Layered double hydroxides intercalated with fluoride and methacrylate anions as multifunctional filler of acrylic resins for dental composites

Abstract ZnAl layered double hydroxides (LDH) was selected as fluorinated filler of photoactivated Bis-GMA/Bis-EMA/TEGDMA resin. The ability of LDH to intercalate fluoride anions and to release them over the time, made this material a good filler to prepare acrylic resin composites with the potential of preventing dental caries. Moreover, LDH in fluoride form was functionalized on the surface by methacrylate anions (MA) which are able to participate to the polymerization process of the resin. This strategy allowed to improve the polymer/filler interactions and subsequently the mechanical properties of the final composite. LDH containing both fluoride and methacrylate anions were prepared with different methods. The best samples, selected on the basis of mechanical properties, were obtained starting from LDH intercalated with fluoride and then exposed to a partial exchange of the fluoride with methacrylate anions (LDH-F/MA). The effect of the presence of the fillers, which were LDH-F/MA and LDH intercalated with MA (LDH-MA), on the resin degree of conversion (DC) and on mechanical properties was investigated. Composites with DC of 75% showed an improvement in the mechanical properties in comparison with those of the pure resin. Moreover, the composites were able to release fluoride anions and to recapture them when contacted with fluoride solution.