Microbial diversity in persistent root canal infections investigated by checkerboard DNA-DNA hybridization

The aim of the present study was to investigate the composition of the root canal microbiota in endodontic failures in order to identify and quantify these microorganisms.

Microbiological samples were taken from 36 root canals with persistent endodontic infection. The presence, levels, and proportions of 79 bacterial species were determined by checkerboard DNA-DNA hybridization. The Pearson correlation coefficient was used to investigate the relations between bacterial counts and clinical conditions (P ≤ .05).

Enterococcus faecium (36%), Streptococcus epidermidis (36%), Eubacterium saburreum (28%), Parvimonas micra (28%), Streptococcus sanguis (28%), Capnocytophaga sputigena (28%), Leptotrichia buccalis (28%), Enterococcus faecalis (28%), and Staphylococcus warneri (28%) were the most prevalent species; and there was a low prevalence of Treponema socranskii (3%), Fusobacterium periodonticum (3%), Capnocytophaga gingivalis (3%), and Spiroplasma ixodetis (3%). The highest mean levels were found for the following species: E. faecium, Dialister pneumosintes, Staphylococcus epidermidis and Helicobacter pylori. There was a statistically significant difference between the levels of gram-negative species and gram-positive species (13.5 × 10(5) vs 6.5 × 10(5), respectively). A positive correlation was found between the area of the periapical lesion and the levels of gram-negative and rod species (P < .05).

The microbiota from teeth with persistent apical periodontitis presents a mixed and complex profile, hosting E. faecium and S. epidermidis as the most highly prevalent species. No correlation was found between any of the species tested and clinical findings; however, periapical lesions with the largest areas presented higher counts of gram-negative and rod species.