From passive binder to active defense: an Ag-functionalized amorphous intergranular phase for mechanically-robust and antibacterial artificial enamel.

The clinical longevity of dental restorations is fundamentally constrained by a critical trade-off where mechanically robust materials typically lack intrinsic biological defense, whereas bioactive composites often suffer from structural degradation. To reconcile this conflict, we constructed a hierarchical nanocomposite that mimics the structural logic of natural enamel. The design centers on engineering a silver-functionalized amorphous zirconia (Ag@ZrO2) coating to serve as a bioactive Amorphous Intergranular Phase (AIP) bridging aligned hydroxyapatite (HA) nanowires. Synthesized via bidirectional freeze-casting, this bioinspired composite effectively unifies mechanical resilience and biological activity. Its flexural strength reaches 111.2 MPa, with an elastic modulus of 77.8 GPa, achieving a 91% improvement over the control group. This performance closely matches natural tooth enamel and surpasses standard dental resin materials. Crucially, the engineered Ag@ZrO2 interface functions as a catalytic platform that delivers potent antibacterial action through a triple-synergistic mechanism involving peroxidase-mimicking reactive oxygen species generation, sustained Ag+ release from AgCl, and bacterial glutathione depletion. This approach achieved 100% eradication of E. coli and S. aureus without compromising the structural integrity of the composite. These findings validate a scalable interface engineering strategy for creating "living" structural materials that actively prevent secondary caries.