Evaluation of peri-implant bone response in implants retrieved for fracture after more than 20 years of loading. A case series.

Abstract Analysis of human retrieved dental implants is a useful tool in the evaluation of implant success and failure. More human histological data are needed from samples of long-term implant service. Aim of the present case series was a histological and histomorphometrical evaluation of the peri-implant bone responses in implants retrieved for fracture after more than 20 years loading. The archives of the Implant Retrieval Center of the Department of Medical, Oral and Biotechnological Sciences of the University of Chieti-Pescara, Italy were searched. A total of 5 implants, retrieved after a loading period of more than 20 years, were found: 2 had been retrieved after 20 years, 1 after 22 years, 1 after 25 years, and 1 after 27 years. All these implants were histologically processed. Compact, mature bone in close contact with the implant surface was observed in all specimens, with no gaps or connective tissue at the interface. Around some implants it was found bone in different maturation stages. Mainly, in proximity of the implant surface it was possible to observe the presence of newly formed bone, while in areas distant from the implant it was detected mature, compact bone with many remodeling areas and cement lines. Many primary and secondary osteons were present. Bone to implant contact percentage varied from 37.2\% to 76\%. In conclusion, histology and histomorphometry showed that, even after many years of function, all implants presented more than adequate bone to implant contact and they appeared to be very well integrated in the peri-implant bone.