Synthesis of a novel isosorbide-based dental material with improved water sorption

We attempted to improve the low water resistance of isosorbide glycidyl methacrylate (IsoGMA), which was developed to replace bisphenol-A glycidyl methacrylate (BisGMA), a bisphenol-A based dental material. For this purpose, a new isosorbide-based methacrylate, isosorbide propyl methacrylate (IsoPMA), which has no hydroxyl groups, was synthesized. IsoPMA had low viscosity compared to IsoGMA (246.6 cP vs 6810 cP at 25 °C) and less water sorption when it was used as a binder of a composite (2.07 vs 28 μg/mm³). Although the flexural strength of the IsoPMA resin was much lower than that of IsoGMA (38.5 vs 74.2 MPa), the reinforcing effect by barium silicate on the flexural strength of IsoPMA was larger than that of IsoGMA (38.5 → 93.0 MPa for IsoPMA vs 74.2 → 78.6 MPa for IsoGMA) because fewer voids were formed. Unlike in the IsoGMA composite, no internal cracks were found in the IsoPMA composite after the water uptake experiment; its flexural strength decreased by 40% from the initial value, but was better than the flexural strength of IsoGMA, which decreased by 70%.