Electrochemical studies of the corrosion behaviour of titanium and the Ti-6Al-4V alloy using electrochemical impedance spectroscopy.

OBJECTIVES: The aim of this study was to compare the electrochemical behaviour of two materials used in oral implantology. METHODS: The resistance to corrosion of Ti grade 2 and the alloy Ti-6Al-4V was studied in an artificial saliva solution. It has been observed that the passivation of titanium by an oxidised layer can be shown both by cyclic voltametry and by electrochemical impedance spectroscopy. Moreover, this latter technique, rarely used in odontology, opens up interesting perspectives, enabling a more quantitative approach to the resistance of the passive layer to be adopted. RESULTS: Also, the impedance data recorded for Ti grade 2 and the alloy Ti-6Al-4V, in the artificial saliva solution were shown that Ti grade 2 has a higher resistance to corrosion and a thicker oxide layer than the alloy Ti-6Al-4V. SIGNIFICANCE: The fact that the electrochemical properties of Ti-6Al-4V are lower than that titanium's ones indicate than a release of ions aluminum and or vanadium ions in the body can occur. This is why we recommend to the dental practitioners to preferably use titanium in implantology.

Comparison of corrosion behaviour in presence of oral bacteria.

The aim of this study was to compare the resistance of the corrosion of dental alloys in a solution containing oral bacteria named Actinomyces viscosus (ATCC19246). In this paper, we explain the choice of this precise species of bacteria, then specify its culture in artificial saliva and the experimental precautions needed to avoid the pollution by other bacteria. The electrochemical behaviour of two dental alloys (Ni-Cr alloy and gold-based alloy) was investigated by electrochemical means in sterile Fusayama artificial saliva (AS), AS enriched with sterile yeast extract (YE) and YE modified by introducing bacteria (AV). Open-circuit potentials, potentiodynamic curves, polarization resistance and impedance spectroscopy are the electrochemical procedures selected for this work. It has thus been shown that the open-circuit potential of the non-precious alloy is always lower than that of the gold precious alloy, and the colonization of metal surface by bacteria caused a drop in open circuit potential. The electrochemical impedance spectroscopy results have shown that the electrolyte resistance decreased between the AS, YE and AV milieu, in the presence of bacteria a slight decrease in polarization resistance was observed with the precious alloy and an increase with the non-precious alloy. The drop in the electrolyte resistance cannot explain the change in polarization resistance. The influence of Actinomyces viscosus might be essentially due to the consumption of oxygen at the metal/electrolyte interface of the specimen. For the non-precious alloy, the absence of oxygen (instigator of corrosion) led to an increase in polarization resistance whereas the slight decrease for the precious alloys might be justified by the organic and inorganic metabolites released by bacteria in to the electrolyte. The scanning electron micrography after electrochemical analysis, confirmed the absence of contaminants. These preliminary results demonstrate the unquestionable influence of this bacteria on the corrosion behaviour of the alloys studied, however, further studies are necessary.

Measurement and evaluation of galvanic corrosion between titanium/Ti6A14V implants and dental alloys by electrochemical techniques and auger spectrometry.

The purpose of this study was to investigate, in different experimental conditions, the galvanic corrosion phenomena which can exist between a dental suprastructure and a dental implant. The electrochemical behavior of 7 alloy superstructures with titanium and titanium alloy (Ti6A14V) implants was investigated by electrochemical means in Fusayama-Meyer de-aerated saliva and Carter-Brugirard (AFNOR) non de-aerated saliva. Different techniques were used to obtain the value of the galvanic coupling current and potential for each couple. All showed very low corrosion rates, ranging from 10(-6) to 10(-8) A. Surface analysis confirmed these results.