Evaluation of the effect of reuse of Co-Cr alloy powders used in laser sinter production on the chemical and physical properties of the alloy powder and the metal-ceramic bond strength

Purpose: The aim of this in vitro study is to evaluate the effect of reuse of Co-Cr alloy powders used in laser sinter production on the chemical and physical properties of the alloy powder and the metal-ceramic bond strength. Material and methods: The production of the 1st Group samples was carried out with virgin metal alloy powder, the remaining powder from the production was sifted and mixed to make 70% virgin powder and 30% reused powder, and the 2nd Group samples were obtained as 50% virgin and 50% reused powder. Group 3 samples were produced by mixing so that 30% were virgin and 70% were reused powder, and Group 5 samples were produced with completely reused powder (N=15). Prior to fabricating the specimens, powder alloy samples were collected from the powder bed for analysis. A total of 75 metal bar-shaped samples were produced with the EOSINT M 270 (EOS GmbH, Krailling, Germany) DMLS device. EOS CobaltChrome SP2 (EOS GmbH) was used as metal alloy powder. After ceramic application, the metal-ceramic joint strength was evaluated by three-point bending test. Statistical analysis of the data was performed using one-way ANOVA and Tukey tests. Scanning electron microscopy (SEM-EDS), Xrd microanalysis, ICP-MS trace element analysis and grain size measurement were performed for alloy powder samples. Results: There was no statistically significant difference was found between the groups in terms of bond strength (P >0.05). The highest bond strength value was observed in Group 2 containing 70% virgin powder (70.69 ± 36.5 MPa), and the lowest bond strength value was observed in Group 3 containing 50% virgin powder (53.26 ± 14.8 MPa). The results of laser grain size analysis and scanning electron microscope images support each other and show that there are no significant differences between the groups. In the Xrd analysis results, it was observed that there was no phase deviation between the groups and all powder alloy samples were in the cubic phase. According to ICP-MS analysis results; the highest values for Mo, W and Co ions are seen in Group 2. The highest value for Si ion is seen in Group 3 and for Nb ion in Group 5. Chromium ion was not detected in any of the groups. Conclusion: Within the limitations of the study, it was concluded that reusing alloy powder have no effect on metal-ceramic bond strength. No change was found in the physical and chemical properties of the metal alloy powder as a result of reuse.