New Radiopaque Bromine-Containing Monomers for Dental Restorative Materials

Four bromine-containing methacrylates 1-4 are synthesized from pentaerythritol tribromide and 2,2,2-tribromoethanol and are characterized by H-1 and C-13 NMR spectroscopy. Their free radical polymerization is performed in dimethylformamide (DMF), using 2,2'-azobis(2-methylpropionitrile) as initiator. The photopolymerization behavior of monomers 1-4 is investigated using a differential scanning calorimeter. Homopolymerizations and copolymerizations with 2-hydroxyethyl methacrylate are carried out. Both the presence of a carbamate group and of bromine atoms result in an increase of the polymerization rate. Dental resins are prepared by replacing a certain amount of 2-(4-cumyl-phenoxy) ethyl methacrylate by monomers 3 and 4 in a model formulation. The incorporation of these methacrylates leads to a significant increase of the radiopacity. Resins based on mono mer 4 exhibit improved mechanical properties.