A graft is defined as a piece of living tissue that is transplanted surgically. The traditional medical definition of a bone graft is: bone taken from one part of a person’s body that is grafted into another part of the same body. However, when the word ‘bone’ is added to ‘graft’, we immediately violate the definition of ‘graft’ because any bone that is transplanted from one part of the body to another is no longer living. The transplanted bone becomes necrotic as evidenced by the death of osteocytes in the grafted material. To complicate things even more, there are many materials not composed of bone that are also being referred to as ‘bone grafts’.
In our opinion, a bone graft is better defined by what it does rather than by its composition. The purpose of a bone graft is to promote the growth of bone. Defining a bone graft by its purpose will allow the user (doctor) to know if the material being placed into the patient is actually a bone graft.
What is a Bone Graft?
BONE GRAFT:
“A material that promotes the growth of normal bone.”
Here are a few examples:
This photomicrograph is from a human extraction socket showing osteoblasts migrating into Socket Graft. Since Socket Graft promotes the spread and migration of osteoblasts throughout the graft material leading to mineralization (osteoconduction), it satisfies the definition of a bone graft.
This photomicrograph is from a human extraction socket showing bone forming on an OsseoConduct βTCP bone graft particle. This example of osteoconduction satisfies the definition of a bone graft.
A common example is calcium sulfate. Calcium sulfate is 50% waste material. The sulfate is not utilized in bone formation therefore, bone cells will not grow onto calcium sulfate. Only after the calcium sulfate has dissolved between 2 to 4 weeks post-grafting, will the normal process of bone formation finally begin. Calcium sulfate has three different formulations: dihydrate, hemihydrate, and amorphous. None of these forms of calcium sulfate or combinations thereof meet the definition of a bone graft because they are not osteoconductive. If you are considering using calcium sulfate as a bone graft, simply request human histology of osteoblasts growing on the manufacturer’s calcium sulfate. If such proof of osteoconduction cannot be provided, then yo know that material will just delay bone formation and it is not a bone graft.
Another good example is PRF. Bone cells will not grow into fibrin. The fibrin must be enzymatically disolved before the normal process of bone formation can begin, thereby delaying bone formation. Look at the thousands of dentists that bought into using PRF for bone regeneration only to find out years later that it does not promote bone growth. If these clinicians would have simply requested human histology of osteoblasts growing in PRF, they could have avoided the mistake.
Bovine collagen is another material that is not osteoconductive and needs to be resorbed before bone growth can begin. Ask the manufacturer for histology of osteoblasts mineralizing the bovine collagen. If no histology can be provided, then the material is simply delaying normal bone formation until the collagen is removed.
Another issue that complicates bone grafting is when a manufacturer of a bone graft material combines an actual bone graft material with a polymer to make the bone graft material easier to place. Request to see human histology of osteoblasts growing into the polymer. If they cannot provide this evidence, you can infer that the polymer must be removed before bone growth can begin yet, another delay in normal bone formation. Find out how long it takes to resorb the polymer (based on human histology) and you can decide if the ease of handling offsets the extra cost and delay in bone formation.
Requesting human histology that shows osteoblasts growing into and onto a proposed bone graft material can arm the clinician with a valuable tool when deciding on what to put into the patient. If we were the patient, this level of due diligence would be the least we would expect of our doctors.
