Biocompatibitiy comparison of laser sintered cocr alloy with cast metal alloys

Direct Selective Laser Sintering Method (SLS) that has been used over the past twenty years is an alternative contemporary technique to casting in dentistry. This new technology has some advantages compared to conventional methods like reducing manufacturing time and cost, reducing the laboratory procedures effects tecnicians health and enables production of structures with high mechanical properties. The aim of this study was to compare the corrosion resistance, ion release and biocompatibility of laser sintered CoCr dental alloy with conventionally cast NiCr and CoCr dental alloys. For electrochemical studies cylindrical specimens with 11mm diameter, 3mm height and a 1 mm hole in the middle (n=5/group) were tested in artificial salivia. For this purpose, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests were used. The same specimens were used to evaluate ion release with the help of inductively coupled plasma mass spectrometry (ICPMS) quantitatively. Specimens with 3mm diameter and 5mm heigth were prepared for cell culture tests (n=6/group). The biocompatibilitiy of groups were evaluated using 3T3 mouse fibroblast cell culture's kept in Dulbecco's Modified Eagle's Medium (DMEM) and mitochondrial activity assay (MTT) was used. Results of elemental release were statistically analysed using two-way ANOVA followed by post-hoc Tukey test and cell culture results were compared using one-way ANOVA followed by the Tukey test (α= 0.05). The results of electrochemical tests showed that laser sintering method increases the corrosion resistance and decreases the ion release. Nickel (Ni) release from cast NiCr alloys (0.0724 ppm) was higher than cast CoCr (0.0027 ppm) and laser sintered CoCr alloys (0.0008 ppm). Cobalt (Co) release from cast CoCr alloy (0.369 ppm) were higher than laser sintered CoCr (0.312 ppm) alloy and the difference was statistically significant. The average viability percentage value (optical absorbance values) of cells that NiCr discs were placed in (0.333 ± 0.102) showed statistically significant differences than the control group (0.554 ± 0.06). Cast CoCr (0.404 ± 0.341) and laser-sintered CoCr (0.450± 0.051) alloys were not statistically significantly different than the cast NiCr and control groups. With the limitations of this study results from the current in vitro experiments can be concluded as that the selective laser sintering method affects the biocompatibility of dental alloys positively.