Cytotoxicity and mutagenicity of restorative systems with/without HEMA/TEGDMA

HEMA and TEGDMA are used in adhesive dentistry as diluents to improve workability or for adhesion purposes. Although cytotoxicity of both molecules is considered less than the one of Bis-GMA or UDMA, they are more water soluble and are found as main constituents of eluates from resin-based composites and adhesives. In concentrations, which are reached in the pulp when applied in deep cavities or directly onto the pulp, HEMA and TEGDMA may cause cellular necrosis or impair the cellular redox balance by increasing the concentration of reactive oxygen species (ROS). The consequence is oxidative DNA-damage followed by a cell cycle delay and apoptosis. Also other pathways may initiate apoptosis, e.g. by the activation of caspase 8 or MAP stress kinases. As a consequence, other cell activities like the activation of mineralization or the immune competence (reaction towards toward LPS) are downregulated. A new adhesive system without HEMA/TEGDMA was therefore tested in comparison with market products (1) in the dentin barrier test according to ISO 7405, and (2) material eluates were analyzed in direct contact to immortalized bovine pulp cells. Furthermore, (3) material eluates were tested for their potential to induce DNA damage (in vitro micronucleus test, V79 cells). The results of the cytotoxicity tests show for the test materials and the control materials no cell reaction in the dentin barrier test and very similar cytotoxic reactions in the direct contact test. However, the HEMA- and TEGDMA-free materials did not induce the formation of micronuclei as a sign of DNA damage. From a biological point of view, materials, which do not lead to DNA damage, may be considered preferable. From the clinical point of view, this finding must be related to other factors, like technical data and durability of these restorative systems.