focussed to improve fix or mobile dental prostheses. For this purpose a large variety of metal alloys is used, making thus difficult to evaluate their technical, biological and clinical properties. A large number of dental allergies, including responses to nickel containing dental alloys, like type IV hypersensitivity reactions, mediated by T-lymphocytes, were reported. Also, nickel containing dental alloys can undergo corrosion with release of metal ions. The present study presents the results concerning the electrochemical behaviour and corrosion of two commercial dental Ni - Cr alloys such as: Vera soft (from AlbaDent Company) and Wirocer plus (from Bego Dental Company). The investigation was performed using a medium of Fusayama-Meyer artificial saliva. Based on the polarization curves and electrochemical impedance spectroscopy (EIS) it was established the type and the intensity of the corrosion process by means of the corrosion currents value. The passivation of all the samples occurred spontaneously at the open circuit potential. The corrosion current values decrease after the alloys maintenance in the corrosive medium due their passivation. The corrosion currents decrease with the increase of the immersion time. The metal alloy of Wirocer plus is in an optimum corrosion resistant condition. The Vera Soft alloy sample presents a deep breakdown potential (about 250 mV). With an advantage of dendritic structure after casting process (producing a better surface quality), the Wirocer plus alloy presents a better electrochemical behaviour and biocompatibility than Vera Soft alloy.