Long‑term effect of acidic pH on the surface microhardness of ProRoot mineral trioxide aggregate, Biodentine, and total fill root repair material putty

The purpose of this study was to compare the microhardness values of ProRoot mineral trioxide aggregate (MTA), Biodentine, and total fill root repair material (TF‑RRM) Putty at varying pH and times.

In this laboratory experiment, materials were mixed and placed in cylinder blocks with internal dimensions of 6 mm × 4 mm. Ten samples of each material were soaked in buffered solutions of butyric acid with 4.4, 5.4, 6.4, and 7.4 pH values and stored at 37°C in 100% humidity. The samples were submitted to the microhardness test at the end of 1 week and then 1 month. Multivariate analysis of variance and Tukey honestly significant difference tests were carried out to compare the mean values at a significance level of P < 0.05.

Low pH caused a significant decrease in the microhardness values of all samples. Surface microhardness increased with time (P < 0.0001). The microhardness values of Biodentine were significantly greater than those of ProRoot MTA and TF‑RRM putty (P < 0.0001). The lowest microhardness values were recorded for TF‑RRM putty groups regardless of the pH of the environment and the evaluation time.

An acidic environment impaired the surface microhardness of all root repair materials tested. Overall, the mean surface microhardness of TF‑RRM Putty was lower than those of ProRoot MTA and Biodentine. Biodentine showed the greatest microhardness values at all pH values, regardless of the evaluation time.