Experimental Evaluation of Dentin Alterations Induced by Different Endodontic Irrigation Protocols

Endodontic irrigation protocols based on sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) are essential for effective root canal disinfection, nevertheless they can induce chemical alterations of coronal dentin that compromise the stability of subsequent adhesive restorations. This study investigates the effect of a clinically relevant irrigation protocol (5% NaOCl followed by EDTA for 30 min) on dentin chemical composition, comparing specimens subjected to direct irrigation with specimens protected by a universal adhesive applied according to the Pre-Endodontic Dentin Sealing (PEDS) protocol. Two experimental groups were compared: Group A, subjected to direct irrigation with 5 % ~ N a O C l followed by 3 0 min of EDTA, and Group B, which received PEDS treatment before the same irrigation protocol. Raman spectroscopy was performed directly on dentin surfaces before and after irrigation, acquiring multiple spectra on the cavity. Mineral- and collagen-related Raman bands were analyzed, and quantitative intensity ratios were calculated to assess demineralization and organic matrix degradation. Raman analysis revealed a significant reduction in phosphate-related signals and mineral-to-matrix ratios after irrigation in non-protected specimens, with marked changes in amide-related ratios indicative of collagen degradation and conformational disorder. In contrast, specimens treated with PEDS exhibited minimal variations in both mineral and organic Raman parameters, demonstrating effective preservation of dentin chemical integrity. These findings indicate that NaOCl and EDTA induce measurable chemical modifications of dentin that may negatively affect adhesive performance, while Pre-Endodontic Dentin Sealing significantly mitigates irrigant-induced damage. Raman spectroscopy proved to be a sensitive and non-destructive tool for characterizing dentin-irrigant-adhesive interactions and supporting optimized protocols for durable post-endodontic restorations.