Confocal imaging of shear tested calvarial bone-bioactive glass interfaces

Introduction: Clinical implant failure typically occurs at the biomaterial-host tissue interface, classically through biomechanical and biochemical mechanisms. By definition, bioactive materials form a strong bond to living bone and occasionally to fibrous tissues (e.g. 45S5 Bioglass). Methods: Unlike many in vitro bond strength investigations, this three month near in vivo study combined novel micro-shear stress techniques and real-time confocal imaging at the point of (presumed) interface failure, yielding a study comparing both strength and longevity of rabbit calvarial bone - 45S5 Bioglass and 58S sol-gel bioactive glass interfaces. Results: The technique yielded valuable new data concerning the predominantly glass cohesive interface failure patterns. Porous 58S monoliths established an earlier, stronger interface (median 4.95MPa peak 5 weeks) as expected from their more rapid bio-reactivity but were not stable in the long term; whereas slower reacting, melt derived 45S5 interfaces increased in number, strength and stability throughout the experiment (median 7.98MPa maximum at 3 months). Conclusions: Superior, long term interfaces were established by the non porous slower reacting melt derived bioactive materials whereas increased surface areas promoted faster formed but less stable interfaces.