Zygomatic Implant Tissue Dehiscence
When the extra sinus zygomatic implant technique started, many questioned themselves about the potential problems with these exposed implants threads.
What has been seen is that these exposed threads do not harm the stability of osseointegration of the zygomatic implants.
At first, we can believe that this is just a problem caused by the lack of keratinized mucosa around the zygomatic implants; however, even in cases where a reasonable range of keratinized tissue is achieved, such dehiscence might occur.
See the case below, recently operated, where a large amount of keratinized tissue was displaced into the buccal region of the implant and, in just three months, there was already a substantial decrease in the amount of gingiva in the same area, which tends in the long term, evolving to exposed implants threads.
According to Medrossian(1), in cases of ZAGA 4, the potential soft tissue dehiscence around the zygomatic implant is not preventable, and, preoperatively, the patient must be aware of this possibility and be instructed to perform adequate hygiene in such situations.
Should these clinical situations be considered complications, or are they just a kind and side effect of the extra sinus technique?
When such situations are evaluated by professionals who do not deal with the zygomatic implant, these professionals generally are promptly concerned with such conditions and even end up using such findings to criticize the zygomatic implant technique. It is because they apply the same way of thinking as conventional implants for the zygomatic implant.
In a conventional implant, if you have a 7mm implant, but on clinical examination, you identify that there is around 2mm of bone exposure, you automatically believe that there is only 5mm of bone insertion. However, this mindset does not apply to zygomatic implants, and you will understand why now.
When we have a completely extra sinus zygomatic implant installed, the predominant bone insertion (and osseointegration) will occur in the portion of the final third of it, and the soft tissue will be covering the rest of the implant up to the cervical region.
If we have tissue dehiscence with exposure of some cervical threads, this does not compromise the bone insertion of the zygomatic implant. Bone insertion is entirely distant from buccal soft tissue dehiscence. Therefore, we can say that:
Threads exposed in a zygomatic implant do not compromise the osseointegration of it.
The only disadvantage of these situations is that maintaining hygiene can be difficult, especially in implants with surface treatment. Hence the importance of advising patients to use extra soft brushes and oral irrigators with care.
If the patient has complaints about the hygiene capacity or some complication, further intervention might be required.
One way to prevent tissue dehiscence in a zygomatic implant is to cover the threads with the buccal fat pad right after the implant installation.
According to Guennal and Guioll(2), of the 25 patients in which this procedure was performed, all of them had a total absence of dehiscence during the follow-up period.
Thus, it is clear that such conduct is valid, especially in risk situations where there is already a lack of keratinized gingiva and in smoking patients.
The tissue trauma due to the frictional movement of the mucosa over the implant threads during chewing and brushing is, in our view, one of the main triggers for the emergence of such dehiscence.
A possible solution to be investigated would be to modify the zygomatic implants' cervical design, leaving them more receptive to tissue accommodation. In 2018, we proposed a new implant design, which is called Slim Zygomatic Implant (patent pending).
In addition to this concavity that precedes the cervical region of the implant, this implant would be totally smooth, without any surface treatment because, from our point of view, osseointegration is not and has never been a problem when it comes to the zygomatic implant, as we are anchoring the implants in a bone with a large amount of cortical bone. In such situations, we know that the surface treatment does not bring so many advantages.
In the cervical region, we could accept that the "new normal" of zygomatic implants fully externalized, in the long term, it would be some degree of buccal soft tissue dehiscence.
Assuming that possibility, if we have a zygomatic implant fully optimized for such an occurrence, we would have some benefits. It would be ready to maintain hygiene more easily, both by design and by polishing. It would be a "tissue friendly" zugomatic implant.
There is also the possibility that its anatomical design prevents the occurrence of such tissue dehiscence.
Such probabilities will only be clarified with scientific investigation.
References
1. Bedrossian, E. & Bedrossian, E. A. Prevention and the Management of Complications Using the Zygoma Implant: A Review and Clinical Experiences. Int J Oral Maxillofac Implants 33, e135-e145, doi:10.11607/jomi.6539 (2018). https://pubmed.ncbi.nlm.nih.gov/30231096/
2. Guennal, P. & Guiol, J. Use of buccal fat pads to prevent vestibular gingival recession of zygomatic implants. J Stomatol Oral Maxillofac Surg 119, 161-163, doi:10.1016/j.jormas.2017.10.017 (2018). https://pubmed.ncbi.nlm.nih.gov/29107123/