- Current bone graft materials are mainly produced from coralline hydroxyapatite (HAp). Due to the nature of conversion process, coralline HAp has retained coral or CaCO3 and the structure possesses nanopores within the inter pore trabeculae resulting in high dissolution rates. Under certain conditions these features reduce durability and strength respectively and hence influence longevity Such materials may not be applicable where high structural strength is required. To overcome these limitations, a new coral, double-conversion technique has been developed. This technique involves a two-stage application route where in the first stage complete conversion of coral to pure HAp is achieved. In the second stage a sol-gel derived HAp (100 nm) coating is directly applied to cover the meso and nano-pores within the intra pore trabeculae material, whilst maintaining the useful large pores. In preliminary studies, biaxial strength was improved by 120% due to this unique double treatment. This application is expected to result in high purity, enhanced durability and strength in the physiological environment through vastly reduced dissolution rates and elimination of intra-trabecular nano and meso-pores. It is anticipated that this new material can be applied to bone graft applications where high strength requirements are pertinent.