Dual-Functional Ionic Liquid Varnishes for Dental Caries Management

The development of caries management materials has concentrated on the dual objectives of inhibiting cariogenic microorganisms and promoting remineralization. In this study, 2 dual-functional ionic liquid (IL) varnishes, exhibiting both antibacterial and remineralization capabilities, were synthesized as novel anticaries agents. The ionic liquids (ILs) were prepared by modifying 1-hexylimidazolium IL with 3-chloropropyltriethoxysilane, followed by anion exchange with F^- and a coordination reaction with Sr²⁺, respectively. The ILs were characterized using energy-dispersive spectroscopy (EDS), ion chromatography (IC), inductively coupled plasma optical emission spectrometry (ICP-OES), and Fourier transform infrared spectroscopy (FTIR). The antibacterial efficacy of the ILs was evaluated through colony counting, live/dead staining, and scanning electron microscopy (SEM). Subsequently, the ILs were blended with rosin to form IL varnishes. The remineralization potential of the IL varnishes was assessed through microhardness test, acid resistance test, SEM, EDS, and X-ray diffraction. In addition, in vivo anticaries treatment with the IL varnishes was conducted using a dental caries animal model. Histopathological and oral microbiome analyses were performed to evaluate the in vivo biocompatibility of the materials. The comprehensive analysis by EDS, IC, ICP-OES, and FTIR collectively confirmed the successful synthesis of the ILs. Antibacterial assays revealed that ILs at concentrations as low as 25 µM eliminated more than 80% of cariogenic bacteria within 60 min and significantly decreased viable bacteria in biofilms within 24 h. Following a 7-d treatment with the IL varnishes, SEM analysis of acid-etched enamel demonstrated reduced interspace depth, along with substantially increased microhardness and significantly improved acid resistance versus the negative control group. As compared with the fluoride varnish, the IL varnishes are more effective in preventing dental caries in rats, without harming oral buccal mucosa, major organs, or microbiota diversity. In conclusion, the IL varnishes developed in this study are not only straightforward to synthesize but also exhibit significant potential against dental caries.