Microorganismsfromcanalsofroot-filledteeth withperiapicallesions E.T. Pinheiro, B. P. F. A. Gomes, C. C. R. Ferraz, E. L. R. Sousa, F. B.Teixeira & F. J. Souza-Filho EndodonticDepartment,PiracicabaDentalSchool,StateUniversityofCampinas,UNICAMP,Piracicaba,SP,Brazil Abstract Pinheiro ET, Gomes BPFA, Ferraz CCR, Sousa ELR, Teixeira FB, Souza-Filho FJ. Microorganisms from canals of root-filled teeth with periapical lesions. International Endodontic Jour- nal , 36, 1^11, 2003. Aim The objective of the present study was to identify the microbial £ora within root canals of teeth with failed root-canal treatment and to determine the asso- ciation of the various species with clinical features. Methodology Sixty root-¢lled teeth with persisting periapical lesions were selected for this study. During nonsurgical endodontic re-treatment, the root-¢lling material was removed and the canals were sampled. Microbial sampling, isolation and species determina- tion were performed using advanced microbiological techniques for anaerobic species. The association of microbiological ¢ndings with clinical features was investigated. Results Microorganisms were recovered from 51 teeth. In most cases, one or two strains percanalwere found. Of the microbial species isolated, 57.4% were facultative anaerobic species and 83.3% Gram-positive microorganisms. Enterococcus faecalis was the most frequently recovered bacterial species. Obligate anae- robes accounted for 42.6% of the species and the most frequently isolated genera was Peptostreptococcus , which was associated with clinical symptoms ( P < 0.01). Signi¢cant associations were also observed between: (a) pain or history of pain and polymicrobial infections or anaerobes ( P < 0.05); (b) tenderness to percussion and Prevotella intermedia/P. nigrescens ( P < 0.05); (c) sinus and Streptococcus spp. ( P < 0.001) or Actinomyces spp. ( P < 0.01); (d) coronally unsealed teeth and Streptococcus spp. or Candida spp. (both with P < 0.01). Conclusion The microbial £ora in canals after fail- ure of root-canal treatment were limited to a small number of predominantly Gram-positive microbial species. Facultative anaerobes, especially E. faecalis , were the most commonly isolated microorganisms, however, polymicrobial infections and obligate anae- robes were frequently found in canals of symptomatic root-¢lled teeth. Keywords: endodontic failure, microbiology, root- canal therapy. Received 4 June 2001; accepted16 August 2002 Introduction Bacteriaortheirproductsareconsideredtobetheprimary aetiological agents of pulpal necrosis and periapical lesions(Kakehashi et al .1965,Mo« ller et al .1981,Takahashi 1998). Therefore, their elimination is one of the most important steps in root-canal treatment. In most cases failure of root-canal treatment occurs when treatment procedureshavenotmetasatisfactorystandardforcon- trol and elimination of infection (Nair et al . 1990, 1999, Lin et al .1991).Persistingbacteriainrootcanalsmaybe thoseoriginallypresentinthenecroticpulpsthatsurvive the biomechanical procedures, which may be located in missed canals or uninstrumented areas of the canals (Fukushima et al . 1990, Ida & Gutmann 1995, Sjo« gren et al .1997). Conversely, bacteria mayoriginate from the oralcavity,contaminatetherootcanalduringtreatment owingtoinadequateasepticcontrol(Siren et al .1997), or invadetheroot-¢llingviacoronalleakageafterroot-canal treatment (Torabinejad et al . 1990, Magura et al . 1991, Ray&Trope1995,Cheung1996). Correspondence:DrBrendaP.F.A.Gomes,PhD,MSc,BDS,Endodontia, FaculdadedeOdontologiadePiracicaba,FOP-UNICAMP,AvenidaLime- ira 901, Piracicaba 13414-018, SP, Brazil (Tel.: þ551934125215, fax: þ551934125218;e-mail:bpgomes@fop.unicamp.br). ß 2003 Blackwell Publishing Ltd International Endodontic Journal, 36, 1^11, 2003 1