Abstract

Organic matrixes of commercial dental composites generally consist of diluent such as triethylene glycol dimethacrylate (TEGDMA) to decrease viscosity. However, the increasing dilution exhibited adverse effects such as higher polymerization shrinkage and water uptake of resin materials. Therefore, the viscosity of the resin matrix should be as low as possible to fabricate resin composites with a minimum content of diluent. To overcome the high viscosity of 2,2-bis[4-(2-hydroxy-3- methacryloyloxypropoxy) phenyl] propane (Bis-GMA) caused by hydrogen bonding between hydroxyl groups, 2,2-bis[4-(2-benzoyl-3-methacryloyloxypropoxy) phenyl] propane (Bz-Bis-GMA) and 2,2-bis[4-(2-valeryl-3-methacryloyloxypropoxy) phenyl] propane (Vr-Bis-GMA) were synthesized by esterification reaction using benzoyl and valeryl as substituent groups for hydroxyl groups. A series of resin composites containing various resin mixtures of Bis-GMA, Bz-Bis-GMA, Vr-Bis-GMA and TEGDMA and the same filler composition with 70 wt% loading were fabricated. The results suggested that the viscosity of Bis-GMA was dramatically reduced from 820 Pa.s to 2.7 Pa.s and 1.6 Pa.s by regulating substituent size of benzoyl and valeryl groups for hydroxyl groups, respectively. Consequently, the amount of TEGDMA included in the Bz-Bis-GMA matrix could be minimized to 20 wt%, as a substituent for the commonly used resin formulation (Bis-GMA/TEGDMA=50/50, wt/wt), resulting in the reduced polymerization shrinkage (2.1%), adequate flexural strength (93.3 MPa) and compressive strength (212.4 MPa) of the corresponding composites, which might provide a new strategy for the design of novel monomer for dental restorative materials with a decreased polymerization shrinkage and acceptable mechanical performance.

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