Peri-implant bone tissues around retrieved human implants after time periods longer than 5 years: a retrospective histologic and histomorphometric evaluation of 8 cases

Only rarely, it is possible to find in the literature histological reports of human retrieved implants, especially after several years of functional loading. These implants can help us in understanding the reactions of peri-implant bone. The aim of this study was to perform a histologic and histomorphometric analysis of the peri-implant tissues behavior and of the bone-titanium interface in titanium dental implants retrieved from patients after time periods longer than 5 years. The archives of the Implant Retrieval Center of the Dental School of the University of Chieti-Pescara, Italy were searched for human dental implants, retrieved after a loading period of more than 5 years. A total of 8 implants were found: 3 of these had been retrieved after 5 years, 1 after 6 years, one after 10 years, 1 after 14 years, 1 after 18 years, 1 after 22 years. Only the bone to implant contact in the three best threads was evaluated. Compact, mature, lamellar bone, with few and small marrow spaces, was present around the implants. Osteons with Haversian canals were present inside some threads, in close proximity to the interface, at both cortical and trabecular regions. Other osteons had a direction perpendicular to the direction of the long axis of the implants. Numerous reversal lines were present. At higher magnification, no gaps or fibrous, connective tissues were present at the interface. The BIC of the three best threads for all implants varied from 94 to 100 %.In conclusion, within the limitations of the present report histology showed that implants with different surfaces all presented the potential to maintain osseointegration over a long period, with a continuous remodeling at the interface, as indicated by the presence of reversal lines.