Granule size and composition of bioactive glasses affect osteoconduction in rabbit.

Bioactive glass granules of three different compositions, regarding particularly Si- and Al- content (S53P4, S59.7P2.5, S52P3) and of two different granule sizes (200–250 μm and 630–800 μm) were implanted for 4 and 8 weeks in the distal part of rabbit femur. The effect of glass composition and granule size on bone formation was studied. The results were evaluated using histology, computerized histomorphometry, scanning electron microscopy and energy dispersive X-ray analysis, and used for mathematical description of bone formation. The results showed that both the composition of the glass and the granule size of the granules, have influence on bone growth from the surrounding tissue. Glass S53P4, which from previous observations is known to be an effective bioactive glass and widely used in the Biomaterial Project of Turku, Finland, showed bone bonding and increasing bone growth between the granules. Glass S59.7P2.5 which due to its high Si-content should be inert, showed bone bonding. At 4 weeks the bone growth was significantly more abundant in bone defects filled with large granules (630–800 μm) than in defects filled with small granules (200–250 μm). Glass S52P3 with an alumina content of 3 wt %, showed good bone conduction, possibly even bone bonding for granules of 630-800 μm size. Granules of 200–250 μm with a high alumina content at the surface of the reaction layer, showed hardly any bone contact at all. This data, therefore, gives new information concerning bone bonding and osteoconduction of bioactive glasses with a high silica or alumina content.