The anchoring of glass ceramics of different solubility in the femur of the rat.

A direct physicochemical bond between alkali-rich bioglass or glass ceramic (45 S 5 A and B, Hench) or alkali-poor glass ceramic (KG S, Brömer) and bone has been well documented. Since long-term studies have revealed the interface to be subjected to remodeling of the bone and to increased focal disintegration of the implant, glass ceramics of reduced solubility have been developed by lowering the Na2O content and adding Al2O3, Ta2O5, TiO2, and Sb2O3. Implants of glass ceramic KG S and different compositions with reduced solubility have been studied histologically 14, 29, or 30, 60, 119, and 245 days after implantation in the femur of male Sprague-Dawley rats. Implants of KG S are anchored at an interface with bone connection, which is known to provide for application of considerable shear and tensile strengths; whereas, at the interface of ceramics of reduced solubility, soft tissue, chondroid and osteoid are mainly observed. The dynamics of the events at the interface indicate a disturbance of the transformation of chondroid cells into osteoblasts and of the mineralization of osteoid. This disturbance of pathophysiologic processes during bone healing or bone regeneration is discussed.