PECULIARITY OF TITANIUM USE FOR DENTAL IMPLANTS MANUFACTURING

Starikova S. L., Starikov V. V.

CONTENTS

Scentific article

In the present time the titanium is used most often for dental implants manufacturing. Such selection is determined by properties combination of the given metal. The high corrosion stability of titanium is provided by oxide that is formed on metal surface. Such oxide film has high continuousness, adhesive and mechanical strength. The increase of protective properties of this film is possible by additional anodic oxidation ensuring forced increase of their thickness. Some researchers are offered to use in addition to ordinary titanium the titanium coating or titanium in nanostructure state. The titanium in both film state and nanostructure state will have other electrochemical activity in comparison to compact metal. There isn’t enough information on this problem now. The purpose of work was the research of electrochemical activity of implant-prosthesis galvanic pairs at use of both nanostructure titanium and titanium film coatings. As object of researches we used the plates of titanium, titanium coating and titanium in nanostructure state which modeled dental implants. The nanostructure state of titanium was obtained by deformation of metal when the metal grains have decreased up from ~ 10-4 m to the size 3·10-8 m. After such processing the stuff essentially increases the strength. The measurements of metals electrode potential in initial state and after anodic oxidation were conducted in an electrochemical cell filled with physiological fluid (0,9 % aqueous solution of NaCl) and an AgCl reference electrode was used. The metal implants were investigated in initial state with thickness of natural oxides ~ 1 nm and after an-odic oxidation when the surface oxide thickness was increased to 200 nm. The analysis of electrochemical activity of titanium was realized depending on its initial state. It was established that the additional forced oxidation of titanium implants surface during their anodic processing leads to their es-sential passivation. After grain refinement the electrode potential of titanium was reduced to value Е= -0,22 V (electrode potential of titanium in initial state E = 0,05 V) that testified about increase of electrochemical activity of metal. It is possible to explain this increase by growth of internal stresses in titanium, essential increase of expansion grain boundaries etc. But this effect can be leveled during an anodic oxidation of titanium. Use of titanium film coatings on the surface of subperiostal implants, made of cobalt-chromium alloy, results in passivation of their surface (electrode potential of cobalt-chromium alloy was changed from E = -0,27 V to E = 0,03 V after deposition of titanium film) and eliminates accumulation of cobalt and chromium in bone tissue because of diffusion barrier formation. We tried to increase electrolytic potential of cobalt-chromium plate with tita-nium coating by anodic oxidation of titanium film, as well as in case of compact titanium. However, experiment has ended in failure because of impossibility of oxide layer preparation of necessary thickness. It could be connected with heterogeneousness of titanium coating thickness, when in thin places practically all titanium was spent for oxide formation and the further increase of oxide thickness already appeared impossible. The future researches will be connected to realization of full-scale tests of implants made of titanium both in film and nanostructure state.

implant, corrosion, passivation, electrode potential, anodic oxidation

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