Porcine fetal enamel matrix derivative enhances bone formation induced by demineralized freeze dried bone allograft in vivo

Background: Embryonic enamel matrix proteins are involved in the formation of acellular cementum during development of the periodontal attachment appa ratus, suggesting that these proteins might be used clinically to promote p eriodontal regeneration. At present, it is unknown if these proteins are os teoinductive, osteoconductive, or osteopromotive. To address this question, we examined the ability of a commercially prepared embryonic porcine ename l matrix derivative to induce new bone formation in nude mouse calf muscle, or to enhance the bone induction ability of a demineralized freeze-dried b one allograft (DFDBA). Methods: Porcine fetal enamel matrix derivative (EMD) was implanted bilater ally in the calf muscle of 4 male Nu/Nu mice per treatment group (N = 8 imp lants): 2 mg EMD alone; 4 mg EMD alone; inactive human DFDBA alone; inactiv e DFDBA + 2 mg EMD; inactive DFDBA + 4 mg EMD; active DFDBA alone; active D FDBA + 2 mg EMD; and active DFDBA + 4 mg EMD, Implants were harvested after 56 days and examined histologically for bone induction using a semi-quanti tative score and histomorphometrically for area of new bone, cortical bone, bone marrow, and residual DFDBA. Results: Implants containing inactive DFDBA, 2 mg EMD, 4 mg EMD, and inacti ve DFDBA + 2 or 4 mg EMD did not induce new bone. Active DFDBA and active D FDBA + 2 mg EMD induced new bone to a similar extent. In contrast, active D FDBA + 4 mg EMD resulted in enhanced bone induction, area of new bone, and cortical bone. Residual DFDBA was also increased in this group. Conclusions: EMD is not osteoinductive. However, it is osteopromotive, due in part to its osteoconductive properties, but a threshold concentration is required.