INTERFACE STRENGTH AND HISTOLOGY--EXPANDABLE TI IMPLANT

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The specific aim of this study is to determine the correlation between histologically definable osseointegration and mechanically tested shear interface strength of commercially pure, expandable smooth surface titanium implants. Consequently, a greater number of samples can be evaluated mechanically without studying each one histologically, thus reducing costs. Expandable endosseous implants exert favorable compressive stresses that provide an environment that enhances bone growth onto the prosthesis. Expansion against bone replaces the need for technique sensitive steps such as threading adn tapping which may lead to failure when not precisely adhered to. The long term objective is to demonstrate expandable implants exert an optimal applied compressive level that improves the prognosis of osseointegration, thereby improving the reliability of complete bony union and shortening the healing period prior to complete osseointegration. This will provide greater predictability for a successful functional implant. Cylindrically shaped implants whose diameters increase uniformly when they are expanded are surgically implanted in femus of rabbits. Control implants of the same configuration are subjected to the same implantation techniques. Two different time periods are selected to examine the change in healing and osseou interface that can resist pushout over time. Bone modeling will be observed for implants having 3 different internally applied loads, suboptimal, optimal and supra-optimal. The amount of osseo-integration will be assessed directly by selected histologic samples and predicted indirectly by the relative level of interface strength. Implantation techniques will follow the principles recommended by P-I. Branemark. Histologic samples will be decalcified and prepared for sectioning before observing under light microscope. The sheer interface strength will be measured on a Materials Testing Systems instrument.