Antibacterial Activity of Propolis versus Conventional Endodontic Disinfectants against Enterococcus faecalis in Infected Dentinal Tubules Guven Kayaoglu, DDS, PhD,* H€ uma € Om€ url € u, DDS, PhD,* G€ ulc ¸in Akca, MD, PhD, † M€ ugem G€ urel, DDS,* € Om€ ur Genc ¸ay, BSc, ‡ Kadriye Sorkun, PhD, ‡ and Bekir Salih, PhD § Abstract Introduction: The antibacterial activity against Enterococcus faecalis of 2 propolis samples was investigated in a dentin block model, and their effective- ness was compared with that of established endodontic disinfectants, chlorhexidine (CHX) and calcium hydroxide [Ca(OH) 2 ]. Methods: Standardized dentin blocks were infected with E. faecalis ATCC 29212. The root canal space was filled with one of the ethanolic extracts of propolis (Artvin or Tekirda g mix [TM]), CHX 2%, Ca(OH) 2 , or ethanol or phosphate-buffered saline for control. Canal dentin was sampled after 1 or 7 days by using a standard-size bur. The dentinal shavings were vortexed vigorously in phosphate-buffered saline, and aliquots were cultured on tryptone soy agar plates. Colonies were counted after 2 days of incubation. Statis- tical significance was set to 5%. Results: All experi- mental agents significantly reduced the number of the cultivable bacteria. CHX was the most potent disinfectant at both times. Compared with the ethanol control, no significant reduction in the number of colonies was found for the propolis extracts at day 1; however, significant reduction was found at day 7. The 2 propolis samples were statistically similar to each other and to Ca(OH) 2 , but the TM sample was also similar to CHX at day 7. This has been linked to the greater concentration of flavo- noids, a group of antibacterially active compounds, in the TM sample as determined by gas chromatography–mass spectrometry analysis. Conclusions: The antimicrobial activity of the propolis samples tested in this study was between Ca(OH) 2 and CHX. Both propolis samples were antimicrobially effective; however, their activity did not exceed CHX. (J Endod 2011;37:376–381) Key Words Antimicrobial, bee glue, disinfection, gas chromatogra- phy-mass spectrometry B acteria are the main causative factors in the development of pulpal and periapical inflammation (1, 2). It has been shown that periapical lesions heal at a higher rate in teeth with negative root canal bacterial cultures obtained at the time of canal filling in comparison with those with positive cultures (3). Therefore, one of the most important objectives of endodontic treatment is to eliminate bacteria from the infected root canal system. Enterococcus faecalis is a gram-positive, facultative anaerobic bacterium commonly recovered from previously root-filled teeth with persistent periapical lesions (4, 5). Its ability to invade dentinal tubules, withstand the ecologically demanding conditions of the root canal, and adapt to lethal challenges are considered among the factors that enable this bacterium to be a persisting endodontic pathogen (6). Numerous studies have shown that E. faecalis cannot be eliminated effectively by calcium hydroxide [Ca(OH) 2 ], currently the most common endodontic disinfectant in use (7–9). On the other hand, disinfectants such as chlorhexidine (CHX), iodine potassium iodide, or their combinations with Ca(OH) 2 have been found to be superior to Ca(OH) 2 alone in reducing the number of viable cells of E. faecalis (9–11). However, complete eradication of the bacteria is still not guaranteed with the use of these agents, and a search for a medicament that can predictably disinfect the root canal continues. Propolis (bee glue) is a resinous substance that honeybees collect from various plants and use in the hive to cover hive walls, fill cracks or gaps, and embalm dead invaders. It has been used as a remedy in folk medicine since ancient times. The chem- ical composition of propolis is very complex and includes organic compounds such as phenolic compounds and esters, flavonoids in all their forms (flavonols, flavones, fla- vonones, dihydroflavonols, and chalcones), terpenes, beta-steroids, aromatic aldehydes and alcohols, sesquiterpenes, and stilbene terpenes (12). The chemical composition of propolis is also highly variable and depends on the local flora at the site of collection (13, 14). Propolis has been shown to possess antibacterial, antifungal, antiviral, anti- inflammatory, hepatoprotective, antioxidant, antitumor, and immunomodulatory effects (12, 13). Among these functional properties, antibacterial activity has been linked mainly to the flavonoid content (15, 16). Phenolic compounds, terpenes, and aromatic acids and esters have also been reported to exert antibacterial activities (13, 17–20). The aim of this study was to investigate the chemical composition and the antibac- terial activity against E. faecalis of 2 propolis extracts obtained from different locations and to compare their effectiveness with established endodontic disinfectants, namely Ca(OH) 2 and CHX. From the *Department of Restorative Dentistry and Endodontics and † Department of Microbiology, Faculty of Dentistry, Gazi University, Ankara, Turkey; and ‡ Department of Biology and § Department of Chemistry, Faculty of Sciences, Hacettepe University, Ankara, Turkey. Address requests for reprints to Dr Guven Kayaoglu, Department of Restorative Dentistry and Endodontics, Faculty of Dentistry, Gazi University, 82. sokak, 06510, Emek, Ankara, Turkey. E-mail address: guvenk@gazi.edu.tr 0099-2399/$ - see front matter Copyright ª 2011 American Association of Endodontists. doi:10.1016/j.joen.2010.11.024 Basic Research—Technology 376 Kayaoglu et al. JOE — Volume 37, Number 3, March 2011