Sarkar N K
LSU School of Dentistry, New Orleans 70119, USA.
Dent Mater. 1999 Nov;15(6):421-5. doi: 10.1016/s0109-5641(99)00069-x.
In reinforced materials, interfacial bonding is critical for efficient transfer of stress from the matrix to the reinforcement. The goal of this study was to characterize the physical and chemical nature of this interface in three metal-reinforced glass ionomers. Two of them were commercial, ESPE-Ketac Silver (KS) and GC-Miracle Mix (MM), and the third, EX, was experimental.
The techniques of scanning electron microscopy (SEM) and infrared spectroscopy (IR) were used to accomplish the stated goal. SEM analysis utilized polished sections of set cylindrical specimens of each material prepared from their respective powder and liquid components. The glass and the liquid in EX were the same as in MM. The reinforcing agent in EX, 50% by weight, was an Ag-base spherical alloy similar in composition to that in MM. For EX, the alloy was oxidized to promote its bonding to the matrix. The specimens for IR study were prepared as follows. The metallic powders of each material were mixed with the corresponding liquid in excess, stored at 37 degrees C for 1 h, washed with warm water (60 degrees C), filtered and dried. The untreated metallic powders served as controls for IR analysis.
SEM revealed a distinct halo shaped internal reaction layer surrounding each alloy particle in EX. A similar layer was not seen in MM and KS. The alloy-matrix interface was continuous and gap-free in EX. In contrast, gaps separating matrix from respective reinforcements were conspicuous features in MM and KS. The IR spectrum of the liquid treated EX alloy powder showed absorbency bands characteristic of unreacted carboxyl groups and carboxylate salts. These bands were absent in the IR spectra of all other powders--treated and untreated.
The absence of interfacial bonding in MM and KS demonstrated in this study provides a reason why these two materials, in spite of metal addition, have not proved to be any stronger or more durable than their metal-free counterparts. A means of creating interfacial bonding presented here could be useful in the design of improved reinforced glass ionomer materials.
在增强材料中，界面结合对于应力从基体有效传递到增强体至关重要。本研究的目的是表征三种金属增强玻璃离子体中该界面的物理和化学性质。其中两种是商业产品，ESPE-Ketac Silver（KS）和GC-Miracle Mix（MM），第三种EX是实验性的。
使用扫描电子显微镜（SEM）和红外光谱（IR）技术来实现所述目标。SEM分析使用由各自的粉末和液体成分制备的每种材料的固化圆柱形试样的抛光截面。EX中的玻璃和液体与MM中的相同。EX中的增强剂，按重量计50%，是一种Ag基球形合金，其成分与MM中的相似。对于EX，合金被氧化以促进其与基体的结合。用于IR研究的试样制备如下。将每种材料的金属粉末与相应的液体过量混合，在37℃下储存1小时，用温水（60℃）洗涤，过滤并干燥。未处理的金属粉末用作IR分析的对照。
SEM显示EX中每个合金颗粒周围有一个明显的晕圈状内部反应层。在MM和KS中未观察到类似的层。EX中的合金-基体界面是连续且无间隙的。相比之下，在MM和KS中，基体与各自增强体之间的间隙是明显特征。液体处理过的EX合金粉末的IR光谱显示出未反应的羧基和羧酸盐的吸收带特征。所有其他处理过和未处理过的粉末的IR光谱中均没有这些谱带。
本研究中证明的MM和KS中不存在界面结合，解释了为什么这两种材料尽管添加了金属，但并未被证明比无金属的同类材料更强或更耐用。这里提出的一种产生界面结合的方法可能有助于改进增强玻璃离子体材料的设计。
