DMAHDM@MPC nanoparticles in orthodontic adhesive inhibit cariogenic bacteria and sugar metabolism to prevent enamel demineralization

During orthodontic treatment, poor oral hygiene often facilitates the proliferation of cariogenic bacteria, particularly <i>Streptococcus mutans</i>, leading to lactic acid accumulation and subsequent enamel demineralization. To mitigate this issue, Dimethylaminohexadecyl methacrylate (DMAHDM) was incorporated onto the protein-repellent surface of 2-Methacryloyloxyethyl phosphorylcholine (MPC), resulting in the formation of a DMAHDM@MPC composite. This composite was then integrated into resin-modified glass ionomer cement (RMGIC) to develop an antimicrobial orthodontic adhesive, termed RMGIC + MPC + DMAHDM (RMD). This study demonstrated that DMAHDM@MPC nanoparticles self-assembled into a core-shell structure, thereby enhancing the antimicrobial activity. A six-month randomized controlled trial (RCT) involving 29 orthodontic patients, along with metagenomic and metabolomic analyses, revealed that RMD significantly reduced plaque accumulation by selectively inhibiting pathogenic bacteria while preserving beneficial microbiota. Additionally, MPC was shown to competitively bind to sucrose-6-phosphatase (SPP) in pathogenic bacteria, inhibiting sucrose synthesis and carbohydrate metabolism, thus reducing the production of organic acids. In conclusion, RMD effectively prevents enamel demineralization by selectively targeting cariogenic bacteria and their associated sugar metabolism pathways during orthodontic treatment.