Biomineralization and anticariogenic effect of nanocomposite suspensions of eggshell-derived hydroxyapatite and carboxymethyl chitosan on demineralized enamel: A laboratory investigation.

This study evaluated the combined effect of chicken eggshell-sourced hydroxyapatite nanoparticles (nEHAp) and carboxymethyl chitosan (CMC) in inducing biomineralization of artificial enamel lesions. nEHAp and CMC were prepared and characterized using high-resolution scanning electron microscopy with energy-dispersive X-ray spectroscopy (HRSEM-EDX), transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, micro-Raman spectroscopy, and thermal analyses (thermogravimetric/differential thermal analysis). The nanocomposite (NC) suspension was created by mixing nEHAp and CMC in an aqueous medium and was analyzed using gas chromatography-mass spectrometry. Sixty demineralized enamel specimens were divided into four groups (n = 15)-artificial saliva, nEHAp, CMC, and NC-and subjected to 14 days of pH cycling. The surface morphology, elemental composition, and microhardness were evaluated using HRSEM-EDX and Vickers hardness testing. The antibacterial activity of the test materials was evaluated against Streptococcus mutans and Lactobacillus acidophilus using fluorescence microscopy whereas cytocompatibility was assessed on cultured dental pulp stem cells (DPSCs) using the MTT assay. The synthesized nEHAp showed typical rodlike nanoparticles (50-100 nm) containing calcium, phosphorous, magnesium and sodium ions whereas CMC revealed flat and homogeneous agglomerates with carbon, calcium, oxygen, sodium and chlorine elements. FTIR, micro-Raman and XRD patterns, along with thermal treatment confirmed the typical features of nEHAp and CMC. Further, the cytocompatibility of the materials was confirmed on DPSCs after a 7-day incubation. The nEHAp-CMC group showed dense apatite deposition, the highest microhardness, and superior antibacterial activity against cariogenic microflora (p < 0.05). These findings suggest that nEHAp-CMC nanocomposites hold promising potential for initial enamel caries treatment through enhanced remineralization and antibacterial action.