Fracture Surface Characteristics of Laser-Sintered Co-Cr Alloys vs. Cast Alloys.

Objectives: Laser sintering has become very popular in dentistry in recent years. Mechanical properties of this given material has been evaluated by our research group in previous studies. The purpose of this study was to evaluate the fracture surface of laser-sintered Co–Cr alloy and compare with cast Ni–Cr and Co–Cr alloys and to associate the fracture surfaces with mechanical properties of these alloys which had already been previously presented. 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: Based on our previous study, fracture surfaces showed correlation with the mechanical properties of this three alloys. While laser sintered Co-Cr alloy group, which have the highest yield strength, showed brittle nature of characteristics on fracture surface, the fracture surface of cast Ni-Cr group consists a combination of brittle and ductile fracture characteristics. The cast Co-Cr alloy fracture surface, showed also correlation with its mechanical properties. Conclusions: Mechanical properties of laser-sintered specimens were superior to the cast alloy groups and fracture surfaces of these alloys were associated with their mechanical properties.