Antimicrobial and Remineralization of Carboxymethyl Chitosan and Xylitol Functionalized Carbon Dots Coating on Orthodontic Brackets.

Purpose: During fixed orthodontic treatment, oral hygiene is difficult to ensure and can easily lead to an imbalance in the oral micro-ecological balance. In this study, based on the adhesive properties of polydopamine (PDA) and the good antimicrobial and remineralization properties of carboxymethyl chitosan (CMC) and xylitol (Xy), new nanocomposites with both antimicrobial and remineralization capabilities were prepared to coat on orthodontic brackets.

Methods: Composite carbon dots (CDs) were synthesized using carboxymethyl chitosan and xylitol, we characterized them and the antimicrobial properties of the CMC-Xy-CDs were investigated by co-cultivation with S. mutans in vitro and in vivo. The composite coating was then adhered to the brackets. After the characterization measurements, antibacterial properties against S. mutans and the ability to promote remineralization of isolated teeth were investigated.

Results: Biological studies demonstrated that L929 cells co-cultured with CMC-Xy-CDs did not observe significant cytotoxicity and CMC-Xy-CDs have good biocompatibility. In the adhesive action of PDA, various characterizations have proved that CDs are modified on the brackets surface. In the antibacterial experiment, CMC-Xy-CDs and the adhesive coating on the brackets were found to have better antibacterial performance than the control group, with an antibacterial rate of up to 80%. In the animal experiment, the results of CMC-Xy-CDs promoting the healing of S. mutans infection wound models showed that there was a significant difference at 7d (P < 0.001), indicating that the experimental group had good antibacterial effects. The SEM of teeth after CMC-Xy-CDs promoted remineralization showed that the structure of the tooth surface became dense and some precipitation appeared, and the surface hardness measurement was significantly increased (p<0.0001).

Conclusion: Our study revealed that new nanocomposites with both antimicrobial and remineralization capabilities coated on orthodontic brackets provide a good basis for future clinical applications.