Morphology of osteogenesis in bioactive glass interface

Bone formation around bioactive glass implants (S56.5P4) in the trabeculous subchondral bone in the distal femur of rabbits was studied by histology and scanning electron microscopy. Three types of tissue: bone, connective and hematopoietic tissue developed around the implants resulting in lamellar new bone covering 76% of the surface of the implants at twelve weeks. Bone formation around implants began as woven bone changing mainly to lamellar, osteon like new bone in contact with the S56.5P4 surface. Endochondral ossification was absent. In the area of bone containing hematopoietic tissue, new bone grew often as a thin layer along the implant surface. However, bone seemed to form adjacent to the implant surface through osteo-conduction. Only 21% of the implant surface was covered by loose connective tissue. Some proteoglycan containing thin fluid filled spaces were seen ten days after implantation. In few areas with apparent breakdown of the implant surface decreased amount or no bone formation was observed. Von Kossa method stained the reaction layer as two parallel dark brown lines, toluidine blue as two blue stripes, whereas van Gieson did not stain the reaction layer at all. In conclusion, the present histological results indicate bone bonding, which is a physico-chemical process observed between S56.5P4 implant and host bone.