title: Patterns of microbial colonization in primary root canal infections.
abstract: OBJECTIVE
  The purpose of this study was to investigate the patterns of microbial infection of root canals in untreated teeth associated with chronic periradicular lesions by use of scanning electron microscopy.
  
  
  METHODS
  Fifteen extracted teeth with extensive carious lesions, radiolucent lesions of varying sizes, and attached periradicular lesions after extraction were selected for study. After fixation, lesions were removed and the teeth were split into 2 halves. The teeth were then dehydrated, sputter-coated with gold, and then examined for the patterns of microbial colonization of the root canal system by using a scanning electron microscope.
  
  
  RESULTS
  All examined root canals were infected, and bacterial cells were seen in practically all areas of the root canal system. The pattern of colonization was not uniform between specimens and even within the same specimen. Most of the root canal walls of all specimens were heavily colonized by a root canal microbiota consisting of cocci and/or rods, often forming mixed communities. Spirilla were occasionally observed as single cells or as small clusters between other bacterial forms. Bacteria were often observed penetrating the dentinal tubules. Although a shallow penetration was the most common finding, bacterial cells could be observed reaching approximately 300 microm in some specimens. Yeastlike cells were observed in 1 specimen together with bacteria.
  
  
  CONCLUSIONS
  The root canals of teeth associated with periradicular lesions were heavily infected by bacteria and occasionally by fungi. The pattern of colonization of the root canal microbiota often showed the characteristic of a climax community, which may require special considerations regarding its elimination and prevention of clinical problems. In addition, the observed propagation of the infection to the entire root canal system in teeth associated with periradicular lesions suggests that proper therapeutic measures may be necessary to eliminate the root canal infection completely.
authors.affiliation: Department of Endodontics, School of Dentitry, EstáCio de Sá University, Rio de Janeiro, Brazil. siqueira@estacio.br
authors.forename: José F
authors.initials: JF
authors.lastname: Siqueira
authors.forename: Isabela N
authors.initials: IN
authors.lastname: Rôças
authors.forename: Hélio P
authors.initials: HP
authors.lastname: Lopes
mesh_terms: D001419:Bacteria / Q000648:ultrastructure; D001424:Bacterial Infections / Q000382:microbiology*; D003786:Dental Pulp Cavity / Q000382:microbiology*; D003788:Dental Pulp Diseases / Q000382:microbiology*; D017753:Ecosystem; D006801:Humans; D008855:Microscopy, Electron, Scanning; D010485:Periapical Periodontitis / Q000382:microbiology; D015003:Yeasts / Q000648:ultrastructure