denticola, it should be mentioned that differences in frequencies of all other species were not observed between gingivitis and health. Macuch and Tanner 35 also found similar INCB018424 cell line bacterial frequency between gingivitis and health. Also, in a previous study by our group with children showing high levels of plaque, some important pathogens (P. gingivalis and T. forsythia) did not differ among three different levels of gingival bleeding. 36 Together, these results suggest that the loss of alveolar bone and soft tissues more than the presence of gingival inflammation may be related to an increased occurrence of some pathogens around periodontal tissues. The second hypothesis

of the present study was to test if bacterial frequencies were comparative in equivalent periodontal and peri-implant status (i.e. healthy peri-implant sites vs. healthy periodontal sites, mucositis vs. gingivitis and peri-implantitis vs. periodontitis), evaluating sites matched for clinical parameters within each clinical condition. The results showed that only C. rectus and T. forsythia presented significantly higher frequencies of detection in periodontal healthy sites than in peri-implant healthy ones as well as in gingivitis than in mucositis. These findings indicate that similarities in bacteria frequencies were evident between periodontal and peri-implant sites when health or a reversible

inflammation process were present. In support of our results, Gerber et al. 37 compared the microbiota at predominantly this website healthy tooth and implant sites and found only minor microbial differences between groups. Aoki et al., 38 studying the sources of peri-implant colonization by periodontal pathogens, observed similar detection rates of selected species in subgingival samples from adjacent periodontal sites and newly formed peri-implant sulci. Nowzari et al. 26 showed higher frequency of detection and higher levels of periodontal pathogens around

clinically healthy periodontal than clinically healthy peri-implant sites, but the difference was not statistically significant. However, it is important to note that the authors used Cepharanthine culture methods and evaluated a small sample size (only 11 subjects). Recently, Heuer et al. 27, using broad-range PCR techniques, demonstrated that the microbial diversity of the microbiota surrounding gingivitis (19 different bacteria genera) was significantly higher than the diversity of the microbiota associated to mucositis (6 different bacteria genera). Vered et al. 39 reported significantly higher numbers of aerobic and anaerobic oral bacteria in samples collected from teeth than those collected from implants within the same mouth. However, no systematic characterization of the clinical statuses of the teeth and implants was described. In this study, dissimilarities in bacteria occurrences between peri-implantitis and periodontitis were more evident, since higher frequencies of T. forsythia, C. rectus, P. intermedia, T.