Synthesis and Characterization of Novel Carbamate-Methacrylate Monomers for Dental Applications

Objective: This investigation seeks to develop and evaluate novel monomers based on carbamate-methacrylate structure with potential to replace BPA derivatives from dental resins, improving conversion, polymerization shrinkage and stress of common dental resin compositions.

Methods: The new monomers were synthesized in a single step procedure in absence of solvent at 70oC. The reaction of the corresponding isocyanate with hydroxyethyl methacrylate was monitored by FT-IR analysis of aliquots of the reaction mixture. After 24h, the isocyanate absorption band at ~2260cm-1 had disappeared, signifying complete reaction. 1H and 13CNMR confirmed the structure of the high viscous monomers. The novel monomers were formulated with either dimer acid derivatives or dimer acid/UDMA. Reaction kinetics as well as final conversion degree was measured by near-infrared spectroscopy. Photo-polymerization shrinkage was determined using a linometer. Polymerization stress was determined using a tensometer. Mechanical strength such as compressive strength, and flexural strength and modulus were also measured. For comparison, all these tests were also performed on a control sample Bis-GMA/TEGDMA 70/30wt%.

Results: The experimental copolymer resin exhibits a 30% reduction in volumetric shrinkage and polymerization stress from the control resins. It does so while achieving a 30% higher functional group conversion.

Conclusion: Novel multifunctional carbamate-methacrylate monomers have been prepared by a simple synthetic route. This is quite general and no purification procedure is required. The higher conversion and lower shrinkage properties associated with polymers containing these monomers makes them attractive as potential replacements for BisGMA and EBPADMA in dental restoratives materials.