Assessment of mechanical properties and microstructure of Co-Cr dental alloys manufactured by casting, milling, and 3D printing.

Abstract

Statement of problem: The mechanical properties and microstructure of cobalt chromium (Co-Cr) alloys should be considered when choosing the best alloy for each clinical situation. More information is needed on the digital manufacturing methods of metals in dentistry, such as computer numerical control (CNC), and direct laser metal sintering (DMLS).

Purpose: The aim of this study was to investigate the effect of the 3 different Co-Cr manufacturing processes on the mechanical properties and microstructure of Co-Cr dental alloys.

Material and methods: Dumbbell-shaped specimens (n=6) were fabricated using casting (CAST), CNC, and DMLS techniques. Tensile, 3-point bend, and microhardness testing were performed, and the microstructure evaluated through scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction analysis. The ANOVA test followed by post hoc Tukey tests were used for statistical analysis (α=.05).

Results: DMLS showed the greatest values for 0.2% yield strength (908.0 ±13.1 MPa), tensile strength (1123.7 ±6.5 MPa), flexural strength (2273.0 ±43.2 MPa), and microhardness (438.2 ±44.9 HV), followed by CAST and CNC. No statistical differences were found for elongation between CNC and DMLS or DMLS and CAST (P>.05). No statistical differences were found in elastic modulus among all groups (P>.05). EDX revealed a slightly different chemical composition among the groups. XRD showed face-centered cubic as the dominant phase and a small amount of hexagonal close-packed structure in all groups. A peak of σ phase was identified in the CAST group.

Conclusions: The mechanical properties and microstructures of Co-Cr dental alloys were significantly influenced by the fabrication method used. DMLS and CNC milling produced better products that traditional methods, leading to the improved durability and reliability of dental prostheses. These advancements underscore the importance of selecting appropriate fabrication methods to optimize clinical outcomes and patient satisfaction.