Residual stress and texture evaluation by diffraction techniques in nano-HA coated implants

Abstract

In order to reduce the delay for implant osseointegration, hydroxyapatite coatings sprayed on titanium substrate are proposed for commercial implants. Clinical failures of these coatings have been reported several months or years after the surgery due to resorption or mechanical failures. Our objectives were to improve the quality of the coating using a plasma thermal spraying process with nanosized powder as feedstock to generate partially nanostructured coatings. In order to be thermally sprayed, the individual nanoparticles are agglomerated into spherical micrometer-sized granules. The main goal of using nanostructured feedstock is to preserve the nanostructure of deposited HA in the morphology of the layers. The behaviour of agglomerated particles before the impact is of crucial importance, especially if they leave the plasma jet axis. The texture of bone crystallites is investigated after implantation near the interface. The preferred orientation is expected to change close to the interface due to reorganization of the bone’s constituents. Our texture study with neutron diffraction of sheep tibia at the interface with implant revealed the great interest to cover implants with a high quality HAp coating.