Zhou Yanan, Dong Xin, Li Ning, Yan Jiazhen
Lecturer, School of Mechanical Engineering, Shandong University of Technology, Zibo, PR China.
Graduate student, School of Mechanical Engineering, Sichuan University, Chengdu, PR China.
J Prosthet Dent. 2023 Apr;129(4):657.e1-657.e9. doi: 10.1016/j.prosdent.2022.11.029. Epub 2023 Feb 25.
Dental cobalt-chromium (Co-Cr) alloy manufactured by selective laser melting (SLM) is not recommended for clinical applications before annealing because of excessive residual stress. However, limited information is available regarding the relationship between annealing temperature and the metal-ceramic bond properties of SLM Co-Cr alloys.
The purpose of this in vitro study was to investigate the effects of annealing temperature on the metal-ceramic bond properties of SLM Co-Cr alloys.
Four groups with different annealing temperatures (850 °C; 950 °C; 1050 °C; 1150 °C) were prepared by using SLM techniques. Bond strengths were measured by using a 3-point bend test; subsequently, debonded surface morphologies and elements were assessed by using a scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). The area fraction of adherence porcelain (AFAP) value was introduced to analyze fracture characteristics. Microstructural and interfacial characteristics were characterized by SEM/EDS and X-ray diffraction analysis. The coefficient of thermal expansion (CTE) test was used to analyze thermal matching. A 1-way ANOVA and the Tukey honestly significant difference tests were used to analyze bond strengths and AFAP values statistically (α=.05).
The mean ±standard deviation values of the metal-ceramic bond strengths were 40.68 ±4.34 MPa for the 850 °C group, 37.54 ±5.34 MPa for the 950 °C group, 45.97 ±2.18 MPa for the 1050 °C group, and 50.79 ±1.79 MPa for the 1150 °C group. Significant differences (P<.05) were observed among all groups. Debonded surfaces and AFAP analysis displayed a mixed fracture mode of adhesive and cohesive fracture, and 1150 °C-annealing specimens exhibited better fracture characteristics close to cohesive fractures. As the temperature increased, native oxide film thicknesses remained unchanged; the 850 °C group had the thinnest diffusion layer, while the other 3 groups had similar thicknesses. Although the 1050 °C and 1150 °C groups displayed higher CTE values, their microstructures were more conducive to atomic diffusion and improved chemical bonding. Microstructure analysis found that ε phase and second-phase precipitates jointly affected metal-ceramic bond strength.
Annealing temperatures affected the metal-ceramic bond strengths of SLM Co-Cr porcelain specimens. 1150 °C annealing SLM Co-Cr specimens displayed higher bond strengths and improved fracture and interface characteristics among the 4 groups.
通过选择性激光熔化（SLM）制造的牙科钴铬（Co-Cr）合金，由于残余应力过大，在退火前不建议用于临床应用。然而，关于退火温度与SLM Co-Cr合金的金属-陶瓷结合性能之间的关系，现有信息有限。
本体外研究的目的是探讨退火温度对SLM Co-Cr合金的金属-陶瓷结合性能的影响。
采用SLM技术制备了四组不同退火温度（850℃；950℃；1050℃；1150℃）的样本。通过三点弯曲试验测量结合强度；随后，使用扫描电子显微镜（SEM）结合能量色散X射线光谱（EDS）评估脱粘表面形态和元素。引入附着瓷面积分数（AFAP）值来分析断裂特征。通过SEM/EDS和X射线衍射分析对微观结构和界面特征进行表征。使用热膨胀系数（CTE）测试来分析热匹配。采用单因素方差分析和Tukey真实显著差异检验对结合强度和AFAP值进行统计学分析（α = 0.05）。
850℃组的金属-陶瓷结合强度的平均值±标准差为40.68±4.34MPa，950℃组为37.54±5.34MPa，1050℃组为45.97±2.18MPa，1150℃组为50.79±1.79MPa。所有组之间均观察到显著差异（P<0.05）。脱粘表面和AFAP分析显示了粘结和内聚断裂的混合断裂模式，1150℃退火的样本表现出更接近内聚断裂的更好的断裂特征。随着温度升高，原生氧化膜厚度保持不变；850℃组的扩散层最薄，而其他三组厚度相似。尽管1050℃和1150℃组显示出较高的CTE值，但其微观结构更有利于原子扩散并改善化学键合。微观结构分析发现，ε相和第二相析出物共同影响金属-陶瓷结合强度。
退火温度影响SLM Co-Cr瓷样本的金属-陶瓷结合强度。在四组中，1150℃退火的SLM Co-Cr样本显示出更高的结合强度，并改善了断裂和界面特征。
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