Objectives: Ring opening molecules like oxiranes maybe suitable for the development of non-shrinking dental composite materials. Since oxiranes are very reactive molecules they can cause adverse effects in living organisms. The introduction of Siloranes, a merger of silane and oxirane, may be a solution to this problem. Therefore, the mutagenicity of four oxiranes and four Siloranes was determined in Salmonella typhimurium tester strains TA97a, TA98, TA100, and TA102. Methods: The experiments were performed in the presence and in the absence of a microsomal fraction from rat liver (S9). The substances were dissolved in tetrahydro-furane (THF) at a ratio of 0,4g/ml and then diluted in THF. Results: The reactive oxirane molecule, epoxy cyclohexyl methyl-epoxy cyclo-hexane carboxylate (K-126) tested positive in S. typhimurium TA100. The numbers of induced mutants were about 3-10-fold higher than spontaneous mutation rates in the presence of S9. However, only a weak mutagenic effect was observed after direct testing (without S9). The substance was inactive in strains TA98, 97a, and TA102. Di(cyclo hexene epoxide methyl)ether also caused a slight increase of mutant numbers in TA100 (2-3 fold) both in the presence and absence of S9. In contrast, no effects were detected with 2,2-Bis(4,1-phenylenoxy-3,1-propanediyl-3-oxatricyclo [3.2.1.02,4]octylcarboxy) propylidene and 2,2-Bis(4,1-phenylenoxy-3,1-propanediyl-3,4-epoxycyclo-hexylcarboxylicacid) propylidene which are both large molecules. 1,4-bis(2,3-epoxypropyloxypropyl-dimethylsilyl)benzene is a direct mutagen in Salmonella typhimurium TA100. It induced a weak but dose-related increase of revertants, and this effect is even activated by a metabolically active microsomal fraction to cause mutant numbers about 7-fold higher than controls. The Siloranes, di-3,4-epoxy cyclohexylmethyl-dimethyl-silane, methyl-bis[2-(7-oxabicyclo[4.1.0]hept-3-yl)phenyl silane, and 1,3,5,7-tetrakis(ethyl cyclohexane epoxy)-1,3,5,7-tetramethyl cyclotetrasiloxane tested negative in all S. typhimurium tester strains. Conclusions: The indicated structure-related mutagenic activities of the resin monomers need to be further analyzed in mammalian cell cultures. Supported by the Bundesministerium für Bildung und Forschung (03N4001B/2).

Back to the Dental Materials: VIII - Others-Non-metallic Program
Back to the IADR/AADR/CADR 80th General Session (March 6-9, 2002)

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