Urethane tetramethacrylates: Novel substitutes as resin matrix in radiopaque dental composites

Dental composites used in conservative and orthodontic dentistry are based on bisphenol A–glycidyl methacrylate (BIS–GMA) resin. However, certain limitations, such as high viscosity and handling difficulties, restrict the use of BIS–GMA and attempts have been made to modify the resin or to seek alternate materials. The synthesis and characterization of a urethane tetramethacrylate resin (UTMA) is reported here, which when reinforced with a silanated radiopaque glass filler, is found to provide composite pastes with superior properties. Composite pastes with formulations of varying BIS–GMA/UTMA blend ratios have been prepared and their effect on the compressive strength, diametral tensile strength, transverse strength, Vickers microhardness, water sorption, and opacity have been studied. The photoinitiator concentration has been varied for 100% urethane‐based composite and its optimum concentration standardized. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 735–746, 1999