Tensile bond between bone and titanium: a reappraisal of osseointegration

When Branemark in the 1970s established the term osseointegration, this implied a direct chemical bond between a titanium implant and bone. However, ultrastructural studies seemed not to support this idea, and osseointegration came to be defined as the absence of interfering fibrous tissue. Titanium was therefore described as bioinert rather than bioactive. We now demonstrate mechanically a chemical bond between bone and titanium, using unloaded cp titanium plates, similar to those used in previous studies on prosthetic loosening. Tensile force can be transmitted only by chemical bonds. Bone-bonding was therefore evaluated by a detachment test. The plates were developed so that a flat titanium surface touched traumatized bone and the rest of the detachable part had no contact with surrounding tissue. The titanium plates were either polished and sterilized in an autoclave or treated in 4 M NaOH and then heated to 600 degrees C according to Yan et al. (1996). After 4 weeks, the plates were separated from the bone by a perpendicular traction force. The detaching load of the untreated titanium plates never exceeded 0.03 MPa, whereas with treatment it increased to median 0.8 MPa, with bone remaining attached to parts of the plates after detachment. Our findings confirm that a chemical bond can be obtained within 4 weeks with the described pretreatment. It may occur also without treatment, after a longer implantation time.