Journal of Dental Research, Vol 76, 682-687, Copyright © 1997 by International & American Associations for Dental Research Online Journals
HRTEM study of biological crystal growth mechanisms in the vicinity of implanted synthetic hydroxyapatite crystals
J. Hemmerle, F. J. Cuisinier, P. Schultz and J. C. Voegel
Institut National de la Sante et de la Recherche Medicale, Unite 424, Federation de Recherches Odontologie, Strasbourg, France.
Calcium phosphates are widely used as biomaterials. Ultrastructural
assessments are of the utmost importance in our understanding of
interfacial phenomena. The aim of this study was to learn more about the
newly formed crystal growth mechanisms. The interfaces between implanted
synthetic hydroxyapatite crystals (HAS) and newly formed crystallites were
thoroughly examined on a molecular level. The bone-grafting material (HAS)
was implanted into two adult patients, and small biopsies were recovered 6
months after implantation. The raw biomaterial was analyzed by x-ray
diffraction and high-resolution transmission electron microscopy (HRTEM).
Six months after their implantation, the HAS aggregates were surrounded by
a mineralized bone matrix. Tiny crystallites also filled the spaces between
the HAS crystals within the aggregates. These newly formed crystallites
growing at the surfaces of the implanted HAS crystals appeared to be
apatitic. The crystallographic investigations of the nucleation and growing
mechanisms of the newly formed crystallites were performed by HRTEM in
association with computer simulation and mathematical processing of
digitized images. A relationship was noted between the orientation axes of
crystallites growing nearby and the zone axes of the implanted HAS, thus
strongly suggesting a guiding or substratum role of the HAS particles.
