We have investigated the bone-implant interface shear strength of hydroxyapatite (HA)-coated Ti-6AI-4V (HA-coating A) (roughness average, Ra = 3.4±0.5 μm) and HA-coated Ti-6AI-4V with a rougher surface (HA-coating B) (Ra = 8.4 ± 1.8 μm). There was no significant difference between HA-coating A and HA-coating B implants with respect to the bone-implant interface shear strength as determined in push-out tests using the transcortical model in adult dogs. The bone-implant interface shear strength of bead-coated porous Ti-6AI-4V was significantly greater than that of both HA-coating A and HA-coating B implants. The failure site, as determined by scanning electron microscopy, was the coating-substrate interface, not the coating-bone interface. This indicates a need to protect the HA coating from the direct shear forces. HA coating enhances early bone growth into the porous surface of the implant. Long-term fixation should depend on bone anchoring to this porous surface. Hydroxyapatite coatings must be developed which do not obstruct the pores of the surface of the implant.
All Science Journal Classification (ASJC) codes
- Ceramics and Composites
- Mechanics of Materials