Evaluation of the Effects of Different Irrigation Solutions on MTA and Dentin Microhardness

Objectives: The objective of this study was to compare the dissolution effects of different chemical solutions, which are commonly used as root canal irrigants, on partially or fully set mineral trioxide aggregate (MTA). Furthermore, the impact of these solutions on dentin microhardness was also assessed. Methods: In this study, a total of 80 extracted single-rooted human teeth were utilized. The roots of the teeth were bisected transversely into slices of 6 mm in length. MTA (NeoPUTTY, Avalon Biomed, USA) was applied in layers of 4 mm in thickness within the cavities, sealed with moist cotton, and stored at 37°C under 100% humidity for 24 hours and 21 days. Forty samples were tested at the 24-hour mark, and the remaining 40 samples were tested at the 21-day mark. The samples were randomly allocated to one of five experimental groups: 17% EDTA, 5.25% NaOCl, 2% CHX, 40% citric acid, and saline (control). The Vickers microhardness test was employed to ascertain the hardness values of the MTA and dentin surfaces that had been exposed to the chemical solutions for a period of 10 minutes. Statistical analyses were performed using MedCalc® v19.7.2 (MedCalc Software Ltd, Belgium), with a significance level set at 0.05. Results: It was observed that the application of EDTA, NaOCl, CHX, and citric acid solutions resulted in statistically significant reductions in the microhardness of both NeoPUTTY MTA (respectively p= .012; p= .012, p= .010; p= .012) and dentin (respectively p= .011; p= .012; p= .012; p= .012). The citric acid group exhibited the most pronounced reduction of MTA (respectively 52.2±1.6; -39±0.9). In contrast, no statistically significant change in microhardness was observed in the control group treated with saline (for dentin p= .311; for MTA p= .415). The impact of the solutions on MTA at 21 days was found to be less pronounced than that observed at 1 day (p= .012). Conclusion: The results of this study indicate that the application of citric acid solutions to MTA results in a statistically significant reduction in microhardness. The highest concentration of citric acid was observed to be more effective than the other solutions in the dissolution of MTA. However, these solutions were also found to significantly reduce the microhardness of dentin. It would be advisable to select solutions that facilitate the removal of MTA without damaging the dentin tissue.