Improvements to light transmittance in light-cured composite resins by the utilisation of low refractive index dimethacrylates.

In an effort to improve the light transmittance of light-cured composite resins while avoiding degradation of their physical properties, 4 dimethacrylates having low refractive indices and a bulky backbones such as alicyclic or fluorine-substituted bisphenol groups were synthesized. The depths of cure and physical properties of 6 experimental composite resins containing these new monomers were, then, examined and compared to those of 3 control composite resins containing UDMA, BisMEPP, or BisGMA. The depths of cure of the experimental group containing the synthesized monomers were greater than those of the control group with the exception of the composite containing UDMA. The depth of cure increased as the difference between the refractive indices of the matrix monomer and silica filler decreased. The physical properties of 2 composites in the experimental group were comparable to those of the control group. The matrix monomers of these 2 composites were a mixture of 4,8-dimethacryloxymethylene tricyclo [5.2.1.0] decane or 2,2-bis (4-methacryloxyethoxy phenyl) hexafluoropropane and TEGDMA in a molar ratio of 1/1.