An understanding of the mechanism that promotes adhesion between roughened titanium implants and mineralized tissue

A previously developed laser spallation technique to determine the tensile strength of thin film interfaces was successfully adopted to study the effect of microsurface roughness of titanium disks on the adhesion strength of mineralized bone tissue. The study demonstrated that mineralized tissue has about 25% higher interfacial strength when it is cultured on the acid-etched titanium surface than on its machined counterpart. Specifically, interfacial tensile strength of 179+/-4.4 MPa and 224+/-2.6 MPa were measured when the mineralized tissue was processed on the machined titanium and acid-etched titanium surfaces, respectively. Since in the laser spallation experiment, the mineralized tissue is pulled normal to the interface, this increase is attributed to the stronger interfacial bonding on account of higher surface energy associated with the acid-etched surface. This enhanced local chemical bonding further enhances the roughness-related mechanical interlocking effect. These two effects at very different length scales--atomic (enhanced bonding) versus continuum (roughness-related interlocking)-act synergistically and explain the widely observed clinical success of roughened dental implants.