Osseointegration is defined as direct contact between the implant surface and the bone on the light microscope level. Osseointegration is often clinically assessed by tactile means. Well integrated implants """"""""ring true"""""""" and are immobile. There is a need to objectively evaluate the bone/implant interface in vivo and to thereby infer the materials properties of the interface. Prior research has assumed a linear model of implant vibration utilizing the concept of impedance as the inverse of mobility. We hypothesize that the mechanical link in the integrated implant is nonlinear in character and that a nonlinear model may be used to characterize, in a quantitative manner, the state of osseointegration of a dental implant. Dr. Ramp's research seeks to establish algorithms which describe this non-linear relationship and thereby develop a technique with which exploits this nonlinear quality of the interface.
The specific aims of this investigation are to establish an initial mathematical model, develop software and algorithms to test this model at simulated degrees of osseointegration, and to develop an instrument which can both produce oscillatory motion, and accurately measure state and oscillatory forces. It is further planned to conduct in vivo laboratory animal model studies and clinical testing. To date, a software simulation program has been developed to test various mechanical models of the interface. Examination of the simulation data has included spectral content, the relationship of output displacement to static preload and statistical analysis of nonlinear responses. The in vitro validation of the instrument is to be carried out by using a physical model which simulated varying degrees of osseointegration. The physical model consists of a stainless steel block having machined cylindrical holes and steel pins, simulating the implant site and implant device, respectively. By graduating the diametral clearance between the pin and hole filling the interposed spaced with a suitable material, a range of osseointegration can be represented. This physical model has been designed and constructed and various polymeric material simulating an incompletely integrated interface are being tested. We are presently assembling and validating the device, and performing validations of the algorithms, and software. Thereafter, animal model studies will be performed.

National Institute of Health (NIH)
National Institute of Dental & Craniofacial Research (NIDCR)
Unknown (K16)
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Toms, Stephanie R; Lemons, Jack E; Bartolucci, Alfred A et al. (2002) Nonlinear stress-strain behavior of periodontal ligament under orthodontic loading. Am J Orthod Dentofacial Orthop 122:174-9
Ramp, L C; Reddy, M S; Jeffcoat, R L (2000) Assessment of osseointegration by nonlinear dynamic response. Int J Oral Maxillofac Implants 15:197-208