Quad ZygomaTechnique and Realities

Rubén Davó, MD, PhDa, Lesley David, DDS, DOMFS, FRCDCb,*

KEYWORDS

� Zygomatic implants � Quad zygoma technique � Graftless implant solution � Atrophic maxilla� Survival rates � Immediate loading

KEY POINTS

� Four zygomatic implants (quad zygoma) can be used in patients with severe maxillary atrophy as analternative to bone grafting to reconstruct the maxilla. This approach is used as the first line of treat-ment or as a rescue solution for failed implants and severe bone loss.

� Initial stability of zygomatic implants is typically excellent; as such, immediate loading with a fixedbridge is often performed and different techniques can be employed to fabricate a provisionalprosthesis.

� The technique of placing a zygomatic implant has evolved over the years. The evolution of this pro-cedure takes into account the potential complications of the use of zygomatic implants and pa-tients’ anatomy (zygoma anatomy guided approach).

� The quad zygoma surgical procedure is technique sensitive and requires advanced surgical skill.The surgical procedure for the quad zygoma is described.

� Various complications can occur with the placement of zygomatic implants such as oral-antralcommunication, paresthesia, infection at the tip of the implant, tissue retraction, and more. Under-standing the etiology of these complications will assist with prevention and management.

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Complete maxillary rehabilitation has changeddramatically since the advent of osseointegration;treatment options have become more varied andless invasive procedures have emerged. This istimely as life expectancy has increased, resultingin more elderly patients seeking treatment.1 Thus,severe maxillary atrophy can present relativelyfrequently in clinical practice. The quad zygomaconcept addresses the severely atrophic maxillaby making use of 4 zygoma implants (Fig. 1). Twoimplants are placed bilaterally with appropriateanterior and posterior spread and inclination forprosthetic rehabilitation. Typically, a fixed pros-thesis is provided although this implant solutionmay also be used to retain an overdenture.

Disclosure Statement: Both authors are global speakers fa Department of Implantology and Maxillofacial Surger5th floor, Alicante 03016, Spain; b Oral and Maxillofaciaonto, Private Practice, Toronto, Canada* Corresponding author. Implant Surgical Care, 1849 YonE-mail address: drdavid@implantsurgicalcare.com

Oral Maxillofacial Surg Clin N Am 31 (2019) 285–297https://doi.org/10.1016/j.coms.2018.12.0061042-3699/19/� 2019 Elsevier Inc. All rights reserved.

Bone loss secondary to dental extractions oc-curs in a predictable manner. Many phenomenaaffect the alveolar bone leading to severe atrophyand a decrease in volume making it difficult toinsert dental implants.2 (Fig. 2) The timeline of pro-gression to severe bone loss is variable among pa-tients; however, with enough time and overlyingcompressive forces of a complete denture, thefate of edentulous jaws is predictable.

Rehabilitation of completely edentulous patientsregardless of the degree of atrophy has historicallyinvolved the use of complete removable dentures.This approach, however, may not meet the func-tional, psychological, and social needs of eachindividual.3

or NobelBiocare.y, Medimar International Hospital, Padre Arrupe, 20,l Surgery, Trillium Health Partners, University of Tor-

ge Street, #302, Toronto, Ontario M4S 1Y2, Canada.

oralmaxsurgery.theclinics.co

Fig. 1. Quad zygoma.

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Over time options evolved:

1. Surgical reconstruction of the jaws involvingbone grafting followed by secondary implantplacement

2. Using implants in a tilted fashion to eliminatethe need for bone grafting and engage availablebone where possible with appropriate distribu-tion of the implants for prosthetic rehabilitation

3. Using an alternate source of bone such as thezygoma or pterygoids for anchorage ofimplants4,5

When severe bone atrophy has occurred, theoption of prosthetic reconstruction to compensatefor the composite defect as opposed to surgicalreconstruction (to rebuild lost anatomy) enablesless invasive surgical interventions for patients(Fig. 3). The synergy between surgery and pros-thetics is paramount. The quad zygoma combined

Fig. 2. (A) Cawood and Howell class V. (B) Cawood and H

with prosthetic reconstruction can address pa-tients’ needs for esthetics and function similar toconventional treatments.3 The reality of needingless surgery to rehabilitate the edentulous maxillais one that beckons surgeons to examine theirgoals of treatment and work closely with prostho-dontists to obtain successful outcomes. Inargu-ably, prosthetic reconstruction of lost anatomyeliminates the morbidity associated with surgicalreconstruction.Bone augmentation techniques are widely

used and are supported by a great deal of scien-tific evidence. Nevertheless, clinical and biolog-ical limitations are inherent, preventing successrates from reaching those of the alternativeapproach based on extra-alveolar implants.6 Inclinical practice, the presence of hyperplasticmaxillary sinuses with uncontrollable infectiousprocesses, severe alveolar atrophy, or other clin-ical situations such as defects secondary totrauma or the treatment of pathology requiringsevere resective surgeries may mean that theonly possible treatment is by means of zygo-matic implants.7

From a biological perspective, autologous bonegrafts are considered the gold standard. However,morbidity at the donor site, bone resorption whensubjected to loading, a prolonged treatment time-line, and problems that can arise with clinicallychallenging scenarios must be weighed in consid-ering this treatment solution. In addition, the needto achieve adequate vascularization internally andexternally makes the technique difficult to apply incases of severe vertical atrophy. It is often impos-sible to achieve adequate internal and peripheralvascularization of the graft in large vertical recon-structions.8 Furthermore, few studies have investi-gated the use of grafts (bone grafts or otherbiomaterials) to regenerate severe maxillary atro-phy. A recent randomized clinical trial conductedwith this profile of patients suggested that,although the use of biomaterials might bepossible, rehabilitation takes an average of430 days. Zygoma implants obtained better out-comes and constituted a much faster means ofrehabilitation.9

owell class VI.

Fig. 3. Provisional bridge: acrylic compensating forlost anatomy.

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Nonalveolar implants offer a predictable alterna-tive to bone augmentation techniques in situationsof severe alveolar atrophy. The placement of im-plants in bone of a different embryologic origin fa-vors high survival rates derived from the absenceof bone resorption and atrophy. In the authors’experience, bone resorption can be seen yearslater in grafted sites with implants; this is not typi-cally seen in the malar bone (Fig. 4).

Zygomatic implants were introduced for therehabilitation of patients with extensive boneloss derived from trauma, neoplasms, or congen-ital pathologies. These implants can be combinedwith intra-alveolar implants or may be used aloneto support a prosthesis. Several anatomic studieshave validated the good quality of zygomaticbone and have stressed the importance of thecortical portion of the zygomatic bone foranchoring implants. It has also been documentedthat the area of zygomatic bone used for implantinsertion has wider and thicker trabecular bone.This may explain the excellent potential for pri-mary stability of zygomatic implants and, thus,the suitability for immediate loading. This advan-tage of immediate loading with zygomatic im-plants normalizes patients’ quality of lifeimmediately.3

Fig. 4. (A–C) Bone loss around implants placed in grafted

INDICATIONS AND CONTRAINDICATIONS

Indications include severe maxillary atrophy, inparticular inadequate bone volume for the place-ment of even a single dental implant both anteriorlyand posteriorly.10 (Fig. 5). The quad zygoma isused as the first option of choice in these patients.It may also be used as a rescue implant in patientswho previously had bone grafting and implantsthat failed.

The concept of using short implants anteriorly inconjunction with a zygoma implant posteriorly iscontroversial with few supporting studies in theliterature. In the authors’ experience, it is prudentto perform a quad zygoma whenever the boneloss anteriorly precludes placement of conven-tional implants of at least 10 mm in length.

The quad zygoma may be used for rehabilitationwith either a fixed or removable prosthesis (Fig. 6).

Contraindications include:

� General contraindications to implant surgery� Radiation to the head and neck region of morethan 70 Gy

� Immunosuppressed or immunocompromisedpatients

� Intravenous amino-bisphosphonates use� Untreated periodontal disease� Poor oral hygiene and motivation� Uncontrolled diabetes� Pregnant or lactating women� Addiction to alcohol or drugs� Restricted mouth opening (<3 cm interarchmeasured anteriorly)

� Acute or chronic infection/inflammation in thearea intended for implant placement

� Acute maxillary sinusitis� Chronic maxillary sinusitis with obstruction ofthe osteomeatal complex

� Abnormalities in the malar bone

Pre-operative planning should include pros-thetic work-up of the patient as per conventionalfull-mouth rehabilitation protocols.

maxilla using iliac crest; 8 years prior.

Fig. 5. (A) 3-dimensional reconstructed view of maxilla. (B) anterior area. (C) posterior area.

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Factors to consider include:

� Vertical dimension� Occlusion� Smile line� Smile curvature� Teeth position� Size of teeth� Buccal corridors� Opposing dentition� Parafunctional habits� Skeletal jaw relationship

In addition, other key factors must be consid-ered such as the restoration of masticatory func-tion, phonation, and aesthetics—all the criteriathat traditionally ensure quality of any completeprosthesis.11 Pre-operative prosthetic treatmentplanning is critical for success.The quad zygoma procedure is a prostheti-

cally driven technique in which the patientmust undergo complete prosthetic preparationbefore implant placement. Once the provisionalprosthesis has been made, a surgicalguide with palatal support is prepared basedon the assembly of the teeth and then used forimplant placement. This is fabricated in trans-parent acrylic resin. It will also be used post-operatively to register implant positions for fabri-cating the definitive prosthesis in thelaboratory.12

Fig. 6. (A) Quad zygoma supporting a bar for an overden

Radiographic Analysis

Plain film radiography in the form of a panoramicradiograph is suitable as a preliminary film only.Appropriate radiographic analysis and planningcan only be done using a computed tomography(CT) scan.Various implant planning software is available to

enable3-dimensional reconstructionof theatrophicmaxilla and enable virtual implant placement. Thisfacilitates determination of the implant lengths andappropriate positioning at the level of the alveolarprocess and the zygoma (Fig. 7). Using conebeam CT (CBCT), the anatomy of the zygomaticprocesses should be analyzed as well as the posi-tion, volume, and amount of the residual alveolarridge, the health of themaxillary sinus, and patencyof the osteomeatal complex bilaterally.

Surgical techniqueThe surgical technique has been described byseveral authors.3,13,14 Intravenous sedation orgeneral anesthesia is typically used with intraoralinfiltrative local anesthesia in the surgical areafacilitating hemostasis and reducing the amountof analgesia required. Pre-operative antibioticsare prescribed. The patient is prepared anddraped such that a sterile field is present and theinfraorbital rim, lateral orbital rim, and body of thezygoma can be palpated by the surgeon duringthe procedure.

ture. (B) Prosthetic bar.

Fig. 7. Virtual planning of implants.

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A full-thickness palatal-crestal incision is madeon the alveolar ridge from first molar to first molar.The palatal incision design is to ensure that agood width of keratinized tissue surrounds theimplants labially/buccally. Distal vertical releasingincisions are made bilaterally to enable goodvisualization of the surgical field by raising amucoperiosteal flap. Subperiosteal dissection isalso carried out superiorly following the path ofthe zygomatic buttress to the frontozygomaticnotch. It is important to visualize several anatomicstructures:

� The maxilla from the piriform apertures up toand including the zygomatic buttress

� The infraorbital foramen� The malar bone� The palate adjacent to the incision

Care must be taken to identify, preserve, andprotect the infraorbital neurovascular bundle.Once the dissection is completed, an obliqueosteotomy is made measuring approximately 0.5� 1.5 to 2 cm in the lateral wall of the maxilla adja-cent to the sinus. The Schneiderian membrane isdissected off the lateral wall of the sinus and the in-ternal cortex of the zygomatic bone. This allows forvisual and/or tactile access to the internal cortex ofthe zygoma. This window can be made usingthe surgeon’s instrumentation typically used toperform a direct sinus lift.

Once the surgical field is appropriately exposed,a retractor is placed in the frontozygomatic notchto allow for good visualization of the malar boneduring osteotomy preparation. This also enablesthe surgeon to appreciate the path of the osteot-omy preparation.

Positioning of the implants takes into accountthe anatomy of the body of the zygoma and themaxilla. The goal is to place 2 zygoma implantsinto a finite space with appropriate prostheticemergence and as midcrestal as possible. This isboth a conceptual and digital exercise for the

surgeon. In a cadaver study assessing the accu-racy of drilling guides, it was demonstrated that 2implants can indeed be placed at the level of thezygoma bone in the vast majority of cases giventhe height and width measurements of a typicalmalar bone.15

The anterior implants are placed first with emer-gence at the level of the canines or lateral incisors.Posterior implants emerge in the molar or premolarareas. The implants must be evenly distributed inthe zygomatic bone and, ideally, be positionedso that they are spacially separated. The drillingsequence corresponds to the manufacturer’s rec-ommendations progressively increasing the diam-eter of the drills to avoid overheating the bone andto facilitate insertion of the implant. Drilling beginswith a 2.9 mm round drill and continues with a2.9 mm twist drill. Depending on the implant sys-tem one uses, the osteotomy may be widenedwith a final 3.5 mm diameter twist drill. Abundantirrigation is crucial at the crest but also equallyimportant at the apex in the malar bone toavoid overheating. While drilling the osteotomy,palpating the malar bone extraorally is prudent.In preparing the osteotomy sites, the clinicianmust bear in mind the desire for immediate loading(as per the prosthetic plan) and ensure appropriateanchorage for this.

After implant insertion, abutments are placed(multi-unit or angulated as required) to supportthe prosthetic rehabilitation. The flap is co-aptedensuring an excellent collar of keratinized tissuearound the implants (Fig. 8).

Prosthetic Phase

During the prosthetic phase, it is preferable for thepatient to be fully conscious, whereby impressionsare taken only a few hours after surgery. Impres-sions can also be taken while the patient is still un-conscious (under intravenous sedation or generalanesthesia), but this will be more difficult.

Following abutment placement, impressioncopings are attached to the implant abutmentsand the transparent surgical guide is used forimpression transfer, placing and joining implantsby means of general purpose acrylic resin. Thesame guide is used to register the patient’s oc-clusion and jaw relationship. Once the occlusionhas been registered and the guide secured, thespace between the impression copings and thesurgical guide is filled with fluid silicone. Assoon as the material has hardened, the copingsare removed in conjunction with the guide andthe transepithelial abutments are covered withprotective caps. The provisional prosthesis isfabricated in the conventional manner casting a

Fig. 8. (A) Window between the lateral wall of the maxilla and zygoma bone. (B) Preparation for the anteriorimplant. (C) Preparation for the posterior implant. (D) Two implants in place. (E) Impression copings in placeon all 4 implants. (F) Site sutured and ready for fabrication of provisional.

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model and connecting laboratory analogues(Fig. 9). If the patient already has a conventionaldenture that fulfills all the prosthetic require-ments, this may be used as a guide for the surgi-cal template and also be used in the conversionprocess to an all-acrylic bridge for immediateloading. Two or three of the impression copingsare picked up in the mouth (Fig. 10). An impres-sion is then made using an impression tray. Thelast implants are picked up on the model andthe intaglio surface is filled in.Six months after surgery, implant integration

is verified and the soft tissues are assessedprior to fabricating the definitive prosthesis3,16

(Fig. 11).

Surgical Techniques for Zygomatic ImplantPlacement

There is a lack of consensus in the literature as tothe ideal surgical technique for the placement ofzygomatic implants. All protocols involve similarincisions designed to expose the surgical site.However, the relationship between the portionof the implant not anchored in the zygoma andthe sinus membrane, sinus cavity, and lateral

Fig. 9. (A) Taking impressions by using the surgical guide

wall of the maxilla vary from one technique toanother. Different approaches have evolved anddeveloped in order to minimize potential sinuscomplications and improve the emergence ofthe implant at the alveolar crest without compro-mising the reported high survival rates. When itcomes to the quad approach, crestal implantemergence is paramount for designing an appro-priate prosthesis.There are several zygoma implant placement

techniques.

The classic Branemark approachThe implant passes through the maxillary sinusand the prosthetic platform is on the palatal crestof the alveolus.16 The lateral antrostomy windowperforates through the sinus permitting direct visi-bility of the roof of the sinus. The Schneiderianmembrane is reflected classically.

Sinus slot approachThe slot made through the zygomatic buttress andthe implant follows the path of the slot with minimalinvasion into the sinus.14 This is a more crestal po-sition of the prosthetic platform.

. (B) Provisional prosthesis.

Fig. 10. (A) Beginning process of picking up (luting anterior 2 copings to the denture); temporary copings inplace and rubber dam placed to prevent material flow into fresh wound. (B) Ensure no interferences. (C) Patientoccluding while acrylic hardening.

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Classic exteriorized approachThis approach was first introduced by Miglior-anca and colleagues in 2006.17 A spherical drillis used for the osteotomy penetrating the residualridge near to the top of the crest from palatal tobuccal. The ridge is then transfixed with the drillemerging in the buccal aspect of the ridgeexternal to the sinus. A maxillary antrostomy isnot necessary. Drilling continues along the outeraspect of the lateral wall of the sinus until reach-ing the lateral portion of the zygomatic bone,which is perforated, surpassing the bone’s outercancellous layer. Implants are placed outsidethe sinus (Fig. 12).

Extramaxillary approachIn 2008, Malo and colleagues modified the exteri-orized approach and used an implant withoutthreads on the coronal two-thirds of theimplant.18,19 The maxilla is prepared to allowburs direct access to the zygoma’s inferioredge. The maxilla is not used for implantanchorage. The implant is anchored exclusivelyin the zygomatic bone which is the main concep-tual difference between this approach and theothers.

Extended sinus liftChow and colleagues (2010) proposed anapproach to eliminate the risk of maxillary sinusitis.An extended sinus lift20 (Fig. 13) is performed witha retained bone window. The aim is to keep the

Fig. 11. (A) Smiling; final prosthesis. (B) Occlusion (C) Pan

sinus membrane intact during zygomatic implantosteotomy preparation.

This procedure has potential advantages:

� Eliminates the risk of maxillary sinusitis� Increases zygomatic implant stability bypromoting bone formation adjacent to theelevated maxillary sinus membrane.

Zygoma Anatomy Guided Approach

In 2011, Aparicio21 developed a classificationsystem based on skeletal forms of the zygomaticbuttress-alveolar crest complex and possibleimplant pathways related to these categories(Fig. 14). The zygoma anatomy guided approach,named ZAGA 0 to 4, is useful for classifying zygo-matic implant cases in terms of operativeplanning.

The authors identified basic skeletal forms of thezygomatic buttress-alveolar crest complex andsubsequent implant pathways among a sampleof 100 patients:

� ZAGA 0 (anterior maxillary wall is flat, maxil-lary horizontal dimension maintained) 15%,of the patient sample

� ZAGA 1 (slightly concave wall, horizontaldimension maintained) 49%

� ZAGA 2 (concave wall, horizontal dimensionmaintained) 20.5%

� ZAGA 3 (very concave wall, horizontal dimen-sion maintained) 29%

oramic radiograph.

Fig. 12. Implants are exteriorized/extramaxillary.

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� ZAGA 4 (extreme vertical and horizontal atro-phy, horizontal dimension NOT maintained)6.5%

Aparicio proposed different implant placementtechniques for these 5 anatomic categories. Inshort, whether the implant runs completely orpartially in the sinus, lateral to the sinus, or lateralto the maxilla is entirely dependent on the pa-tient’s anatomy. In theory, any of these tech-niques for placing zygomatic implants may beused in the quad zygoma approach. Typicallyquad zygoma treatment is reserved for severemaxillary atrophy. These patients often presentwith ZAGA 3 or ZAGA 4 anatomy. As such, oftena significant portion of the implants will be exteri-orized or extramaxillary.

Fig. 13. (A) Extended sinus lift for the placement of 2 zyg

POINTS TO NOTE REGARDLESS OFTECHNIQUE

Implants must be well distributed in the maxillaryarch to obtain adequate anterior and posteriorsupport. Implants should be positioned on themaxillary crest with stable anchorage in the zygo-matic bone.Quad zygoma represents a cross-arch stabiliza-

tion system in which the provisional prosthesis of-fers implant stabilization immediately aftersurgery. Although insertion torque above 35Ncmfor every single implant is always a goal, it is notmandatory.Given that in many scenarios there is lack of

implant integration at the crest, a slight bending(but not rotational) movement can be expectedwith some implants. This ceases as soon as theprosthesis is connected.If adequate primary stability is not achieved

(rare), the implants are submerged. Under no cir-cumstances should the implants be loaded freestanding.

POST-OPERATIVE CARE

Post-operative care is similar to that of anyimplant surgery. In addition, sinus instructionsare given. Analgesics and anti-inflammatoriesare prescribed, as well as antibiotics for a1 week course. Post-operative follow-up visitsare scheduled 1 and 2 weeks after surgery andthen at 2, 3 and 6 months after surgery. After 4to 6 months of loading, the acrylic resin provi-sional prosthesis is removed to assess the

oma implants. (B) Implants in place.

Fig. 14. Zygoma anatomic guided approach. (A) ZAGA 0 (B) ZAGA 1 (C) ZAGA 2 (D) ZAGA 3 (E) ZAGA 4.

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implants and soft tissues prior to fabrication of thedefinitive prosthesis.

COMPLICATIONS OF ZYGOMATIC IMPLANTSPenetration into the Orbital Cavity

It is possible to penetrate the orbital cavity espe-cially in zygomatic bones less than 1.8 to 2 cm inheight.3 Damage to the orbital contents andsurrounding musculature can ensue. Appropriatetraining and experience are required to performzygomatic implants and in particular thequad zygoma technique. Pre-operative planning,adequate exposure, and an in-depth knowledgeof the regional anatomy are fundamental to per-forming this procedure safely. Caution must betaken to avoid inappropriate positioning of the im-plants; some authors advocate having a 3-dimen-sional printed model from the patient’s CT scan toenable appropriate study of the site as well asplanning and rehearsal of the surgery.22

Peri-Implant Mucositis, Peri-Implantitis, andRetraction of Buccal/Labial Peri-Implant Tissue

These complications partly depend on theapproach selected for implant placement. In aretrospective study, the classic intrasinus

approach was compared with ZAGA.23 Both pro-cedures obtained similar clinical outcomes withrespect to implant survival. Nevertheless, theZAGA concept minimized the risk of maxillary si-nus associated pathology and resulted in lessbulky, more comfortable, and easier-to-cleanprostheses. The relationship between the soft tis-sues, the bone, and the portion of the implantoutside the malar bone remains controversial.Inflammation and tissue retraction can occuraround zygomatic implants especially when theimplant is placed on the crest without being sur-rounded by bone (Fig. 15). Zygoma implantswithout threads in the coronal two-thirds of theimplant are available for use in these scenarios,with the goal to minimize soft tissue complications.Interestingly, it has been shown that there is nor-mally gingival attachment at this level.19 Some au-thors suggest the use of the buccal fat pad24,25 tothicken the tissues at the crestal implant level toprevent retraction of the tissues in the extramaxil-lary technique. These reports need to be sup-ported by scientific studies. The surgeon shouldbear in mind that if the patient’s anatomy dictatesan exteriorized or extramaxillary approach, it iscritical that at the crestal level, the implant is actu-ally embedded in the maxilla rather than lying truly

Fig. 15. (A-B) Retraction of tissue around zygomatic implant.

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lateral to it. The implant should not alter the crestalanatomy and be bulky.

Infection at the Implant Apex

An extraoral swelling just lateral to the malar bonewith or without a cutaneous fistula is indicativeof an underlying infection in the malar bone(Fig. 16). This may occur years after the implantshave been placed. It can be treated with systemicantibiotics, debridement of the area (via intraoral orextraoral approach), and resecting the apex of theimplant so that it is flush with the surrounding boneas needed. This complication can be avoided byensuring that the implant length is appropriate;the implant apex should engage the outer zygomacortex but not extend much beyond it. In addition,lack of contamination and ensuring good irrigationof the area throughout the procedure and specif-ically prior to closure is important.

Sinusitis

Sinusitis is the most common complication ofzygomatic implants historically.The prevalence of sinus pathology associated

with zygomatic implant surgery remains contro-versial. It would appear that the risk can bereduced by meticulously assessing the status ofthe sinuses before implant placement, treatingany factors that will predispose the patient tosinus pathology, and by using the exteriorized or

Fig. 16. (A) cutaneous fistula. (B) Bone loss at apex of zyg

extramaxillary approach or the extended sinus liftapproach when indicated. If sinusitis occurs thatdoes not resolve with antibiotics, functional endo-scopic sinus surgery is required to clear the sinusand ensure patency of the osteomeatal complex.The implant does not require removal.

Oral-Antral Communication

In cases in which the alveolar bone is very thin orvirtually nonexistent, even a slight overpreparationof the osteotomy site or bone loss over time at thealveolar crest may result in an oral-antral commu-nication (OAC) (Fig. 17). Caution in preparing thisarea is crucial. Closure of the OAC in these casesare difficult. The use of the buccal fat pad has beenreported.25 A different approach to deal with thiscomplication is the use of bone morphogenic pro-tein.26 There is no consensus on the best way tomanage this negative outcome. Evidence in theliterature is required to determine the most pre-dictable method of resolution and prevention.

Paresthesia/Dysesthesia

Patients may experience temporary or permanentaltered sensation in the distribution of the infraor-bital nerve. Careful identification of this neurovas-cular bundle, preservation, and protection arecrucial to prevent this complication. The zygoma-ticofacial nerve may also be injured resulting inloss of feeling over the cheek prominence.

omatic implant.

Fig. 17. (A, B) OAC. (C) minimal bone at crest; susceptibility to OAC.

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Fracture of the Zygomatic Implant

Fracture of the zygomatic implant is due to inap-propriate implant positioning resulting in overload-ing and biomechanical failure (Fig. 18). This is arare complication.

Prosthetic Complications

These include loosening of the transepithelialabutments, loosening of the prosthesis fixationscrews, and fracture of the prosthetic teeth orprosthetic structure.

SCIENTIFIC EVIDENCE FOR THE QUADZYGOMA

There is an abundance of literature to date sup-porting the use and high survival rates of zygo-matic implants when combined with anteriorimplants. The quad zygoma concept came intoclinical practice years after the single zygomaticimplant (combined with conventional implants)proved itself. The literature in this regard is reflec-tive of this timing. There are only a few studies onthe quad zygoma procedure. This is certainly notreflective of the international use of this techniqueand the frequency of its use. The authorsencourage others to report on this implantsolution.

Fig. 18. Fractured zygoma implant.

In 2007, Duarte and colleagues12 analyzed 12patients who were treated with 4 zygomatic im-plants to address severe maxillary atrophy. Imme-diate loading was performed. Forty-eightzygomatic implants were placed. One implantfailed to achieve osseointegration at the 6-monthfollow-up; integration was maintained for all otherimplants at 30 months. There were no prostheticcomplications.

Stievenart and Malevez13 in 2010 reported on aclinical series of 20 patients with extremelyresorbed maxillae rehabilitated with 4 zygomaticimplants: 10 had 2-stage implant treatment andthe remaining 10 had single stage implant treat-ment. The cumulative survival rate after 40 monthswas 96%.

In a 5-year prospective study, Davo and Pons3

obtained high long-term survival rates (implants98.5% and prosthesis 100%) with few complica-tions. The oral health-related quality of life of thesepatients was found to be normal even with thepassage of time.

A meta-analysis by Wang and colleagues27 in2015 revealed that the quad zygoma treatment so-lution is a reliable technique for maxillary rehabili-tation. The zygomatic implant survival rateweighted mean was 96.7%.

A systematic review and meta-analysis byAboul-Hosn Centenero and colleagues28 evalu-ated the survival rates of 2 zygomatic implantscombined with regular implants versus 4 zygo-matic implants. No statistical differences wereseen using 1 treatment over the other in terms ofsurvival and failure rates.

A recent randomized clinical trial comparedimmediately loaded cross-arch maxillary prosthe-ses supported by zygomatic implants to conven-tional implants placed in augmented bone. Thisstudy revealed that immediately loaded zygomaticimplants are associated with significantly fewerprosthetic and implant failures (1 out of 36 patients

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with zygomatic implants, compared to 6 out of 37patients with conventional implants) and a shortertime required for functional loading (1.3 days withzygomatic implants, compared with 444.3 daysfor conventional implants).9

All studies report some complications with thequad zygoma technique. Surgeons and patientsmust be aware and informed of the potentialadverse outcomes; steps must be taken to mini-mize such occurrences. The evidence compiledto date suggests that implants placed in thequad zygoma format may still offer a better reha-bilitation modality for the severely atrophic maxilla.Nevertheless, long-term data and more studiesare needed to confirm or dispute these preliminaryfindings. There are no randomized controlled clin-ical trials comparing surgical techniques for theplacement of zygomatic implants. It is the authors’opinion, however, that the prudent approach isone in which the patient’s anatomy dictates thesurgical technique as per Aparicio and colleagues.Future developments needed in quad zygoma

surgery encompass the ability to accurately trans-fer virtually planned implant positions clinically. Todate, stereolithographic templates, either bone-supported or mucosa-supported, have beenused to install zygomatic implants in the desig-nated positions based on computer-assisted plan-ning. However, there is no effective mechanismyet to physically control the drilling trajectory forzygomatic implants and ensure precision of place-ment. Therefore, deviation between the actual andplanned implant position is inevitable. This isclearly less tolerable in circumstances of extremeresorption in which the quad zygoma approach isutilized. The exact position of both implants inthe malar bone is critical. A novel device designedto increase the precision of guided surgical place-ment of zygomatic implants has recently beenpublished.29 To date, however, given the limiteddata in the literature, guided zygoma surgeryshould be considered experimental.An alternative novel approach to achieving pre-

cision with zygoma placement entails surgical nav-igation. A recently published study examined theuse of surgical navigation for zygomatic implantplacement in patients with severe maxillary atro-phy. The results seem to be promising.30 Moredata in this regard will be most interesting.

SUMMARY

The quad zygoma provides a predictable and effi-cient way to rehabilitate the severely atrophicmaxilla. It is an advanced surgical procedurethat requires appropriate training, planning, andmeticulous surgery. It is not without potential

complications. If executed appropriately, how-ever, these can be minimized. Provided that thesurgeon has significant clinical experience, theuse of 4 zygomatic implants with an immediateloading protocol is typically predictable. It en-ables implants to be placed in an alternateanchorage site, eliminating the need for moreinvasive and lengthy surgical reconstruction ofthe maxilla.

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