Initial versus subsequent release of elements from dental casting alloys

The release of elements from dental casting alloys is directly related to a dverse biological effects they may have. Longer-term (>1 month) studies of elemental release have suggested that release decreases significantly after a higher initial release of elements. The aim of the current study was to measure the release of elements from a variety of clinically relevant denta l casting alloys and compare the release at weekly intervals through 4 week s. The hypothesis was that the release during the initial week should be hi gher than in subsequent weeks, and that cytotoxicity should decrease as ele mental release decreases. Alloy samples were exposed to-cell-culture medium which was changed at weekly intervals and assessed for elemental release b y means of atomic absorption spectrometry. The cytotoxicity of the medium w as also measured. The results showed that for single phase alloys, initial release was often significantly higher in the first weeks than in subsequen t weeks, but not for all elements in an alloy. Multiple phase alloys showed steady or increasing release relative to the first week. Cytotoxicity rela tionships were complex depending on which elements were released and the ra tios of elements released. This study suggests that short-term tests (<1 we ek) may not be appropriate to evaluate longer-term elemental release or cyt otoxicity because of changing rates of elemental release.