OBJECTIVEThis study aims to assess and compare the prevalence of Porphyromonas endodontalis (P. endodontalis) in root canals associated with primary and secondary endodontic infections by using 16s rDNA PCR and real-time fluorescence quantitative polymerase chain reaction (RTFQ-PCR).

METHODSA total of 120 adult patients with one radiographically documented periapical lesion were included. Sixty teeth presented with primary endodontic infections and 60 with secondary endodontic infections requiring retreatment. P. endodontalis was identified by using 16s rDNA PCR techniques. The positive DNA expression of P. endodontalis in two types of infected root canals were quantitatively compared by using SYBR GREEN I RTFQ-PCR.

RESULTSThe prevalence of P. endodontalis in the root canals with primary endodontic infections was significantly higher than that in root canals with secondary endodontic infections (P = 0.001). However, RTFQ-PCR results showed no significant difference in DNA expression quantities between the primary and secondary endodontic infections root canals (P = 0.303).

CONCLUSIONP. endodontalis is more highly associated with root canals having primary endodontic infections, although P. endodontalis colonize in both root canals with primary and secondary chronic apical periodontitis.