Abstract
In order to study the changes of the intraoral metals, the surface condition and composition of the crowns removed from mouths were analyzed by SEM and EPMA. Thirty-four samples were categorized into four types of alloys. Corrosive changes were evaluated by comparing the analysis results between the crown surface and its fresh sectioned surface, and also with the data from former studies.
1. Changes observed in the Au alloys were slight compared to the other three types, both in surface feature and composition, except for a slight decreace in Cu.
2. In some Au-Ag-Pd alloys, nearly no dissolution was evident. Composition changes were small, with a slight decrease in Ag and relative increase in Pd.
3. The greatest changes were observed in the Ag-Sn-Zn alloys and Ag-In alloys, even with short intraoral usage period. Generally, their surfaces were rough, with thick layers of organic materials. The dendritic structure was distinct, and dissolution between each dendrite was observed.
4. Many of the Ni-Cr alloys presented dendritic structure with dissolution. Decrease in Ni and relative increase in Si and Cr were observed.
5. Corrosive changes showed a close resemblance to the results obtained by the conven-tional basic tests. However, there were some features which did not coincide, depending on the types of alloys.
