Preparation and Evaluation of Visible Light-Cured Multi-Methacrylates for Dental Composites

To explore new VLC oligomers exhibiting low shrinkage, low water sorption, and improved mechanical properties, a family of multi-methacrylates, based on poly(isopropylidenediphenol) resin (BPA), was synthesized, characterized, and evaluated. The BPA resin, having an average of eight phenolic hydroxyl groups per molecule, was treated with ethylene carbonate and the resultant product esterified at four different grafted levels, using methacryloyl chloride. Structures of these EEBPA oligomers, were confirmed by FT-IR and 13C NMR. The EEBPA oligomer/TEGDMA (50/50, w/w) blends were combined with 0.5 wt% camphoroquinone(CQ) and 1.0 wt% N,N-dimethylaminoethyl methacrylate (DMAEM). The control was BisGMA/TEGDMA (50/50, w/w) blends having the same levels of CQ/DMAEM. Differential photocalorimetry (DPC) and differential scanning calorimetry (DSC) showed the multi-methacrylate/TEGDMA (neat resin) blends have polymerization characteristics comparable to the BisGMA/TEGDMA control. These multi-functional oligomers have lower polymerization shrinkage and lower uptake of water and other liquids. In addition, two experimental oligomers EEBPA #2 and #3 have higher compressive strength than the BisGMA and comparable diametral tensile strength to the BisGMA control. These results suggest that the new type of multi-functional methacrylate oligomers (EEBPA) have potential application in formulating dental composites with improved properties.