Papers by Keyword: In Vitro Reactions

Abstract: In vitro reactions of bundles of fibers with diameters 20-500 μm and crushed glasses of fractions 500-800 μm were compared with the reactions of plates of the same bioactive glasses. The samples were immersed in simulated body fluid (SBF) for 2-7 days. After immersion the changes on the surfaces of the samples were observed by SEM/EDXA. Layer formation on the glass surface was found to vary with glass composition, sample shape and local condition of single particle/fiber. However, only some fibers or particles formed similar in vitro reaction layers as the plates. The product form did not change the in vitro bioactivity of particles or fibers exposed to the bulk immersion solution. When the glasses were used as fiber bundles or particle beds, the packing degree and the flow of body fluids within the system interfered with the reactivity. Also a clear correlation between in vivo layer formation in bone and in vitro of the glass plates could be found.

Abstract: Implants with long lasting bioactivity and mechanical sustainability would be of interest in several novel clinical applications. By processing bioactive glass fibers and biodegradable polymers into 3D structures, bone formation ability of glasses and flexibility of polymers can be combined. In order to achieve desired physiological response, reactivity of bioactive glass fibers must be specified. Bundles of fibers within the range of bioactivity were soaked in the simulated body fluid at stationary conditions for several time intervals after which the cross-sectional surfaces of the fibers were studied with SEM-EDXA. The reaction layers and precipitations formed on the fiber surfaces suggest that the fibers react according to three mechanisms depending on the glass composition. Fibers with a high in vitro bioactivity showed the formation of distinct and thick silica –rich and calcium phosphate –rich layers already at one day’s immersion. Fibers of medium bioactivity did not show any clear silica –rich layer but a formation of calcium phosphate precipitations or layers at one day’s immersion. Slow glasses showed sporadic calcium phosphate precipitation only after the longest immersion times. The results indicate that the medium and slow glasses are interesting alternatives for applications where a long term mechanical durability suggested by their slow reactivity in combination with their osteoconductive tendency is desired.