Comparative evaluation of remineralizing potential of Galla chinensis with nanohydroxyapatite, chicken egg shell and fish scale derived nanohydroxyapatite on early enamel caries- A single-blinded in vitro study

Introduction: The earliest clinical sign of enamel caries is subsurface demineralization beneath an intact surface. At this stage, remineralizing agents can potentially reverse or halt lesion progression. Aim: To evaluate and compare the remineralization potential of plant-based Galla chinensis extract (GCE) with nanohydroxyapatite (nHAp), chicken eggshell-derived nHAp (CES nHAp), and fish scale-derived nHAp (FS nHAp), against casein phosphopeptide-amorphous calcium phosphate fluoride (CPP-ACPF), on early artificial enamel lesions in human premolars. Design: In-vitro study performed under pH cycling stimulating oral conditions. Methodology: A total of 148 specimens were taken. Among these, 48 samples were used for microhardness testing by Vicker’s hardness test, 60 for lesion depth evaluation using Polarized Light Microscopy (PLM), 30 for Energy Dispersive X-ray (EDX) analysis, and 10 for Scanning Electron Microscopy (SEM). All samples were demineralized except for five intact controls designated for baseline EDX assessment. Microhardness was measured before demineralization (SMH1), after demineralization (SMH2), and following remineralization (SMH3). These values were used to calculate the Surface Microhardness Recovery percentage (SMHR%). The demineralized samples were categorized into the following experimental groups based on the remineralizing agent applied: Demineralized control (no treatment); Group 1: CPP-ACPF; Group 2: GCE with nHAp; Group 3: CES nHAp; and Group 4: FS nHAp. Each group included 12 samples for microhardness testing, 12 for lesion depth evaluation, 5 for EDX, and 2 for SEM. A seven-day pH cycling model simulated oral conditions before post-remineralization analysis. PLM was utilized for morphometric lesion depth assessment. EDX was used to assess changes in calcium-to-phosphorus (Ca/P) ratio, and SEM evaluated surface topography. Results: GCE nHAp showed the highest surface microhardness recovery and the shallowest lesion depth, indicating effective, uniform remineralization. CES nHAp and CPP-ACPF demonstrated moderate potential, while FS nHAp was the least effective. EDX analysis revealed a significantly higher calcium-to-phosphorus (Ca/P) ratio in the GCE nHAp group. No significant difference was found between CPP-ACPF and FS nHAp. SEM images confirmed smoother, more uniform surfaces in the GCE group. Conclusion: GCE combined with nHAp was the most effective remineralizing agent, followed by CES nHAp and CPP-ACPF. These results suggest biogenic materials from plant and animal sources may offer effective, biocompatible alternatives for non-invasive enamel caries treatment.