The Monomer Compoment And Fillers Microstructure Effect On The Properties Of Dental Resin Composites

Dental resin composites have been widely used instead of conventional amalgam alloys for restoring dental caries and other defects, because the advantages of resin composites include excellent aesthetic quality, mechanical properties, biocompatibility, easy handing, and so on. The application of dental resin composites has been extended from anterior restorations to posterior restorations. However, the undesired high polymerization shrinkage, low wear resistance and secondary carious still prevent these materials from being used in heavy-load and large area restorations.In order to improve the perfonnance of dental resin composites, modifications in both resins and inorganic fillers have been intensively studied in this dissertation. Silanized nano-sized silica (OX-50) and diatomite at different mass rations were used as co-fillers to reinforce dental composites and their mechanical properties were investigated. The volume shrinkage, depth of cure and light transmission of the composites were also examined. In order to further modify the performance of the composites and better applied in the clinical application, TiO2 nanoparticles were introduced to tune the color of dental resin composites and the influence of TiO2 amounts on color change was investigated by using the CIE-Lab-values. The CIE-Lab color parameters (L*, a*, b*) data showed that the color changes of resin composites can be visual perceived obviously, when TiO2 particles sized from 300 to 400 run were introduced. It has high reference value in dental restorative application.To develop a dental composite that has a low amount of volume shrinkage and excellent mechanical properties, modifications in both inorganic fillers and resin monomers may be studied. Monodispersive silica microspheres in a diameter of 400 nm were synthesized via the Stober process and used as fillers. Additionally, ethoxylated bisphenol A dimethacrylate (EBPADMA) with lower viscosity and higher molecular mass was introduced as a base resin monomer. EBPADMA or bisphenol A diglycidyl dimethacrylate (Bis-GMA) or both of them and diluents triethylene glycol dimethacrylate (TEGDMA) were used as primary resin matrix, the addition of TEGDMA was reduced to 30 wt% in the resin matrix, which could make the resin composites achieve a lower volume shrinkage. Various resin mixtures were prepared, which had the similar filler content. The physics mechanical and optical properties results revealed that the resin composites filled with SiO2 microspheres have higher light transmission and adequate mechanical properties than that only used nano-sized SiO2 as fillers. In comparison to Bis-GMA/TEGDMA resins system, the use of the monomer EBPADMA is an effective way to reduce the curing shrinkage and improve light transmission and depth of cure of the resin composites. Among them, the resin mixture containing 70 wt% EBPADMA and 30 wt% TEGDMA exhibited the best compression strength (238.1±5.4 MPa), depth of cure (4.02±0.04 mm) and the volume shrinkage as low as of (2.27%).