title: Morphology of bacterial flora in root canals associated with apical abscesses.
abstract: BACKGROUND
  Apical abscess is an inflammatory process in the peri-radicular tissues caused by biofilms in the necrotic root canal systems. Therefore, a comprehensive analysis of the bacterial colonization is required for a better understanding of the pathogenesis. This study aimed to investigate the patterns of bacterial infection of root canals of teeth with apical abscesses and to determine whether histological and microbiological findings correlated with clinical conditions.
  
  
  METHODS
  Eighteen samples from 18 teeth with apical pathological lesions were analyzed. Nine patients with acute apical abscesses experienced severe pain, and nine patients were asymptomatic with a sinus tract. After extraction, each affected root was divided into two halves. One half was processed for histobacteriologic analysis and examined using light microscopy, and the other half was analyzed using scanning electron microscopy (SEM) to determine the patterns of microbial colonization of the root canals.
  
  
  RESULTS
  The appearance of each sample subjected to SEM was consistent with the histobacteriologic findings despite the presence or absence of clinical symptoms. Intraradicular biofilms comprising cocci, rods, and/or filaments of amorphous materials were observed in the apical third of the main root canals in all samples. The bacterial biofilms covering the main root canal walls also penetrated the dentinal tubules to varying depths. The morphologies of biofilms varied, and a unique pattern of intraradicular infection was not identified.
  
  
  CONCLUSIONS
  Intraradicular infections formed complex and variable multispecies biofilms and their presence did not correlate with clinical symptoms.
authors.affiliation: Department of Stomatology, People's Hospital, Peking University, Beijing 100044, China.
authors.forename: Huijie
authors.initials: H
authors.lastname: Guo
authors.affiliation: Department of Stomatology, People's Hospital, Peking University, Beijing 100044, China.
authors.forename: Chengzhi
authors.initials: C
authors.lastname: Gao
authors.affiliation: Comprehensive Dental Care, Endodontics, Faculty of Dentistry, University of Hong Kong, Hong Kong, China.
authors.forename: Chengfei
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Electron Microscopy Labrotary, People's Hospital, Peking University, Beijing 100044, China.
authors.forename: Shuying
authors.initials: S
authors.lastname: Zheng
authors.affiliation: Department of Cariology, Endodontology and Operative Dentistry, Peking University School and Hospital of Stomatology, Beijing 100081, China. Email: kqlinyue@bjmu.edu.cn.
authors.forename: Lin
authors.initials: L
authors.lastname: Yue
mesh_terms: D000038:Abscess / Q000382:microbiology*; D000368:Aged; D001424:Bacterial Infections / Q000382:microbiology; D018441:Biofilms / Q000254:growth & development; D003786:Dental Pulp Cavity / Q000382:microbiology*; D005260:Female; D006801:Humans; D008297:Male; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged