Novel orthodontic adhesives with antibacterial, mineralization and fluorescence properties for enamel demineralization prevention

Enamel demineralization is one of the most common adverse effects of fixed orthodontic treatment, mainly because the appliances affect oral hygiene maintenance, potentially leading to plaque accumulation and oral flora dysbiosis. Adhesives are essential for fixed orthodontic treatment, but excessive adhesives on tooth surfaces might be stained aesthetically and serve as additional sites for plaque accumulation. Some research gaps exist for simultaneously addressing orthodontic enamel demineralization and proper adhesive removal. In this study, novel multifunctional orthodontic adhesives (MFOAs) were developed using amino-silane functionalized zinc oxide quantum dots (AF-ZnO_QDS) with fluorescence property, antibacterial agent dimethylaminohexadecyl methacrylate (DMAHDM), and mineralizing material 45S5 bioactive glass (BG-45S5) as the modifiers. The three were incorporated into Transbond XT adhesive at different mass fractions and relevant properties were evaluated in vitro and in vivo. The results indicated that the MFOA-3 with 3 wt% AF-ZnO_QDS, 5 wt% DMAHDM, and 7.5 wt% BG-45S5 possessed long-term antibacterial ability, dual-mineralization activity, and strong fluorescence properties. It had clinically acceptable physicochemical properties and good biocompatibility, providing a desirable anti-demineralization effect. Therefore, MFOA-3 provides a new strategy to solve the two major challenges of enamel demineralization and proper removal of adhesives during fixed orthodontics, and thus has great value in clinical application.