Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 11 5 2014 10 15 560 8 Abdollah Ghorbanzadeh Assistant Professor, Dental Research Center, Dentistry Research Institute, Department of Endodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran. Noushin Shokouhinejad Associate Professor, Dental Research Center, Dentistry Research Institute, Department of Endodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran ; Iranian Center for Endodontic Research, Research Institute of Dental Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Bita Fathi Postgraduate Student of Endodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran. Maryam Raoof Oral and Dental Diseases Research Center/Department of Endodontics, Kerman University of Medical Sciences, Kerman, 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 This study compared the marginal adaptation of mineral trioxide aggregate (MTA) and MTA-like materials as root-end fillings after incubation in phosphate buffer saline (PBS), a synthetic tissue fluid, for either 1 week or 2 months.In this experimental study, seventy-two extracted human single-rooted teeth were prepared and obturated with gutta-percha and AH26 sealer. The apical 3 mm of the roots were resected. Root-end cavities were prepared with an ultrasonic retrotip. The specimens were randomly divided into three groups (n=24) and filled with either ProRoot MTA, OrthoMTA, or RetroMTA. Half of the specimens in each group were stored in PBS for 1 week the other half for 2 months. Epoxy resin replicas from the resected root-end surfaces and longitudinally sectioned roots were fabricated. The gaps at the material/dentin interface were measured using a scanning electron microscope (SEM). Transversal, longitudinal, and overall gap sizes were measured. The data were analyzed using Kruskal-Wallis and Mann-Whitney tests. The significance level was set at p < 0.05.There were no significant differences between the marginal adaptation of ProRoot MTA, RetroMTA, and OrthoMTA in both transverse and longitudinal sections after incubation for either 1 week or 2 months (p > 0.05). In addition, the test groups were not significantly different regarding the overall mean gap values (p > 0.05).Under the conditions of this study, there was no difference between the marginal adaptation of ProRoot MTA, OrthoMTA, and RetroMTA as root-end filling materials after exposure to PBS for either 1 week or 2 months. https://fid.tums.ac.ir/index.php/fid/article/view/386 https://fid.tums.ac.ir/index.php/fid/article/download/386/362