A Non-Discoloring Bioactive Hydrogel for Caries Management: An In Vitro Study

OBJECTIVE: To develop a novel anti-caries hydrogel with non-discolouring, antibacterial and mineralising properties. METHOD: The fCS/nSPS hydrogel was developed by incorporating nanostrontium phosphosilicate (nSPS) into a functionalised chitosan (fCS) matrix, followed by ultraviolet-induced photocrosslinking. The hydrogel's phase formation and composition were identified by X-ray Diffraction spectroscopy (XRD), whereas its functional groups were detected by Fourier Transform Infrared spectroscopy (FTIR). Surface morphology was observed by Scanning Electron Microscopy (SEM). Antibacterial effects of fCS/nSPS were evaluated using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Mineralising properties were studied using SEM and XRD on fCS/nSPS-treated dentine blocks after cariogenic challenge. Cytocompatibility of fCS/nSPS-treated dentine was tested towards human gingival fibroblasts (HGF-1). Dentine discolouration after intervention (ΔE) was quantified using colour spectrophotometry. Silver diamine fluoride (SDF) and deionised water were used as controls. RESULTS: NMR, XRD, FTIR, and SEM confirmed the synthesis of fCS/nSPS. The MIC/MBC values (mean±SD) of fCS/nSPS against Streptococcus mutans, Actinomyces naeslundii, and Lactobacillus acidophilus are 87±20/200±35, 129±38/373±80, and 110±36/253±53 µg/mL, respectively. SEM revealed a smooth mineralised surface on fCS/nSPS-treated dentine. XRD confirmed deposition of strontium phosphosilicate. HGF-1 viability (mean±SD) of fCS/nSPS, SDF and Water group were 135.7±4.9%, 0.5±0.1% and 131.7±3.5% (p<0.001, SDF<fCS/nSPS, Water). The ΔE values (mean±SD) of fCS/nSPS, SDF, and water groups were 6.4±2.6, 47.7±6.6, and 7.5±2.0, respectively (p<0.001; fCS/nSPS, Water<SDF). CONCLUSION: The developed fCS/nSPS hydrogel did not cause significant tooth discolouration, exhibited antibacterial activity, promoted dentine's surface mineral deposition, and was cytocompatible. These properties support further investigation of this material for non‑restorative caries management.