en عمومى General گزارش مورد case report <p><strong>Background</strong>: One of the major causes of failure in root canal treatment is microorganisms like <em>Enterococcus faecalis</em>.</p> <p><strong>Methods</strong>: This study aimed to examine the effectiveness of triple antibiotic paste (TAP) containing ciprofloxacin, metronidazole, and minocycline in comparison with modified TAP (MTAP) containing metronidazole, ciprofloxacin, and clindamycin and calcium hydroxide on <em>Enterococcus</em> strains isolated from root canal of tooth associated with pre-apical lesion. Moreover, we evaluated the <em>E. faecalis</em> resistance and antibiotic susceptibility. To do so, 25 patients with previous failure of endodontic treatment were enrolled in this study.</p> <p><strong>Results</strong>: The antimicrobial effect of MTAP10%, MTAP1%, TAP10%, TAP1%, and CaOH was significantly better than the positive control group (<em>P</em> <0.05). There was no significant difference between antimicrobial effect of TAP1% and MTAP1%, and CaOH was the least effective one. The antimicrobial effect of TAP10% was significantly better than MTAP10% (<em>P</em> = 0.007). Out of 11 <em>E. faecalis</em> samples, 1 sample was resistant to MTAP1% and MTAP10%, though it was sensitive to other drugs; meanwhile, it showed the highest sensitivity to TAP10%.</p> <p><strong>Conclusion</strong>: TAP10% was the most effective choice followed by MTAP10%, but calcium hydroxide was not effective compared to other choices. Thus, MTAP might be a good choice for root canal medicament instead of TAP</p> Drug susceptibility, Enterococcus faecalis, Modified triple antibiotic paste, Triple antibiotic paste 60 64 http://ajpr1.umsha.ac.ir/browse.php?a_code=A-10-2-33&slc_lang=en&sid=1 Nazanin Zargar 1003194753284600185 1003194753284600185 No Iranian Center for Endodontic Research, Research Institute of Dental Sciences, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Mohammad J Nasiri 1003194753284600186 1003194753284600186 No Department of Microbiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran Hengameh Ashraf 1003194753284600187 1003194753284600187 No Department of Endodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Bahareh Hajikhani 1003194753284600188 1003194753284600188 No Department of Microbiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran Shirin Etminani Esfahani shirin. etminaniesfahani@gmail.com 1003194753284600189 1003194753284600189 Yes School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Maryam Etminani Esfahani 1003194753284600190 1003194753284600190 No Department of Clinical Pharmacy (Pharmacotherapy), School of Pharmacy, Hamadan University of Medical Sciences, Hamadan, Iran