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 (