Predictive value of clinical and microbiological parameters for the treatment outcome of scaling and root planing

Objectives: To compare the clinical and microbiological outcome of non-surgical periodontal therapy after 6 months with data obtained after hygienic phase or 6 weeks after completion of non-surgical therapy, in order to evaluate the value of clinical and microbiological parameters to predict treatment success. Materials and Methods: Clinical and microbiological data were available from 271 sites in 10 systemically healthy non-smokers with moderate-to-advanced chronic periodontal disease (24-32 sites per individual). Subgingival plaque samples were tested for the presence of Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, Tannerella forsythensis and Treponema denticola using RNA probes. Results: Stepwise multiple linear regression analysis revealed a significant impact of the number of sites with visible plaque index > 1 after hygienic phase on the bleeding tendency of a subject at month 6 (p < 0.01). Furthermore, an association could be demonstrated between the number of residual pockets (PD > 3 mm) 6 months after therapy and the number of bleeding sites and suppurating sites after hygienic phase (p=0.016). Six weeks after therapy, the mean total bacterial loads had a significant impact on the bleeding tendency of a subject at month 6 (p < 0.01). Although the average numbers of sites with persisting P. gingivalis, A. actinomycetemcomitans, T. forsythensis and T. denticola seemed to be very similar 6 weeks and 6 months after therapy, large variations were noted between subjects, and therefore the microbiological status of a subject at week 6 could not predict the status at month 6. Conclusions: The present study showed a limited potential of microbiological tests, performed after hygienic phase or shortly after non-surgical periodontal therapy, to predict the clinical outcome 6 months later, but confirmed the importance of an establishment of perfect oral hygiene before non-surgical therapy.