Microorganisms in root canal-treated teeth from a German population.

Posttreatment apical periodontitis is usually associated with persistent or secondary intraradicular infection. This study evaluated the presence and relative levels of 28 bacterial taxa in treated root canals of teeth with posttreatment apical periodontitis from German patients using 16S ribosomal RNA (rRNA) gene probes in a reverse-capture checkerboard hybridization assay. Species-specific polymerase chain reaction (PCR) was also performed to detect Enterococcus faecalis and Candida albicans. Bacterial DNA was detected in all samples. Twenty of the 28 taxon-specific probes tested were reactive with at least one sample. Taxa detected more frequently included Streptococcus species (47%), Lactobacillus species (35%), Dialister invisus (29%), Eubacterium infirmum (29%), Prevotella intermedia (29%), Selenomonas sputigena (29%), Synergistes oral clone BA121 (29%), and Treponema denticola (29%). Only eight taxa were present at levels >10(5). Of these, streptococci and T. denticola were the most prevalent. Species-specific PCR detected E. faecalis in 47% of the cases and C. albicans in 6%. Findings of this study confirm the strong association between persistent/secondary intraradicular infection and posttreatment apical periodontitis. Most cases harbored a mixed infection, and E. faecalis, if present, was never the most dominant species in the consortium. Several other bacterial taxa were detected, and an involvement with the etiology of posttreatment apical periodontitis is suspected.