Core-shell structured SiO2@ZrO2@SiO2 filler for radiopacity and ultra-low shrinkage dental composite resins

Abstract

To overcome the interfacial problem between X-ray radiopaque ZrO2 fillers and polymer resin in dental composites, monodispersed SiO2@ZrO2@SiO2 (SZS) microspheres with narrow size distribution were prepared by a controlled sol-gel method. In the presence of SiO2 coating layer over SiO2@ZrO2 (SZ) microspheres, they were easily silanized same as SiO2 microspheres. Ethoxylated bisphenol A dimethacrylate (EBPADMA) with a higher molecular weight and a lower viscosity was used as base resin monomer mixed with a low amount of diluent triethylene glycol dimethacrylate (TEGDMA). Additionally, the addition of a small amount of pore agent acetone dicarboxylic acid (ADCA) produced some voids, thereby effectively reducing the polymerization shrinkage of the resin. The prepared dental composites combining 52 wt% monodispersed silica microsphere, 20 wt% SZS microspheres, exhibited significantly enhanced capacity in radiopacity (higher than tooth enamel) and very low shrinkage (<0.1%). It also has better mechanical properties than resin composites filled with SiO2 microspheres, and its strength can meet practical applications. The properties of the radiopaque dental composite were to be further tuned by varying the amount of SZS microspheres contents, and the radiopaque resin has an advantage over the commercial one in that it is clinically nondestructive.