A bone graft or biocomposite for treating osseous defects and neogenesis of bone which is a composite of a biodegradable polymer and granules of beta-tricalciumphosphate, further comprising as active ingredient and embedded in the biodegradable polymer a physiologically effective amount of underglycosylated recombinant human BSP as a multi-dental clathrate with a basic organic compound which simulataneously is active as a plasticizer for the biodegradable polymer. The biocomposite is moldable and shapeable, hardens rapidly in situ when placed by surgery or prosthetic dentistry and which furthers osseous repair and the healing of damage or diseased tissues and lesions.