COMPARISON OF BONE-IMPLANT INTERFACE SHEAR-STRENGTH OF HYDROXYAPATITE-COATED AND ALUMINA-COATED METAL IMPLANTS

We performed a transcortical push-out test to determine the effect of surface roughness of hydroxyapatite (HA)-coated implants on bone-impla nt shear strength in a canine model. Hydroxyapatite- and alumina-coate d SUS316L with the same surface roughness (roughness average: Ra = 5 m u m) and HA-coated Ti-6Al-4V (Ra = 8.4 mu m), sintered HA (Ra = 0.9 mu m), and dense alumina (Ra = 1.3 mu m) were inserted into the dog's fe mur. The interface shear strength of the dense alumina was significant ly lower than that of other implants at both 4 and 12 weeks after impl antation. At 4 weeks after implantation, the interface shear strength of the alumina-coated SUS316L was significantly lower than that of oth er implants (P <.05) except the dense alumina, but at 12 weeks, there was no significant difference between the implant types except the den se alumina. This indicates that the surface roughness of the HA coatin g affects the enhancement of the bone-implant interface shear strength at the early period after implantation, and that a surface roughness of several micrometers does not influence the bond strength between bo ne and HA. A scanning electron microscopic study indicated that in alm ost all cases at 12 weeks, the failure site after push-out testing was the coating-substrate interface, not the coating-bone interface. Ther efore, protection of the coating-substrate interface from direct shear loading is needed. (C) 1995 John Wiley and Sons, Inc.