Effects of heat in the properties of NaOCl alone and mixed with etidronate and alkaline tetrasodium EDTA

• Published in: International endodontic journal Vol. 54; no. 4; pp. 616 - 627
• Main Authors: Tartari, T., Borges, M. M. B., Araújo, L. B. B., Vivan, R. R., Bonjardim, L. R., Duarte, M. A. H.
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.04.2021
• Subjects: Animals; Cattle; Chelating agents; chelation; Chlorine; Dental Pulp Cavity; Dentin; Dissolution; Edetic acid; Edetic Acid - pharmacology; Endodontics; Etidronic acid; Etidronic Acid - pharmacology; Hot Temperature; Immersion; irrigation solutions; Kruskal-Wallis test; Microscopy, Electron, Scanning; Organic matter; Root Canal Irrigants; Root Canal Preparation; Scanning electron microscopy; Smear Layer; Sodium hypochlorite; Sodium Hypochlorite - pharmacology; temperature; tissue dissolution; Variance analysis; temperature; irrigation solutions; smear layer; sodium hypochlorite; tissue dissolution; chelation
• ISSN: 0143-2885; 1365-2591
• DOI: 10.1111/iej.13450

Aim To assess the free available chlorine concentration (FAC), organic tissue dissolution and smear layer removal capacity of sodium hypochlorite (NaOCl) alone and when mixtured with etidronate (HEDP) and tetrasodium EDTA (Na4EDTA), and heated to different temperatures. Methodology Mixtures at 1 : 1 ratio of 5% NaOCl with distilled water (considered NaOCl alone), 18% HEDP or 10% Na4EDTA were heated to 25 °C, 37 °C, 48 °C and 60 °C. The FAC in the mixtures was assessed at 5, 10, 20, 30, 60 and 120 min. Samples of bovine muscle tissue (n = 10) were prepared with similar size and weighed before and after 5, 10 and 15 min of immersion in the mixtures heated to the different temperatures to verify organic matter dissolution. The intergroup results were compared statistically using one‐way analysis of variance (anova) and intragroup by two‐way analysis of variance (anova), both followed by Tukey’s multiple‐comparison test (α < 0.01). Bovine dentine blocks (n = 10) were analysed by scanning electron microscopy before and after immersion in the mixtures, and the time taken to remove the smear layer from the surfaces of the samples was determined. The Friedman test was used to compare the scores of the same group (α < 0.01), and the Kruskal–Wallis test with Dunn’s post hoc was used to compare the different groups (α < 0.01). Saline solution was used as a control in the experiments of tissue dissolution and smear layer removal, Results Heating NaOCl alone did not affect its FAC. The higher the temperature of the mixtures with the chelators, the lower the FAC. Organic tissue dissolution was improved by increases in temperature of NaOCl alone and its mixture with HEDP (P < 0.01); however, the mixture with Na4EDTA had no improvement (P > 0.01). Smear layer removal by NaOCl alone was enhanced by heating resulting in lower scores in some samples and became more rapid in the mixtures with the chelators. The saline solution did not promote tissue dissolution nor smear layer removal (P > 0.01). Conclusion In this laboratory study, heating NaOCl alone or when mixed with HEDP improved its capacity to dissolve organic matter and remove the smear layer. However, the mixture with HEDP required frequent refreshment to retain these effects when heated. Due to the acceleration in the reaction between the irrigants, very rapid reductions in the free available chlorine in the mixtures with Na4EDTA heated to the different temperatures occurred.