Gaps were prepared surgically in femora of 42 albino rats, and were kept apart by a looped wire. Grafts of Kiel bone (KB) and HTR™ polymer in different environments were implanted into those gaps. The control groups showed a nonbony healing 36 days after the osteotomy. KB or HTR polymer alone failed to induce bone bridging, while KB with autologous bone marrow induced bone bridging in the gaps. The most significant finding in this study was the ability of calcium hydroxide [Ca(OH)2] grafted with either KB or HTR polymer to cause differentiation of bone matrix in the surgical gaps. The combination of HTR polymer and Ca(OH)2 induced formation of trabecular bone bridging to a greater extent than all the other material combinations.