Tooth-shaded dental restorations are becoming more and more popular. Currently used dental restorative materials are visible-light curing hybrid materials consisting of a resin matrix, which is a mixture of various free radical crosslinking dimethacrylates such as Bis-GMA (2,2-bis[4-(2-hydroxy-3-methacryloyloxypropyl)phenyl]propane) and TEGDMA (triethylene glycol dimethacrylate) as diluent. TEGDMA shows a relative high cytotoxicity and water solubility, and may cause dose-dependent mutagenic effects in mammalian cell cultures.
In this context, we synthesized new crosslinking monomers, which may substitute diluent TEGDMA in dental resins or composites. The new synthesized monomers were characterized by spectroscopic methods. The photopolymerization behavior of the new monomers was investigated by photo-DSC using the monomolecular Ge-based photoinitiator Ivocerin® (bis-(4-methoxybenzoyl)diethylgerma¬nium). Furthermore, the synthesized crosslinker were tested in experimental dental resin or composite formulations to determine their influence on selected mechanical properties and polymerization shrinkage. Finally, the toxicological properties of the monomers were investigated.
The new synthesized monomers are colorless liquids of relatively low viscosity. Particularly, the urethane unit containing crosslinkers showed a high reactivity in the free radical photopolymerization, which is probably, caused by hydrogen bridge linkages between the urethane monomers. All new monomers formed insoluble highly crosslinked polymer networks and can be used as reactive diluent for the preparation of dental resins or composites.