What every general dentist should know about dental implants

0:00 Why do general dentists need to know about implants?

Hi. Today's lecture is "what every general dentist should know about dental implants." In general, I like to do this lecture for anyone who's a general dentist who wants to know a little bit more about dental implants — what they're all about. The main thing, what I feel, is that all dentists should really know some basic information about dental implants, and unfortunately it's not really well taught at the undergraduate level. I remember back in my days at university in 1996 that indeed this topic was touched on by maybe one lecture. So it's becoming more and more common that patients are having dental implants, and you might find that in your dental practice there are more and more patients coming in from standard routine recalls who might have had implants, in the UK or abroad.

0:53 What are the parts of a dental implant?

So the basics you need to know about dental implants is really the anatomy of an implant. The main area to know is the implant screw itself that goes in the bone. There are over 300 different manufacturers. They generally go by the same system: an implant screw in the bone, followed by an abutment that screws into the implant. That could be an internal connection, as we see here, where the abutment actually has a screw and it goes into the implant. That connection could be a Morse taper, or it could be a square taper. And generally we use something called platform switching, which is a concept where the butt joint between the abutment and the bone is away from the bone — the platform is switched away from the bone. We do that (and current design does that) because what we found is that there's microleakage of bacteria that causes bone loss, and we try to keep that joint away from the bone. So, mainly: you have an abutment and you have an implant, and the main relevance for you is when the patient comes in, you may need to tighten things up — and we're going to go through that today with you.

2:08 What is a healing cap — and what does osseointegrated mean?

So here we see the implant is placed in bone, and you may well have something called a healing cap. An implant surgeon may have placed the implant, and you might have the healing cap — that can be taken in and out after the implant is osseointegrated, which means it's fused with the bone. That particular process takes about four months after placement. So you might see a patient with one of these little caps on, which looks like a button flush with the gum.

2:35 Which hex driver fits which implant system?

When you take it out, you would need to use something called a hex driver. There are various different sizes of hex driver for each different manufacturer of implants. In general the hexes come in different sizes — for example, you could get a long one, which is a 1.2 hex or 1.25 hex — or you can get a specific star-shaped hex configuration for a Straumann implant, and a Unigrip configuration, as you can see here, for a Nobel Biocare implant. So it's very much dependent on the implant system. Now, if you don't know the implant system, and nor does your patient, then you can try out a few hex drivers. In general, what I feel every general practice should have is what we call a multi-system kit, which has both long and short drivers. You've also got to consider that you have to use a torque wrench, and certain manufacturers have different torques of insertion of the abutment. If you are to tighten them up, or have different components — if in doubt, just go finger-tight if you can engage it. If you have any doubt, send it to somebody more experienced who does implants in the local area. But in general, one of the hexes will fit one of the implant systems: the modern implants, say in the last 10 years, all have a fairly universal system, so a universal kit is highly recommended.

4:05 How do you access a screw-retained implant crown?

You might get a patient back who's had a crown, and on that crown you have a hole in it and you see some composite — that crown's been screw-retained, which means the composite should be filling the hole. Underneath the composite you find either a cotton roll or PTFE tape. What that does is protect the head of the implant as you're drilling the composite out. Then you can use something like a bur to take that small piece out, and it'll give you clean access to the head. The reason we place this little plug over the actual screw head is that if you're drilling composite, it can flow into the screw itself and it will block it, so you cannot unscrew it. So that little bit of cotton roll or PTFE tape that we place above the screw head allows us to take it out cleanly once we've drilled all that composite out and get that hex driver on there.

5:05 Screw-retained or cement-retained — which is better?

The main advantage of having it screw-retained is that it's retrievable — however, we do find now that they tend to loosen a little bit more often than not. The other prosthesis is a cement-retained prosthesis, effectively where we put the abutment straight onto the implant, tighten that up, and — like crown and bridge — we cement a crown on top of it. It's gone out of fashion in general because of the advent of what we call cementitis, or inflammation around the cement at the bottom. And it was mostly true, because a lot of people who were restoring implants — be it the surgeons — didn't know where to actually put the margins, which were dictated by the laboratories. The laboratories have models and they put the margins near the head of the implant, and you couldn't get that cement out. But for juxta-gingival or supra-gingival margins, it doesn't pose as much of a problem as people think. The other thing about cement-retained prostheses: they do have advantages, because they generally have a cement luting gap, so they tend to be more passive than the actual screw-retained — unless those are done with a very, very good laboratory using laser welding, etc., to make them passive on the implants. If you have two implants and you create tension with the screwing-down of your prosthesis, that can cause problems, and that can cause bone loss.

6:14 How do you remove a loose cement-retained implant crown?

So the main thing: if it is cement-retained and it becomes loose, it generally means that — unless that crown has been put on with temporary cement (and even then they're quite difficult to take off) — you need to try to pry it off, perhaps giving some LA, using some forceps and a bit of cushioning tissue to try to pry it off. Failing that, it does mean you have to drill through the crown to try to make it screw-retained, or destroy the crown to get to the bottom of the abutment itself. It can be quite a long-winded procedure, and if you're unfamiliar with your implant system, it's something you should really refer on to somebody who does this quite commonly — because it takes a little bit of finesse to actually remove a crown and save an implant. In some cases, if you do drill through the screw head as well, you basically stuff the implant and you need a new implant — so you've got to consider that as a risk and discuss that with patients.

7:17 What does unhealthy peri-implant soft tissue look like?

The other thing you need to know is about peri-implant soft tissue, and this is something you need to see. Here we see a case where we've got a full-arch prosthesis that's evidently cement-retained; there's been some recession, and there's a big lack of keratinised mucosa. One of the big no-nos are these muscle pulls that you can see, and that often leads to recession and repeated infection or pus around the implants.

7:38 Peri-implant mucositis vs peri-implantitis — what's the difference?

It's peri-implant mucositis that we define it as, where no bone loss is seen — but you'll see early pus, no mobility, generally pain-free, like any other "perio." We're also seeing that quite commonly in patients who have pre-existing or untreated perio; they're more susceptible, because those bugs tend to populate those implant surfaces. So pus, inflammation, bleeding — all those sorts of signs that you can see. If you don't see any bone loss, it's early peri-implant mucositis, and again, referral to the person who placed it, or a periodontist, is recommended.

Peri-implantitis is where you've had a longstanding chronic inflammatory process around the implant itself, which has led to bone loss, granulation, invagination of fibroblastic tissues around the actual implant — which could be 360°. This really needs to be assessed by somebody who knows what they're doing, because sometimes we're able to graft the site, disinfect the implant threads, and clean things out. So if you do see a lot of pocketing, a lot of inflammation around the actual implant itself, and your x-rays look like this one where you've got a very classical pocketing kind of bone loss, you need to refer to someone who knows what they're doing, or advise the patient there's a diagnosis you've made of peri-implantitis and you're seeing bone loss. This could be progressive, or it could need intervention.

9:19 How should you monitor implants at recall?

Everything you record during your six-monthly recalls — we generally say you would take an intraoral periapical (IOPA) view yearly. You need to take the baseline pockets at restoration, because pocket depth doesn't mean much around implants — what you've really got to know is what the pockets were originally. So let me give you an example. If you had a tooth — an upper seven — which was an implant, and when you placed the crown you had a lot of thickness of gum, if you probed that and measured the pocket at the point of restoration, you probably have a 10 mm pocket. That doesn't mean it's an infected pocket; it's pocketing like around teeth — it means you just had a lot of gum to start with, very thick gum. So that would be your baseline pocket chart on three, and then you can compare that on a yearly basis to see if it's getting any worse, and look at the obvious signs of inflammation as you go along. You need to compare your intraoral x-rays, again from the point of the restoration placed on the implant, to one year, two years down the line. The clinical evidence leads to the fact that 2 mm of loss a year was acceptable — but nowadays, with modern techniques, we shouldn't be getting any at all: the zero bone loss concept. Another interesting area we can dive into in a lot more detail during our courses.

10:53 What are the warning signs of a failing implant?

So, to summarise, warning signs for failures of implants — originally stated in the clinical evidence by Albrektsson, was pus, bleeding, mobility. Any pain you get, you need to assess what's going on. If it's painful bleeding, peri-implant mucositis or peri-implantitis; mobility may actually be screw loosening, so you have to see the components in sections. It's either from the crown cement lute, to the crown loosening, to the abutment loosening at the abutment level — or, worst-case scenario, the actual implant being mobile. Implants are not like teeth; they're effectively ankylosed onto bone. If the implant is mobile, there is no recovery — that implant has failed. You can't really recover a mobile implant; there's no grading of one, two, three — it's just mobile or not mobile.

11:42 What is the 5-to-5 rule for implant referrals?

It's also really important to know that when you are referring for implants, you keep to a 5-to-5 rule. That means you need 10 teeth — a shortened dental arch — into the occlusion. So if you had a patient with a lower four-to-four who wanted an upper central replaced, you couldn't do it, because there are insufficient teeth to distribute the force. Now, the slightly grey area here is when they have a six in occlusion — with an upper six — and they've got four-to-four; one could argue the force distribution is equivalent to a five-to-five. But it's very much individual, so I would definitely take that into consideration. Furthermore, once you're doing the 5-to-5 rule, understand that patients who just want the one done will be told by their implant surgeon that they need a 5-to-5 implant occlusion.

12:42 Why do occlusion and bruxism matter around implants?

Now, this is a really interesting yet complex area. The first thing we've got to look at is the differences between a natural tooth and a dental implant. What we're seeing more and more is that a natural tooth has proprioceptive fibres — you can feel when you're biting on a natural tooth. You can't really feel when you're biting on a dental implant. You've got to understand that, because of that, your patient could be putting excessive forces through the tooth itself. So natural teeth are associated with high occlusal awareness; the lack of proprioception, and basically the absence of the periodontal shock absorption within the tooth, is often associated with problems with the implant prosthesis breaking, and excessive occlusal trauma onto the patient. So when you are treating bruxists, or patients who come in with a broken tooth, you've got to really think about the occlusion. Always remember that a natural tooth is a better overall, longer-lasting element in someone's mouth than an implant. An implant is really to treat a terminal tooth or a missing tooth; it's not elective — to remove a tooth that could be saved.

14:16 Can dental implants fracture?

So we've got to really work out — implants do fracture. Here we see an implant that's actually broken; it's fractured. Sometimes, when it's loose, or you have peri-implantitis or mobility, it could be the implant that's fractured. We often find that when we try to tighten something up, we're seeing that it's not actually tightening — and then do we have to refer for explantation and replacement of the implant? Implant fracture with bruxism is becoming more and more common these days. Remember, with implant positioning, you can't assess it via a 2D x-ray — you've got to look at this carefully.

15:01 Wrap-up: what's next?

Okay, so there's some basics for you today. We'll continue this series of lectures to give you some more tips as we go along.