The hydration characteristics of demineralized and nondemineralized allograft bone: Scientific perspectives on graft function.

Demineralized bone matrix grafts are osteoinductive due to the increase in bioavailability of bone morphogenetic proteins that occurs from demineralization. The manner by which demineralization increases their bioavailability, however, is not known with certainty. It is known that the mineral phase of bone masks the proteins of the organic matrix. Proteins depend on their interaction with water for their three-dimensional conformation, biologic activity, and stability. It is possible that demineralization allows a more complete hydration of bone matrix, changing the local environment and allowing the bone morphogenetic proteins to desorb and form a concentration gradient, signaling the appropriate cell types to begin the process of bone regeneration. Under similar test conditions, it was discovered that hydration of demineralized bone matrix powder produces a strong exotherm on the order of 14 degrees C whereas hydration of bone powder produces a smaller exotherm of about 2 degrees C. The details of the hydration reactions of demineralized bone matrix and bone were investigated by measuring the exotherm produced under varying conditions. The results suggest that bone mineral does mask, or limit, the ability of the organic matrix to interact with water. An understanding of the hydration characteristics of demineralized bone matrix can also help in the development of carrier systems that optimize osteoinductive potential.