We often need to regain bone in the jaws, bone that has been lost for all kinds of reasons. The main indications for bone grafting are site preparation for dental implants, and periodontal surgery, to regenerate the bone support that can be lost by periodontal disease.
The idea of "grafting" bone is easily misunderstood. Although we can add large volumes of grafting materials, it is still the patient's own body that does the healing and rebuilding. Our regenerative materials mostly provide a scaffolding into which the body sends blood vessels, immune cells and eventually the cells called osteoblasts and osteoclasts that can form new bone.
What, then, are these substances that we use to provide this scaffolding? We'll get into definitions in a minute, but first let's review the most common sources that are used. The current commercially available sources for dental bone grafts include: human, bovine (cow), porcine (pig), equine (horse), and totally mineral (rock).
Gosh, the incredible variety of origin of these materials, and thoughts of how different cultures and religious traditions might view them, reminds me of the old joke. You know- there's a Jewish dentist, a Muslim dentist, a Hindu dentist and a Lutheran rodeo star and...oh, never mind!
When teeth are lost, the bone is often damaged beforehand, as the tooth slowly fails. It also pretty much flies away after the extraction. This is especially so on the outer, or buccal, bone. The buccal plate is very thin in humans and does not have much ability to repair itself; see:
A fine example of increasing the amount of bone in preparation for placing a dental implant is to be found in moi! I never developed my two upper 2nd premolars. My primary teeth hung in there for a long time but were finally getting weak, and to prevent breakdown of bone in the area that could affect the adjacent healthy teeth, I had my friend Thomas Kohler, periodontist extraordinaire, extract them in 2010. The thing was, there was not anywhere near enough bone height or volume for implant placement. I'll just show one side since right and left were both very similar. I've marked a thin black line along the boundaries of my bone, before and after the procedure. To the south is gum tissue, and to the north is my sinus. Dr. Kohler skillfully raised my sinus with the bone graft in order to create an acceptable implant site. The graft material, in this case highly inert, processed bone from a human source, was turned over into my own bone by my body's metabolism in about four months. Let's have a look at the X-rays:
What a difference! Oh, ok, and since you asked, here's the implant in place:
The funny-looking part between my teeth is just the impression coping, not the final crown or any sort of device that picks up enemy radio transmissions. It is used to register the precise position of the implant and my teeth and gums so that the lab can make me my new premolars.
Clarification of these choices in bone graft materials is my main goal with this post. Patients often want to know details about what materials are being used in any medical procedure.
We first need to define the general categories of bone graft materials. The first sentences are all from dictionary.com:
Autograft: A tissue or an organ grafted into a new position in or on the body of the same individual. So, for our purposes here, Own Grown Bone.
Allograft: A tissue or organ obtained from one member of a species and grafted to a genetically dissimilar member of the same species. In other words, bone from someone else, but still from a human. (Which means politicians cannot be donors under any circumstances.)
Zenograft: A tissue or organ obtained from a donor of a different species from the recipient. That's the bovine/porcine/equine vibe.
Synthetic or Artificial Bone can be made from purely mineral sources. Put simply, synthetic bone grafts don't come from a human, a cow, a pig or a horse- they come from a rock.
We can sometimes get autograft from other parts of the mouth during periodontal or implant surgery, but it's often difficult to get very much of it. Own Grown Bone can also be obtained from the iliac crest of the hip, but of course this involves a separate surgery and the skills of someone in addition to the dentist. (Our training includes lips, but not hips.) Also, the street cred on autografts is that they are preferable because the bone is "live" in some way, but the research clearly shows that whatever we place into an extraction socket is a dead mass until the body sends new blood vessels in there and starts rebuilding. So there is really not an advantage in that respect.
Allografts are readily available for purchase and the treatment of bone materials from human sources is rigorous, making them extraordinarily safe. The steps include donor screening, serum testing, delipidization with acetone and ultrasound, gamma irradiation, and hydrogen peroxide oxidation treatment. In any way of measuring risk, going to a restaurant is more dangerous than having these materials placed in an oral surgical site.
Xenografts are also readily available. I'm not aware of definitive research on all products, but studies in Sweden and the U.S. have shown that not all of the xenograft particles "turn over" (or "resorb") so that one's own bone replaces them completely. In other words, and in particular with bovine bone, each graft particle remains like a sort of mini-implant, an island of mineral bone matrix within the host's newly formed bone. This is not at all a problem, in fact these sites can have excellent form and function; it's just different than when all the bone eventually becomes the host's, as in autografts and allografts.
Synthetic bone, as I mentioned above, is derived from mineral sources. The trick is to make them properly porous so that blood vessels can invade and bone matabolism can start within them. This porosity is of course provided naturally in the other sources we've talked about. These products claim to be completely resorbable.
As a final exercise for patients who are considering oral surgery involving bone graft materials, let's run down some specific brands and product with which I am familiar. There are certainly others, and I do not mean to endorse any particular product, nor am I paid or otherwise compensated by any commercial interests everrr, although that's probably a sweet deal if you can get it.
Ok, here we go:
Puros. This is an allograft. It is manufactured by Zimmer:
This is also the one in me. Well, it was in me, now it's all my own bone, the turnover is essentially complete. It is now available in particulate form or particles in a paste form, so it is widely adaptable to various surgical situations. Dr. Kohler and I chose it together for my case for reasons of performance. Meaning, in our hands, with our skill sets and instrumentation, we have noted the best results from Puros over time. For now. This is where the experience of the individual practitioner intersects with the body of controlled scientific research that exists at any given time, and the best decisions are made when both realms are considered.
IngeniOs. Also a Zimmer product, this is synthetic. Specifically, it is a resorbable, silicated beta-tricalcium phosphate, for the chemists in the audience. The key thing is that it is porous and it does turn over into Own Grown Bone eventually.
This is a new product and, as the name indicates, is equine. They seem to have discontinued Bio-Oss, which was bovine, in favor of this new graft material.
I hope that this helps to make sense out of these choices for patients. There are further complexities like the choice between particles versus pastes versus block grafts for larger reconstructions. There are also formulations that add various bone growth factors in attempts to speed up bone growth, or make it more thorough.
The choice of bone graft materials is a highly individual one and is best made between the dentist and patient working together. Autografts are very appealing if enough bone can be obtained from the mouth, but few patients would want a second surgery on their hip unless it was vital to the case outcome. Allografts are quite safe, yet some patients have reservations about them in spite of all the processing that they undergo, or even because of what some describe as "the yuck factor" when they admit they have no real reservations about them. Bone grafts from animal sources may be unacceptable for some patients due to religious reasons. These are all valid concerns and I am happy to have completely synthetic sources as well, although as I stated when discussing my own case, I understand the safety quite well and went with an allograft for reasons of performance. I wanted lots of strong, dense bone, and I got it. Thanks, Dr. Thomas Kohler and all the little people, the osteoblasts and osteoclasts, who helped me have upper second premolars for the first time in my life!
I was very young when I first heard of the ancient tale from India of the blind men and the elephant. This tale spread far and wide, but the Indian version is probably the original and is definitely the most succinct.
Ramakrishna Paramahamsa used this parable to discourage dogmatism: "A number of blind men came to an elephant. Somebody told them that it was an elephant. The blind men asked, ‘What is the elephant like?’ and they began to touch its body. One of them said: 'It is like a pillar.' This blind man had only touched its leg. Another man said, ‘The elephant is like a husking basket.’ This person had only touched its ears. Similarly, he who touched its trunk or its belly talked of it differently. In the same way, he who has seen the Lord in a particular way limits the Lord to that alone and thinks that He is nothing else."
I shall refrain from any discussion of how this applies to modern American politics and the religious sphere. But to dentistry, it also has tremendous relevance.
For my entire career I've been intrigued by how 2-dimensional X-ray images represent, and misrepresent, 3-dimensional objects. I've posted before on how the level of bone or a small chip in enamel can be superimposed over the rest of the tooth in such a way that it looks like a cavity. Well, we took some X-rays recently that show a large cavity with tremendous variation in how it actually looks.
As we look at the images, recognize that the dark curvy lines inside the teeth are the outlines of the root canal. The white lines are an existing root canal treatment and post. The other white things are metal restorations.
In this first image, focusing on the tooth with the question mark, we see a hint of darker gray under the light filling, which could be a cavity:
However a dentist could perhaps be excused for thinking nothing of this shady shading and, if no open decay was visible to the eye (or touchable to those little sharp silver things that we're always poking around with), leaving this tooth be. Because, you see, the line of the dense bone throws a shadow right along this part of the tooth and it's supposed to look a little darker there. Same picture, with a line drawn along the bone crest:
Lighter below, darker above. Definitely a confusing area for interpretation.
Yet a Full Mouth Series of radiographs picks up different views of the same tooth. Much like those chaps investigating the elephant, we start to see different aspects of the same thing:
And for the win:
The bone may set the tone, but that's decay!
So multiple radiographic views of teeth are often vitally important in diagnosis. This is even more true when we get into diagnosing periodontal disease, endodontic lesions (infections in root canals), cysts and the like. The new 3-D scanners are a great advancement in this regard. They do not yet have the resolution to detect small cavities, but in short order they probably will. Until then, it's sometimes a challenge to know the tusk from the trunk.