Iranian Dental Association Journal of Iranian Dental Association 3060-8201 18 2 2006 05 01 The effect of environmental PH on the setting of Mineral Trioxide Aggregate 100 105 EN Mohammad hosein Nekoofar Mohammad saeid SheikhRezayee Sedigheh Salari Journal Article 2006 12 23 2013 02 25 The effect of environmental PH on the setting of Mineral Trioxide Aggregate Dr. MH. Nekoofar* - Dr. MS. SheikhRezayee** - Dr. S. Salari** *- Assistant Professor of Endodontics Dept. - Faculty of Dentistry – Tehran University of Medical Sciences. **- Dentist. Background and Aim: 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. Materials and Methods: In this interventional study, tooth-colored MTA (Pro Root, Dentsply, USA) was mixed according to the manufacture’s 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. Results: 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. Conclusion: The results indicate that the acidic pH of inflamed tissues can adversely affect the setting of MTA. Key words: MTA - Acidic pH - Setting time - Microhardness - Electron microscope.