This turns us around to osseointegration, and what is osseointegration? It’s pretty interesting. A lot of things that get discovered in science actually get discovered accidentally, or the person who’s looking or researching a particular aspect is looking at something and the outcome is totally different.
Osseointegration was actually discovered in the late 1950s and early 1960s by a Swedish orthopedic surgeon by the name of Professor Branemark. What he was doing was studying how bone heals in animals. He wanted to know what the healing process is, and this is in the late 1950s. What they had done in their lab was, they had animals (rabbits) that they placed a cylinder, made out of metal, through the skin into the long bone. It had a glass opening through which they could look in with the microscope and see what blood flow was going on and what cells were coming in this area of trauma.
They studied this for about 45 days, and when they finished the study, they went to remove this metal chamber out. They couldn’t get it out. The lab had made that chamber out of titanium because we knew titanium was an inert material that did not elicit a lot of response. So, he didn’t want something that was put in there that created inflammation because if it did, you wouldn’t be able to study the normal healing process which is what he was looking at.
So, this titanium cylinder that was placed in the bone and came out through the skin after 45 days. When they wanted to take it out, they couldn’t get it out, and that’s when his gray cells started to turn. He says, “This is pretty amazing,” because if you think about it, the teeth are the only organs that we have in our body that are actually embedded in the bone and penetrate soft tissue and come out into the open environment, maybe through the mouth but it’s still the outside. You don’t have anything sticking through your skin coming out, right? It’s not going to heal. You’re going to get an infection, and you’re going to have a problem.
This was pretty amazing. Not only did this stay in place for those 45 days and healed, but they couldn’t get the thing out. So, he started to look at it and say what was really going on. What was very interesting was that he found the lines here was a titanium surface, and what he had on this titanium surface was bone that was directly growing onto the titanium surface which was very, very unusual.
In effect, bone was treating titanium like another piece of bone, like a fracture. You had a fracture in your bone, and the two pieces come together. They’re going to heal against each other, provided you keep them stable and don’t allow movement to occur. That’s why we have a plaster cast.
What was interesting in all other implants that were done before that, between the implant (the metal component) and the bone there was a layer of soft tissue which was a connective tissue, histologically. Therefore, this is what actually what caused it to fail because if there’s no direct contact between the bone and the mini implant, that was a pathway for bacteria to get into and create and infection or inflammation.
Now, if you think of teeth, that’s what happens. I was pointing out to you in the slide earlier that teeth are attached to the bone with a ligament, a periodontal ligament. That’s why teeth can actually move a little bit. That’s why kids have braces. You can put braces on your teeth. You can move them because if you pull the tooth in one direction, that ligament stretches in one direction, and it’s compressed on the other side. So, the side that’s compressed, the bone’s going to resorb, and the ligament is going to come back. The side that the ligament’s stretched, it’s actually going to grow the bone with it and close that space up. That’s why you can move teeth.
If you put an implant in. You can put braces on them. They’re not moving. They’re not going any place. They’re integrated. They’re solid. They’re staying there. The reason why teeth fail when you say gum disease, that’s periodontal disease. That’s the periodontal ligament that’s breaking down. That’s the one that’s getting inflamed, and bacteria’s going in. Therefore, you end up losing teeth.
This whole process of bone actually growing on a surface of titanium was pretty amazing. We actually still don’t understand why that happens. We know it happens predictively, about 98% of the time. It doesn’t have 100% of the time in healthy bone, but the question is what’s so magical about titanium that’s allowing this bone to grow on the surface?
Studies after that original one actually showed it’s not the titanium surface directly that it’s growing to. It’s actually on to titanium oxide. Though titanium is not a material that evokes a foreign body response in the patient, it’s bioactive and bio-inert at the same time. If you take a piece of titanium and you put it out there, it develops a layer of titanium oxide almost instantly, and it’s this titanium oxide that the bone happens to grow to.
It’s a critical part that when the implants are being placed in surgically, that layer of titanium oxide is not disturbed because if you contaminate it, you’re going to find that the bone won’t grow to it. So, it’s very interesting, and it happened to work.
Now, the other interesting part of this whole process was that when you had an implant placed, we wanted to be able to chew on that. Therefore, you had to allow a period for the bone to grow first because if you just put the screw on it and you started to chew right away, you’re not providing that initial stability for the healing to occur, just like a fractured bone. If you start chewing on it right away, you get micromovement, and you’re not going to get a boney union. Just like a fracture site, you get a fibrous connective tissue or fibrous union.
That was a mistake that a lot of dentists made in the past because we would put teeth in there, and we would put something in the jawbone, implant something. We would attach a tooth, and we would say, “Okay, start chewing right away.” We didn’t give it that interim period for the healing process.
The question was, “What’s changed in the last five years?” Well, the whole process of osseointegration is a whole long drawn-out process. Because of that, you have to surgically drill a hole in bone, you place the screw, you cover up the gum, and you let it sit for three to six months, depending on how good the quality of the bone is from what the surgeon feels when he’s placing the implant in the bone.
After that three to six-month period, you go back, and you make a second little connection or cut in the gum and connect this implant to the external surface. Only then can we put a tooth on it. Now, most of us don’t want to wait that long. We want patients that come in my chair want their teeth yesterday. They don’t want to wait six months or eight months to get their teeth.
So, there are times when we can do, and you’ll hear advertisements say about teeth in a day, teeth in 24 hours, or something like that. Yes, it’s possible in very, very selected scenarios where we could put enough number of implants, connect them all in such a way that those individual screws are not moving when people chew on them. Even though they get teeth in a day, they’re on liquid diet for the first month. Right.
There are important things that you need to understand because if you try to hasten the process off, you’re disturbing the concept, the initial idea that bone has to grow onto the surface of the titanium. That’s going to take a while. It’s not going to happen instantly.
The surfaces of these titanium, the oxide layers, have been messed with by companies. They’re trying to make the surface more bioactive. So, instead of sitting there passively and saying, “Hey, sell it bone. Come grow on me,” they’ve got something put on there that’s going to make that process go a little bit faster or attract more cells. So, instead of waiting to six months, you can wait three months. Every implant manufacturer out there claims that their surface is superior to the next one, and it’ll heal in 15 days or two months or two weeks. The basic concept still has to be that until the bone has not grown onto that surface of the implant, you can’t actually load it.
So, what Branemark defined osseointegration was a very simple definition. He said there has to be a direct functional and structural connection between living bone and the surface of a load bearing implant. That’s the critical part, load bearing. What do we want? We want teeth to chew on. If you just want teeth to make them look good or you’re not going to work on it or load them, it doesn’t matter. That is not going to be under function.
So, is this connection between the bone and the implant going to survive loading? That’s the critical part of it. Now, this is a slide that in this day and age is not easy to show, but this is what Professor Branemark showed around in the first few days when they were testing this theory out because after they did it on rabbits, they used beagle dogs. They took out teeth in beagle dogs. They placed titanium implants. They let it heal. They attached a tooth, and in fact, they’re actually showing this poor beagle dog being suspended directly on this implant, just one implant. The entire load of the dog was on that implant, and they were trying to demonstrate as to how solid that implant was.
You think about it. You take a screw, and you put it in wood. Unless you’ve got solid teakwood, the more load that you put on it, the screw’s going to come out because the screw’s just mechanically held in place. There’s no bond between the screw and the wall that you placed it in, and that’s the critical part that an implant is a screw because you want that initial stabilization. You want to be able to screw it in so it’s stable and doesn’t move around during that healing phase, but then you’re not really dependent on the threads. The threads just happen to be there, and in fact, they are an advantage because they increase the surface area for bone-implant contact rather than having a straight flat surface because you’re going in and out. You’re increasing it almost 30%.
When you look a tooth now, on a patient, you’re looking at a natural tooth and an implant, and you can see this a threaded screw of titanium. This screw was placed in the bone. This is the threaded part that I was talking about, and then we have another tooth that’s made about six months later. It actually gets a screw going all the way through, and you can see this little screw which is holding or tightening the natural tooth onto the implant. This screw can then be removed. In fact, if this tooth, which has the porcelain on it, chips or cracks, you can repair it and screw it back in.
The key part of success here is atraumatic surgery and you need a period of healing without load. I’ve already emphasized that. The atraumatic surgery’s very important because you want the bone that’s going to be in immediate contact with this titanium screw to be alive.
If you take a drill, and you drill it at 100,000 revolutions per minute (rpm) because if you drill really fast, what’s happening? You’re generating a lot of heat. If you’re generating a lot of heat, it’s killing the bone cells, and the critical part for us is the bone where these threads are going to go into. We want this part of the bone to be alive. If we drill too fast, too quickly, we’re going to kill that bone. So, you’re going to have a bunch of dead bone around the titanium, and there’s going to be nothing to grow onto it. It’s very critical that the surgeons who are doing this, do this slowly. In fact, the last part of the drilling happens at 5revolutions per minute.
