#Full-Arch 29. Nov 2024

Zygomatic implants: A paradigm shift in the treatment of patients with severely atrophied maxilla

Implant rehabilitation of patients with severely atrophic maxillae was always extremely challenging, and the number of predictable treatment options was limited. If at all possible, the procedure would involve extensive bone augmentation along with the placement of endosseous implants and a supporting prosthesis, which is complex, time-consuming, and costly for patients. Until 1998, when an improved treatment option was developed and described.

Marcin Maj

A scientific review.

Early developments

Zygomatic implants were first introduced by Per-Ingvar Brånemark in 1998 for maxillectomy patients and later adapted for edentulous patients with severely atrophied maxillae1.

Placement methodologies evolved to the concept of 2 posterior zygomatic implants (one in each quadrant) and the "quad zygoma" approach with four zygomatic implants (two for each quadrant)t, allowing loading within 24 hours. Early studies by Brånemark et al. showed a 96% rehabilitation rate with 52 implants in 28 patients over at least 5 years. However, despite success, complications like rhinosinusitis and soft-tissue infections were common2. To reduce invasiveness, Stella and Warner proposed the “slot technique” in 2000, using a crestal entry to eradicate the problem of bulky prostheses3. In 2006, Migliorança et al. reported outcomes of 150 externally positioned zygomatic implants in 75 patients, reducing rhinosinusitis risk4. Aparicio’s group later proposed an exteriorized implant pathway to avoid sinus perforation5, though buccal soft tissue recession was observed6. In an extension of other studies, Malo et al. introduced a modified extra-maxillary technique, requiring alveolar ridge contouring, which sometimes caused sinus infections7. This led Aparicio to introduce and describe the anatomically guided ZAGA approach in 2011 following his long-term experiences with similar complications while placing zygomatic implants in patients with severe atrophy8.

Patient’s anatomy first, the ZAGAclassification

The zygomatic anatomically guided approach (ZAGA) is an evolution of the above methods devised to provide patients with long-term, complication-free, predictable implant solutions, whatever their anatomical situation8. The rationale is that patients present with differing anatomical variations, and even site variations, within the same patient. Hence, the need to have an adaptable solution rather than a one-size-fits-all protocol is paramount. Treatments can be intra-, extrasinus, or a combination of both. Aparicio developed an anatomical evaluation process known as ZAGA classification to aid the right treatment protocols in any given situation. Initially, in a cross-sectional survey9 based on 200 sites across 100 patients, he identified and classified five anatomical pathway situations as ZAGA 0-4. Classifications range from ZAGA 0 (straight lateral maxillary wall with the implant platform on the crest and the middle portion inside the sinus) to ZAGA 4 (extreme resorption of the maxillary sinus with or without significant concavity of the lateral sinus wall). This allowed for a better understanding of the shape of the maxillary wall and how it would predetermine the implant pathway9.

Such classification aims to provide the right prosthetically driven implant pathway to prevent long-term complications. The implant path is studied to achieve this aim, and three key areas are defined: the anchor zone, the antrostomy zone, and the zygomatic implant critical zone (ZICZ). As a result, everything from the initial incision and the implant path to the closing of the soft tissue is individually tailored, depending upon the classification of the patient. The classifications were identified as ZAGA 0-4 and would later be branded with an “A” or a “P” to determine anterior or posterior atrophy.

Therefore, the anatomically guided approach is more than just a treatment protocol; it’s a philosophy where everything, including the tools and technologies, is adapted to the patient’s anatomy. One such adaptation is the redesign of the zygomatic implant itself.

ZAGA Flat and ZAGA Round zygomatic implants

Because a typical zygomatic implant pathway involves the atrophic alveolar bone, the maxillary wall, and the zygoma bone, such a clinical picture may present greater difficulties in treatment planning and implementation than a conventional implant route. To overcome those obstacles and facilitate the treatment, 2 different topographies of zygomatic implants (ZAGA Flat and ZAGA Round) were proposed, designed, and developed. Both aim to improve treatment outcomes by matching the patient's anatomy, ensuring a maximum anchorage in available bone.

In clinical cases, with the presence of sufficient bone around the implant platform allowing for better occlusal force distribution, Straumann® Zygomatic Implant ZAGA Round is recommended. The bone around the implant platform will enhance occlusal force distribution and connective soft-tissue attachment, which is crucial for the stability of the facial gingival margin. On the other hand, in cases of extreme maxillary resorption and sinus wall concavity (ZAGA 4) or total/partial maxillectomy, the implant needs to be positioned below the vestibular soft tissue, making vestibular dehiscence difficult to prevent. To reduce this risk, the Straumann® Zygomatic Implant ZAGA Flat is the ideal choice. Its flattened shaft allows deeper submersion in the bone crest, and partial coronal threads maximize bone-to-implant contact and seal the bone wound. This design minimizes soft-tissue irritation and exposure, ensuring high anchoring despite severe atrophy and promoting a favorable long-term soft-tissue response.

Clinical performance of Straumann® Zygomatic implants

The body of evidence regarding the clinical performance of ZAGA Flat and ZAGA Round implants is continuously growing and demonstrating they can be considered a viable treatment option for patients with severely atrophied maxilla. When used in conjunction with the corresponding channel and tunnel osteotomies, research shows that after an average follow-up of 18.8 months utilizing the Offset, Rhinosinusitis, Infection, and Stability (ORIS) criteria, rehabilitation with ZAGA flat and ZAGA round implants resulted in no surgical complications, making them a viable treatment option when restoring atrophic maxillae10. Moreover, a recent non-interventional study by Aparicio et al. highlights the clinical effectiveness of ZAGA Round and Flat zygomatic implants in patients with severely atrophied maxillae. In this study, the patients receiving 2, 3, or 4 ZAGA implants were followed for up to 53 months, with an average follow-up of 46.5 months. This effectiveness of the treatment approach is reflected in a 100% survival rate for both implants and prostheses, along with minimal changes in the frequency of late complications compared to earlier one-year follow-up11.

The ITI gets into the game

Finally, in 2023, a meeting of 25 ITI experts in the field of zygomatic implants took place in Frankfurt, Germany, to provide consensus statements and standardized clinical recommendations for using zygomatic implants12. Three systematic reviews13–15 and one narrative review16 were compiled to address focus questions based on indications, post-surgical complications, long-term survival rates, and biomechanical principles under immediate loading. As the outcome, 21 consensus statements were substantiated, focusing on indications, quad zygoma, loading protocols, surgical risks, biological and technical complications, and PROMs. Additionally, 17 clinical recommendations were formulated around planning, case selection, diagnostics, surgical aspects, complications, restorations, and outcomes, including clinical advantages and survival rates. The meeting also highlighted recommended areas for future research, namely the development of standardized reporting data, further evaluation of implant geometry, and more randomized controlled trials for better management of sinusitis and oroantral communications. The experts also recommended continuing longer-term and multi-center case studies on zygomatic implants in patients with complete maxillary loss and congenital and resection-related defects. Establishing standardized clinical recommendations and consensus statements by leading experts provides a strong foundation for these procedures' continued success and refinement. This means that patients with little quality of life before may now experience full dental rehabilitation using proven or trusted techniques and protocols that surgeons can follow.

Conclusions

In conclusion, zygomatic implants offer a viable treatment option for patients with severely atrophic maxillae. They have demonstrated high short- and long-term survival rates, making them a reliable solution and preferred choice for complex cases where extensive GBR could be avoided. Consequently, patients report high satisfaction levels due to significant improvements in chewing functionality and esthetics17–21. The future of zygomatic implants looks bright, with a commitment to innovation driving the field forward. With ongoing research and the development of new techniques, zygomatic implants will continue to evolve, providing reliable and tailored treatment options, improving patients' quality of life, and equipping dental professionals with the tools and knowledge to deliver optimal care.

References:

  1. Brånemark PI. Surgery and Fixture Installation: Zygomaticus Fixture Clinical Procedures. 1st ed. Goteborg, Sweden: Nobel Biocare AB; 1998. p. 1 
  2. Brånemark P, Gröndahl K, Öhrnell L, Nilsson P, Petruson B, Svensson B, et al. Zygoma Fixture in the Management of Advanced Atrophy of the Maxilla: Technique and Long-Term Results. Scand J Plast Reconstr Surg Hand Surg. 2004;38:70-85. 
  3. 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;15(6):889-93. 
  4. Migliorança RM, Coppede A, Dias Rezende RC, de Mayo T. Restoration of the edentulous maxilla using extra-sinus zygomatic implants combined with anterior conventional implants: a retrospective study. Int J Oral Maxillofac Implants. 2011;26:665-72.
  5. Aparicio C, Olivo A, de Paz V, Kraus D, Luque MM, Crooke E, et al. The zygoma anatomy-guided approach (ZAGA) for rehabilitation of the atrophic maxilla. Clin Dent Rev. 2022;6:2. 
  6. Wu XY, Shi JY, Buti J, Lai HC, Tonetti MS. Buccal bone thickness and mid-facial soft tissue recession after various surgical approaches for immediate-implant placement - A systematic review and network meta-analysis of controlled trials. J Clin Periodontol. 2023;50(4):533-46. 
  7. Maló P, Nobre Mde A, Lopes I. A new approach to rehabilitate the severely atrophic maxilla using extramaxillary anchored implants in immediate function: A pilot study. J Prosthet Dent. 2008;100:354-66. 
  8. Aparicio C, Polido WD, Zarrinkelk HM. The Zygoma Anatomy-Guided Approach for Placement of Zygomatic Implants. Atlas Oral Maxillofac Surg Clin North Am. 2021 Sep;29(2):203-231. 
  9. Aparicio C. A proposed classification for zygomatic implant patients based on the zygoma anatomy-guided approach (ZAGA): a cross-sectional survey. Eur J Oral Implantol. 2011;4(3):269-75.
  10. Aparicio C, Polido WD, Chow J, Davó R, Al-Nawas B. Round and flat zygomatic implant effectiveness after a 1-year follow-up non-interventional study. Int J Implant Dent. 2022;8. 
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  13. Polido WD, Machado-Fernandez A, Lin WS, Aghaloo T. Indications for zygomatic implants: a systematic review. Int J Implant Dent. 2023;9(1):17. 14. Kam
  14. merer PW, Fan S, Aparicio C, Bedrossian E, Davo R, Morton D, et al. Evaluation of surgical techniques in survival rate and complications of zygomatic implants for the rehabilitation of the atrophic edentulous maxilla: a systematic review. Int J Implant Dent. 2023;9(1):11. 
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  16. Bedrossian E, Brunski J, Al-Nawas B, Kammerer PW. Zygoma implant under function: biomechanical principles clarified. Int J Implant Dent. 2023;9(1):15.
  17. Tuminelli FJ, Walter LR, Neugarten J, Bedrossian E. Immediate loading of zygomatic implants: A systematic review of implant survival, prosthesis survival and potential complications. Eur J Oral Implantol. 2017;10 Suppl 1:79-87.
  18. Boyes-Varley JG, Howes DG, Lownie JF, Blackbeard GA. Surgical Modifications to the Branemark Zygomaticus Protocol in the treatment of the severely resorbed Maxilla: A Clinical Report. Int J Oral Maxillofac Implants. 2003;18:232-7.
  19. Wang F, Monje A, Lin GH, Wu Y, Monje F, Wang HL, et al. Reliability of four zygomatic implant-supported prostheses for the rehabilitation of the atrophic maxilla: a systematic review. Int J Oral Maxillofac Implants. 2015;30(2):293-8.
  20. Chrcanovic BR, Albrektsson T, Wennerberg A. Survival and Complications of Zygomatic Implants: An Updated Systematic Review. J Oral Maxillofac Surg. 2016;74(10):1949-64.
  21. Sáez-Alcaide LM, Cortés-Bretón-Brinkmann J, Sánchez-Labrador L, Pérez-González F, Forteza-López A, Molinero-Mourelle P, et al. Patient-reported outcomes in patients with severe maxillary bone atrophy restored with zygomatic implant-supported complete dental prostheses: a systematic review. Acta Odontol Scand. 2022;80(5):363-73.