A 16S rDNA-directed polymerase chain reaction method was used to assess the
occurrence of four black-pigmented anaerobic rods in root canal infections
. Samples were obtained from 54 infected teeth. Ten cases were diagnosed as
acute periradicular abscesses. DNA was extracted from the samples and anal
yzed using a polymerase chain reaction-based identification assay. The meth
od allowed detection of black-pigmented bacteria anaerobes in 59.3% of the
examined teeth. Twelve cases yielded more than one black-pigmented species.
In general Porphyromonas endodontalis was found in 42.6%, Porphyromonas gi
ngivalis in 27.8%, Prevotella nigrescens in 7.4%, and Prevotella intermedia
in 5.6% of the cases. P. endodontalis was found in 70% of the pus samples,
P. gingivalis in 40%, and P. intermedia in 10%. P. gingivalis was always f
ound associated with P. endodontalis in abscessed teeth. P. nigrescens was
not found in any pus sample. The high prevalence of P. endodontalis and P.
gingivalis suggests that they can play an important role in the pathogenesi
s of periradicular diseases.