Efficacy of various concentrations of NaOCl and instrumentation techniques in reducing Enterococcus faecalis within root canals and dentinal tubules V. B. Berber, B. P. F. A. Gomes, N. T. Sena, M. E. Vianna, C. C. R. Ferraz, A. A. Zaia & F. J. Souza-Filho Department of Restorative Dentistry, Dental School of Piracicaba, State University of Campinas (UNICAMP), Piracicaba, SP, Brazil Abstract Berber VB, Gomes BPFA, Sena NT, Vianna ME, Ferraz CCR, Zaia AA, Souza-Filho FJ. Efficacy of various concen- trations of NaOCl and instrumentation techniques in reducing Enterococcus faecalis within root canals and dentinal tubules. International Endodontic Journal, 39, 10–17, 2006. Aim To evaluate the efficacy of 0.5%, 2.5% and 5.25% sodium hypochlorite (NaOCl) as intracanal irrigants associated with hand and rotary instrumen- tation techniques against Enterococcus faecalis within root canals and dentinal tubules. Methodology A total of 180 extracted human premolar teeth were infected for 21 days with E. faecalis. The specimens were divided into 12 groups, as follows: group 1: 5.25% NaOCl + Hybrid technique (Valdrighi et al. 1998); group 2: 5.25% NaOCl + nickel–titanium (NiTi) rotary technique 4 mm shorter than the apex (by FOP-UNICAMP); group 3: 5, 25% NaOCl + NiTi rotary technique (Hero 642); group 4: 2.5% NaOCl + Hybrid technique; group 5: 2.5% NaOCl + NiTi rotary technique 4 mm shorter than the apex; group 6: 2.5% NaOCl + NiTi rotary technique (Hero 642); group 7: 0.5% NaOCl + Hybrid technique; group 8: 0.5% NaOCl + NiTi rotary technique 4 mm shorter than the apex; group 9: 0.5% NaOCl + NiTi rotary technique (Hero 642); group 10: sterile saline solution + Hybrid technique; group 11: sterile saline solution + NiTi rotary technique 4 mm shorter than the apex; group 12: sterile saline solution + NiTi rotary technique (Hero 642). Canals were sampled before and after preparation. After serial dilution, samples were plated onto brain heart infusion (BHI) agar, and the colony forming units (CFU) that were grown were counted. The teeth were sectioned into three thirds and dentine chips were removed from the canals with conical burs. The samples obtained with each bur were immediately collected into test tubes containing BHI broth, and were incubated at 37 °C and plated onto BHI agar. The CFU were counted and analysed. Results At all depths and thirds of the root canals and for all techniques used, 5.25% NaOCl was shown to be the most effective irrigant solution tested when dentinal tubules were analysed, followed by 2.5% NaOCl. No differences among concentrations in clean- ing the canals were found. Conclusions Especially at higher concentrations, NaOCl, was able to disinfect the dentinal tubules, independent of the canal preparation technique used. Keywords: bacteria, dentinal tubules, instrumenta- tion techniques, intracanal irrigants, sodium hypo- chlorite, root canal treatment. Received 8 February 2005; accepted 22 August 2005 Introduction Bacteria has long been recognized as the primary aetiological agent in the development of periapical bone lesions (Kakehashi et al. 1965). After root canal treatment, root canal failure from persistent infection Correspondence: Dr Brenda P. F. A. Gomes, Department of Restorative Dentistry, Dental School of Piracicaba, University of Campinas, Piracicaba, Brazil, Av. Limeira, 901 Piracicaba, SP CEP: 13 414-903 Brazil (Tel.: 0055 19 3412 5215; fax: 0055 19 3412 5218; e-mail: bpgomes@fop.unicamp.br). International Endodontic Journal, 39, 10–17, 2006 ª 2006 International Endodontic Journal 10 DropBooks DropBooks