Background: Osseointegrated dental implants have been shown to be a predictable approach to provide the adequate support for the replacement of missing teeth. It has been observed that implants showing signs of peri-implantitis contain subgingival microbiota similar to that around natural teeth with periodontal disease. This study identified the subgingival microbiota around implants with peri-implant lesions and natural teeth in partially edentulous patients.

Methods: Clinical and radiographic parameters were recorded and microbial samples taken from 16 implants with signs of pocketing, 12 neighboring and 11 non-neighboring teeth to the affected implants in 11 patients and 15 stable implants in eight patients (controls). Samples were cultured using techniques for Enterobacteriaceae spp and facultative/anaerobic periodontal pathogens. Statistical analysis included Friedman test to establish differences between the subgingival microbiota cultured from implants and teeth and two-tailed Mann Whitney test and chi square to find differences in two separate samples (P ≤0.05).

Results: There were statistical differences between the subgingival microbiota in peri-implant lesions and stable implants for Gram-negative enteric rods (P <0.05). P. gingivalis (1.42%) was detected in peri-implant lesions but not in stable implants. A significant correlation between the subgingival microbiota from implants and neighboring teeth for Gram-negative enteric rods (P = 0.023) and implants and non-neighboring teeth for P. gingivalis (P = 0.042) was found. The frequency detection of Gram-negative enteric rods (75%) and P. intermedia/nigrescens (25%) was higher in peri-implant lesions (P <0.05).

Conclusions: The subgingival microbiota in peri-implant lesions showed high levels of periodontopathic bacteria and superinfecting bacteria compared to healthy stable implants. The role of superinfecting bacteria in the pathogenesis of periimplant lesions needs further investigation. J Periodontol 2005; 76:1490-1495.