The subgingival microbiota of Brazilians with untreated chronic periodontitis were complex, including high proportions of periodontopathogens commonly found in other populations, as well as some unusual species.

There were no statistically significant differences in the measured immunologic and microbiologic parameters between subjects with GCP and GAgP.

This study fails to show any significant differences between severe forms of GCP and GAgP in response to non-surgical periodontal treatment.

In Brazilians with untreated chronic periodontitis, SRP led to clinical improvement associated with a decrease of certain periodontal pathogens, and an increase of beneficial species for up to 9 months after therapy.

Actinobacillus actinomycetemcomitans (Aa) is considered a major etiologic agent of aggressive periodontitis but this species has also been associated with other forms of periodontal disease. Further, highly leukotoxic strains are related to severity of disease. The purpose of this study was to determine the prevalence of Aa and the occurrence of the leukotoxin gene 530-bp deletion in patients with generalized aggressive periodontitis (GAP) from a Brazilian population. Thirty periodontally healthy and 29 GAP subjects participated in the study. Full-mouth periodontal examination including probing pocket depth (PPD), clinical attachment level (CAL), supragingival biofilm (SB) and bleeding on probing (BOP) was carried out at 6 sites/tooth for all subjects. Whole saliva samples were collected for bacterial DNA isolation. The detection of Aa and the presence of the 530-bp genetic deletion were determined directly in the samples by polimerase chain reaction. Differences on clinical and microbiological parameters between the two groups were sought using the Mann-Whitney, Fisher´s exact and Chi-square tests. Associations between clinical and microbiological parameters were tested using the Pearson correlation coefficient. Aa was detected significantly more often in GAP patients (96.6%) than healthy subjects (76.7%) (χ 2 = 4.9; p < 0.05). The genetic deletion was observed in 16 of the 28 (57.1%) GAP patients who were positive for Aa. However, none of the samples from individuals with periodontal health presented this deletion (χ 2 = 19.15; p < 0.001). Strong correlations between the presence of the deletion and PPD (r=0.312, p<0.05), CAL (r=0.409, p<0.01), SB (r=0.278, p<0.05) and BOP (r=0.406, p<0.01) were found. A high frequency of Aa was observed in Brazilians with GAP and periodontal health. However, the highly leukotoxic genotype was observed only in subjects with generalized aggressive disease.