Histologic Evaluation of Threaded HA-Coated Root-Form Implants After 3.5 to 11 Years of Function: A Report of Three Cases

This article presents a histologic evaluation of three hydroxyapatite (HA)-coated root-form implants retrieved from humans after being in function for 3.5 to 11 years. If the coronal portion, where bone loss was observed clinically and radiographically, is excluded, all implants appeared to be well osseointegrated, with intimate contact between the surrounding bone and the coating. There was no sign of resorption or dissolution of the HA coating. The coating had a uniform thickness (50 µm) equal to the thickness originally provided by the manufacturer. In the few areas where there was no bone contact, the HA coating appeared to line the implant with no sign of dissolution. The few detached particles had tight contact with the bone, demonstrating the biocompatibility of the HA. The observations from the three reported cases suggest that the HA coating of dental implants may not be susceptible to resorption or dissolution under long-term function.