Is Zygomatic Implant Slot Technique a Russian Roulette?
Yes, the installation of zygomatic implants by the Stella Technique is a Russian roulette.
Perhaps you were lucky in your first cases where you followed the "success recipe" and had an excellent bone anchorage of the zygomatic implant in the body of the zygoma.
However, randomness and probability will sooner or later be expressed, and you will install the zygomatic implant too far or even dangerously out of the ideal position, despite having strictly followed the technique. If you believe that this finding does not make sense, I invite you to read this post and then draw your own conclusions.
The original technique for installing zygomatic implants proposed by Branemark recommended installing a totally intra-sinus zygomatic implant path. This hindered the surgical procedure and promotes a palatal displaced position prosthesis screw.
Stella (1) proposed the Slot Technique for installing zygomatic implants. In this technique, we would have a possible improvement in the emergence of the prosthetic screw, a disposition of the antrostomy that can be obliterated by the implant installation itself, and a greater facility for the surgical execution technique.
If we compare the Branemark technique, where the installation of the zygomatic implant was totally intra-sinus, the Stella Technique really was a significant advance and, in fact, facilitated the surgical approach.
But there is a hazardous one.
This attempt to create reproducible anatomical references to "facilitate" and standardize the surgical technique can cause significant problems in zygomatic implants' proper direction.
The Stella Technique recommends the creation of a slot in the region of the zygomatic pillar. Following this slot, the zygomatic implant drill entrance into the body of the zygoma would happen naturally.
In the image below, we can see the complete sequence, where initially the demarcations are made, the points are joined to create the slot, and in the sequence, the drill is introduced for drilling into the zygoma body until the complete exteriorization of the drill occurs through the outer bone cortical of the zygomatic bone body.
The right direction of the drill following the slot may do happen, but it can also lead the surgeon to introduce the drill into the infratemporal fossa or even to perforate the posterior wall of the maxillary sinus.
The violation of the infratemporal fossa can have several consequences and even some indications, and I explain this subject in more detail in this post. The surgical installation of the zygomatic implant without understanding this concept can be problematic.
Perforation of the maxillary sinus's posterior wall and installing the zygomatic implant in this place makes the implant unstable and mobile when receiving pressure, even when it is osseointegrated. This is because the anchorage of the zygomatic implant in such cases is extremely low.
Despite that, I received a patient in my clinic with rehabilitation with a zygomatic implant over 10 years old and complaining to the prosthetist that the zygomatic implant was swinging.
Take a look at the right position of the zygomatic implant concerning the slot. It seems perfect. The surgeon strictly follows the principles of the Slot Technique.
But, on CT scan, it was clear that the zygomatic implant installation was entirely outside the zygomatic bone! It was inside the infratemporal fossa, and both zygomatic implants were only osseointegrated in the thin cortical of the posterior wall of the maxillary sinus.
In these cases, the treatment choice is to remove all implants and install new zygomatic implants with the proper planning and execution, placing the implants in maximum bone availability in the zygoma bone body.
Many surgeons make the basic mistake of worrying too much about anchoring the zygomatic implant in the alveolar ridge region, the anterior wall of the maxillary sinus, and/or zygomatic buttress.
Even with the anchorage of the zygomatic implant in this region, this anchorage is small, in most cases, negligible compared to the possibility of bone anchoring of the zygomatic implant in the zygomatic bone body.
Stella's technique passes this false sensation to the surgeon, where filling the slot with the zygomatic implant gives us a feeling of increased bone anchorage, which is not always true.
Another problem with the Stella Zygomatic Implant Technique.
Believing that the Slot will always lead you to the region of maximum bone availability in the body of the zygoma bone is like believing that you can always install 8mm implants in the posterior part of the mandible because you read a review that said the average distance from the mandibular canal to the top of the crest is 7mm. You would be right in some cases and wrong in others. Using the Stella Technique, you are making use of that same way of thinking.
The most important, and that needs to be repeated systematically, is that the zygomatic maxillary region's anatomy is hugely variable between individuals and even in the same individual. Following a "success recipe" when installing the zygomatic implant is like playing Russian roulette.
It is not uncommon to install a totally extra-maxillary (extra-sinus) zygomatic implant on one side and the position of the zygomatic implant on the opposite side to follow a completely different path.
The ideal position of the zygomatic implant is defined taking into account two factors:
1) the position of the zygomatic implant head in the region of the residual ridge
2) the area of maximum bone availability in the zygomatic bone body
When these two factors are considered, it is clear that the personal choice of a specific technique is not possible, whatever it may be, but the patient's anatomy.
It is easy to give a theoretical class on zygomatic implants based on theory only. But in practice, things are entirely different.
The surgeon learns the Slot technique, and in his first zygomatic implant surgery, he could anchor the implant with an excellent bone insertion and high torque. So, he believes that he discovered the path to "infinite success," that he learned the infallible technique, and that from now on, just follow the same technique, and everything turns out just OK.
He goes to the second surgery, follows the same technique, and his osteotomy falls entirely in the infratemporal fossa, and anxiety sets in. At that moment, he doesn't know what to do anymore because his foolproof technique proved to be fallible for the case in question. Guess how I learned this? Going through it all.
It was there that the ZYGOMA 2.0 concept started to be developed.
Most surgeons give up the zygomatic implant because they believe it is difficult and "not very predictable." In fact, they are victims of a flawed teaching process of the zygomatic implant technique.
That is why we believe so much in need to expand the surgeon's way of thinking when it comes to zygomatic implant placement. It is essential not to be attached to dogmas based on medium distances or "all size fit all" formulas.
Of course, planning in 3D software is more complicated; it takes work, mental energy, and time. It is much easier to follow a standard formula. It is easier just to take a look at the panoramic radiograph.
However, the installation of a zygomatic implant is the most challenging procedure in implant dentistry. It is not for lazy surgeons. In the same way that orthognathic surgery was only predictable with virtual planning, the same can be said about zygomatic implants.
Subsequently, installing externalized zygomatic implants (extra sinus technique) was introduced and brought a significant advance in installing zygomatic implants.
But even so, the anatomy is what ends up telling us the best positioning of the implants. After understanding and experiencing this concept, we will see cases where it is totally possible to position the zygomatic implants completely outside the maxillary sinus. Still, already in others, the implants will be entirely inside the maxillary sinus, inevitably.
The individualization of each case is essential. Merely choosing a technique and applying it in all cases does not make the least sense from a prosthetic, anatomical, and surgical point of view.
The surgical procedure for installing a zygomatic implant is a science. You need to use technology to optimize results; otherwise, we could playing Russian roulette. And as we know, sooner or later, in Russian roulette, the worst will always come; it is only a matter of time.
REFERENCES
(1) Stella JP, Warner MR. Sinus slot technique for simplification and improved orientation of zygomaticus dental implants: a technical note. Int J Oral Maxillofac Implants. 2000 Nov-Dec;15(6):889-93. PMID: 11151591.
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