Objective: The aim of the study was to investigate the bacterial contamination of different prosthetic components with periodonto-pathogens in healthy edentulous patients wearing long-standing implant-supported overdentures. Patients and Methods: Bacteria samples were harvested from the peri-implant sulcus, the inside of the implant, and the soft tissue side of the denture base in nine patients from the Tuebingen Implant Registry on occasion of their annual hygiene and check-up visit. Samples were assessed by PCR (Hain MicroIdent Test). Five patients could be re-evaluated four weeks after the professional implant maintenance procedures. Results: Orange complex representatives species dominated at all three locations, others were found only sporadically. P. intermedia and F. nucleatum were the predominant species at the denture base (p = 0.02). F. nucleatum alone and in conjunction with P. intermedia showed a statistically significant upward shift on the follow-up appointment (p = 0.03 for F. nucleatum and p = 0.02 for both). This effect was accompanied by a decrease in red complex species means, but not on a statistically significant level. Conclusions: The presence of periodonto-pathogenic bacteria in healthy individuals should be recognized. The present investigation supports the idea that with a decrease in counts of the red complex species the number of bacteria in the orange complex increases, indicating a shift in plaque composition towards a slightly more favorable flora following professional maintenance procedures. Schlagwörter: parodontopathogene Keime, Kontamination, Deckprothese, professionelle Mundhygiene, Follow-up