Aresin-modifiedglass-ionomercement(Vitrebond[M) exhibited strong genotoxic action. Extracts of this rmGlC induced sister chromatid exchange in human peripheral lymphocytesinvitro.Genotoxicitywasverifiedbythreedif- ferent in vitro and in vivo assays: the procaryotic umu test, the eucaryotic DIT, and the in vivo NFE assay. Analysis of waterextractsofthisGICindicatesthatleachingoftheini- tiator, DPIGI, may contribute to this strong genotoxic action(Heiletal 1996;Steaetal.,1998)(Table2).