Comparison of bone-implant interface shear strength of solid hydroxyapatite and hydroxyapatite-coated titanium implants.

The interface shear strength of uncoated Ti-6Al-4V, dense sintered hydroxyapatite (HA), and HA-coated Ti-6Al-4V were compared. Interface shear strength was determined using a transcortical push-out model in dogs 4 and 12 weeks after implantation. The interface shear strength of dense sintered HA and HA-coated Ti-6Al-4V was significantly higher than that of uncoated Ti-6Al-4V (P < .001). There was no significant difference between the interface shear strength of dense sintered HA and HA-coated Ti-6Al-4V. After the push-out test for HA-coated implants, the regions fractured at the bone-coating interface and at the coating-titanium interface coexisted at 4 weeks after implantation. At 12 weeks, the fracture site was, in all cases, the HA coating-titanium interface, and, in a few samples, fractures inside the coating layer also were visible.