OBJECTIVE: Long fimbriae (FimA) are important virulence factors of Porphyromonas 
gingivalis. Based on the diversity of the fimA gene, this species is classified 
into 6 genotypes. This study surveyed samples from primary endodontic infections 
for the presence of these P. gingivalis fimA variants.
STUDY DESIGN: Genomic DNA isolated from samples taken from 25 root canals of 
teeth with chronic apical periodontitis and 25 aspirates from acute apical 
abscess was used as template in polymerase chain reaction (PCR) assays directed 
toward the detection of the different P. gingivalis fimA genotypes.
RESULTS: Porphyromonas gingivalis was detected by a 16S rRNA gene-based PCR in 
36% of the total number of cases sampled (44% of chronic apical periodontitis 
and 28% of abscess aspirates). In cases of chronic apical periodontitis, P. 
gingivalis variant type IV was the most prevalent (24%), followed by types I 
(20%), II (16%), and III (8%). In acute abscess samples, variant type II was the 
most prevalent (12%), followed by types III and IV (8% of each) and type I (4%). 
Combinations of up to 3 different genotypes were detected in a few cases. No 
single fimA genotype variant or combination thereof was significantly associated 
with symptoms. Overall, fimA types IV (16%), II (14%), and I (12%) were the most 
prevalent.
CONCLUSIONS: Findings demonstrated that different P. gingivalis fimA genotypes 
can be present in primary endodontic infections.