Stability of hydroxyapatite-coatings on titanium oral implants (IMZ) - 2 retrieved cases

2 hydroxyapatite(HA)-coated titanium oral implants (IMZ) were retrieved from 2 patients after more than three years in clinical function. One implant (case I) was removed because of extensive bone resorption and loss of integration, and the other (case II) was retrieved due to fracture of the abutment in sprit of clinical rigidity. The implants and the surrounding soft (case I) and hard (case II) tissues were examined histologically and by scanning electron microscopy (SEM). In case I, the HA-coating was almost degraded, as SEM revealed a resulted rough titanium surface. Histology showed HA particles and inflammation were seen near the implant. In Case II, the HA-coating seemed to be intact and bonded to bone, but scattered HA particles, embedded in bone at a distance from the implant were also observed. The results indicate that HA-coatings may come loose during clinical function. The long-term stability of HA-coatings and the clinical indications for HA-coated implants warrant further study.