Significance of peak value and duration of the interfacial shear load in evaluation of the bone–implant interface

Objective. To determine if there is any merit in measuring peak load duration in studies of bone–implant interface during a pull-out test was performed to record the interfacial shear load. Design. Mechanical and histological investigations were performed to determine the bone–implant interfacial strength. Background. A common long-term problem following artificial joint replacement is the formation of an intervening fibrous tissue seam at the interface between bone and a prosthesis. To investigate the nature and strength of interfacial attachment between bone and an implanted biomaterial, a detaching method such as pull-out test can be used. Methods. Four porous surfaced alumina ceramic implants with or without glass-ceramic containing apatite and wollastonite coating at the surface of the beads and the substrate were implanted into canine the femoral condyles. Peak value and its duration of the interfacial shear load for the different types of implants were analyzed. Tissue formed at the bone–implant interfaces were examined histologically. Results. The peak value of interfacial shear load of the apatite and wollastonite glass-ceramic-coated implant was significantly greater than that of the non-coated implant at every stage, but the peak value duration in the control at each time period was greater than that of the coated implant. Histologically, more bone tissue ingrowth in the pores of coated implants, whereas a gap was observed at the interface of bone and the non-coated implant. Conclusions. The interfacial shear load values, peak and its duration, are significantly influenced by the direct bone bonding or the intervening fibrous tissue which formed at the bone–implant interface.