COMPARATIVE-STUDIES ON CYTOTOXIC EFFECTS OF DENTAL AMALGAMS AND ALTERNATIVE ALLOYS ACCORDING TO ISO STANDARDS IN-VITRO

Deleterious effects of dental alloys, especially those of dental amalg ams, have become an important issue in current discussions on biomater ials. Cytotoxicity and further related risks of amalgams are discussed in a controversial way in the literature without leading to a final c onclusion. There is still a need for basic clinical and pre-clinical r esearch, especially with respect to the wide distribution of dental am algams. Standardized methods of cytotoxicity testing have been establi shed by the ISO. It was the aim of the present study to detect and com pare possible cytotoxic effects of dental amalgams and alternative non -amalgam alloys in vitro. According to the ISO standards, direct conta ct tests and extract dilution tests were performed using the cell line s HeLa and L-929 as well as primary isolated human fibroblasts, a rele vant cell type of the human gingiva. For direct contact tests the samp les were fixed on thermanox discs. Zn and Ni-chloride in defined molar concentrations were used as positive controls in the extract dilution tests, while copper was the positive control in the direct contact te sts. The tested amalgam was a Non-Gamma-2 amalgam. For extract dilutio n tests sixteen extraction dilutions were performed. The different cel l types were incubated with the extracts in 96-well microtitre plates. MTT-testing was performed to evaluate the effects on cellular metabol ism. The BrdU labelling index was determined with the help of EIA meth ods to analyse the effects of the extracts on the cellular proliferati on at DNA synthesis level. The morphological status of the cells seede d on the materials (direct contact test) were studied with the help of light microscopy. No cytotoxic effects of formerly extracted dental a malgam was found, although fresh amalgam elicited a significant cytoto xic effect, in general the non-amalgams have to be regarded as non cyt otoxic. The negative control and the non-amalgams elicited no measurab le cytotoxicity in the indirect contact assays, independent of the num ber of extraction dilutions. This applied to all cell types studied. T he tested amalgam also gave a significant cytotoxic effect in the MTT- assays, while in addition a significant reduction of BrdU incorporatio n after incubation with the extracts of the first dilution series, com pared to the silicone control was found. The effects were reduced afte r an incubation with the extracts of the higher dilution series. It is suggested by the presented results that amalgams might have cytotoxic effects, especially when being freshly applied. The cytotoxic effects were no longer detectable after extraction procedures. Nevertheless, a negative effect around such amalgams must be considered. The insight s provided by the present studies might be helpful for a rational choi ce of dental materials.