Research Article Comparing the Coronal Seal of Different Thicknesses of MTA with Gutta-Percha after Post Space Preparation Mohammad Frough Reyhani, 1 Hamidreza Yavari, 1 Negin Ghasemi, 1 Saeed Rahimi, 2 Mohammad Hosien Soroush Barhaghi, 3 Hadi Mokhtari, 1 and Payman Sarikhani 4 1 Department of Endodontics, Dental Faculty, Tabriz University (Medical Sciences), Tabriz 5154613475, Iran 2 Dental and Periodontal Research Center, Dental Faculty, Tabriz University (Medical Sciences), Tabriz 5154613475, Iran 3 Department of Microbiology, Medical Faculty, Tabriz University (Medical Sciences), Tabriz 5154613475, Iran 4 Dental Faculty, Tabriz University (Medical Sciences), Tabriz 5154613475, Iran Correspondence should be addressed to Negin Ghasemi; moh-reyhani@gmail.com Received 24 January 2015; Accepted 30 March 2015 Academic Editor: Dennis Flanagan Copyright © 2015 Mohammad Frough Reyhani et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Introduction. Te aim of this study was to compare the coronal seal of diferent thicknesses of MTA with gutta-percha afer post space preparation. Materials and Methods. A total of 50 maxillary central incisors randomly divided into 5 experimental groups (=8). Afer preparation of the root canals with step back technique, in groups 1 and 2, post spaces were prepared and 4 or 5 mm gutta-percha remained in the apical, respectively. In groups 3, 4, and 5, there was 1-2 and 3 mm MTA in the apical, respectively. Te ten teeth serve as control groups. Te teeth were connected to a bacterial microleakage evaluation system. Te study period was 120 days and the samples were evaluated on ten-day intervals; Meier-Kaplan technique was used for estimation of the mean time of microleakage to occur. Log-rank test was used for comparison of microleakage. Results. Number of samples exhibiting microleakage in MTA was less than those of gutta-percha at all intervals. Means of days with no microleakage were maximum and minimum with 3 mm MTA and 4 mm gutta-percha, respectively. Conclusion. Obturation of root canals using the MTA technique provides a proper seal with the minimum thickness of MTA in teeth requiring post space preparation. 1. Introduction Te aim of root canal obturation is to achieve a hermetic corono-apical seal and inability to achieve a proper seal is one of the most common reasons for failures of endodontic treatment [1]. Endodontically treated teeth should be properly restored to replace coronal structures, restore function, and pre- vent reinfections [2]. In the majority of cases, endodon- tically treated teeth have inadequate remaining structure and require post placement to increase the retention of the coronal restoration [3]. In addition, the post protects the apical seal against bacterial contamination due to coronal leakage [4]. To prepare the post space, some obturation material should be removed from the root canal, which afects the apical seal [2]. Te integrity of the apical seal depends on the amount of obturation material remaining within the root canal [3, 5–7]. Studies have shown that in teeth, in which less than 3 mm of gutta-percha has remained afer post space preparation, there is a higher incidence of lesions compared to greater gutta-percha lengths and the best coronal seal is achieved when at least 6 mm of gutta-percha remains in the root canal [3, 7]. In cases in which the roots are short, it is difcult to leave an adequate amount of gutta-percha in the apical end of the root canal during post space preparation. Terefore, in such cases it is advisable to use materials that provide adequate seal at a minimum thickness. Mineral Trioxide Aggregate (MTA) might be used as a root canal obturation material due to its favorable antimicrobial activity, biocompatibility, and sealing ability [6, 8–10]. Hindawi Publishing Corporation e Scientific World Journal Volume 2015, Article ID 708639, 5 pages http://dx.doi.org/10.1155/2015/708639