Yellow light and ultrasound Dual-responsive strontium-doped zinc oxide composites for dental caries prevention and remineralization

Dental caries is one of the most prevalent chronic infectious diseases, mainly due to acid production by bacteria in the plaque biofilm, leading to enamel demineralization, tooth defects and pulpitis. Most of the current treatments are invasive and do not combine restoration of dental tissues, resolution of tooth staining or prevention of dental caries. In this study, a polydopamine (PDA)-encapsulated strontium-doped zinc oxide composite (Sr-ZnO@PDA, denoted as SZ@PDA) has been developed for caries prevention and remineralization. The PDA wrapping endows SZ@PDA with a narrow energy band gap (1.78 eV), which can simultaneously respond to yellow light (YL) with favorable biosafety and ultrasound (US) with high tissue penetration. The synergistic piezo-photocatalytic action of YL and US with the enhanced catalytic efficiency can generate an appropriate amount of reactive oxygen species (ROS), thus destroying the structure of bacterial cellular membranes and decomposing pigments for caries prevention and improvement of tooth staining, respectively. In addition, strontium ions (Sr²⁺) released by SZ@PDA, as an active element, can promote the remineralization of enamel and dentin, repairing defective dental tissues. Collectively, this versatile system (SZ@PDA) provides an effective strategy for the prevention and treatment of caries.