The optical properties of some dimethacrylic composites

One series of composites based on 2,2-bis-4(2-hydroxy-3-methacryloyloxy propoxy)phenyl propane (BisGMA), ethylene glycol dimethacrylate (EGDMA) and colloidal silica, quartz or titanium dioxide filler were formulated and investigated by UV-visible spectroscopy and optical microscopy. Also the FTIR spectrum of BisGMA–EGDMA copolymer was reported and discussed to offer adequate 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. The composite opacities were determinated in terms of visible light transmission through the thickness of composites. The visible transmission spectra within the range 350–850 nm wavelength show that transmittance values decrease with increasing wt% of filler incorporated in composites. It was found that the filler nature influences the transmission degree of such composites. The feature of the visible absorption spectra has been discussed by taking into account light scattering phenomena, filler size and the degree of mismatch of the refractive indices of the filler and resin.