Epoxy resin/ Thermoplastic polymethyl methacrylate (PMMA)/SiO₂ dental composites were synthesized successfully at last after the following two steps: polymerization of MMA act as the initiator at this first process. Then the obtained PMMA was incorporated into epoxy resin and SiO₂ to prepare the hybrid thermosets. The structural characteristics of epoxy resin/PMMA/SiO₂ composites were characterized by Fourier transform infrared spectroscopy (FT–IR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). What is more, the mechanical properties and water solubility of the composites have also been tested. It is found that the stability has been improved after adding SiO₂ nanoparticles. In addition, the mechanical properties of composites which were modified by silica indicated that the mechanical properties of materials could be improved after preprocessing of SiO₂ nanoparticles in epoxy resin/PMMA composites. Interference of epoxy resin produced magnetic adsorption and chemical reaction with the existence of hydroxyls, ether bonds and epoxy groups. In conclusion, the improvement in surface properties was ascribed to the enrichment of epoxy resin moiety on the surface of the nanostructured thermosets.