BACKGROUND: The purpose of this study was to compare the microbiota around natural teeth and dental implants with different restorative platforms. Attention was focused on whether the microbiological environment could change according to the implant platform used i.e. traditional or Platform Switching implants. As the latter show less signs of bone resorption, a correlation with the presence of certain periodontal bacteria was suggested. METHODS: Seven partially edentulous patients with dental implants, either traditional or Platform Switching, were included in this study. All the implants were in function at least for 1 year. Gingival crevicular fluid samples were obtained before any periodontal probing from natural teeth and different implant platforms and assayed using DNA extraction and PCR sequences in order to determine quality and quantity of microbiota. Statistical analysis included chi square test were used to establish differences in the microbiological distribution between the two implant platforms. RESULTS: There were not statistical differences neither regarding the distribution of microbiota around natural teeth and implants nor between the two implant platforms. The presence of B.forsythus was revealed in the majority of the samples (from 90 to 100 percent) while A.actinomycetemcomitans was rarely found (from 0 o 25 percent). As for the other periodontal microbiota, their presence or absence showed a variation according to different sites or patients, without a predictable pattern. CONCLUSIONS: It was not possible to find a link between the colonization of certain types of bacteria and the reduction of bone loss which occurs around Platform Switching implants. Therefore the preservation of bone crest is only due to biomechanical aspects, which are related to the reposition of the implant-abutment interface away from the outer edge of the implant platform and from the bone.