title: Polymerase chain reaction-based analysis of microorganisms associated with failed endodontic treatment.
abstract: OBJECTIVE
  In this study, we aimed to investigate the occurrence of several microbial species in cases of failed endodontic therapy by means of the polymerase chain reaction (PCR). Study design Root canal samples were taken from 22 root-filled teeth with persistent periradicular lesions selected for re-treatment. DNA was extracted from the samples and analyzed for the presence of 19 microbial taxa by using the polymerase chain reaction.
  
  
  RESULTS
  All samples were positive for at least 1 of the target microbial species. Enterococcus faecalis was the most prevalent species-detected in 77% of the cases. The other most prevalent species were Pseudoramibacter alactolyticus (52%), Propionibacterium propionicum (52%), Dialister pneumosintes (48%), and Filifactor alocis (48%). Candida albicans was found in 9% of the samples. The mean number of species in samples filled up to 2 mm short of the radiographic apex was 3 (range, 1-5), whereas cases in which the filling was greater than 2 mm from the apex yielded a mean of 5 species (range, 2-11). This difference was statistically significant (P <.05).
  
  
  CONCLUSIONS
  Microorganisms occurred in all cases of root-filled teeth associated with periradicular lesions, which lends strong support to the assertion that treatment failures are rather of infectious etiology, caused by persistent or secondary intraradicular infections. E faecalis was the most prevalent species, followed by 4 other anaerobic species: P. alactolyticus, P. propionicum, D. pneumosintes, and F. alocis. All examined samples harbored at least 1 of the following gram-positive bacterial species: E. faecalis, P. alactolyticus, or P. propionicum.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, Brazil. siqueira@eastacio.br
authors.forename: José F
authors.initials: JF
authors.lastname: Siqueira
authors.forename: Isabela N
authors.initials: IN
authors.lastname: Rôças
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001419:Bacteria / Q000145:classification*; D002176:Candida albicans / Q000145:classification; D003786:Dental Pulp Cavity / Q000382:microbiology*; D013293:Enterococcus faecalis / Q000145:classification; D005051:Eubacterium / Q000145:classification; D005260:Female; D005673:Fusobacterium / Q000145:classification; D016965:Gram-Negative Anaerobic Straight, Curved, and Helical Rods / Q000145:classification; D006801:Humans; D008297:Male; D008875:Middle Aged; D010483:Periapical Diseases / Q000382:microbiology / Q000628:therapy; D016133:Polymerase Chain Reaction; D011424:Propionibacterium / Q000145:classification; D019233:Retreatment; D012387:Root Canal Filling Materials / Q000627:therapeutic use; D012390:Root Canal Therapy; D019227:Tooth Apex / Q000382:microbiology; D017211:Treatment Failure
chemical_list: D012387:Root Canal Filling Materials