Biomechanical evaluation of osseous implants having different surface topographies in rats

Biomechanical and biological factors can co-dependently influence the estab lishment of implant-tissue integration; thus, concurrent evaluation of thes e factors should provide a better understanding of osseointegration. This s tudy aimed to establish and validate an in vivo rat model frequently used i n molecular/cellular biology for implant biomechanical studies. We tested t he hypotheses that the implant push-in test assesses the degree of osseoint egration by the breakpoint load at the implant-tissue interface and that it sensitively differentiates between the effects of different implant surfac e topographies. The implant push-in test, which produces a consistent load- displacement measurement, was used to test miniature cylindrical titanium i mplants placed at the distal edge of the adult rat femur. The push-in test values obtained at each post-implantation healing point (weeks 0, 2, 4, and 8) significantly increased in a time-dependent manner. The implant surface after the push-in test was associated with remnant tissues containing host -derived elements, such as calcium, phosphate, and sulfate. In this model, acid-etched implants (average roughness, 0.159 mum) showed significantly gr eater push-in test values than did turned implants (average roughness, 0.06 3 mum) throughout the experimental period (p < 0.0001). These results suppo rt the validity of the push-in test in rats, which may be used as a rapid a nd sensitive biomechanical assay system for implant osseointegration resear ch.