Researcher, Department of Prosthodontics/Dental Materials Science, Institute of Odontology, The Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden; Researcher, Department of Prosthetic Dentistry, Institute for Postgraduate Dental Education, Jönköping, Sweden.
Professor, Department of Prosthodontics/Dental Materials Science, Institute of Odontology, The Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden.
J Prosthet Dent. 2023 Aug;130(2):255.e1-255.e10. doi: 10.1016/j.prosdent.2023.05.005. Epub 2023 Jun 23.
Cobalt chromium (Co-Cr) alloys possess beneficial mechanical properties because alloys, even in thin sections, can resist high mastication forces and exhibit an acceptable bond to the surface porcelain layer. Traditional manufacturing techniques of Co-Cr alloys such as casting have been replaced with newer fabrication techniques, such as milling, laser melting, and presintered milling. Despite scarce documentation, these new manufacturing techniques are being used to fabricate dental and implant constructions.
This in vitro study investigates the hardness, yield strength, elastic modulus, and microstructure of the most commonly used Co-Cr alloys for fixed prosthodontics based on manufacturing technique. In addition, this study investigates the effect of heat treatment on the mechanical properties and microstructure of these materials.
Five Co-Cr alloys were included (dumbbell and rectangular shaped) based on four manufacturing techniques: cast, milled, laser melted, and presintered milled. Commercially pure titanium grade 4 and titanium-6 aluminum-4 vanadium ELI (extra low interstitial) were included for comparison, and yield strength and elongation after fracture were evaluated. The specimens were tested for hardness using the Vickers test and for elastic modulus using a nondestructive impulse excitation technique. The microstructure of selected specimens was analyzed using focused ion beam-scanning electron microscopy (FIB-SEM) and energy dispersive X-ray spectroscopy (EDS).
The mechanical properties depend on the manufacturing technique used; the laser-melted and presintered Co-Cr specimens demonstrated the highest mechanical properties, followed by the milled and cast groups. Both the laser-melted and the presintered milled Co-Cr specimens showed smaller grain size compared with the cast and milled Co-Cr specimens. The titanium-6 aluminum-4 vanadium ELI demonstrated higher hardness and yield strength compared to commercially pure titanium grade 4. No major differences were observed for the selected materials regarding the mechanical properties and microstructural appearance after heat treatment.
The laser melting and presintered milling techniques produced higher mechanical properties compared with the cast and milled Co-Cr. These findings were confirmed through microstructural analysis with respect to the grain size, precipitation, and number of pores.
钴铬（Co-Cr）合金具有有益的机械性能，因为即使在较薄的截面中，它们也能抵抗高咀嚼力，并与表面瓷层保持良好的结合。钴铬合金的传统制造技术，如铸造，已被新型制造技术，如铣削、激光熔化和预烧结铣削所取代。尽管文献资料稀缺，但这些新的制造技术正被用于制造牙科和植入物结构。
本体外研究根据制造技术，研究最常用于固定修复的钴铬合金的硬度、屈服强度、弹性模量和微观结构。此外，本研究还研究了热处理对这些材料的机械性能和微观结构的影响。
基于四种制造技术，包括铸造、铣削、激光熔化和预烧结铣削，纳入了五种钴铬合金（哑铃形和矩形）。还纳入了商用纯钛 4 级和钛-6 铝-4 钒 ELI（超低间隙）进行比较，并评估屈服强度和断裂后伸长率。使用维氏测试测量硬度，使用无损脉冲激励技术测量弹性模量。使用聚焦离子束-扫描电子显微镜（FIB-SEM）和能谱分析（EDS）分析选定试样的微观结构。
机械性能取决于所使用的制造技术；激光熔化和预烧结钴铬试样表现出最高的机械性能，其次是铣削和铸造组。与铸造和铣削钴铬试样相比，激光熔化和预烧结钴铬试样的晶粒尺寸更小。钛-6 铝-4 钒 ELI 表现出比商用纯钛 4 级更高的硬度和屈服强度。经热处理后，所选材料在机械性能和微观结构外观方面没有明显差异。
激光熔化和预烧结铣削技术比铸造和铣削钴铬合金产生更高的机械性能。这些发现通过晶粒尺寸、析出物和孔隙数量的微观结构分析得到了证实。
