Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 14 1 2017 02 15 7 12 EN Omid Dianat Associate Professor, Department of Endodontics, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran Mandana Naseri Associate Professor, Department of Endodontics, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran Seyedeh Farnaz Tabatabaie Postgraduate Student of Restorative and Cosmetic Dentistry, Department of Restorative and Cosmetic Dentistry, Islamic Azad University, Tehran, Iran 2016 07 20 2016 11 25 Objectives: Mineral trioxide aggregate (MTA) is extensively used in endodontics. However, MTA is difficult to handle because of its granular consistency, low mechanical properties and initial looseness. The objective of this study was to assess the compressive strength (CS), diametral tensile strength (DTS), and pH of set MTA using methyl cellulose as liquid. Materials and Methods: White ProRoot MTA was used as the control group; modified MTA cement was prepared by mixing Portland cement, bismuth oxide and calcium sulfate (75%, 20% and 5%, respectively) as the experiment group. Methyl cellulose was used as hydrating liquid and compared with deionized water. The data were analyzed by two-way ANOVA. Results: The pH values of modified MTA cement set using deionized water and methyl cellulose were slightly, but not significantly, different (P>0.05). The DTS and CS tests for modified MTA cement hydrated with methyl cellulose showed a significant difference at one day and one week (P<0.05). Conclusions: The results suggest that using methyl cellulose as the hydrating liquid enhances some mechanical properties but does not compromise pH of white ProRoot MTA.   https://fid.tums.ac.ir/index.php/fid/article/view/1421 https://fid.tums.ac.ir/index.php/fid/article/download/1421/934