The optical properties of some dimethacrylic composites

One series of composites based on 2,2-bis-4(2-hydroxy-3-methacryloyloxy pro poxy)phenyl propane (BisGMA), ethylene glycol dimethacrylate (EGDMA) and co lloidal silica, quartz or titanium dioxide filler were formulated and inves tigated by UV-visible spectroscopy and optical microscopy. Also the FTIR sp ectrum of BisGMA-EGDMA copolymer was reported and discussed to offer adequa te information for identification purpose. The investigation was centred on the evaluation of some important effects of the filler level and nature on such composites opacity by comparison with unfilled dimethacrylic resin. T he composite opacities were determinated in terms of visible light transmis sion through the thickness of composites. The visible transmission spectra within the range 350-850 nm wavelength show that transmittance values decre ase with increasing wt% of filler incorporated in composites. It was found that the filler nature influences the transmission degree of such composite s. The feature of the visible absorption spectra has been discussed by taki ng into account light scattering phenomena, filler size and the degree of m ismatch of the refractive indices of the filler and resin. (C) 1999 Elsevie r Science S.A. All rights reserved.