Amyloid-Mediated Remineralization for the Prevention of White Spot Lesions in Orthodontic Treatments

White spot lesions (WSLs) are a common side effect of orthodontic treatments (particularly those involving fixed appliances) and arise from localized enamel demineralization caused by acidic byproducts of bacterial biofilms. This study introduces a novel approach to prevent WSLs via a “bottom-up” mineralization strategy using phase-transitioned lysozyme (PTL) coatings. The PTL-induced mineralized layer, which is formed via a simple dipping method, promoted the growth of hydroxyapatite crystals in a layer-by-layer architecture, closely mimicking the composition and structure of natural enamel. Characterization revealed the excellent mechanical properties, acid resistance, and strong interfacial adhesion of the mineral layer. The protective efficacy of the PTL-induced layer is evaluated under controlled demineralization conditions and acid exposure induced by biofilms. The PTL layer effectively protected against acid challenges by acting as a sacrificial barrier and supporting repeated mineral deposition for repair. These findings demonstrate the potential of PTL coatings as a robust strategy for preventing the occurrence of WSLs during orthodontic treatment. By maintaining enamel integrity and enabling the repair of damaged surfaces, the PTL-induced mineralized layer offers a practical and innovative solution to one of the most persistent challenges in orthodontic care.