Abstract
To our knowledge, the biocompatibility of nickelโtitanium (NiTi) single crystals has not been reported. Yet certain orientations of single crystals present several advantages over the polycrystalline form in terms of maximal strain, fatigue resistance, and temperature range of superelasticity. Therefore we tested the in vitro biocompatibility of 50.8% NiTi single crystals in the orientation ใ001ใ after four different heat treatments in a helium atmosphere followed by mechanical polishing. The study was performed on the material extracts after immersion of the specimens in cell culture medium (DMEM) for 7 days at 37ยฐC. Cytotoxicity studies were performed on Lโ929 mouse fibroblasts using the MTT assay. Jโ774 macrophages were used to assess the potential inflammatory effect of the extracts by IL1โฮฒ and TNFโฮฑ dosages (sandwich ELISA method). Exposure of Lโ929 to material extracts did not affect cell viability. In addition, IL1โฮฒ and TNFโฮฑ secretion was not stimulated after incubation with NiTi extracts compared to the negative controls. These results were predictable since atomic absorption spectroscopy did not detect nickel ions in the extracts with a resolution of 1 ppm. Within the limits of in vitro testing, our results demonstrate that the TiNi~50.8%~ single crystals do not trigger a cytotoxic reaction. ยฉ 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 641โ646, 2003