The effect of reusing metal powders in laser sinter production without adding new powder on the chemical properties of the metal and the metal-porcelain connection

Purpose: The aim of this in vitro study is to evaluate the effect of reusing Co-Cr alloy powders used in laser sinter production without adding new powder on the chemical, physical properties and metal-ceramic bonding of the alloy powder. Material and methods: In the research, EOSINT M 270 (EOS GmbH, Krailling, Germany) DSLM device was used to prepare all metal samples and AdorBond CC Plus (Ador Dental GmbH, Hilden, Germany) was used as metal alloy powder. 20 kg of unprocessed powder was loaded into the laser sintering device. Samples were produced in the first (Group 1), fourth (Group 2), seventh (Group 3), tenth (Group 4), and thirteenth (Group 5) production cycles (N=15). Powder alloy samples were collected from the powder bed for analysis before the production of the samples. After porcelain was applied to the samples, elastic modulus and metal-porcelain bond strength were calculated using the three-point bending test. The chemical properties of the alloy powder samples were examined by SEM-EDS, laser particle size distribution, Xrd Microanalysis Phase Analysis, ICP-MS - trace element analysis. One-way ANOVA and Tukey tests were used for statistical analysis. Results: 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 5 (78.26 ± 39.5 MPa), and the lowest bond strength value was observed in Group 3 (56.86 ± 8.2 MPa). No significant differences were found between the groups in terms of laser particle size analysis, scanning electron microscope images, and XRD test results. According to the ICP-MS results, Mo, W, and Co ions reached the highest value in Group 5. The highest value for Si ion was detected in Group 4, and for Nb ion in Group 3. No Cr ions were found 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. There has been no significant change in the physical and chemical properties of the metal alloy powder as a result of reuse.