Determination of the Optimized Conditions for Preparation of Bis-GMA Based Dental Composite Reinforced by a Nanostructure of Silica Aerogel

In the present research, a new dental composite based on bisphenol A-glycidyl methacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) containing a hydrophobic silica aerogel filler with a porosity more than 80%, the average pore size of 10 nm, and specific surface area of 811 m2/g was prepared. The effect of important processing parameters including light exposure time, the mass ratio of the resins, and preparation method on the properties of the composite was investigated. The characterization of silica aerogel and investigation of the dental composite properties were performed by FT-IR, adsorption/desorption of nitrogen, color change, and compressive strength. The results showed that the use of silica aerogel filler increases the whiteness index of the composite in comparison with the primary resin. By increasing the light exposure time to 40 s, the yellowness index of the composite was significantly decreased, while the whiteness index was increased. After that, both indexes remained constant. The compressive strength of the dental composite was increased up to 50% in the presence of aerogel particles. In addition, the composite prepared by Bis-GMA/TEGDMA with a mass ratio of 50/50 showed a higher compressive strength, due to the low viscosity of the resin which has a better penetration into the pores of the filler, in comparison with the composite prepared by a 30/70 mass ratio. The composite with a higher compressive strength was prepared by mixing silica aerogel with a more dilute monomer TEGDMA and then vacuum degassing and mixing with Bis-GMA and the initiator. The use of silica aerogel as a reinforcement of the dental resin also resulted in increasing the percentage of the cell survival and decreasing the toxicity of the prepared dental composite.