title: Quantitative and qualitative analysis of microorganisms in root-filled teeth with persistent infection: Monitoring of the endodontic retreatment.
abstract: OBJECTIVE
  The aim of this study was to investigate in vivo microorganisms detected in root-filled teeth with post-treatment apical periodontitis and quantify colony-forming units (CFU) during endodontic retreatment.
  
  
  METHODS
  Fifteen root-filled teeth had their previous gutta-percha removed and were randomly instrumented before being divided into three groups and medicated with either [Ca(OH)2 + 2% CHX gel], [Ca(OH)2 + 0.9% NaCl] or 2% CHX gel. Samples were taken after removal of gutta-percha (S1), after chemomechanical preparation using 2% CHX gel (S2), and after inter-appointment dressing (S3) for 7 or 14 days later. Cultivable bacteria recovered from infected root canals at the three stages were counted and identified by means of culture and PCR assay (16S rDNA). Quantitative data were statistically analyzed by using Mann-Whitney test in which pairs of groups were compared (P < 0.05).
  
  
  RESULTS
  CFU counts decreased significantly from S1 to S2 (P < 0.05). No significant difference was found between S2 and S3 (P = 0.3093) for all three experimental groups. Chemomechanical preparation and intra-canal dressing promoted significant median reductions of 99.61% and 99.57%, respectively, in the number of bacteria compared to S1 samples. A total of 110 cultivable isolates were recovered by culture technique from 32 different species and 7 different genera. Out of the 13 target species-specific primer of bacteria analyzed, 11 were detected during endodontic retreatment.
  
  
  CONCLUSIONS
  The great majority of taxa found in post-treatment samples were Gram-positive bacteria, although Gram-negative bacteria were found by molecular methods. Moreover, our results showed that gutta-percha removal and chemomechanical preparation are effective for root canal disinfection, whereas additional intra-canal dressing did not improve disinfection.
authors.affiliation: Department of Restorative Dentistry, Endodontics Division, Piracicaba Dental School - State University of Campinas - UNICAMP, Piracicaba, SP, Brazil.
authors.forename: Marcos S
authors.initials: MS
authors.lastname: Endo
authors.affiliation: Department of Restorative Dentistry, Endodontics Division, Piracicaba Dental School - State University of Campinas - UNICAMP, Piracicaba, SP, Brazil.
authors.forename: Caio C R
authors.initials: CCR
authors.lastname: Ferraz
authors.affiliation: Department of Restorative Dentistry, Endodontics Division, Piracicaba Dental School - State University of Campinas - UNICAMP, Piracicaba, SP, Brazil.
authors.forename: Alexandre A
authors.initials: AA
authors.lastname: Zaia
authors.affiliation: Department of Restorative Dentistry, Endodontics Division, Piracicaba Dental School - State University of Campinas - UNICAMP, Piracicaba, SP, Brazil.
authors.forename: Jose F A
authors.initials: JFA
authors.lastname: Almeida
authors.affiliation: Department of Restorative Dentistry, Endodontics Division, Piracicaba Dental School - State University of Campinas - UNICAMP, Piracicaba, SP, Brazil.
authors.forename: Brenda P F A
authors.initials: BPFA
authors.lastname: Gomes
keywords: Endodontic failure; endodontic outcome; intra-canal dressing; nonsurgical retreatment; root canal infection