Zygoma implants are an alternative for rehabilitating severe maxillary atrophy. Since 2004, when Prof. Branemark first reported the long-term findings on zygomatic implants using the original intra-sinus approach, various surgical techniques have been introduced. In 2006, an anatomy-guided approach was developed, applying different implant trajectories based on alveolar atrophy levels and sinus concavity. The purpose of this review is to clarify the existing techniques and long-term outcomes of ZI rehabilitation over the past 20 years. Additionally, it aims to enhance the quality of current practices and identify gaps in the understanding of ZI treatment for future studies.
Key points
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The high survival rate of zygomatic implant in patients with severely atrophic maxilla has been consistently reported in long-term investigations.
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Zygomatic implant treatment provides several benefits to patients, such as avoiding extensive grafting, facilitating immediate functional loading, and normalizing the oral health-related quality of life.
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Utilization of the surgical approach based on the patient’s individual anatomy is fundamental to achieving ideal prosthetic outcomes and avoiding certain complications.
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The most commonly reported complications are sinusitis, orofacial inflammation, and soft tissue recession. Majority of these complications can be properly managed without affecting implant longevity.
Background
In 2004, Prof. Branemark first reported the long-term findings on the use of zygomatic implants (ZIs) in the rehabilitation of the edentulous atrophic maxilla. The innovative implant design was described as a “zygoma fixture” primarily anchored in the zygoma bone, inserted via an intra-sinus approach. In this study, a classic approach was indicated for patients with insufficient posterior bone height, combining the placement of 1 ZI posteriorly and conventional implants anteriorly with a staged loading protocol. Later, a Quad Zygoma protocol was introduced to treat extreme maxillary atrophy, involving the placement of 2 ZIs on each side of the zygoma bone for the full-arch reconstruction. , The high survival of ZIs demonstrated that they are a viable alternative to extensive grafting procedures. , Additionally, the provision of immediate functional loading facilitated further advantages for patients’ quality of life. ,
Over time, various insertion techniques have been developed to address the challenges associated with surgical and prosthetic aspects. The extra-sinus placement of ZIs, with the implants positioned outside the maxillary sinus, is advocated to preserve the integrity of the maxillary membrane and to allow direct visualization of the surgical field. Stella and colleagues described a trajectory involving placing ZIs in the sinus lateral wall to avoid the risk of unfavorable implant position. However, conclusive evidence regarding the superiority of one technique over another is limited due to factors such as the patient’s individual anatomy and the surgeon’s experience.
Therefore, instead of resorting to only 1 insertion technique for various anatomies, the use of different techniques based on the patient’s individual anatomic structure was introduced in 2010. , This Anatomy-Guided Approach (AGA) applied different implant trajectories with the above-mentioned techniques depending on the levels of alveolar atrophy and the concavity of the sinus wall. Subsequently in 2011, a radiological classification of ZI trajectory was classified into 5 groups, following a similar concept. In 2023, the pros and cons of using different surgical techniques were critically evaluated in the International team for implantology (ITI) zygomatic implant consensus by 24 international experts.
However, until now, few standardized success criteria for ZI have been established, and those that exist have not been widely employed in the long-term observation. The relationship between the long-term success and surgical technique remains uncertain. Hence, it is crucial to provide a comprehensive overview of the surgical techniques, survival rates, and complications to enable clinicians to successfully tailor a ZI treatment. The purpose of the current review is to clarify the existing techniques and long-term outcomes of ZI rehabilitation over the past 20 years of clinical evolution. Additionally, it aims to enhance the current knowledge and identify gaps in the understanding of ZI treatment.
Current evidence: what do we know after 20 years of clinical evolution?
The Decision-Making Process in the Choice of Surgical Technique
The AGA techniques can be categorized into 3 groups based on the trajectory between the implant body and the sinus wall: intra-sinus, in the wall of the sinus, and extra-sinus (panels in Table 1 ). Instead of using only 1 technique for all patients, in 2010, the first clinical study applied an AGA classification in patients with different anatomic structures, as reported by Davo and colleagues The term AGA was finally adopted after thorough investigation and discussion during the ITI zygomatic implant consensus debate in 2023. The systematic review during the endeavor to reach the consensus evaluated different techniques for placing ZIs in terms of survival and complications, all of which showed high survival rates.
Nonetheless, an important principle in choosing the ideal technique is to consider the individual’s anatomy and follow prosthesis guidance. A detailed description of the AGA decision-making is provided in Table 1 .
Long-Term Survival and Implant Design
The clinical outcomes of ZIs have been widely reported, especially in recent years. Investigations into survival and complications have been the focus endpoints of many studies. In 2004, the first study of Branemark was published with a 5-year to 10-year follow-up revealing a 94% survival rate in 28 patients who had ZIs placed by intra-sinus technique. Subsequent studies by Davo, Bedrossian, and Aparicio consistently reported high survival rates using different surgical approaches and loading protocols from studies with over 5 years of observation. An overview of 14 studies comprising 1022 patients with a 5-year of follow-up is summarized in Table 2 , , Out of the total of 2681 ZIs placed in these patients, 143 ZIs (5%) failed, with 29 ZIs (1%) failed at the early stage (within the first 6 months), and 98 ZIs (3%) failed at the later stages; the timing of the remaining failures was not reported. In terms of surgical techniques, 7 studies followed a “pure” technique strategy, , , , , with 5 being intra-sinus , , and 2 extra-sinus. , Conversely, 5 studies employed an anatomy-guided approach, where 3 utilized with AGA , , and 2 zygoma anatomy-guided approach (ZAGA) classification. , The 2 remaining studies , compared intra-sinus and extra-sinus techniques. Survival rates varied between and across techniques: intra-sinus ranged from 94.0% to 97.4%, extra-sinus ranged from 98.2% to 100%, AGA ranged from 89.9% to 98%, and ZAGA ranged from 76.2% to 94.3%. Regarding loading protocols, 5 studies , , , , that solely used delayed loading reported survival rates ranging from 94% to 97.4%, while 5 studies , , , , utilizing immediate loading had survival rates ranging from 97.2% to 100%. Four studies , , , that employed both protocols reported survival rates ranging from 76.2% to 97.4%. As far as complications, sinusitis emerged as the most common one, with 202 cases (19.7%). However, other complications were more challenging to analyze with the descriptive statistics due to the lack of standardization in reporting.
| Authors, Year | Type of Study | Mean Follow-up | Patients | Mean Age | Zygomatic Implant (ZI) | Dental Implant (n) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Zygomatic implant (ZI) Approach (n) | Surgical Approach | No. of ZI [n] | ZIs Brand | ZI’s Survival Rate (Failed Implant) | Early Failure | Late Failure | Prothesis Type | Loading Protocol (Immediately Delayed) | ||||||
| Brånemark et al, 2004 | R | At least 60 mo | 28 | 58.3 | Unilateral (4) Classic (24) |
Intrasinus | 52 | Nobel Biocare | 94%(3) | 2 | 2 | 106 | Fixed | Delayed |
| Davó, 2009 | R | 60 mo | 24 | 51.4 | 1 ZI (1) Classic (23) |
Intrasinus | 45 | Nobel Biocare | 97.4%(1) | 1 | 0 | 109 | Overdenture(3) Fixed(21) |
Delayed |
| Bedrossian, 2010 | P | 5–7 y | 36 | NM | Classic(36) | Intrasinus | 74 | Nobel Biocare | 97.2%(2) | 2 | 0 | 98 | Fixed | Immediately |
| Aparicio et al, 2012 | R | At least 10 (y) | 22 | 63 | Hybrid | Intrasinus | 41 | Nobel Biocare | 95.12%(2) | 0 | 2 | 131 | Fixed | Delayed |
| Maló, 2015 | R | 6–84 mo | 352 | 55.2 | Classic Quad |
Extrasinus | 747 | Nobel Biocare | 98.2%(7) | 4 | 3 | 795 | Fixed | Immediately |
| Davó & Pons, 2015 | P | At least 5 y | 14 | 57.5 | Quad(14) | AGA | 52 | Nobel Biocare | 98.0%(1) | 1 | 0 | 0 | Fixed | Immediately |
| Bothur et al, 2015 | R | 9.3 (y) | 14 | 60 | quad(8) Hybrid(6) |
Intrasius | 58 | Nobel Biocare | 97.0%(2) | 2 | 0 | 13 | Fixed | Delayed |
| Aleksandrowicz et al, 2019 | R | 94.36 mo | 22 | 50.41 | 1 ZI (12) 2 ZIs (8) 3 ZIs (1) Quad (1) |
Intrasinus(24) Extra-sinus(11) |
35 | Nobel Biocare | 97.15%(1) | NM | NM | NM | Fixed | Delayed |
| Chana et al, 2019 | R | 90 mo | 43 | NM | NM | ZAGA | 80 | Nobel Biocare | 94.32%(5) | 1 | 4 | 79 | Removable Fixed |
Delayed Immediately |
| Agliardi et al, 2021 | R | 92.33 mo | 34 | 64.76 | Quad (11) Classic(19) Hybrid (4) |
Extrasinus | 90 | Nobel Biocare | 100%(0) | 0 | 0 | 53 | Fixed | Immediately |
| D’Agostino et al, 2021 | R | 60 mo | 42 | 54 | Quad (16) Hybrid(21) |
Intrasinus(32) Extrasinus(10) |
116 | Nobel Biocare | 97.41%(3) | 2 | 1 | 70 | Overdenture(11) Fixed(31) |
Delayed (36) Immediately(6) |
| Di Cosola et al, 2021 | R | 141 mo | 33 | 59.1 | Classic Quad | ZAGA | 67 | Southern Implants, Nobel Biocare | 76.2%(16) | NM | NM | NM | NM | Delayed and Immediately |
| Davo, 2024 | R | 8.8 y | 56 | 57 | Quad(56) | AGA | 284 | Nobel Biocare | 97.7%(5) | 2 | 3 | 0 | Overdenture(2) Fixed(54) |
Immediately |
| Vrielinck et al, 2023 | R | 7.9 y | 302 | 58 | Classic Quad Hybrid |
AGA | 940 | Nobel Biocare | 89.9%(95) | 12 | 83 | 451 | NM | Delayed(486) Immediately(454) |
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