Long-term changes of hydroxyapatite-coated dental implants

There are many controversies about the long-term prognosis of hydroxyapatit e (HA)-coated implants. Failure mag be related to compositional and structu ral changes of the coating occurring during implantation. Two retrieved and two unused HA-coated blade-type implants were examined by stereomicroscopy , secondary electron microscopy, Fourier transform infrared spectroscopy, X -ray diffraction, and electron probe microanalysis. The objective was to in vestigate the HA morphology, composition, and structure, and to characteriz e the changes that occurred in the retrieved implant coatings. Retrieved im plants presented partial Loss of the coating, especially at the apical and mesiodistal edges. Remaining HA was thick and Battened in the cervical and central areas and gradually thinner and rougher towards the apical and mesi odistal edges. Increase of CI and Mg, decrease of OH, and X-ray diffraction peak broadening mere found in the retrieved implant coatings, in compariso n with the unused implants. Morphological changes of the retrieved implants seem to depend on stress values in the surrounding bone and on implant mob ility, Compositional changes and increased amount of lattice imperfections appeared in the retrieved implant coatings, as a result of ion substitution s in the apatite lattice. However, the present study could not confirm the influence of these changes on implant failure. (C) 2000 John Wiley & Sons, Inc.