Objectives: Although dental implant therapy has been becoming a standard prosthodontic treatment, implant fixture material has still limitation in mechanical strength such as fatigue fracture.Against this problem, alloying commercial pure titanium (cp Ti) with zirconium (Zr) could be one of the solution due to its high mechanical strength which was reported by our past study that tensile strength of Ti30Zr (980Mpa) showed much higher than that of cp Ti (345Mpa). In addition, metal-based materials should be needed to be stable in living body without abrasion or corrosion. In this study, we tested the corrosion resistance of Ti-Zr binary alloy with compositional change. Methods: The target samples (cp Ti, Ti-1 OZr, Ti-30Zr, Ti-50Zr, Ti-70Zr and pure Zr (mol% of Zr)) were prepared from titanium sponge and zirconium bar using arc-melting machine. Ti-Zr disks with 10 mm diameter and 2.0 mm thickeness were used. The corrosion resistance was evaluated by anodal polarization analysis using Fusayama artificial saliva and lactic acid + NaCl aq as base solutions. The passive film on the surface of the Ti-Zr alloy was analyzed by X-ray photoelectron spectroscopy (XPS). Results: Localized corrosion sensitivity were observed in the case of more than 50% Zr content alloy in both solutions, which would be due to the deterioration of the oxide layer (Fig.1). On the other hand, the surface less than 30% Zr alloy were not injured by both solutions with enough corrosion resistance. On the other hand, the dissolution test showed that higher amount of dissolved ions was detected from cp Ti disk in the acid condition. However, the metal ion release was drastically suppressed by adding more than 10 mol% of Zr (Fig.2). Little metal ions were released in the artificial saliva. From the results of the XPS, the oxide layer was detected from all of the alloy, indicating that the properties of the passive film depends on the characteristics of Ti or Zr. Discussion and Conclusions: All of the samples in this study showed good corrosion resistance even in the accelerating corrosion environment. This finding indicated that improvement of the corrosion resintance in T-Zr alloy was due to the protection reinforced passive film, especially in 10 to 50 % Zr added alloy. Taken together with mechanical property findings, to contain around 10 to 50 % Zr with Ti alloy may be acceptable to clinical application in implant dentistry. Fig.1 Results of anodic polarization test in 1% Lactic acid +0.9% NaCl Fig.2 Results of elution test in 1% Lactic acid +0.9% NaCI.
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