Core–Shell CaF2@ZnO Nanoparticles as Inorganic Fillers for Dental Restorative Composites

This study aimed to address the clinical challenge of secondary caries prevention in dental restorations. Leveraging the sustained fluoride-releasing capacity of calcium fluoride (CaF2) and the broad-spectrum antibacterial activity of zinc oxide (ZnO), we designed and synthesized a novel core–shell CaF2@ZnO nanoparticle filler to synergistically enhance the functional performance of dental resin composites. The filler was successfully prepared via a co-precipitation-hydrothermal method, and its well-defined core–shell architecture was systematically confirmed using XRD, SEM, and TEM. When incorporated into the resin matrix at 10 wt.% loading, the composite containing CaF2@30ZnO demonstrated optimal overall performance. Notably, this formulation enabled sustained fluoride ion release, potent antibacterial efficacy, and excellent in vitro cytocompatibility. Collectively, these findings demonstrate that the CaF2@ZnO nanofiller confers multifunctional benefits—including improved mechanical integrity, long-term fluoride release stability, and targeted antibacterial action—thereby holding significant promise for clinical application in mitigating secondary caries around resin-based restorations.