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.