CYTOTOXICITY OF DENTAL ALLOY EXTRACTS AND CORRESPONDING METAL SALT-SOLUTIONS

Adverse tissue reactions of the gingiva and the periodontium close to dental cast alloys may be caused by the effects of released metal elem ents. Tissue reactions depend upon the amounts of elements available w hich are a function of corrosion rates. Since pH values of standard co rrosion solutions are as low as 2.3, such extracts are a priori not bi ocompatible. In the present study, elements released from dental cast alloys into cell-culture media were determined, and the cytotoxicity o f these medium extracts was compared with the effectiveness of metal s alt solutions prepared according to the metal elements found in extrac ts. The elements Ag, Cu, Ni, and Zn were detected in extracts of denta l alloys and copper (positive control) by inductively coupled plasma a tomic emission spectrometry (ICP-AES). Medium extracts of dental alloy s were non-toxic in mouse fibroblasts (L929 cells). However, the amoun ts of elements found in these extracts were weakly cytotoxic when test ed as salt solutions prepared from chloride (Cu2+, Zn2+, Ni2+) or sulf ate (Ag1+) salts. When the test specimens were heat-treated before ext raction, extracts were clearly cytotoxic in a dose-related manner. Aga in, the amounts of elements that caused 50% cell death (TC50) were sli ghtly lower in corresponding salt solutions than in extracts. In gener al, cytotoxicity of medium extracts consistently proved to be slightly less than that of the corresponding salt solutions, probably due to t he limitations of the chemical analysis of extracts. This should be ta ken into account if salt solutions are used instead of the medium extr act.