On the transformation behaviour, mechanical properties and biocompatibility of two NiTi-based shape memory alloys: NiTi42 and NiTi42Cu7

The transformation behaviour, mechanical properties and cytotoxicity of a b inary NiTi42 and a ternary NiTi42Cu7 alloy have been investigated. The tran sformation temperatures were determined via differential scanning calorimet ry, the mechanical properties have been investigated in 3-point bending tes ts in the temperature range between 6 and 60 degreesC. The cytotoxicity tes ts were performed on both alloys in cultured epithelial cells from human gi ngiva. The cytotoxicity investigations included both MTT tests and morpholo gical observations. It is shown that although the ternary alloy is characte rised by a narrower hysteresis and superior mechanical properties, includin g fatigue resistance, its cytotoxicity is higher than that of the binary al loy. This is thought to arise from the release of copper ions in the medium , which upon atomic absorption spectroscopy measurements amount to approxim ately 2.8 mug cm(-2) for an incubation period of 7 days. (C) 2001 Elsevier Science Ltd. All rights reserved.