Posts Tagged screw fracture

Implant Risk Factors: Implant Fracture

Any experienced implant practitioner would have seen a good number of failures. From a surgical standpoint, success rate can be well over 90%. It’s not difficult to achieve such success rates because all that is needed to determine success of the implant is osseointegration - the process whereby bone grows onto the implant surface and “fuses” with it. This implant can then be loaded with a crown.

What happens after loading? It’s just like what happens after marriage. Nobody can be certain as many factors come into play. There are patients with poor oral hygiene. There are patients who grind their teeth at night. There are patients who love to chew on bones to get to the marrow. There are patients who abuse their teeth in ways we can’t even imagine. Practitioners who handle restorations and follow up over a period of time will be able to tell you that implants restorations can be highly problematic over the long term. Some patients will be quite happy with their implant restorations. Some will need to see their dentist every few months for some adjustments. The most common problems are screw coming loose, gum inflammation, bone loss, exposed threads. Sometimes, we see porcelain fracture. Sometimes, we get fractured abutments, fractured screws and even fractured implants. Practitioners who have not had any of such problems on their hands probably haven’t done enough implants.

Yes, in spite of all the hype about implants lasting a lifetime, some implants do fracture after just 3 years and here is one of them. It’s one of the most uncommon complications and this is my first fracture case. As usual, the manufacturer blames it on everything except the product. But if we take a close look at the design of the implant, it is not difficult to see why this American implant might be more likely to fracture than other systems.

fracture1

What wasx my reason for using this implant system? The patient has a deep bite. We’ve often been told that a fractured screw is the worst disaster you can face and implant screws are pretty small. This system does away with screws and employs a phenomenon called cold welding to hold the abutments inside the implant wells. We have been told by the experts that if biting forces were excessive, screws can break, but for this system, the abutments would just pop out. Replacing the abutments can be as simple as just tapping it back in place. They made it sound like an excellent system for patients who are bruxers, or in this case, someone with a deep bite.

fracture2
Here with are with a fractured implant. The abutment post was still securely cold-welded to the fractured top part of the implant when the restoration was removed. The bottom tip of the fractured implant was still firmly embedded in bone. Something is not right. Let’s take a close look at the fractured cross section. This implant is 3.5mm in diameter. Most implants have tiny threads on their surfaces. This American system boasts of a radiator fin design and a whole list of merits based on it. However, if we look at the radiator fins - and this is the first time I had a chance to see the cross section of the implant I’ve been using for years, we’ll see that the fins run quite deeply into the body of the implant, unlike threads which only score the surface.

fracture31

What is the implication? Instead of 3.5mm of solid titanium, we have only 1.6mm of solid titanium at the core beneath the implant well. This is shocking news to me. I didn’t know that the implant’s weakest point is that weak. True enough, the implant fractured at the 1.6mm juncture between 2 fins, just past the bottom of the implant well. Far from the system of choice for patients who are bruxers, this may well be the system to avoid in such cases.

In this age of compulsory continuing education where course directors and expert speakers can have vested interests in a system, dentists are as victimised as patients when fed with biased information from sponsors and manufacturers.

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