[Extended push-out test to characterize the failure of bone-implant interface]

To study the mechanical behaviour of the implant-bone interface the push- or pull-out test was overtaken from material science. Most authors equate the maximum load (break point) with the failure of the implant integration. Extending the test procedure by acoustic emission analysis reveals the possibility to detect the failure of the interface more in detail and from its earliest beginning. The development of disconnection between host and implant was found to start long before the ultimate load is reached and can be monitored and quantified during this period. The active interface mechanisms are characterized by the distribution function of acoustic emissions and the number of hits per time defines the kinetics of the failure. From clinical studies a gradual subsidence of loaded implants is known starting long time before the definite implant failure. The presented extension of the push-out test with acoustic emission analysis allows the detection of a critical shear stress tc which demarks the onset of the gradual interface failure. We believe this value to represent the real critical load which should not be exceeded in the clinical application of intraosseous implants.