title: Microbial culture and checkerboard DNA-DNA hybridization assessment of bacteria in root canals of primary teeth pre- and post-endodontic therapy with a calcium hydroxide/chlorhexidine paste.
abstract: OBJECTIVE
  To investigate the root canal microbiota of primary teeth with apical periodontitis and the in vivo antimicrobial effects of a calcium hydroxide/chlorhexidine paste used as root canal dressing.
  
  
  METHODS
  Baseline samples were collected from 30 root canals of primary teeth with apical periodontitis. Then, the root canals were filled with a calcium hydroxide paste containing 1% chlorhexidine for 14 days and the second bacteriologic samples were taken prior to root canal filling. Samples were submitted to microbiologic culture procedure to detect root canal bacteria and processed for checkerboard DNA-DNA hybridization.
  
  
  RESULTS
  Baseline microbial culture revealed high prevalence and cfu number of anaerobic, black-pigmented bacteroides, Streptococcus, and aerobic microorganisms. Following root canal dressing, the overall number of cfu was dramatically diminished compared to initial contamination (P <0.05), although prevalence did not change (P > 0.05). Of 35 probes used for checkerboard DNA-DNA hybridization, 31 (88.57%) were present at baseline, and following root canal dressing, the number of positive probes reduced to 13 (37.14%). Similarly, the number of bacterial cells diminished folowing application of calcium hydroxide/chlorhexidine root canal dressing (P = 0.006).
  
  
  CONCLUSIONS
  Apical periodontitis is caused by a polymicrobial infection, and a calcium hydroxide/chlorhexidine paste is effective in reducing the number of bacteria inside root canals when applied as a root canal dressing.
authors.affiliation: Department of Clinical Analysis, Toxicology and Bromatology, School of Pharmaceutical Sciences of Ribeirão Preto, Ribeirão Preto, SP, Brazil.
authors.forename: Izabel Yoko
authors.initials: IY
authors.lastname: Ito
authors.forename: Fumio Matoba
authors.initials: FM
authors.lastname: Junior
authors.forename: Francisco Wanderley Garcia
authors.initials: FW
authors.lastname: Paula-Silva
authors.forename: Léa Assed Bezerra
authors.initials: LA
authors.lastname: Da Silva
authors.forename: Mário Roberto
authors.initials: MR
authors.lastname: Leonardo
authors.forename: Paulo
authors.initials: P
authors.lastname: Nelson-Filho
mesh_terms: D000704:Analysis of Variance; D001420:Bacteria, Aerobic / Q000187:drug effects; D001421:Bacteria, Anaerobic / Q000187:drug effects*; D001439:Bacteroides / Q000187:drug effects; D002126:Calcium Hydroxide / Q000494:pharmacology; D016009:Chi-Square Distribution; D002648:Child; D002675:Child, Preschool; D002710:Chlorhexidine / Q000494:pharmacology; D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000032:analysis; D003786:Dental Pulp Cavity / Q000382:microbiology*; D003790:Dental Pulp Necrosis / Q000382:microbiology* / Q000628:therapy; D005260:Female; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D006801:Humans; D008297:Male; D009693:Nucleic Acid Hybridization; D010485:Periapical Periodontitis / Q000382:microbiology* / Q000628:therapy; D012388:Root Canal Irrigants / Q000494:pharmacology*; D018915:Root Canal Preparation / Q000379:methods; D018709:Statistics, Nonparametric; D013291:Streptococcus / Q000187:drug effects; D014094:Tooth, Deciduous / Q000382:microbiology*
chemical_list: D004269:DNA, Bacterial; D012388:Root Canal Irrigants; D002126:Calcium Hydroxide; D002710:Chlorhexidine