Surface and structural changes in root dentine by various chelating solutions used in regenerative endodontics

Aim To evaluate the effects of the prolonged use of various irrigant solutions used during regenerative endodontic procedures on the physical and chemical structure of root canal dentine in extracted human teeth. Methodology Sixtyroot dentine samples from extracted, single-rooted, human teeth were assigned to 10 groups. Eight groups were irrigated with 1.5% NaOCl for 5 min, followed by 3%, 10%, 17% EDTA or 10% citric acid (CA) for 5 or 10 min. One group received only NaOCl irrigation, and samples with only distilled water irrigation were used as a control group. The changes in microhardness and flexural strength were determined using Vickers and 3-point flexural tester, respectively. Molecular and elemental compositions were recorded using FTIR and EDS spectroscopy. Data were analysed using one-wayanova, Kruskal-Wallis and Mann-WhitneyUtests. Results The application of 1.5% NaOCl for 5 min did not affect the mineral content or microhardness of dentine (P > 0.05). However, it significantly decreased the dentine collagen peak values (P < 0.05), which was similar to the control group after the use of chelating agents (EDTA and 10% of CA) (P > 0.05). The effect of EDTA on the inorganic content was not concentration and time dependent (P > 0.05). CA resulted in a significantly greater reduction in the inorganic contents compared with the control and EDTA groups (P < 0.05). Regardless of the time, EDTA and CA significantly decreased dentine microhardness compared to the control (P < 0.05) with the greatest reduction in the CA groups (P < 0.05). NaOCl alone was associated with the lowest flexural strength, while none of the other irrigation regimens significantly decreased the flexural strength compared to the control group (P> 0.05). Conclusions Use of 1.5% NaOCl for 5 min decreased the collagen content of samples of human dentine from extracted teeth while EDTA and 10% citric acid mostly affected the inorganic content and microhardness of dentine surfaces. None of the irrigant solutions significantly decreased the mechanical properties of the entire dentine specimen.