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The purpose of this study was to evaluate the corrosion resistance of experimental dental Ti-Ag alloys in 0.9% NaCl solution. Open-circuit potential (OCP) measurement and elution tests of the alloys with 5–30% Ag were performed. The amounts of both Ti and Ag ions released from the alloys with Ag � 20% were below the detection limit. A very small amount of Ti ions was released from some of the 22.5% Ag specimens and some of the 25% Ag specimens. The time for the Ti-Ag alloys with 5–25% Ag to become the stable potential was earlier than that for titanium, and the OCP of the alloys was higher than that of titanium. These results indicated that the corrosion resistance of the alloys with 5– 25% Ag was equivalent to that of titanium. On the other hand, it was suggested that the precipitation of TiAg deteriorated the corrosion resistance of Ti-Ag alloys because TiAg dissolved preferentially in the NaCl solution. Ti-Ag alloys with 5–25% Ag can be used not only as dental restorative materials but also as dental implant materials. [doi:10.2320/matertrans.M2009355]

This study is an investigation of the machinability of experimental Ti-Cu alloys (2, 5, and 10 mass% Cu) as new dental titanium alloy candidates for CAD/CAM use. The alloys were slotted with a vertical milling machine and carbide square end mills under two cutting conditions. Their machinability was evaluated through cutting force using a three-component force transducer fixed on the table of the milling machine. The horizontal cutting forces of the Ti-Cu alloys tended to increase as the concentration of copper increased. The feed force for Ti-10%Cu was more than twice as large as that for titanium under both cutting conditions. Alloying with copper reduced the machinability of titanium under the present cutting conditions. The adverse effect on the cutting force was attributed to the higher degree of tensile strength and hardness of the Ti-Cu alloys than of titanium.

Titanium and some of its alloys are successfully used for biomaterials. The surface oxide films on these materials play important roles in maintaining corrosion resistance and biocompatibility. In this study, Ti‐6Al‐4V, Ti‐56Ni, and Ti‐ xZr (x = 0, 25, 50, 60, 75, 100) alloys in mass% were abraded and kept for 300 s in water and Hanks’ solution. The regenerated surface oxide film in Hanks’ solution was characterized using X-ray photoelectron spectroscopy. As a result, phosphate ions were preferentially taken up in the surface oxide film during regeneration. Ions constituting Hanks’ solution other than calcium and phosphate were absent from the surface oxide film. In the case of titanium and Ti‐ 6Al‐4V, calcium phosphate was formed on/in the surface oxide film regenerated in Hanks’ solution. However, Ti‐56Ni, Ti‐Zr, and zirconium did not form calcium phosphate on themselves but formed phosphate without calcium. These results are in good agreement with those for titanium alloys immersed in Hanks’ solution.

1Division of Dental Biomaterials, Department of Oral Rehabilitation and Materials Science, Tohoku University Graduate School of Dentistry, Sendai 980-8575, Japan 2Department of Dental Technology, Daegu Polytechnic College, Daegu 706-711, Korea 3Institute for Metals Research, Tohoku University, Sendai 980-557, Japan 4Department of Dental Materials, College of Dentistry, Kyungpook National University, Daegu 731-744, Korea