Quantitative assessment of osseointegration remains a goal of researchers and clinicians alike. In this study, an instrument was designed for this purpose and tested in an animal model. Effective mechanical impedance, linearized for quasi-static force, was measured in 22 implants placed in the hind tibiae of 2 large hounds. The results demonstrate that in this animal long-bone model, the effective impedance of titanium root-form implants exhibits a degree of nonlinear behavior correlated with their state of osseointegration. This observation may be the basis for useful clinical instrumentation. Keywords: animal model, dental, histomorphometry, impedance, implant, mechanical, nonlinear, osseointegration