Fish bone and chitosan based nanogels in green dentistry: sustainable and eco-friendly biomimetic remineralizing agents for early enamel caries

Biomimetic enamel reconstruction represents an innovative strategy in restorative dentistry and materials science, providing a biologically and eco-friendly inspired approach for managing early enamel caries. This study aimed to evaluate the remineralizing potential of organically derived biomimetic nanogels—chitosan nanogel (n-C) and fish bone nanogel (n-FB)—on demineralized enamel, using scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis for semi-quantitative calcium/phosphate assessment. Fifty-seven extracted primary molars were demineralized for 96 h. Three samples were used as the demineralized control group, while the remaining 54 were randomly assigned to three groups: [1] Artificial Saliva (AS) group—specimens incubated in artificial saliva at 37 °C for seven days; [2] Nano-Fish Bone (n-FB) group—n-FB gel applied once daily for five minutes, rinsed, then incubated in refreshed artificial saliva; [3] Nano-Chitosan (n-C) group—n-C gel applied similarly. Specimens were analysed using SEM and EDX for surface morphology and elemental Ca/P ratio, and data were statistically analysed. Both biomimetic nanogels significantly reversed the demineralization effects, showing enamel prism reformation. For the calcium-to-phosphorus (Ca/P) ratio, the highest mean value was recorded in the AS group (2.77 ± 0.06), followed by the NC group (2.58 ± 0.61), the n-C group (2.45 ± 0.18), and the lowest in the n-FB group (2.19 ± 0.38). ANOVA analysis demonstrated a significant difference between groups (P = 0.020). The n-C group and n-FB produced a more uniform and well-mineralized surface structure closest to normal enamel. Both nanogels provided enhanced remineralization, however, nano–fish bone exhibited more uniform surface morphology and significantly higher phosphate levels than nano–chitosan, suggesting a comparatively greater remineralization potential.