Potentiation of the action of calcium hydroxide on Enterococcus faecalis by proton pump inhibitor omeprazole

  • Deborah Meirelles Cogo Pontifical Catholic University of Rio Grande do Sul
  • Sílvia Dias de Oliveira Federal University of Rio Grande do Sul
  • Fernanda Camargo Antunes Federal University of Rio Grande do Sul
  • Patrícia Maria Poli Kopper Pontifical Catholic University of Rio Grande do Sul
  • Jéssica Stephanie Rodrigues Nasário Federal University of Rio Grande do Sul
  • Fabiana Vieira Vier-Pelisser Pontifical Catholic University of Rio Grande do Sul
Keywords: In vitro, Bacteria, Enterococcus faecalis, Calcium hydroxide, Omeprazole.


Purpose: Calcium hydroxide is not fully effective against Enterococcus faecalis (E. faecalis), a facultative anaerobic bacterium proven to be resistant to most conventional disinfection processes. The aim of this in vitro study was to evaluate the effect of calcium hydroxide, omeprazole and the association of these substances against Enterococcus faecalis, as well as to evaluate if the acidcatalysation of the omeprazole had any influence in the results.
Methods: The Minimum Inhibitory Concentration (MIC) of these drugs against E. faecalis (ATCC 29212) was determined using macrodilution test adapted from the CLSI (Clinical Laboratory and Standards Institute). Solutions with different concentrations of calcium hydroxide, associated or not to omeprazole, were tested. Data were statistically analyzed using ANOVA test with Tukey post-hoc, with a level of significance of 5%.
Results: The MIC to calcium hydroxide was 32 mg mL-1 and, when associated with omeprazole, this was reduced reduced to 16 mg mL-1. The omeprazole and acidified omeprazole had similar activity. 
Conclusions: Omeprazole potentiated the effect of calcium hydroxide, since the association of these drugs reduced the MIC for E. faecalis. The acidification of omeprazole, when associated with calcium hydroxide in different concentrations, did not influence its effect.


Roças IN, Siqueira JF Jr, Santos KR. Association of Enterococcus faecalis with different forms of periradicular diseases. J Endod. 2004;30:315-20.

Sundqvist G, Figdor D, Persson S, Sjögren U. Microbiologic analysis of teeth with failed endodontic treatment and the outcome of conservative re-treatment. Oral Surg, Oral Med, Oral Pathol.1998;8:86-92.

Souza-Filho FJ, Soares AJ, Vianna ME, Zaia AA, Ferraz CCR, Gomes BPFA. Antimicrobial effect and pH of chlorexidine gel and calcium hydroxide alone and associated with other materials. Braz Dent J. 2008; 19:28-33.

Figdor D, Davies JK, Sundvist G. Starvation survival, growth, and recovery of Enterococcus faecalis in human serum. Oral Microb Immunol. 2003; 18:234-9.

Abdullah M, Ng Y-L, Gulabivala K, Moles DR, Spratt DA. Susceptibilities of two Enterococcus faecalis phenotypes to root canal medications. J Endod. 2005;31:30-6.

Orstavik D, Haapasalo M. Disinfection by endodontic irrigants and dressings of experimentally infected dentinal tubules. Endod Dent Traumatol. 1990;6:142-9.

Orstavik D, Kerekes K, Molven O. Effects of extensive apical reaming and calcium hydroxide dressing on bacterial infection during treatment of apical periodontitis: a pilot study. Int Endod J. 1991;24:1-7.

Evans M, Davies JK, Sundqvist G, Figdor D. Mechanisms involved in the resistance of Enterococcus faecalis to calcium hydroxide. Int Endod J. 2002;35:221-8.

Padan E, Zilberstein D, Schuldiner S. pH homeostasis in bacteria. Biochim Biophys Acta. 1981; 650:151-66.

Gomes BPFA, Souza SFC, Ferraz CCR, Teixeira FB, Zaia AA, Vladrighi L, Souza-Filho FJ. Effectiveness of 2% chlorexidine gel and calcium hydroxide against Enterococcus faecalis in bovine root dentine in vitro. Int Endod J. 2003;36:267-75.

Sirén EK, Haapasalo MPP, Waltimo TMT, Orstavik D. In vitro antibacterial effect of calcium hydroxide combined with chlorexidine or iodine potassium iodide on Enterococcus faecalis. Eur J Oral Sci. 2004;112:326-31.

Loo VG, Fallone CA, De Souza E, Lavallée J, Barkun AL. In-vitro susceptibility of Helicobacter pylori to ampicillin, clarithromycin, metronidazole and omeprazole. J Antimicrob Chemother. 1997;40: 881-3.

Andersen LP, Colding H, Kristiansen J. Potentiation of the action of metronidazole on Helicobacter pylori by omeprazole and bismuth subcitrate. Int J Antimicrob Agents. 2000;14: 231-4.

Jonkers D, Stobberingh E, Stockbrügger R. Omeprazole inhibits growth of Gram-positive and Gram-negative bacteria including Helicobacter pylori in vitro. Journal Antimicrob Chemother. 1996;37:145-50.

Pallota RC, Ribeiro MS, Machado MEL. Determination of the minimum inhibitory concentration of four medicaments used as intracanal medication. Aust Endod J. 2007;33:107-11.

Wagner C, Barth VC, Oliveira SD, Campos MM. Effectiveness of the proton pump inhibitor omeprazole associated with calcium hydroxide as intracanal medication: an in vivo study. J Endod.2011;37(9):1253-7.

National Committee for Clinical Laboratory Standards. Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically-Sixth Edition: Approved Standard M7-A6. 2003. NCCLS, 940 West Valley Road, Suite 1400, Wayne, Pennsylvania 19087-1898 USA.

Portenier I, Waltimo T, Orstavik D, Haapasalo M. The susceptibility of starved, stationary phase, and growing cells of Enterococcus faecalis. J Endod. 2005;31:380-6.

Estrela C, Bammann LL, Estrela CRA, Silva RS, Pécora JD. Antimicrobial and Chemical Study of MTA, Portland Cement, Calcium Hydroxide Paste, Sealapex and Dycal. Braz Dent J. 2000;11(1):3-9.

Tobias RS. Antibacterial properties of dental restorative materials: a review. Int Endod J. 1988;21:155-60.

Gomes BPFA, Vianna ME, Sena NT, Zaia AA, Ferraz CCR, Souza Filho FJ. In vitro evaluation of the antimicrobial activity of calcium hydroxide combined with chlorhexidine gel used as intracanal medicament. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2006;102: 544-50.

Morgental RD, Vier-Pelisser FV, Oliveira SD, Antunes FC, Cogo DM, Kopper PMP. Antibacterial activity of two MTA-based root canal sealers. Int Endod J. 2011;44:1128-33.

Silveira CFM, Cunha RS, Fontana CE, Martin AS, Gomes BPFA, Motta RHL, Bueno CES. Assessment of the Antibacterial Activity of Calcium Hydroxide Combined with Chlorhexidine Paste and Other Intracanal Medications against Bacterial Pathogens. Eur J Dent. 2011;5:1-7.

Estrela C, Holland R, Bernabe PFE, Souza V, Estrela CRA. Antimicrobial potencial of medicaments used in healing process in dog´s teeth with apical periodontitis. Braz Dent J. 2004;15:181-5.

Zehnder M. Root canal irrigants. J Endod. 2006;32:389-98.

Original Article