The present invention relates generally to the field of bone graft substitutes and methods for making the same, particularly the invention relates to bone graft substitutes for use in dental or orthopaedic implants. The bone graft substitutes described herein comprise a silicate based material. The silicate based material is a silicate network with a porous structure. The silicate network has one or more metal cations incorporated therein. Preferably a phosphate is also incorporated into the silicate network. The bone graft substitute may have a low density, preferably a density of less than 1.1 g/cm3. The bone graft substitute may be an aerogel or a cryogel.
