ABSTRACT Objective The aim of this study was to evaluate the association of Porphyromonas endodontalis, Filifactor alocis and Dialister pneumosintes with the occurrence of periodontitis. Material and Methods Thirty subjects with chronic periodontitis (ChP) and 10 with periodontal health (PH) were included in the study.

Nine subgingival biofilm samples were collected as follows:

i) PH group - from the mesial/buccal aspect of each tooth in two randomly chosen contralateral quadrants; ii) ChP group - from three sites in each of the following probing depth (PD) categories: shallow (≤3 mm), moderate (4-6 mm) and deep (≥7 mm). Checkerboard DNA-DNA hybridization was used to analyze the samples. Results We found the three species evaluated in a higher percentage of sites and at higher levels in the group with ChP than in the PH group (p<0.05, Mann-Whitney test). We also observed these differences when the samples from sites with PD≤4 mm or ≥5 mm of subjects with ChP were compared with those from subjects with PH (p<0.05, Mann-Whitney test). In addition, the prevalence and levels of D. pneumosintes, and especially of F. alocis were very low in healthy subjects (0.12x105 and 0.01x105, respectively). Conclusion F. alocis and D. pneumosintes might be associated with the etiology of ChP, and their role in the onset and progression of this infection should be further investigated. The role of P. endodontalis was less evident, since this species was found in relatively high levels and prevalence in the PH group.