Enamel Matrix Proteins: Effect on Osteoinductivity of Human Bone Allograft

Objectives: Recent clinical reports suggest a potential therapeutic benefit of combining enamel matrix derivative(EMD) with bone allografts on regenerative outcomes in periodontal osseous defects. Although allografts serve an important function as scaffolds, inherent differences in the osteoinductive capacity of allografts may affect the regenerative outcome. Methods: The purpose of this study was to evaluate the effects of EMD on the osteoinductivity of bone allografts derived from the same donor, differing in residual mineral content and inherent osteoinductive activity. Methods: Demineralized freeze-dried bone allograft (DFDBA) with 1% residual calcium content (minimally osteoinductive) and freeze-dried bone allograft (FDBA; non-osteoinductive) were processed from the same donor. Particulate grafts were implanted into the gluteal muscle of 36 athymic nude mice (nu/nu), either alone or in combination with 2 or 4 mg EMD. DFDBA with 2% residual calcium content from the same donor was implanted in 6 mice to serve as a positive control. Grafts were explanted at 28 days and submitted for histomorphometric analysis to assess percent vital bone formation. Results: FDBA alone and in combination with EMD did not support vital bone formation. In contrast, minimally active DFDBA was found to support significantly enhanced levels of vital bone formation when used with 2 mg EMD and 4 mg EMD compared to DFDBA alone (ANOVA, p £ 0.05). Comparable levels of bone formation were found for both the 2 and 4 mg EMD groups. Conclusion: In the absence of inherent osteoinductive activity, low levels of EMD evaluated in this in vivo model failed to support bone formation; whereas, EMD synergistically enhanced the osteoinductivity of minimally active DFDBA.