Denaturing gradient gel electrophoresis analysis of bacterial communities associated with failed endodontic treatment

Objective A great deal of evidence indicates that persistent infections of the root canal of human teeth play an important role in the failure of the root canal treatment. The present study was undertaken to apply the PCR-DGGE fingerprinting approach to examine the structure of the bacterial population infecting previously treated root canals of humans associated with persistent periradicular lesions. Study design Samples were taken from 14 filled root canals, DNA was extracted, and part of the 16S rDNA of all bacteria was amplified by PCR and separated by DGGE, generating banding patterns representative of the community structure. Species-specific PCR for the detection of Enterococcus faecalis was also performed. Results The mean number of bands detected in the 16S rDNA community profiles was about 6, ranging from 1 to 26 bands. Each sample showed a unique structure of the microbial community. The species-specific PCR assay revealed the presence of E. faecalis in 10 of 14 samples, but DGGE analysis revealed it was not the dominant species. Conclusions Results revealed that the intraradicular bacterial community associated with failed endodontic treatment significantly varied in composition from teeth to teeth. Persistent intraradicular infections were present in all root-filled teeth.