ORIGINAL ARTICLE Endodontics Time-dependent antibacterial effects of Aloe vera and Zataria multiflora plant essential oils compared to calcium hydroxide in teeth infected with Enterococcus faecalis Abbas Abbaszadegan 1 , Safoora Sahebi 1 , Ahmad Gholami 2 , Alireza Delroba 3 , Amin Kiani 3 , Aida Iraji 4 & Paul Vincent Abbott 5 1 Department of Endodontics, Faculty of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran 2 Pharmaceutical Sciences Research Center and Department of Pharmaceutical Biotechnology, School of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran 3 Undergraduate Student, Student Research Center Committee, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran 4 Central Laboratory, Shiraz University of Medical Sciences, Shiraz, Iran 5 School of Dentistry, University of Western Australia, Perth, Western Australia, Australia Keywords Aloe vera, antimicrobial activity, calcium hydroxide, root canal treatment, Zataria multiflora. Correspondence Dr Ahmad Gholami, School of Pharmacy, Shiraz University of Medical Sciences, Akbarabad Ring Way, Shiraz, Iran. Tel: +98-91-7314-0518 Fax: +98-71-1626-3192 Email: gholami@sums.ac.ir Received 20 February 2014; accepted 2 July 2014. doi: 10.1111/jicd.12123 Abstract Aim: In the present in vitro study, we investigated the time-related antimicro- bial efficacy of Aloe vera and Zataria multiflora (Z. multiflora) plant essential oils compared to calcium hydroxide ([Ca[OH] 2 ) to eliminate Enterococcus fae- calis (E. faecalis) from root canals. Methods: A new strain of E. faecalis (Enterococcus spp. AGH04) was isolated from a previously root-filled tooth with persistent apical periodontitis. The 16S rRNA sequence was analyzed and deposited in GeneBank under accession number KF465681. A total of 108 extracted human single-rooted teeth were contaminated with this bacterial strain and treated with Aloe vera essential oil, Z. multiflora essential oil, and Ca(OH) 2 for 1, 7, and 14 days. Gas chromatog- raphy–mass spectrometry (GC–MS) was used to determine the chemical com- position of the oils. The percentage reduction from initial c.f.u./mL counts were calculated and analyzed. Results: Carvacrol, thymol, and linalool were the main constituents of both essential oils. The c.f.u./mL count reductions significantly increased for all three medicaments when the contact time was extended. A statistically-significant dif- ference was observed between the medicaments after 1 and 7 days, but there was no significant difference after 14 days. Conclusions: Both medicinal herbs showed equal antimicrobial efficiency against E. faecalis, comparable to Ca(OH) 2 for the prolonged contact time of 14 days. Introduction The aim of root canal treatment is either prevention or the treatment of periapical pathosis caused by microor- ganisms. 1 Achieving this goal is highly related to the degree of reduction of the intracanal bacterial popula- tion. 2 Although complete elimination of bacteria is chal- lenging and might not always be successful, it is generally achieved by chemomechanical root canal preparation with the aid of antimicrobial irrigation solutions and intracanal dressings between treatment visits. 3 Applying an interap- pointment antimicrobial dressing in infected root canals is recommended, as instrumentation and irrigation do not reliably eradicate all of the bacteria. 4 Enterococcus faecalis (E. faecalis) is one of the most resistant bacteria found in infected root canals, especially ª 2014 Wiley Publishing Asia Pty Ltd 1 Journal of Investigative and Clinical Dentistry (2014), 5, 1–9