Effects of Non-Surgical Mechanical Therapy on the Subgingival Microbiota of Brazilians With Untreated Chronic Periodontitis: 9-Month Results

Mechanical periodontal therapy is the most common treatment of periodontal infections. It is directed primarily towards removing biofilm and calculus from the root surfaces, leading to ecological changes in the subgingival environment. Thus, the purpose of this study was to evaluate the effects of scaling and root planing (SRP) on the subgingival microbiota of Brazilian subjects with untreated chronic periodontitis over a 9-month period.Twenty-five untreated chronic periodontitis patients (mean age 43 +/- 5 years; 20% smokers; 45% males) were selected from a Brazilian population. At baseline, probing depth (PD), clinical attachment level (CAL), visible supragingival biofilm (SB), bleeding on probing (BOP), and suppuration (SUP) were measured at six sites/tooth. Subgingival plaque samples were obtained from 10 sites with the deepest PD (or =5 mm) of each subject and tested for the presence of 25 oral species by DNA probes and the checkerboard technique. Patients received full mouth SRP and oral hygiene instructions. Clinical and microbiological assessments were repeated at 3, 6, and 9 months after therapy. During this period, all patients received maintenance therapy, including supragingival prophylaxis and reinforcement in home care procedures. The clinical and microbiological parameters examined were computed for each subject and at each visit. Differences over time were sought using the Friedman test.Significant reductions in mean CAL and PD (P0.01), percent of sites with SB (P0.01), BOP and SUP (P0.05) were observed during the course of the study. In general, microbial changes were more pronounced for the mean counts than for the frequency of the microorganisms, particularly at 3 months post-therapy. Significant reductions in prevalence and levels were observed for certain periodontal pathogens including P. gingivalis (P0.05; P0.01), T. forsythensis (P0.01), C. rectus (P0.01), and A. actinomycetemcomitans (P0.01; P0.05). Nevertheless, the frequency of A. actinomycetemcomitans increased to baseline values at 9 months after therapy. Treponema ssp. and Prevotella spp. showed a modest decrease in prevalence, whereas marked reductions in their levels were observed. In contrast, the frequency and counts of the suspected pathogens P. micros and F. nucleatum increased after treatment. Species considered beneficial including Actinomyces spp., some oral streptococci, and V. parvula increased in prevalence, although these two last species tended to return to baseline levels at 9 months.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.