Bone bonding through bioadhesives: present status.

Until recently use of adhesives was confined to cases in which glued areas could be pre-treated or at least cleaned. Thus, grease or oil contaminated surfaces could not be joined together by glueing. More recently, some adhesives have been developed which allow previous treatment of greasy surfaces to be avoided. Among these we find epoxy resins, acrylics and polyurethances. These adhesives have been used until now in various industries. We have begun a research program with these products and in aiming to design an adhesive which would enable immediate and strong bone bonding and avoid problems of metallic fixation, this study is a continuation of our previous research. Thus we tested - currently available surgical and dental adhesives - original mixtures developed in our laboratory. Mechanical assays were performed on bone samples from human femurs in different conditions : dried, cleaned, fresh, or after immersion in physiological solution. They consist essentially of tensile tests on Lhomargy and Zwick's machine wherein the stress is directed perpendicular to the interface. Variations of tensile strength (in h bar) are related to hardening time and to mixture composition. The specimens are joined together either in monolayers or in multilayers. The use of adequate catalysts ensures setting at room temperature. Torsion tests and fatigue tests are carried out concomitantly. Standardized bevel fermoral osteotomies were performed on mice with a dental saw after I.P. Nembutal anesthesia in order to test biological tolerance : - for the control group we study the evolution of bone repair after circumferential wiring - for the animals under test, bones are glued together with one of the proposed adhesives. Radiological and histological studies (using classical Azantrichrome staining after demineralization) are carried out at regular time intervals. In the control animals particular attention is paid to the time course of the formation, constitution and evolution of callus. In the test animals, we can observe callus formation, bone growth into the adhesive material and glue resorption, and look for specific antigenic phenomena. Despite expected improvements, bone glueing remains a challenge and only restricted clinical applications can be proposed.