Evaluation of glass-ionomer cements for use as bone substitutes with reference to their value for treatment of atrophic alveolar bone

Progressive resorption of alveolar bone occurs following loss teeth and results in severe functional, social and aesthetic problems for those individuals who are unable to cope with dentures. Existing biomaterials used to augment the jaws with the aim of restoring the alveolar bone to enable successful denture wear suffer from problems of migration and require complex surgical techniques to achieve success. The aim of this study was to investigate glass-ionomer (polyalkenoate) cements (GIC) as a class of materials for use as bone substitute and cements and compare them with currently used calcium phosphate ceramics. Initial biological testing was undertaken using primary bone cell and organ cultures based on explants of rat calvarial bone. In vivo evaluation involved implantation of GIG, into or onto, the mid-shaft of rat femora and study of diffusion chambers containing GIC implanted into baboons (supplied by Prof L M Jonck). In vitro certain formulations of GIC were colonised by bone cells which regained their phenotype and laid down a collagen-containing extra-cellular matrix, cells responded less favourably to unset and fluoride-containing GIC and material with a rough surface. In vivo direct bonding of bone to GIC based on fluoro-alumino-silicate glass occurred, with a mineralised collagen-containing extra-cellular matrix being deposited on the surface of the GIC. Aqua Cem and a fluoride-free GIC showed incomplete osseointegration. Study of GIC indicated that this ionomeric group of materials, which can be made to resemble bone biomechanically, have potential advantages over currently available calcium phosphate ceramic bone substitutes