用于金属陶瓷牙科修复体的铸造和热压 CoCrMo 合金的微观结构、硬度、耐腐蚀性和瓷剪切粘结强度比较。
Microstructure, hardness, corrosion resistance and porcelain shear bond strength comparison between cast and hot pressed CoCrMo alloy for metal-ceramic dental restorations.
机构信息
Center for Mechanical and Materials Technologies, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal.
出版信息
J Mech Behav Biomed Mater. 2012 Aug;12:83-92. doi: 10.1016/j.jmbbm.2012.03.015. Epub 2012 Mar 30.
OBJECTIVES
The purpose of this study was to compare the microstructure, hardness, corrosion resistance and metal-porcelain bond strength of a CoCrMo dental alloy obtained by two routes, cast and hot pressing.
METHODS
CoCrMo alloy substrates were obtained by casting and hot pressing. Substrates' microstructure was examined by the means of Optical Microscopy (OM) and by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). Hardness tests were performed in a microhardness indenter. The electrochemical behavior of substrates was investigated through potentiodynamic tests in a saline solution (8g NaCl/L). Substrates were bonded to dental porcelain and metal-porcelain bond strength was assessed by the means of a shear test performed in a universal test machine (crosshead speed: 0.5 mm/min) until fracture. Fractured surfaces as well as undestroyed interface specimens were examined with Stereomicroscopy and SEM-EDS. Data was analyzed with Shapiro-Wilk test to test the assumption of normality. The t-test (p<0.05) was used to compare shear bond strength results.
RESULTS
Cast specimens exhibited dendritic microstructures whereas hot pressed specimens exhibited a typical globular microstructure with a second phase spread through the matrix. The hardness registered for hot pressed substrates was greater than that of cast specimens, 438±24HV/1 and 324±8HV/1, respectively. Hot pressed substrates showed better corrosion properties than cast ones, i.e. higher OCP; higher corrosion potential (E(corr)) and lower current densities (i(corr)). No significant difference was found (p<0.05) in metal-ceramic bond strength between cast (116.5±6.9 MPa) and hot pressed (114.2±11.9 MPa) substrates. The failure type analysis revealed an adhesive failure for all specimens.
SIGNIFICANCE
Hot pressed products arise as an alternative to cast products in dental prosthetics, as they impart enhanced mechanical and electrochemical properties to prostheses without compromising the metal-ceramic bond strength.
目的
本研究旨在比较两种途径（铸造和热压）获得的 CoCrMo 牙科合金的微观结构、硬度、耐腐蚀性和金属-陶瓷结合强度。
方法
通过铸造和热压获得 CoCrMo 合金基底。通过光学显微镜（OM）和扫描电子显微镜（SEM）和能谱（EDS）观察基底的微观结构。使用显微硬度计进行硬度测试。通过在盐溶液（8g NaCl/L）中进行动电位测试研究基底的电化学行为。通过万能试验机（十字头速度：0.5mm/min）进行剪切试验将基底粘结到牙科瓷上，并评估金属-陶瓷结合强度，直到断裂。用立体显微镜和 SEM-EDS 检查断裂表面和未破坏的界面样品。用 Shapiro-Wilk 检验法检验正态性假设。使用 t 检验（p<0.05）比较剪切结合强度结果。
结果
铸造样品表现出树枝状微观结构，而热压样品表现出典型的球形微观结构，第二相散布在基体中。热压基底的硬度大于铸造基底，分别为 438±24HV/1 和 324±8HV/1。热压基底的耐腐蚀性优于铸造基底，即更高的 OCP；更高的腐蚀电位（E(corr)）和更低的电流密度（i(corr)）。铸造（116.5±6.9 MPa）和热压（114.2±11.9 MPa）基底的金属-陶瓷结合强度无显著差异（p<0.05）。失效类型分析表明所有样品均为黏附性失效。
意义
热压产品可作为牙科修复体中铸造产品的替代品，因为它们在不影响金属-陶瓷结合强度的情况下赋予修复体增强的机械和电化学性能。
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