A common belief in the full-arch community is that it is wise to place a “backup” implant. Many practitioners place five or six implants every case with the idea that they are building in a backup should a failure occur. The idea is that if an implant fails, they simply remove it, and no additional implant needs to be added to the arch.
However, the problem with this thought process is that, most of the time, even with a backup implant, the failure of any one implant still requires additional implant placement. It is incredibly rare that the additional backup implant actually saves the day and prevents the need for further implant surgery.
As such, the consistent use of a backup implant has the following unfortunate downsides, with often little value actually created for the surgeon or patient:
- Extra, unnecessary surgery for both the patient and surgeon.
- Extra, unnecessary surgical risks.
- Increased surgical and anesthesia time.
- Increased practice overhead (either for the surgeon or passed on to the patient)
- Occasionally, poorly placed “extra” implants can actually prevent and/or hinder the proper rescue of an implant failure.
Let me use some illustrations to highlight how ineffective a backup implant can often be. We will look at two common “backup” configurations.
First, the midline five-implant configuration.
Second, consistent use of pterygoid implants in a six-implant configuration.
Note that a 6-implant configuration is not always used as a backup, and when clinically indicated, I use this configuration in my practice as well. However, I know it is also popular to use this configuration for every surgery, “just in case”. This “just in case” treatment planning is what I am referring to with regard to a pterygoid backup configuration.
The Midline Five-Implant Configuration
In this scenario, a fifth midline implant is added to the traditional four-implant configuration.
This is the classic configuration I see used, with the argument that five implants are better than four because they provide a built-in backup.
I will admit that there is a theoretical benefit of eliminating the anterior cantilever with this technique, although I feel there are better ways to accomplish this. However, cantilever management has nothing to do with an implant backup.
This technique has two variations. One with a midline implant and adjacent implants at the canine position. The other with adjacent implants at the lateral incisor position.
Now here’s where the “backup” thought process breaks down. If we look at the more evenly distributed canine technique and we assume that we have a posterior implant failure, the additional midline implant does nothing for us. We can all agree that it is obvious that we would need to replace it with a new posterior implant or risk having a three-tooth cantilever, which is not biomechanically sound.
Additionally, if we had failure of either adjacent canine, we would also very likely require replacement of an additional implant in this region. Why? The distance between anterior and posterior implants is now so great, likely approaching 30+mm, that a weak point is created in an acrylic temporary restoration or zirconia restoration, increasing the risk of prosthetic fracture. The one caveat would be a titanium bar prosthetic, which would likely be able to span this gap successfully, but is not the restoration commonly used by most providers. Yet again, the additional implant did not prevent the need for implant replacement.
In the third scenario, we have had a failure of the midline implant. However, because our adjacent implants are back at the canine position, we now have roughly a 15-20+ mm anterior cantilever created. This is not wise from a prosthetic standpoint, and necessitates removing and replacing the failed anterior midline implant.
So, despite having placed a “backup” implant, any implant failure scenario still requires replacing an additional implant to maintain sound biomechanical principles. An extra implant was added to every single surgery…and nothing was gained.
Ok, now let’s briefly look at the 5th midline implant configuration, where adjacent implants are at the lateral incisor positions. As we have established already, for the same reasons, failure of a posterior implant site and/or lateral incisor site would necessitate implant replacement.
But, aha! In this scenario, we likely do not need to replace a failed midline implant because the lateral incisor implant positions are located more anteriorly and, if positioned properly, will not significantly increase the resultant anterior cantilever, despite the loss of the midline implant. So it worked!
Wait…but did it? Let’s think about this. We just added an additional implant to EVERY single arch as a backup. But the only implant that isn’t required to be replaced should it fail…is that “extra” implant. Why? Because it was never necessary in the first place….
The 6-Implant Pterygoid Configuration
In this scenario, bilateral pterygoids are added as 5th and 6th implants in the arch. I want to be clear that I use this configuration myself when indicated. And there are actually many reasons a configuration like this may be indicated clinically. However, what I am specifically discussing here is the arbitrary use of this configuration in every case as a backup.
Here’s what this configuration looks like most of the time.
In this scenario, should we have a failure of an anterior implant #7 or #10, it is highly likely that most providers would elect to replace this implant. In an acrylic temporary prosthesis and/or a zirconia prosthesis, the distance between implants would very likely create a weak point in the prosthesis and lead to fracture. Now, while we may be able to argue that you could potentially not replace this implant, most practitioners using those types of prostheses would lean toward wanting support in that region.
Ok, what if our posterior 2nd bicuspid/molar implant locations failed? We run into a similar issue as stated above. The distance between anterior implants and posterior pterygoid implants is now likely somewhere between 35- 45+ mm, depending on arch size. This will very likely create a fracture point in an acrylic or all-zirconia prosthetic.
Ok, but wait…we have one scenario in which we will have successfully avoided needing to replace a failed implant! If either pterygoid implant fails (assuming a remaining posterior implant site of 2nd bicuspid or molar), we do not, in fact, need to replace that implant! But, yet again, if we really think about why we do not have to replace this implant, it is because it was never necessary in the first place…
While treatment planning is not always this simple and straightforward, and we can find indications for multiple different implant configurations in full-arch surgery, as a general rule, I follow the guidelines above. I feel it is difficult to make a sound argument for a backup implant when we really break down clinically how failed implants need to be managed from a surgical and prosthetic standpoint.
I challenge you to rethink this popular habit in your practice.
P.S.
Be sure to check out tomorrow’s newsletter article to see the shockingly high cost and increased overhead the “backup technique” creates for your practice.