research Effects of Block Bone Substitutes Loaded with Escherichia Coli-Produced Recombinant Human Bone Morphogenetic Protein-2 on Space Maintenance and Bone Formation in Rat Calvarial Onlay Model 06 Mar Effects of Block Bone Substitutes Loaded with Escherichia Coli-Produced Recombinant Human Bone Morphogenetic Protein-2 on Space Maintenance and Bone Formation in Rat Calvarial Onlay Model