Are demineralized bone allografts (cortical or cancellous) fully bio-resorbable?

The sclerosis is a result of the immune response to the foreign proteins and not the mineral portion. In regard to bone quality produced by demineralized vs mineralized both of these graft materials produce such poor bone quality that I refuse to place implants in sites grafted with these materials. These graft materials produce high mineralization with very poor vitality and no ability to adapt or remodel. Greg Steiner Steiner Biotechnology

Andre Osteoclasts have never been found resorbing allografts. With over 200 allograft histologic studies in the literature the allograft particles are encased in sclerotic bone and there has never been histology showing an osteoclast on an allograft particle in a resorption pit. Resorption and remodeling of allografts do not occur. Greg Steiner Steiner Biotechnology

Andre That is a complex issue but the short version is osteoclasts do not destroy bone they process bone and the proteins in the mineralixed matrix of bone are moved through the cytoplasm of the osteoclast into the surrounding extracellular matrix to be reused. Osteoclasts are multinucleated cells made by the joining together of macrophages. Macrophages patrol the body and look for pathogens or foreign proteins to destroy and present them to our acquired immune system. A cells whose role in life was to destroy foreign proteins is not going to process those foreign proteins and release them into the extracellular fluid. An osteoclast has never been found on a allograft particle in a resorption lacunae and allografts are never resorbed once mineralization occurs. Failure of allografts will be shown to be the largest reason for implant failure and the reason they are still popular grafts is because the people using them and the people promoting them do not understand their biology. You will note that there are those that challenge me personally but they never provide an intellectual debate because they have no science to support their position. Greg Steiner Steiner Biotechnology

Greg I'm here to learn with an open mind. Unfortunately, despite several posts you still have not provided any explanation as to WHY the foreign proteins in allografts can't be resorbed. For a meaningful discussion, simply making claims is not helpful. So again I would ask the same question and hope for a real, stimulating explanation: Once swallowed by the osteoclasts, WHY are the foreign proteins not digested completely by acid, collagenase and enzymes inside the osteoclasts?

Andre When an allograft is placed the site is filled with inflammatory cells for a few months while mineralization occurs. Mineralization forms on the surface of the allograft particles and when the allograft particles care covered with mineralized material then the inflammation subsides. At this point you have sclerotic bone that will never be modified through remodeling and that is why it is called sclerotic. Osteoclasts never come in contact with the allograft particles in this process. So proving or disproving weather an osteoclast will process foreign proteins is a moot point. If you really want to understand the process come to the course we are putting on in Las Vegas next month. Greg Steiner Steiner Biotechnology

Greg There seems to be a self contradiction between your last 2 posts in this thread. In your last post you said "osteoclasts never come in contact with the allograft particles". But in the post prior to that you said "the proteins in the mineralized matrix of bone are moved through the cytoplasm of the osteoclast into the surrounding extracellular matrix to be reused". This implies the foreign substance must have been engulfed by the osteoclast, which means a direct contact between osteoclasts and allograft particles. Would you care to explain this self contradiction?

Peter, well said, as always! A balanced approach.