Comparison of the mechanical properties and microstructures of fractured surface for Co-Cr alloy fabricated by conventional cast, 3-D printing laser-sintered and CAD/CAM milled techniques

Abstract

Purpose:The purpose of present study is to compare mechanical properties and microstructural characteristics of fractured surface for cast, 3-D printing laser sintered and CAD/CAM milled cobalt-chromium (Co-Cr) alloy specimens and to investigate whether laser sintered technique is adequate for dental applications. Materials and methods: Thirty six flat disc shape Co-Cr alloy specimens were fabricated for surface hardness test and divided into three groups according to the manufacturing methods; 12 specimens for casting (n=12), 12 specimens for laser sintered technology (n=12) and 12 specimens for milled technology (n=12). Twelve dumbbell shape specimens for each group were also fabricated for a tensile test. Statistical comparisons of the mechanical properties for the alloys were performed by Kruskal-Wallis test followed by Mann-Whitney and Bonferroni test. The microstructural characteristics of fractured surfaces were examined using SEM. Results: There were significant differences in the mean Vickers hardness values between all groups and the cast specimen showed the highest (455.88 Hv) while the CAD/CAM milled specimen showed the lowest (243.40 Hv). Significant differences were found among the three groups for ultimate tensile strength, 0.2% yield stress, elongation, and elastic modulus. The highest ultimate tensile strength value (1442.94 MPa) was shown in the milled group and the highest 0.2% yield strength (1136.15 MPa) was shown in the laser sintered group. Conclusion: Different manufacturing methods influence the mechanical properties and microstructure of the fractured surfaces in Co-Cr alloys. The cast Co-Cr alloy specimens showed the highest Vickers hardness, and the CAD/CAM milled specimens revealed the highest tensile strength value. All alloys represent adequate mechanical properties satisfying the ISO standards of dental alloy. (J Korean Acad Prosthodont 2014;52:67-73)

Additive Technology: Update on Current Materials and Applications in Dentistry

“…In comparison, digital workflow methods are improving and becoming on par with the sometimes less predictable traditional techniques; however, as noted earlier, the current subtractive manufacturing technique has issues with material wastage, stress on cutting tips, and shrinkage during processing. This can make milling machines less than ideal for the fabrication of CoCr structures …”

“…For tensile testing of DMLS‐fabricated CoCr, most did not use specimens with dimensions or methodology according to standardized testing criteria . Others did not analyze the adhesion strength between porcelain and metal, although it is one of the most common modifications to CoCr metals in dental prostheses and is also the most likely site of failure . Even when adhesion testing was done, the number of specimens used was either too small for proper statistical analysis, did not use a known standard testing method, or appears to have been done incorrectly .…”

“…The popularity of this alloy is attributed to its relatively inexpensive cost and good physical properties, making it an ideal material for certain dental restorations such as crown substructures. This is because traditional manufacturing methods, such as casting, are usually difficult due to the high melting point of CoCr, its hardness, and lack of ductility . This article will review current applications, materials, advantages, and limitations of additive manufacturing.…”

“…This is because traditional manufacturing methods, such as casting, are usually difficult due to the high melting point of CoCr, its hardness, and lack of ductility. 6 This article will review current applications, materials, advantages, and limitations of additive manufacturing. Because of its emerging use within manufacturing technique, particular focus will be given to current research and the manufacturing method of CoCr alloy.…”

Rehabilitación de rebordes severamente atróficos mediante prótesis híbridas confeccionadas con tecnología de sinterización láser cromo-cobalto; reporte de caso

“…La evidencia no ha demostrado diferencias importantes en el desempeño clínico de subestructuras confeccionadas con aleaciones nobles respecto a no nobles 8 . En este contexto, aleaciones cromo-cobalto constituyen una alternativa viable para la confección de subestructuras protésicas sobre implantes, con un módulo de elasticidad de 225.000 Mpa 9 , resistente a la corrosión y más económica comparada con aleaciones de oro o titanio 10 .…”