Mechanical Properties of Laser Sintered Co-Cr Alloys vs. Cast Alloys

Even though laser sintering and rapid manufacturing are popular in dentistry, mechanical properties of the corresponding material should be investigated before clinical application. Objective: To compare mechanical properties of laser-sintered Co–Cr alloy with cast Ni–Cr and Co–Cr alloys. Methods: Fifteen specimens were prepared according to ISO 22674 standards for each group. Tensile testing was performed on a universal testing machine to obtain tensile strength, percent elongation and yield strength. Each specimen was tested with a crosshead speed of 1 mm/min until the fracture occurred. Statistical analysis was performed using ANOVA followed by Tukey test. Fractured specimens were observed with stereomicroscope and scanning electron microscope. Finally, fractured halves of each specimen were linked to measure percent elongation. Results: The yield strength of specimens were 344,8 ± 40.5 MPa for cast Co-Cr group, 245.9 ± 65.9 MPa for cast Ni-Cr group and 375.6 ± 35.9 MPa for laser-sintered Co-Cr group. While there was a significant difference between cast Co-Cr and cast Ni-Cr specimens (P<0.001), no statistically significant difference was found between cast Co-Cr and laser sintered Co-Cr (P=0.329). The ultimate tensile strength was highest for the laser-sintered specimens (1143,9 ± 38,7 MPa) and there was no significant difference between cast Ni-Cr (439.6 ± 58.1 MPa) and Co-Cr (450.6 ± 85.7 MPa) specimens (P=0.910). For elongation, significant differences were found among three groups. Percent elongation values were 13 ± 2 for cast Co-Cr alloy, 34 ± 8 for cast Ni-Cr alloy and 11 ± 1 mm for laser sintered Co-Cr alloy. The cast Ni-Cr specimens showed the highest value and a significant difference was found between the cast and laser sintered Co-Cr alloys (P<0.001). Conclusions: Mechanical properties of laser-sintered specimens were comparable to the cast alloy groups. Further research has to be established before common clinical application.