There is substantial evidence supporting the role of certain oral bacteria species in the onset and progression of periodontitis. Nevertheless, results of independent-culture diagnostic methods introduced about a decade ago have pointed to the existence of new periodontal pathogens. However, the data of these studies have not been evaluated together, which may generate some misunderstanding on the actual role of these microorganisms in the etiology of periodontitis. The aim of this systematic review was to determine the current weight of evidence for newly identified periodontal pathogens based on the results of "association" studies. This review was conducted and reported in accordance with the PRISMA statement. The MEDLINE, EMBASE, and Cochrane databases were searched up to September 2013 for studies (1) comparing microbial data of subgingival plaque samples collected from subjects with periodontitis and periodontal health and (2) evaluating at least 1 microorganism other than the already-known periodontal pathogens. From 1,450 papers identified, 41 studies were eligible. The data were extracted and registered in predefined piloted forms. The results suggested that there is moderate evidence in the literature to support the association of 17 species or phylotypes from the phyla Bacteroidetes, Candidatus Saccharibacteria, Firmicutes, Proteobacteria, Spirochaetes, and Synergistetes. The phylum Candidatus Saccharibacteria and the Archaea domain also seem to have an association with disease. These data point out the importance of previously unidentified species in the etiology of periodontitis and might guide future investigations on the actual role of these suspected new pathogens in the onset and progression of this infection.

The adjunctive use of MTZ+AMX significantly improved the clinical and microbiological outcomes of SRP in the treatment of type 2 diabetic subjects with ChP.

The aim of this study was to assess the changes occurring in subgingival biofilm composition and in the periodontal clinical parameters of subjects with periodontitis and type 2 diabetes mellitus (DM) treated by means of scaling and root planing (SRP) only or combined with systemic metronidazole (MTZ) and amoxicillin (AMX). Fifty-eight subjects were randomly assigned to receive SRP only (n = 29) or with MTZ (400 mg/thrice a day [TID]) and AMX (500 mg/TID) (n = 29) for 14 d. Six subgingival plaque samples/subject were analyzed by checkerboard DNA-DNA hybridization for 40 bacterial species at baseline and 3 mo, 1 y, and 2 y posttherapy. At 2 y posttherapy, the antibiotic-treated group harbored lower mean proportions (5.5%) of red complex pathogens than the control group (12.1%) (P < 0.05). The proportions of the Actinomyces species remained stable in the antibiotic group but showed a statistically significant reduction in the control group from 1 to 2 y in subjects achieving a low risk clinical profile for future disease progression (i.e., ≤4 sites with probing depth [PD] ≥5 mm). The test group also had a lower mean number of sites with PD ≥5 mm (3.5 ± 3.4) and a higher percentage of subjects reaching the low risk clinical profile (76%) than the control group (14.7 ± 13.1 and 22%, respectively) (P < 0.05) at 2 y posttreatment. MTZ + AMX intake was the only significant predictor of subjects achieving the low risk at 2 y (odds ratio, 20.9; P = 0.0000). In conclusion, the results of this study showed that the adjunctive use of MTZ + AMX improves the microbiological and clinical outcomes of SRP in the treatment of subjects with generalized chronic periodontitis and type 2 DM up to 2 y (ClinicalTrials.gov NCT02135952).