Methods: Clinical data and subgingival plaque samples were collected from 176 individuals: 67 individuals with Gingivitis (G), 71 with Chronic Periodontitis (CP) and 38 with Aggressive Periodontitis (AP). The clinical samples were processed by real-time PCR and quantification was performed with primers and probes based on species-specifc highly conserved regions from 16S rRNA gene and serial dilutions of plasmid standards.
Results: The presence of target pathogens was detected in all the periodontal disease groups and there was significant association between group and presence of bacteria for P. gingivalis, T. forsythia, T. denticola and D. pneumosintes (p<0.01). The bacterium A. actinomycetemcomitans presented similar frequencies of detection in the three groups (G: 100%; CP: 94.4%; AP: 92.1%), and there was no significant association between group and presence of this bacterium (p=0.09). The subgingival quantities of A. actinomycetemcomitans and T. forsythia were significantly higher in the Group AP (1.66*106 ± 5.39*106 and 1.96*106 ± 4.82*106, respectively), in comparison with Groups G (8.28*104 ± 1.76*105 and 3.86*105 ± 1.96*106, respectively) and CP (2.25*104 ± 3.11*104 and 3.59*105 ± 1.40*106, respectively), there being no significant differences among the groups with regard to the subgingival loads of the other bacteria.
Conclusions: Although the presence of A. actinomycetemcomitans was similar in the three forms of periodontal disease, a higher bacterial load of this pathogen and T. forsythia was detected only in the individuals with Aggressive Periodontitis. There were no significant differences between groups G and CP regarding the quantification of target pathogens.