Comparison of in vitro biocompatibility of a Co-Cr dental alloy produced by new milling/post-sintering or traditional casting technique

The purpose of this study was to evaluate metal ion release of a cobalt-chromium (Co-Cr) alloy produced by using both the new milling/post-sintering (MPS) and traditional casting (CAST) techniques and the influence of ion release on cell response. The concentration of released ions from the specimens immersed in artificial saliva (pH 5.3 and 2.3) and cell culture medium was measured by inductively coupled plasma-mass spectroscopy. Cell (L929 mouse fibroblasts) response to the specimens was evaluated by water-soluble tetrazolium salt-8 assay (1, 3, and 7 days). The microstructure of the MPS specimen was characterized by fine grain size and predominant ε (hexagonal close-packed) phase. The MPS specimens showed consistently significantly smaller releases of Co ions than the CAST specimens (P<0.05) regardless of the immersion solutions used. Although the cell morphology was normal in both groups, cell viability was consistently significantly higher in the MPS group than in the CAST group (P<0.05). These findings suggest that the MPS-fabricated Co-Cr alloy showed better in vitro biocompatibility than the cast one.