“It is impossible to talk about predictability before looking at long-term data."

Rehabilitation of edentulous patients with severely atrophic maxilla is still one of the most challenging clinical indications. In this interview, Dr. Rubén Davó sheds light on the long-term prognosis of quad zygoma protocol using the anatomy-guided approach, where the challenges of zygomatic implant therapies lay, and how he sees the future of this treatment option.

Q: Dr. Davó, please tell us about your recent publication, “Long-term survival and complications of quad zygoma protocol with anatomy-guided approach in severely atrophic maxilla: A retrospective follow-up analysis of up to 17 years”.

In short, this was a retrospective cohort study to look at the long-term outcomes of the quad zygoma protocol (QZP).¹ 56 consecutive patients with severely atrophic edentulous maxilla and insufficient bone height and width bilaterally underwent rehabilitation with the QZP between 2006 to 2021 and were immediately loaded with acrylic prostheses. Our most important learning from all analyses was the predictability of QZP, as for many years, the question about the long-term outcomes of QZP was still there. Based on this study, the survival rate of implants after 17 years of follow-up (mean follow-up time of 8.8 ± 3.9 years) was 97.7% and the successful rate for the definitive prosthesis was 98.2%. I think these success rates are impressive, and better than most long-term data published for treating the edentulous maxilla. Of course, like in any real clinical setting, some complications occurred, but they could be resolved, and patients were satisfied.

Surgical view of QZP in a patient with previously failed sinus floor augmentation and failed guided-bone regeneration in the maxilla prior. Creative Commons Attribution © Drs R Davo, Fan, Wang & Yiqun open access Clin Implant Dent Relat Res

Q: Anatomy-guided approach: what does it mean?

When I started with zygomatic treatment in 1999, everybody used the intra-sinus protocol which was established by Brånemark. It was around 2004-2005 that some clinicians started to place zygoma implants outside of the sinus for the first time, to have more crestal emergence of the zygomatic implant, and also to reduce the rate of sinus complications, at least theoretically.

When I started in 2006 with the quad-zygoma approach, together with Chantal Malevez, we realized the most logical protocol is the one that adapts the anatomy, as the maxilla can have different curvatures in different patients. To follow a mainly prosthetically guided or driven approach, and or to use always the same technique in all the patients, could lead us to unfavourable circumstances, especially in quad zygoma patients. In the severely atrophic maxilla, the way of resorption is very different from one patient to another, and even in one patient, one side can be different from the other. In 2006, we started a prospective study on immediate function quad-zygoma using the anatomically guided approach,² which means depending on the different patient anatomies, we used intra-sinus, extra-sinus, and/or sinus slot technique (lateral wall of the maxilla), with three main goals in mind: 

• Having anchorage in the zygomatic bone
• Having the most crestal emergence as possible
• Avoiding the sinus cavity whenever possible

I experienced fewer complications when following this protocol, instead of the Brånemark approach, even if we do not have comparative data to prove this claim. Since 2006, in all my publications and in all courses, I have given around the world, I showed the anatomy-guided approach, even before it was called with this name. In ITI zygoma consensus 2023 our work on quad zygoma since 2006 was categorized in the anatomy guided approach (AGA). ⁵

In the study, more than 90% of the anterior zygoma implants were placed in extra-sinus.

Q: Did you use zygomatic implants with different designs?

90% of the implants in this study were Nobel Biocare zygomatic implants. The main reason was that our study included patients from 2006, when only Nobel Biocare and Southern Implants offered zygomatic solutions, and no one else. Also, Nobel Biocare was committed to scientific and clinical research from its inception and supported innovating concepts and solutions, that are clinical trends of today. Anatomically guided quad-zygoma was developed in the Nobel Biocare environment. I was involved, through my PhD thesis and my early work,^2-3 in the development and FDA approval of Immediate Function for zygoma implants by Nobel Biocare. It is fair to say, it is because of the Nobel Biocare investment in science, that we can talk about the safety and predictability of immediate loading/function of zygomatic implants.

Q: Does the choice of the implant system and premium design contribute to the predictability of the outcome?

To talk about the predictability of a solution or a medical device, we should know the long-term behavior. The QZP was questioned and discussed for years and years, even by many zygoma key experts, and only now, after publishing this long-term study,¹ we can talk confidently about the predictability of the protocol. Today, we know a lot about the behavior of the Nobel Biocare zygomatic implants, tested in different modalities and in patients for a long period of time, as the manufacturer has supported many clinical studies. Such long-term evidence for manufactured zygomatic implants by most companies is not available yet. In the long run, we do not know how a zygoma implant with a narrower diameter, for instance, works in patients with severely atrophic maxilla. Sometimes I miss the scientific mindset today. Many studies designed to prove the predictability of different products and protocols are poor, sample sizes are underpowered, or follow-up times are not representative.

Q: What were the most frequent complications in QZP? How were they fixed?

Facial swelling is the first symptom when patients realize something is not correct and they contact us. Facial inflammation occurred in 35% of the cases at any time of their evolution. Sometimes the origin of inflammation has an easy fix, like when it is triggered by the positioning of the prosthesis. And sometimes it is more serious, like sinusitis. CBCT showed sinusitis in seven patients, of which five were treated with antibiotics and anti-inflammatory drugs. Nasosinus surgery (FENS) was necessary for the other two patients. The other complications were soft tissue-related, like recession, which occurred mostly with older implant generations. To avoid soft tissue-related complications, surgical skills, soft tissue planning, and placing the implants in the correct position are crucial. It was interesting to see that not all sinus complications happened when implants were placed intra-sinus. We also had sinus-related complications with extra-sinus implants. These observations confirm the origin of sinusitis is complicated and cannot be linked only to the surgical technique. In my experience, once the sinus membrane is opened, independent from the intra- or extra-sinus positioning of the implant, we should monitor the patient more carefully, and inform them about the possibility of sinus related complications so they commit to regular control visits.

Q: What are the best strategies to prevent zygomatic complications?

The key to success is good planning. It starts with a 3D virtual reconstruction of the patient beforehand to precisely analyze the geometry of the sinus cavity. Each zygoma patient is different from the others - the foundation of the anatomy-guided approach that I taught in my courses since 2006. The implant position should be individual based on each patient's anatomy, to avoid protrusion, or to be placed in the right crestal or palatal position. Also, proper soft tissue planning is crucial, given that the zygoma patients have severely atrophic maxilla, and the residual alveolar bone might resorb in the next 2-3 years after loading.

Q: Do complications impair the quality of life? What does the OHIP show?

Please keep in mind where the zygomatic patients come from. These patients have usually experienced other types of complications in the past, e.g. implant failure, graft failure or major accidents, trauma, and cancer. They can accept all risks associated with sinusitis or soft tissue retraction, which are all treatable, for the huge social, psychological and functional benefits of having an immediate fixed denture. In our study, we were surprised to see that even patients with complications reported a normal oral health-related quality of life, similar to the general population. And the normalization of the Oral Health Impact Profile (OHIP) was maintained over time, even for patients who experience complications. The mean score of the OHIP-14 questionnaire was 1.7 ± 2.6 with a follow-up period of 9.0 ± 4.1 years.

Q: Would you be able to share a patient story that is unique to you?

Every patient’s story is as unique as they are. I often talk about one of my first QZP patients, a 40-year-old who had lost her teeth after a scooter accident at the age of 17. It was very shocking for me to listen to her story, and the impact of the trauma on all aspects of her life. Having no teeth, and no maxilla to receive a fixed denture can truly destroy a life. Once after her treatment in 2006, she told me, “I think I am even more intelligent today.” I did not understand how a fixed denture could make someone intelligent and asked why. She said, “If you had to spend all your energy keeping your denture in place every single time you are with people, would you be able to think at all?”. Edentulous solutions are not only about biting on an apple as most of the publicity shows. The psychological downsides of edentulism can impact our social life, push us to solitude, and eventually reduce our life expectancy. Training and education is fundamental to keep on spreading these concepts and I firmly believe that digital workflow and guided surgery (especially dynamic guided surgery) will facilitate these procedures to many more practitioners and patients.