Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 11 2 2014 04 15 161 6 Noushin Shokouhinejad Associate Professor, Dental Research Center Dentistry Research Institute, Department of Endodontics, School of Dentistry Tehran University of Medical Sciences, Tehran, Iran. Kazem Ashofteh Yazdi Associate Professor, Dental Research Center Dentistry Research Institute, Department of Endodontics, School of Dentistry Tehran University of Medical Sciences, Tehran, Iran. Mohammad Hossein Nekoofar Assistant Professor, Dental Research Center Dentistry Research Institute, Department of Endodontics, School of Dentistry Tehran University of Medical Sciences, Tehran, Iran ; Endodontology Research Group, School of Dentistry, Cardiff University, Heath Park, Cardiff, UK. Shakiba Matmir Dental Student, School of Dentistry Tehran University of Medical Sciences, Tehran, Iran. Mehrfam Khoshkhounejad Assistant Professor, Dental Research Center Dentistry Research Institute, Department of Endodontics, School of Dentistry Tehran University of Medical Sciences, Tehran, Iran. 2015 10 16 The aim of this study was to compare the effect of an acidic environment on dislocation resistance (push-out bond strength) of EndoSequence Root Repair Material (ERRM putty and ERRM paste), a new bioceramic-based material, to that of mineral tri-oxide aggregate (MTA).One-hundred twenty root dentin slices with standardized canal spaces were divided into 6 groups (n = 20 each) and filled with tooth-colored ProRoot MTA (groups 1 and 2), ERRM putty (groups 3 and 4), or ERRM paste (groups 5 and 6). The specimens of groups 1, 3, and 5 were exposed to phosphate buffered saline (PBS) solution (pH=7.4) and those of groups 2, 4, and 6 were exposed to butyric acid (pH= 4.4). The specimens were then incubated for 4 days at 37°C. The push-out bond strength was then measured using a universal testing machine. Failure modes after the push-out test were examined under a light microscope at ×40 magnification. The data for dislocation resistance were analyzed using the t-test and one-way analysis of variance.In PBS environment (pH=7.4), there were no significant differences among materials (P=0.30); but the mean push-out bond strength of ERRM putty was significantly higher than that of other materials in an acidic environment (P https://fid.tums.ac.ir/index.php/fid/article/view/529 https://fid.tums.ac.ir/index.php/fid/article/download/529/505