Mussel-Inspired Polydopamine-Induced Minocycline Release and Fluorapatite Coating for the Design of Novel Orthodontic Appliances with Both Antibacterial and Remineralization Abilities

Many types of antibacterial coating have been applied to fixed orthodontic devices to prevent bacterial attachment and subsequent dental caries. However, challenges such as weak adhesion, lack of remineralization ability, cytotoxicity, and a short duration of effectiveness remain unresolved. Therefore, there is a critical need for coatings that offer strong surface adherence, long-lasting antibacterial properties, and remineralization potential. In this study, we achieved controlled release of the antimicrobial agent minocycline through a polydopamine coating chemically grafted onto the surface of orthodontic appliances. Additionally, fluorapatite coating was synthesized to minimize enamel demineralization and promote remineralization after acid etching. The coating did not affect the key properties of the appliances, including their corrosion resistance, surface hardness, and friction performance. Under simulated oral conditions, the modified brackets demonstrated exceptional and prolonged antibacterial activity, effectively preventing bacterial biofilm formation. Furthermore, evidence of the ability of the biocompatible coating to suppress bacteria and promote remineralization was confirmed through <i>in vivo</i> tests. Our study offers new solutions and strategies to address the hazards caused by bacterial adhesion on orthodontic appliances.