Microbiological markers for prediction and assessment of treatment outcome following non-surgical periodontal therapy

Background: Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Bacteroides forsythus are considered major putative periodontal pathogens. However, it remains unclear what combinations or what levels of these bacteria influence treatment outcome. The purpose of the present study was to establish useful pathogenic markers for prediction and assessment of treatment outcome following scaling and root planing (SRP). Methods: A total of 1,149 sites in 104 chronic periodontitis patients were clinically examined at baseline. Three months after SRP, 606 sites in 56 of these patients were reexamined. Subgingival plaque samples taken from the examined sites at baseline and 3 months were analyzed for the detection and quantification of A. actinomycetemcomitans, P gingivalis, and B. forsythus using a colorimetric polymerase chain reaction technique. Results: At baseline, high levels and a combination of P. gingivalis and B. forsythus were frequently detected in diseased sites (74%). SRP reduced the levels and the coexistence of P. gingivalis and B. forsythus (from 75% to 43%). However, in treated sites where there was less reduction of probing depth (<2 mm), or where bleeding on probing (BOP) or suppuration was detected, residual coexistence of P gingivalis and B. forsythus and a high level of P. gingivalis after SRP were significantly more frequent. Furthermore, SRP did not improve BOP at sites exhibiting initially high levels of A. actinomycetemcomitans. Conclusions: These results suggest that the combination of P. gingivalis and B. forsythus, as well as the level of P. gingivalis, is useful in assessing treatment outcome. Furthermore, the high level of A. actinomycetemcomitans before SRP is a possible valuable predictor of treatment outcome.