Cyclopolymerizable monomers for use in dental resin composites

The simple reaction of conventional monofunctional acrylate monomers with paraformaldehyde has yielded a new class of difunctional monomers. The unique proximity of the double bonds within these compounds allows a facile cyclopolymerization to incorporate a cyclic ether structure into the polymer backbone. The external position of the acrylate esters means that these pendant groups can be varied for alteration of the physical properties of the monomers and the corresponding polymers. A series of the new monomers has been prepared and polymerized under dilute solution and bulk conditions to yield non-crosslinked and crosslinked polymers, respectively. The polymers exhibited high degrees of conversion and significantly reduced polymerization shrinkage, compared with polymers obtained from conventional diacrylate or dimethacrylate monomers. These properties appear to be a direct result of an efficient cyclopolymerization process. The combination of improved conversion to polymer with less contraction makes these monomers ideal candidates for use in dental resin composites. A preliminary evaluation of their potential in this application has shown that with suitable ester functionality, they can be formulated to provide composites with excellent mechanical strength properties.