title: Microorganisms from canals of root-filled teeth with periapical lesions.
abstract: OBJECTIVE
  The objective of the present study was to identify the microbial flora within root canals of teeth with failed root-canal treatment and to determine the association of the various species with clinical features.
  
  
  METHODS
  Sixty root-filled teeth with persisting periapical lesions were selected for this study. During nonsurgical endodontic re-treatment, the root-filling material was removed and the canals were sampled. Microbial sampling, isolation and species determination were performed using advanced microbiological techniques for anaerobic species. The association of microbiological findings with clinical features was investigated.
  
  
  RESULTS
  Microorganisms were recovered from 51 teeth. In most cases, one or two strains per canal were 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 anaerobes accounted for 42.6% of the species and the most frequently isolated genera was Peptostreptococcus. which was associated with clinical symptoms (P < 0.01). Significant 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).
  
  
  CONCLUSIONS
  The microbial flora in canals after failure 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 anaerobes were frequently found in canals of symptomatic root-filled teeth.
authors.affiliation: Endodontic Department, Piracicaba Dental School, State University of Campinas, UNICAMP, Piracicaba, SP, Brazil.
authors.forename: E T
authors.initials: ET
authors.lastname: Pinheiro
authors.forename: B P F A
authors.initials: BP
authors.lastname: Gomes
authors.forename: C C R
authors.initials: CC
authors.lastname: Ferraz
authors.forename: E L R
authors.initials: EL
authors.lastname: Sousa
authors.forename: F B
authors.initials: FB
authors.lastname: Teixeira
authors.forename: F J
authors.initials: FJ
authors.lastname: Souza-Filho
mesh_terms: D001421:Bacteria, Anaerobic / Q000302:isolation & purification; D015373:Bacterial Typing Techniques; D016009:Chi-Square Distribution; D003731:Dental Caries / Q000209:etiology; D003786:Dental Pulp Cavity / Q000382:microbiology*; D019232:Dental Restoration Failure; D006094:Gram-Positive Bacteria / Q000302:isolation & purification; D006801:Humans; D010510:Periodontal Diseases / Q000209:etiology; D019233:Retreatment; D012389:Root Canal Obturation / Q000009:adverse effects*; D014098:Toothache / Q000209:etiology