Why do we concern ourselves with bone replacement materials?
In addition the various bone replacement materials are unfortunately often disregarded by Professors (heads of clinical departments in universities) and Consultants (Heads of Hospitals), who are often involved in the promoting or otherwise of these materials, directly or indirectly. The “objective” information is therefore often obscured. We’d like to share a few insights here.
Implants and Bone-Building
Often, due to long-untreated periodontitis, or longstanding loss of teeth and no treatment of the resulting gap, we hear of the diagnosis of alveolaratrophy or the loss of the tooth-bearing bone of the upper or lower jaw.
A successful setting of tooth implants in the remaining bone of the jaw is no longer possible, since nerves or nasal sinuses would be harmed. In order to fix tooth implants a certain volume of bone is necessary.
The solution is the building up of the bone which can be carried out with material from the patient’s own body or with foreign material. Material from the patient’s own body involves additional operations so foreign material is often resorted to.
What’s the best bone material one can use to build up bone?
As a rough rule, the more similar the donor bone is to human bone, the better it integrates. The patient’s own bone integrates best – when the necessary portion of bone doesn’t exceed a certain size. If it does, then the portion must be transplanted microvascularly.
Doctors observe with bone transplants that as soon as the transplanted portion exceeds a certain size the body re-absorbs a large part of the transplanted bone over a few months. For a long time it wasn’t clear why this happened, but now we know quite well why this happens. The reason is the following: In the transplanted bone there are cells, i.e. bone cells.
As long as the bone is still whole, the cells are well-supplied with nutrients by small blood vessels. As soon as the segment of bone is taken out, the cells within it are cut off from the flow of nutrients. With a small segment of bone the cells are soon supplied again with nutrients by means of diffusion in their new environment. By means of diffusion the cells within a small segment can survive long enough for new blood vessels to develop.
If the portion of bone is too large however then diffusion is not enough to reach the innermost cells in the segment and it would take days for the new blood vessels to reach them. For these cells this is too long and the cells die. The death of these cells brings out an immune reaction later and since the immune system destroys cells this will result in a loss of bone.
Introducing the patient’s own cells (blood cells) into artificial bone is also useless. One either makes use of a little human bone, or one uses animal bone e.g. from cattle. There are also bone replacement materials from seaweed or synthetic products. Synthetic bone replacement materials take longest to heal, although intensive research is under way and the development of these products is progressing rapidly.
The impregnation of donor bone with for example their own cells doesn’t do anything. The combination of donor bone with, for example, their blood serves mainly for the better working of the material during the operation. Whether it leads to better healing is questionable.
Where do human bone products and bone donations come from?
Human bone or tissue in general usually comes from corpses or as by-products of operations as a rule (for example from broken femur necks). The use of tissue and bone is normally strongly regulated and overseen by national and international laws. For example, it’s not possible to make use of material which has become available as a result of an operation without the express consent of the patient, since the material is completely legally the property of the patient.
In the case of death the legal situation is different in different countries. Many countries have their own register of donors in which people must be listed during their own lifetime in order to enable the use of their organs and tissues after their death. Other states work in the opposite way. They have an objector’s register, therefore in principle organs and tissues may be taken from anyone, as long as he/she is NOT registered in the objectors’ register during his lifetime.
These facts may seem macabre to you but the possibility is in your hands to follow the procedures to make your organs and tissues available and thereby to save people’s lives or to mitigate illness through organ or tissue transplants. In addition it should also be mentioned that such “removals” can only be carried out by state-registered and controlled institutions.
Bone-buildup – Is the transmission of disease through replacement bone material possible?
Cattle bones are often used to replace bones in people. Is it possible to infect someone with prions through these bones? It’s not possible to make a categorical statement here since it all depends on the procedure followed, how the bone was harvested, handled and packed.
In Europe the most frequently used bone building material is Bio-Oss®, from the Geistlich company. This Bio-Oss ‘xenogenic’ (meaning animal) bone replacement material is deproteinised, meaning that all proteins in the bones have been removed, leaving only the calcium structure. It is comprehensively described in scientific literature and in a study in 2003 was identified as the most used bone replacement material ever.
The German Federal Office for Medical Products has in this respect stated: “We can also inform you that the Geistlich company have provided proof that conditions for the eradication of BSE pathogens have been put in place at all stages of the treatment of the bone material.
Based on this proof, the “Authorised Body” responsible for the assessment of Bio-Oss in the EU has established that by the end of September 2004, in addition to the CE certification (the basic requirement for the product to be used or traded at all) additional certification has been granted, which attests to the neutralisation of the risk of transmission of spongiform encephalopathy (e.g. prion diseases).
We can therefore confirm once again on the basis of our present knowledge that there is absolutely no reason for the assumption that Bio-Oss bone replacement material could possibly be any cause for concern.”
In view of this evidence and of the statement by the German Federal Office for Medical Products the question of the risk of transmission of prions does not exist any more.
Bone material for bone-building from a stranger?
Whatever material we would prefer for ethical purposes, biological materials currently produce much better end results than synthetic ones. With regard to bone building you can find several articles, film clips and forum entries here. We will soon be introducing a new and innovative process, with the help of which we hope to prepare people for the donation of human bone. Let us keep to human donor bone.
Up to now donor bone has been and will be cleaned by means of liquid solutions. The problem here is that the bone can never be 100% clean. There will always be cell remains in the bone segment. These cell remains in the bone segment will be destroyed by an inflammatory reaction of the immune system of the receiver as soon as the bone is transplanted and unfortunately the transplanted bone itself will also be lost. Nowadays there’s a company in Europe which cleans the bone not with liquid solutions but rather with highly critical CO2.
Highly critical means that the CO2 is neither in liquid nor in gas form but is rather made up of an aggregation of both these states (liquid/gas). Simply explained, you know that H2O in solid state is ice, in liquid state is water and in gaseous state is steam. In the highly critical state the CO2 retains the superlative fat-dissolving properties of liquid CO2 and also the excellent diffusion properties of gaseous CO2.
The result of this cleaning process is absolutely clean bone, down to the last pore. It is white, unlike normally-cleaned bone which is yellowish. The entire calcium framework of the bone, hydroxylapatite, is white! These bones can be bought pre-inoculated with an antibiotic, thus saving one from having to take antibiotics.
Building up jawbone with the help of bone transplanted from the iliac crest is no longer required in dental surgery since such good bone replacement materials exist. Through the long-standing absence of teeth and/or periodontitis the bone of the jaw is destroyed. This often means that there is then not enough space for an implant. For a long time it was usual to use bone transplanted from the pelvis to build it up again. You simply took a segment of bone from the pelvis and attached it to the jawbone with screws – with very varying results.
Some technical terms in bone-building
By onlay augmentation we mean a special technique in a bone-building operation by means of which an increase in the alveolar ridge is produced. The missing bone is restored with the help of a segment of bone which is laid down – hence onlay. (This donor bone could be either donor bone or the patient’s own, from the chin, for example). After a few weeks the transplanted segment has healed and an implant treatment is possible.
The sinus lift operation is a so-called inlay-plastic – exactly the opposite. Here the bone is deposited on the inside, in this case between the bone and the mucosa of the maxillary sinus. The height of the alveolar crest remains unchanged with this procedure.
Despite precise planning it could happen that implants project into the maxillary sinus. It is important that you are informed about this. Too many patients have an implant put in and have no idea that the maxillary sinus has been injured in the process. The danger in such a situation is that if sinusitis occurs in the nasal sinuses, for example as a result of a simple runny nose, theoretically the implants could be infected due to the missing protective layer of bone. There are currently no known EBM studies about this topic.
The Relationships between Bone Metabolism, Weight and Sexual Function
Leptin – a neurotransmitter which regulates our body weight, our sexual function and our bone metabolism. For a long time we concentrated only on the local effects of hormones, so complex functional networks remained largely unrecognised.
Leptin was regarded for a long time as a hormone with local effect which affected bone metabolism but what it really does has now been made clear in recent studies. Various studies have demonstrated that this central-effect hormone (works from the brain outwards) affects our entire metabolism significantly. Leptin regulates the overall biology of our reproduction, our bone metabolism and our body weight. However it has a peripheral effect totally opposed to its central one.
Leptin has a peripherally stimulatory but a centrally inhibitive effect on bone metabolism.
How can these different effects of leptin be explained? If there’s a lack of nutrition, the sudden drop in leptin causes activation of the hypothalamus-pituitary-adrenal axis, with the resulting increase in catabolic hormones like cortisone, and a simultaneous inhibition of the thyroidal and gonadal function. In humans similar neurotransmitters also cause an increase in growth hormone and a decrease in insulin.(IGF-1).
These changes in case of lack of nutrition seem to make sense, since reproduction and the basal metabolism generally will be restricted and by means of the reduction of IGF-1 anabolic effects (build-up of muscle tissue) will also be stopped. All this would however necessarily lead to increased loss of bone, a situation which could have deadly effects.
Nature has solved this problem by means of a centrally modulated process, by means of which, in the case of a drop in leptin the depletion of bone stops, in fact, quite the contrary, the drop in leptin in the brain in fact has a positive effect on the bone. The drop in leptin puts into effect centrally, namely over a neural relay, a reduction in bone depletion. This central management feature overcomes the local effects of other hormones. When the organism once again has plenty of nutrition available then this mechanism is reversed.
This post is also available in: German