Zygomatic & Pterygoid Implants

§4.9.1 — Overview

When the alveolus can no longer hold an implant

There is a category of maxilla in which conventional implant dentistry simply runs out of bone. The alveolar ridge has resorbed to a knife-edge, the maxillary sinuses have pneumatized down to a paper-thin floor, and the patient either cannot face — or has already failed — the years of grafting that would be needed to rebuild a foundation. For these patients, the answer is to stop trying to anchor in alveolus that no longer exists and instead borrow the dense, reliable bone that sits behind and above it: the body of the zygoma and the pterygoid plates. This is the domain of extra-maxillary anchorage, and it is, without qualification, specialist, referral-level surgery.²

The zygomatic implant — first described by Brånemark for the rehabilitation of the cancer-resected and severely atrophic maxilla — is an unusually long fixture (typically 30–52.5 mm) that traverses from the residual alveolar crest, past or through the maxillary sinus, to engage the thick cortical bone of the malar body.² The pterygoid implant takes a different route, angling distally from the posterior maxilla to lock into the pterygomaxillary junction and the pterygoid plates, supplying posterior support without a graft and eliminating the distal cantilever that plagues short posterior arches.⁴ Both techniques share a defining feature that the rest of this chapter turns on: the working bone lies a long way from the operative field, in intimate relationship with the orbit, the infratemporal fossa, and the maxillary sinus, so a small angular error at the crest becomes a large, sometimes catastrophic, error at the target.

The zygoma and pterygoid plates are not where the tooth was lost — they are simply where reliable bone still is.

◆ Key concept · This is a referral chapter

Zygomatic and pterygoid implants are advanced, anatomically hazardous procedures whose complication profile includes sinusitis, orbital and infratemporal injury, and oroantral communication that can be very difficult to salvage. The purpose of this module is to help the referring clinician recognize the severely atrophic maxilla, understand the graftless options, and counsel the patient — not to serve as an operative manual. Placement should be planned and performed by surgeons with specific zygomatic/pterygoid training and adequate case volume.³

Who is a candidate

The classic indication is the severely atrophic edentulous maxilla — Cawood–Howell Class V–VI — where residual alveolar volume is insufficient for conventional fixtures even after sinus elevation, or where the patient has failed previous grafting or declines it on the grounds of morbidity, cost, or treatment time.¹ A second, distinct indication is the post-maxillectomy or oncologic defect, the very problem for which the zygoma fixture was originally conceived: when tumour resection removes the alveolus and part of the sinus floor, the zygoma may be the only remaining anchorage for an obturator-retaining or fixed reconstruction.² Across all of these, the appeal is the same — a graftless, frequently immediately loaded, fixed result delivered in a single surgical episode.

§4.9.2 — Classification

The ZAGA concept and types 0–4

The single most important conceptual advance in zygomatic implantology was the recognition that the implant trajectory should follow the patient's anatomy rather than a fixed surgical recipe. Aparicio's Zygoma Anatomy-Guided Approach (ZAGA) replaced the rigid "one technique fits all" placement — in which every fixture ran through the sinus along the same path — with a CBCT-based classification of the concavity of the lateral maxillary wall at each implant site, from which the appropriate trajectory (more intra-sinus or more extra-sinus) is derived.¹ The clinical pay-off is direct: matching the path to the wall shape keeps the fixture body in supportive bone, reduces unsupported intra-antral spans, and is associated with lower rates of late sinusitis than rigid placement.¹

The classification grades the lateral sinus wall from a flat, convex profile (where the implant naturally runs largely through the sinus) to a deeply concave one (where the implant runs largely outside the sinus along the malar surface), with intermediate forms in between. Five types — ZAGA 0 through ZAGA 4 — span this continuum, as set out below. The type is read from the CBCT before surgery and dictates the osteotomy, the soft-tissue management, and the prosthetic emergence.

Figure 1. The ZAGA continuum. As the lateral maxillary wall becomes more concave (left to right), the anatomy-guided trajectory shifts from a fully intra-sinus path (ZAGA 0) to a fully extra-sinus path along the malar surface (ZAGA 4), with wall-engaging intermediates. Reading the wall concavity from CBCT — not applying a single fixed path — is the core of the concept. Schematic; not to anatomical scale.¹

Table 1 · ZAGA types 0–4 — wall profile and trajectory
ZAGA type	Lateral sinus-wall profile	Implant trajectory	Practical note
Type 0	Flat / convex wall; crest broad	Fully intra-sinus — fixture body within the antrum	Closest to classic Brånemark path; needs intact crestal bone window
Type 1	Slightly concave wall	Mostly intra-sinus, body grazing the wall	Minor wall contact; standard antrostomy management
Type 2	Moderately concave wall	Body engages and runs along the wall	Wall-supported; intermediate sinus exposure
Type 3	Markedly concave wall	Mostly extra-sinus along the malar surface	Limited antral involvement; favours sinus health
Type 4	Deeply concave wall; severe palatal crest resorption	Fully extra-sinus on the malar surface	Soft-tissue coverage of the externalized body is critical

§4.9.3 — Anatomy & risk

The hazards that define the technique

What separates extra-maxillary anchorage from routine implant surgery is the company the working bone keeps. The zygomatic trajectory passes within millimetres of the orbital floor superiorly and traverses the maxillary sinus along much of its length; the pterygoid trajectory drives toward the infratemporal fossa and the maxillary artery's terminal branches. Each carries a signature complication.³

Sinusitis is the most common late complication of zygomatic implants. Across the largest systematic review — 68 studies, 4,556 zygomatic implants in 2,161 patients — the pooled sinusitis prevalence was roughly 2.4% (95% CI 1.8–3.0%), although individual series report a much wider range and the authors caution the true figure may be underestimated; it often appears years after surgery and usually responds to antibiotics, though some cases require revision.³ It is precisely this complication that the ZAGA concept is designed to reduce, by minimizing unsupported intra-antral fixture spans and respecting sinus drainage. Orbital injury — penetration of the floor or, rarely, the globe — is the feared catastrophic event of a trajectory drifting too superiorly, while oroantral communication at the crest and infratemporal / neurovascular injury (especially for pterygoid placement near the maxillary artery) round out the profile.³ A failed zygomatic implant is also far harder to salvage than a failed conventional fixture, because there is no alternative anchorage in the same region.

✦ Clinical pearls

Despite its reputation, the zygomatic implant is highly durable when well placed: the updated systematic review reports a ~95% 12-year cumulative survival, with most failures occurring within the first 6 months.³
Pre-treat sinus disease. Address pre-existing sinusitis, polyps, or ostial obstruction before placement, and counsel that lifelong sinus surveillance is part of the contract.
Classify every site by ZAGA type from CBCT before committing — the wall, not the textbook, sets the path.

▲ Common pitfalls

Applying a single rigid intra-sinus path to every patient — the historical source of unsupported antral spans and elevated sinusitis rates.
Letting a zygomatic trajectory drift superiorly toward the orbital floor, or a pterygoid trajectory medially toward the maxillary artery, because of poor angular control at the crest.
Offering these procedures — or accepting referral for them — without the specific training, navigation/planning, and case volume they demand. When in doubt, refer up, not across.

§4.9.4 — Decision pathway

A severity-driven approach selector

The choice among grafting, zygomatic anchorage, and pterygoid support is driven by two CBCT-readable variables: how much usable residual bone remains, and how the sinus has pneumatized. The interactive selector below maps the three principal scenarios to their approach, and — critically — flags the point at which a case exceeds conventional implant therapy and should be referred. It reproduces the decision logic of the source algorithm in book form.

Select the maxillary atrophy / pneumatization picture read from CBCT.

Table 2 · Indication → approach → key risks (with evidence grade)
Indication	Approach	Key risks	Evidence
Moderate atrophy, graftable sinus	Conventional implants + sinus floor elevation / ridge augmentation (staged or simultaneous)	Graft failure, membrane perforation, longer timeline	Syst. review
Severe atrophy, intact zygoma (Cawood–Howell V–VI)	Zygomatic implant(s) per ZAGA type; ± anterior conventional implants	Sinusitis (~2.4% pooled), orbital injury, oroantral communication, difficult salvage	Syst. review
Posterior support deficit, inadequate tuberosity	Pterygoid implant into the pterygomaxillary region (avoids distal cantilever)	Neurovascular injury, restricted access, steep angulation, D3-bone failure	Cohort / consensus
Post-maxillectomy / oncologic defect	Zygomatic ± pterygoid anchorage for fixed or obturator-retained reconstruction	Irradiated-bed healing, ORN risk, complex defect anatomy	Cohort / consensus

◆ Key concept · The referral threshold

The dividing line in this table is between the first row and the rest. Moderate atrophy with a graftable sinus remains within the reach of well-trained general implant practice. Everything below it — zygomatic, pterygoid, and oncologic reconstruction — is specialist territory. The most valuable thing a referring clinician can do is recognize that line on the CBCT and route the patient before, not after, an attempt that compromises the remaining anatomy.

§4.9.5 — Glossary

Key terms

Zygomatic implant: An extra-long fixture (≈30–52.5 mm) anchored in the dense bone of the zygomatic (malar) body, bypassing an unusable maxillary alveolus.
Pterygoid implant: A fixture angled distally from the posterior maxilla into the pterygomaxillary junction / pterygoid plates to provide posterior anchorage without a graft and avoid a distal cantilever.
ZAGA (Zygoma Anatomy-Guided Approach): Aparicio's CBCT-based concept in which the implant trajectory is dictated by the concavity of the lateral maxillary wall rather than a fixed surgical path.
ZAGA type (0–4): A five-grade classification of lateral sinus-wall concavity (and crestal resorption) running from a fully intra-sinus path (Type 0) to a fully extra-sinus malar path (Type 4).
Cawood–Howell classification: A staging of edentulous ridge resorption; Classes V–VI denote the severely atrophic ridge that typifies the zygomatic indication.
Oroantral communication: An abnormal connection between the oral cavity and the maxillary sinus — a recognized complication of crestal entry in atrophic maxillae.
Malar body: The thick cortical bulk of the zygomatic bone that provides the apical anchorage for a zygomatic implant.

§4.9.S — Self-test

Specialist-referral preparation

1. The ZAGA classification (Aparicio) is fundamentally a grading of:

B is correct. ZAGA is an anatomy-guided concept: the CBCT-read concavity of the lateral maxillary wall (and crestal resorption) defines the type and thus the trajectory. It is not a torque, systemic-risk, or fixture-count scale.

2. As the ZAGA type increases from 0 to 4, the zygomatic implant trajectory shifts:

A is correct. A flatter wall (Type 0) is matched by an intra-sinus path; an increasingly concave wall (toward Type 4) is matched by a path that runs progressively outside the sinus along the malar surface.

3. The most common late complication of zygomatic implants is:

B is correct. Sinusitis is the most frequently reported complication (pooled ~2.4% in the largest systematic review, with wide variation between series), often appearing years after placement and usually responsive to antibiotics. Orbital injury is feared but rare.

4. Which residual-ridge staging best characterizes the typical candidate for zygomatic anchorage?

C is correct. Classes V–VI denote the severely atrophic ridge in which conventional fixtures cannot be supported even after sinus elevation — the core zygomatic indication.

5. The pterygoid implant achieves its anchorage by engaging the:

C is correct. Pterygoid fixtures angle distally into the pterygomaxillary region and pterygoid plates, supplying posterior support and eliminating a distal cantilever.

6. A principal prosthetic rationale for adding a pterygoid implant is to:

B is correct. Posterior anchorage from the pterygoid region removes the distal cantilever that otherwise loads short posterior arches, improving biomechanics.

7. Compared with the historical rigid intra-sinus technique, the ZAGA concept is associated with:

B is correct. By tailoring the trajectory to wall concavity and minimizing unsupported intra-antral spans, ZAGA is associated with reduced sinusitis relative to a fixed "one technique fits all" path.

8. Approximate reported sinusitis incidence after zygomatic implant placement is:

B is correct. The updated systematic review reports a pooled sinusitis prevalence of about 2.4% (95% CI 1.8–3.0%), generally antibiotic-responsive, though individual series vary and the figure may be underestimated.

9. The reported long-term cumulative survival of zygomatic implants is best summarized as:

B is correct. Chrcanovic et al. (2016) reported a ~95.2% 12-year cumulative survival across 4,556 implants, with failures concentrated in the first 6 postsurgical months.

10. For a ZAGA Type 0 site, the expected trajectory is:

B is correct. A flat/convex wall (Type 0) corresponds to the classic intra-sinus path, closest to the original Brånemark trajectory.

11. For a ZAGA Type 4 site, soft-tissue management is critical because the fixture body is:

B is correct. A deeply concave wall (Type 4) yields a fully extra-sinus path in which much of the body lies on the malar surface; adequate soft-tissue coverage is essential to its long-term health.

12. The original clinical problem for which Brånemark introduced the zygoma fixture was:

B is correct. Brånemark described the zygoma fixture for advanced maxillary atrophy and post-maxillectomy/oncologic defects — the same indications that anchor this chapter.

13. A patient with moderate atrophy and a graftable sinus is best served first by:

A is correct. When usable alveolar bone remains and the sinus can be augmented, conventional grafting-based therapy avoids extra-maxillary risk; zygomatic anchorage is reserved for when this is not feasible or fails.

14. The structure most at risk from a zygomatic trajectory drifting superiorly is the:

B is correct. A trajectory that climbs too high threatens the orbital floor and, rarely, the globe — the catastrophic complication of zygomatic placement.

15. The structure most at risk from a poorly controlled pterygoid trajectory is the:

B is correct. The pterygoid path heads toward the infratemporal fossa and the terminal maxillary artery; neurovascular injury and restricted access are its signature hazards.

16. Which feature best supports immediate loading of zygomatic implants?

B is correct. Immediate fixed loading is common when stability is adequate; the cortical engagement of the malar body (and often the crest) provides the rigid anchorage that permits it.

17. Salvage of a failed zygomatic implant is difficult chiefly because:

B is correct. Because the zygoma is the anchorage of last resort for that segment, a failure leaves limited fall-back options — one reason the procedure is reserved for trained specialists.

18. A pre-existing condition that should be addressed before zygomatic placement is:

B is correct. Pre-existing sinus disease raises postoperative sinusitis risk; it should be treated and drainage confirmed before a fixture is passed through or alongside the antrum.

19. In the post-maxillectomy patient, zygomatic anchorage is attractive primarily because:

B is correct. Tumour resection often removes the alveolus and sinus floor, leaving the zygoma as the principal — sometimes sole — anchorage for reconstruction. Irradiated beds add ORN considerations.

20. The single most useful action a referring clinician can take for a severely atrophic maxilla is to:

B is correct. Extra-maxillary anchorage is specialist, referral-level surgery. Early, appropriate referral — before an attempt that damages remaining bone or the sinus — is the highest-value decision in general practice.

1. Explain the ZAGA concept to the examiner and say why it represents a shift away from the original zygomatic technique.

Model answer. The Zygoma Anatomy-Guided Approach holds that the implant trajectory should be dictated by the patient's own anatomy rather than a single fixed path. Specifically, the surgeon reads the concavity of the lateral maxillary wall (and the degree of crestal resorption) from CBCT and classifies each site as ZAGA Type 0 through 4. A flat wall (Type 0) is matched by a largely intra-sinus path; an increasingly concave wall is matched by a progressively extra-sinus path along the malar surface (toward Type 4). This is a deliberate move away from the historical "one technique fits all" intra-sinus method, in which every fixture ran the same antral course regardless of anatomy — an approach that produced unsupported intra-antral spans and higher sinusitis rates. By matching the path to the wall, ZAGA keeps the body in supportive bone and respects sinus health.

Examiner follow-ups:

How would a Type 0 and a Type 4 osteotomy differ?
Why does an extra-sinus path lower sinusitis risk?

2. Take me through the principal complications of zygomatic implants and how you would mitigate each.

Model answer. The most common is maxillary sinusitis — a pooled prevalence of roughly 2.4% in the largest systematic review, sometimes appearing years later, and usually antibiotic-responsive. I mitigate it by treating pre-existing sinus disease beforehand, using a ZAGA-matched trajectory to minimize unsupported antral spans, and committing to lifelong sinus surveillance. The feared catastrophic event is orbital floor or globe injury from a trajectory drifting too superiorly; I mitigate it with careful CBCT planning, navigation where available, and disciplined angular control from the crest. Oroantral communication at the crest and difficult salvage (because there is no alternative anchorage in the region) round out the profile. For pterygoid placement the analogous hazard is neurovascular injury near the maxillary artery in the infratemporal fossa. Crucially, despite all this the technique is durable — about 95% twelve-year survival when well placed.

Examiner follow-ups:

When does sinusitis typically present?
What would make you abort and stage the case?

3. A 64-year-old with a Cawood–Howell Class VI maxilla and an intact zygoma asks you to place implants. Walk me through your decision and your duty as a clinician.

Model answer. Class VI denotes severe atrophy in which conventional fixtures cannot be supported even after sinus elevation, so the realistic graftless option is zygomatic anchorage, possibly combined with anterior conventional implants where bone permits. My first duty, however, is to recognize that this case exceeds conventional implant practice: zygomatic placement is specialist, referral-level surgery with serious anatomical risk and difficult salvage. If I am not specifically trained and high-volume in the technique, the correct action is to refer to a surgeon who is — before any attempt that might compromise the remaining bone or the sinus. I would obtain CBCT, classify each site by ZAGA type, screen and treat any sinus disease, and counsel the patient fully on the sinusitis, orbital, and salvage risks, and on the need for long-term surveillance. Immediate fixed loading may be possible if primary stability from malar engagement is adequate.

Examiner follow-ups:

What if the patient had failed a prior sinus graft?
How does ZAGA type change your soft-tissue plan?

4. Compare zygomatic and pterygoid implants — their targets, indications, and biomechanical roles.

Model answer. Both are graftless extra-maxillary solutions but they solve different problems. The zygomatic implant is an extra-long fixture that bypasses an unusable alveolus to engage the dense malar body; its indication is severe global maxillary atrophy or the post-maxillectomy defect, and it provides the principal anchorage for the rehabilitation. The pterygoid implant angles distally from the posterior maxilla into the pterygomaxillary junction and pterygoid plates; its indication is a posterior support deficit with an inadequate tuberosity, and its biomechanical role is to eliminate the distal cantilever by adding a posterior pillar, usually in combination with anterior conventional or zygomatic implants. Each carries region-specific hazards — the zygoma near the orbit and sinus, the pterygoid near the infratemporal neurovascular structures — and both are specialist-level. They are frequently combined within a single full-arch plan.

Examiner follow-ups:

Why does eliminating the cantilever matter biomechanically?
Which bone quality concerns you most in the pterygoid region?

5. The examiner challenges you: "Zygomatic implants have a sinusitis rate, so aren't they just too risky to recommend?" Defend the technique with the evidence.

Model answer. Risk must be read against benefit and alternatives. Sinusitis does occur — a pooled prevalence of about 2.4% in the largest systematic review, with wide variation between series — but it usually appears late and responds to antibiotics, and the same review reports a high long-term cumulative survival of roughly 95% at twelve years, with failures concentrated in the first six months. The realistic alternative for a Class V–VI maxilla is extensive grafting over years, with its own failure and morbidity, or no fixed rehabilitation at all. The ZAGA concept further reduces sinusitis by matching the trajectory to wall anatomy. So the defensible position is not that the technique is risk-free, but that in correctly selected patients, planned and placed by trained specialists, it offers a durable, graftless, often immediately loaded result whose benefit outweighs a manageable, mostly treatable complication. I would still pre-treat sinus disease, counsel thoroughly, and arrange surveillance.

Examiner follow-ups:

What survival figure would you quote, and from which study?
How does patient selection change the risk–benefit balance?

§4.9 — References

References

Aparicio C. A proposed classification for zygomatic implant patient based on the zygoma anatomy guided approach (ZAGA): a cross-sectional survey. Eur J Oral Implantol. 2011;4(3):269–275. PMID: 22043470
Brånemark PI, Gröndahl K, Ohrnell LO, 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(2):70–85. doi:10.1080/02844310310023918. PMID: 15202664
Chrcanovic BR, Albrektsson T, Wennerberg A. Survival and complications of zygomatic implants: an updated systematic review. J Oral Maxillofac Surg. 2016;74(10):1949–1964. doi:10.1016/j.joms.2016.06.166. PMID: 27422530
Raouf K, Chrcanovic BR. Clinical outcomes of pterygoid and maxillary tuberosity implants: a systematic review. J Clin Med. 2024;13(15):4544. Pterygoid/tuberosity implants provide posterior anchorage and avoid distal cantilevers; reported 10-year cumulative survival ≈92.5% (pterygoid) and ≈96.9% (tuberosity). doi:10.3390/jcm13154544. PMID: 39124809

Reference numbering follows the full reference set of the standard module; this prototype displays the subset cited in-text. Evidence grades: Systematic review Consensus / cohort Preclinical.

Zygomatic & Pterygoid Implants

When the alveolus can no longer hold an implant

Who is a candidate

The ZAGA concept and types 0–4

The hazards that define the technique

A severity-driven approach selector

Key terms

Specialist-referral preparation

Related modules

References

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