title: Microbial diversity in failed endodontic root-filled teeth.
abstract: BACKGROUND
  Persistent/secondary infections of human root canals play an important role in the failure of endodontic treatment. This study used 16S rRNA sequencing to assess microbial diversity in root-filled teeth associated with failed endodontic treatment.
  
  
  METHODS
  DNA was extracted from 15 teeth with persistent intraradicular infections, and the 16S rRNA of all present bacteria were amplified by PCR, followed by cloning and sequencing of the 16S rRNA amplicons.
  
  
  RESULTS
  All sample extracts were positive for PCR amplification using the universal 16S rRNA gene primers. Negative control reactions yielded no amplicons. Sixty-five phylotypes belonging to seven phyla were identified from 760 clones; a mean of 9.4 phylotypes were detected in each sample (range 3 - 15). Twenty-eight phylotypes were detected in more than one sample, revealing a high inter-sample variability. Parvimonas micra (60%, 9/15), Solobacterium moore (47%, 7/15), Dialister invisus (33%, 5/15), Enterococcus faecalis (33%, 5/15), Filifactor alocis (27%, 4/15), and Fusobacterium nucleatum (27%, 4/15) were the prevalent species. Nineteen as-yet-uncultivated phylotypes were identified, comprising a substantial proportion of the bacteria in many cases.
  
  
  CONCLUSIONS
  Persistent intraradicular infections were present in all root-filled teeth associated with failed endodontic treatment. The current observations reveal new candidate endodontic pathogens, including as-yet-uncultivated bacteria and phylotypes that may participate in the mixed infections associated with post-treatment apical periodontitis.
authors.affiliation: School of Stomatology, Capital Medical University, Beijing 100050, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Zhang
authors.forename: Ben-xiang
authors.initials: BX
authors.lastname: Hou
authors.forename: Huan-ying
authors.initials: HY
authors.lastname: Zhao
authors.forename: Zheng
authors.initials: Z
authors.lastname: Sun
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001419:Bacteria / Q000145:classification / Q000302:isolation & purification*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D019553:Tooth, Nonvital / Q000382:microbiology*; D017211:Treatment Failure
chemical_list: D012336:RNA, Ribosomal, 16S