ABSTRACT
One of the materials used for repairing root-end fillings is mineral trioxide aggregate [MTA]. MTA has been reported to remain soft when placed in perforations with a high degree of inflammation. The purpose of this study was to evaluate the effect of environmental pH on the setting and micro structure of MTA. In this interventional study, tooth-colored MTA [Pro Root, Dentsply, USA] was mixed according to the manufactures instructions. The mixture was placed into cylindrical polycarbonate tubes. The specimens were randomly divided into four groups of 9 and were subjected to a pressure of 3.22 Mpa - 6kg applied for 1 minute in a custom-made condenser device. Each of the 9 specimens were then stored at room temperature and saturated humidity in four plastic plates containing buffer solutions of butyric and propyonic acid with a pH of 4.4, 5.4, 6.4 and 7.4, for 4 days. The Vickers hardness test was performed on each specimen. The microstructures of the specimens were analyzed using a scanning electron microscope after sectioning the specimens with a scalpel. Data were subjected to one-way ANOVA. The lowest and highest pH values were 4.4 and 7.4, respectively. A statistically significant difference was observed between all four groups [p<0.05]. Unreacted MTA particles scattered in a non uniform matrix were seen in specimens stored in pH 4.4 solutions whereas cases kept in a pH 7.4 environment had distinctive crystalline structures embedded in a more uniform matrix. The results indicate that the acidic pH of inflamed tissues can adversely affect the setting of MTA