Annealing-temperature dependence of adhesion strength of hydroxyapatite layers coated on zirconia substrates by droplet elimination pulsed-laser deposition scheme

High-purity, high-crystallinity hydroxyapatite coatings on zirconia substrates were successfully fabricated at annealing temperatures >360 degrees C. The coatings did not dissolve in vivo within a short period and enhanced the formation of new bone. If the coating layer physically adheres to the zirconia substrate, strong bonding is expected on the coating layer. The adhesion strength of the coating layer was measured using an oscillation-type micro-scratch test. The adhesion strength was found to increase with increasing substrate surface temperature during deposition, irrespective of whether an in situ annealing process or a post-annealing process was used. These results indicated that the proposed coating layer will survive for a prolonged period in vivo and enable strong bone bonding with medical implants.