Predoctoral student, School of Manufacturing Science and Engineering, Sichuan University, Chengdu, PR China.
Professor, School of Manufacturing Science and Engineering, Sichuan University, Chengdu, PR China.
J Prosthet Dent. 2019 May;121(5):848-857. doi: 10.1016/j.prosdent.2018.08.017. Epub 2019 Jan 16.
The metal-ceramic bond strength of dental casting Co-Cr alloys may be improved by the addition of the rare earth element lanthanum (La), but studies are lacking.
The purpose of this in vitro study was to evaluate the effects of the rare earth element La on the metal-ceramic bond strength of dental casting Co-Cr alloys.
Four groups of specimens with different La content (0; 0.02 wt%; 0.04 wt%; 0.06 wt%) were prepared using conventional casting methods. The metal-ceramic bond strength was assessed by using the 3-point bend test. The microstructures were characterized by metallurgical microscopy, scanning electron microscopy, and X-ray diffraction analyses. The morphology and element distribution of metal-ceramic interfaces were evaluated by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The results of bond strengths were statistically analyzed by the Tukey honest significant difference (HSD) test (α=.05).
The specimens showed typical dendritic microstructures, few defects, and island-shaped intermetallic compounds rich in Mo and Cr, mainly consisting of α-Co phase of a face-centered cubic (FCC) structure and ε-Co phase of a close-packed hexagonal (HCP) structure. As the amount of La increased, the thickness of the native oxide layer and the diffusion layer at the interface increased, and the wettability between the oxide layer and the metal matrix improved. The mean ±standard deviation values of the metal-ceramic bond strengths were 28.11 ±4.53 MPa for group 0%, 33.13 ±5.65 MPa for group 0.02%, 37.48 ±7.86 MPa for group 0.04%, and 40.70 ±5.17 MPa for group 0.06%. The statistical analysis indicated that significant differences (P<.05) were observed among all groups tested, except for group 0.04% and 0.06% (P>.05). The debonded surfaces of Co-Cr specimens showed a mixed type of adhesive and cohesive fractures.
The microstructures, morphologies, and compositions of oxide films were influenced by the La content, and the La addition could significantly improve the metal-ceramic bond strength of dental casting Co-Cr alloys.
在牙科铸造 Co-Cr 合金中添加稀土元素镧（La）可以提高金属-陶瓷结合强度，但目前相关研究较少。
本体外研究的目的是评估稀土元素 La 对牙科铸造 Co-Cr 合金金属-陶瓷结合强度的影响。
采用常规铸造方法制备了 4 组不同 La 含量（0、0.02wt%、0.04wt%、0.06wt%）的试件。采用三点弯曲试验评估金属-陶瓷结合强度。采用金相显微镜、扫描电子显微镜和 X 射线衍射分析对微观结构进行了表征。采用扫描电子显微镜结合能谱分析对金属-陶瓷界面的形貌和元素分布进行了评估。采用 Tukey 诚实显著差异（HSD）检验（α=.05）对结合强度结果进行了统计学分析。
试件呈现典型的树枝状微观结构，缺陷较少，且富含 Mo 和 Cr 的岛状金属间化合物，主要由面心立方（FCC）结构的α-Co 相和密排六方（HCP）结构的ε-Co 相组成。随着 La 含量的增加，界面处的自然氧化层和扩散层厚度增加，氧化层与金属基体的润湿性提高。0%组、0.02%组、0.04%组和 0.06%组的金属-陶瓷结合强度的平均值±标准差分别为 28.11±4.53 MPa、33.13±5.65 MPa、37.48±7.86 MPa 和 40.70±5.17 MPa。统计分析表明，除 0.04%组和 0.06%组（P>.05）外，其余各组间差异均有统计学意义（P<.05）。Co-Cr 试件的脱粘表面呈现出混合的黏附性和内聚性断裂。
La 含量影响氧化膜的微观结构、形貌和组成，添加 La 可显著提高牙科铸造 Co-Cr 合金的金属-陶瓷结合强度。
