EFFECT OF ALLOY SURFACE-COMPOSITION ON RELEASE OF ELEMENTS FROM DENTAL CASTING ALLOYS

The release of elements from dental casting alloys is a continuing con cern because of the potentially harmful biological effects the element s may have on local tissues. The surfaces of the alloys appear to be m ost important in controlling the release of these elements. In the cur rent study, the surfaces of high-, reduced-, and no-gold dental alloys were analysed by X-ray photoelectron spectroscopy before and after th ey were exposed to a biological medium for up to 96 h. The goal was to relate the release of elements from these alloys to their surface com position, and to determine the depth of the effect of the medium. The depth of the effect of the exposure was determined by argon milling of the alloy surface after exposure to the medium. Elements that were re leased into the medium were measured by means of atomic absorption spe ctroscopy. The release of elements from alloys was greater when the at omic ratio of noble to non-noble elements at the surface was less than l. The depth of the effect of the medium varied with the alloy, but w as always less than 100 Angstrom. The surface composition was signific antly different from layers only 5 Angstrom below. It was concluded th at the surface concentration of noble elements is important in control ling the release of non-noble elements from these alloys, and the surf ace composition appeared to be only one or two atomic layers thick. Of the three types of alloys, the high-gold alloy appeared to develop th e most stable surface composition which released the lowest levels of elements.