In vitro cytotoxicity evaluation of a 50.8% NiTi single crystal.

To our knowledge, the biocompatibility of nickel–titanium (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 〈001〉 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 37°C. Cytotoxicity studies were performed on L-929 mouse fibroblasts using the MTT assay. J-774 macrophages were used to assess the potential inflammatory effect of the extracts by IL1-β and TNF-α dosages (sandwich ELISA method). Exposure of L-929 to material extracts did not affect cell viability. In addition, IL1-β and TNF-α 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. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 641–646, 2003 [ABSTRACT FROM AUTHOR]