RESUMO
AIM: To refine a FTIR protocol for detection of NaOCl-induced dentinal collagen changes using an ex vivo irrigation model, and to apply it to determine the collagen change within 0.5 mm of canal or root surfaces, with or without mature roots or periodontal involvement. METHODOLOGY: The root canals of extracted human roots were irrigated with control saline (n = 3) or 5% NaOCl (n = 3) and sectioned into transverse disks for FTIR analyses, 0.5 mm from both the canal lumen and root surface, before and after surface treatment with 17% EDTA. Amide I/phosphate and amide II/phosphate absorbance ratios were compared using the Wilcoxon sign rank test. Mature roots without periodontal involvement were irrigated with: saline (n = 7), 5% NaOCl (n = 7) or 5% NaOCl + 17% EDTA (n = 7); those with periodontal involvement (n = 7) or immature roots (n = 7) were irrigated with 5% NaOCl. Dentine disks were then prepared for FTIR analyses. The effects of irrigant/root maturity/periodontal involvement were analysed using linear mixed models. RESULTS: FTIR analyses of the irrigated samples revealed a significant (P < 0.05) reduction in collagen bands near the canal lumen after NaOCl irrigation using surface EDTA-treated samples. Irrigation with the test solutions resulted in significant (P < 0.0001) dentinal collagen changes in the mature roots, whilst those in the immature roots were significantly (P < 0.05) greater compared with the mature roots with or without periodontal involvement; but there was no difference between the latter groups. CONCLUSION: EDTA surface treatment of polished dentine surfaces enhanced FTIR detection of NaOCl-induced collagen changes. Both root maturity and irrigation protocol influenced the ability of NaOCl to alter dentinal collagen up to 0.5 mm from the canal lumen.
