Initial situation

A 66-year-old lady in good health presented with extremely resorbed maxilla and mandible as the major consequence of 40 years of complete denture wearing. No internal sinus lesions were depicted clinically nor radiologically.

She referred to be an active person, non-smoker and whose life has been wasted by non-retentive and unstable removable prostheses since a long time. She complained about her discomfort in private and social life.

For a long time she refused to receive a bone grafting procedure because she considered it as a complex and long treatment that would not allow her to wear a prosthesis during a healing period.

Treatment planning

As a general principle, the clinical evaluation dictates the final prosthesis design and the radiographic evaluation directs the number and type of implants.

The distance between the crestal gingiva and the occlusal plane is indicative of the degree of resorption of the jaws. The patient was lacking teeth and gingiva volume on both arches, and therefore was a candidate for grafting reconstruction or artificial gingiva.

The position of her smile line confirmed that an esthetic hybrid fixed prosthesis was indicated at the maxilla.

The dental technician manufactured a radiological template based on the patient's removable prosthesis which gave the relationship between the emergence of the implants and the future prosthesis on a 3-dimensional Xray analysis.

The 3D X-ray analysis (CS 8100 3D Carestream Dental with CS Imaging) confirmed the the composite aspect of the bone defect (vertical and horizontal dimensions) (Fig. 1).

The maxillary 3D imaging showed a large pneumatized sinus and an alveolar ridge lacking width. A depression of the right zygomatic bone was also detected, and this was the result of a serious facial trauma when the patient was young.

The maxillary ridge resorption was centripetal and apical, whereas at the mandible, the remaining ridge shifted centrifugally and apically. Consequently, the resulting edentulous maxillary arch was internal to the mandibular arch (Fig. 2).

The continuous bone resorption of the edentulous jaws resulted in a knife-edge type of residual ridge.

An extra-sinus or intra-sinus technique was not chosen as it was foreseen to insert the drill through the knife-edge residual ridge and through the zygoma bone.

The goal was to preserve the vestibular bone located at ​​the implant platform providing immediate mechanical stability as well as periodontal durability and avoiding vestibular dehiscence.

With such a maxillary morphology the placement of the implant heads at anatomical dental position results in an “off alveolar ridge” positioning. In order to preserve the gingival support and because of mechanical reasons it was decided to keep as much bone as possible around the implant platforms to prevent soft tissue dehiscence.

Four zygomatic implants were planned to avoid extensive on-lay bone grafts in conjunction with bilateral sinus in-lay grafts, consequently avoiding complications due to bone grafting morbidity, and allowing for immediate loading with a screw-retained provisional bridge.

The horizontal bone thickness at mandible dictated the insertion of 4 mini-implants.

The conclusion of the clinical examination plaid for the insertions of a final hybrid fixed prosthesis at maxilla and an over-denture at mandible.

Surgical procedure

The entire surgery was performed under local anesthesia without IV sedation. The implants were placed free-hand.

There were no bone augmentation procedures with autografts, allografts nor biomaterials but the soft tissues were managed with attention.

In the maxilla, a flap was carefully raised to get a good visual access to the crest and to the zygomatic arch. A crestal incision was made on the palatal side from the top of the residual ridge to provide a large amount of keratinized gingiva around the emergence of the implants at a later surgical stage. This approach allows for a soft tissue peri-implant protection essential for the long-term survival of the implant.

Special care was taken to stay away from the palatal artery in the posterior area.

Retractors were positioned to protect the soft tissue from drilling and to ensure the preparation of the zygomatic implant beds under visual control.
As the surgery was performed under local anesthesia, the flap was not raised over the entire jaw but in one sector firstly (left maxillary in this case) followed by the second sector (right maxillary).

For each half maxillary jaw, two vertical releasing incisions were made in the retro-tuberosity area and in the distal side of the nasal spine.

A corticotomy of the anterolateral wall of the maxillary sinus was performed with a diamond ball drill and allowed for a direct visualization of the corner of the maxillary sinus roof and a clear view on the path and the tip of the drills.

In the left side of the maxilla, the crestal bone could not support conventional implants due to the severely horizontal and vertical resorbed ridge. Therefore, a slot was made with a special Straumann drill at the second premolar site, and one Straumann® Zygomatic Implant ZAGA™ Flat (47,5mm) was placed in order to get the implant neck submerged into the bone crest.

At the lateral incisive site, the bone was partially present and one Straumann® Zygomatic Implant ZAGA™ Round (40mm) was inserted. The tapered design provided a good grip in the zygomatic bone (Fig.3). Afterwards, two Straumann^® Zygomatic Screw-retained Abutments 3,5mm were screwed at 35N/cm and the flap was closed.

In the right side of maxilla, two Straumann® Zygomatic Implant ZAGA™ Round were placed keeping a knife-edge ridge in vestibular protection. The coronal threads and micro-threads stabilized the implant in this residual crestal bone and the implants were anchored through the zygomatic bone with the tapered apical portion. An Straumann® Zygomatic Implant ZAGA™ Round 45mm was placed in the lateral incisor site, while a Straumann® Zygomatic Implant ZAGA™ Round 40mm in the first premolar site. Finally,

two Straumann^® Zygomatic Screw-retained Abutments 3,5mm were screwed at 35N/cm. (Fig. 4, 5, 6 and 7).

For both sides, a pedicled buccal fat pad was used for the closure of the open sinus wall   creating a protective layer between the implants and the mucosa to prevent an erosion of the mucosa. Suturing was performed using resorbable 5.0 monofilament (Monofast 5.0).

In the mandible, a crestal incision preserving the keratinized gingiva was attentively performed and the alveolar ridge prepared to place 4 Straumann® Mini Implant 12mm between the two mental foramina (Fig. 8) achieving initial primary stability.

Immediately after surgery completion, impression caps were snapped onto the mandibular Straumann® Mini Implant, and the removal prosthesis itself was used as an impression tray.

For the maxilla   abutment-level open tray impression posts were screwed on and a total impression was taken using the perforated impression tray and vinyl polysiloxane material (Honigum Mono DMG).

The dental laboratory completed  the final work and six hours after surgery the temporary bridge was screwed onto the Straumann® Zygomatic Implant and their zygomatic SRA.
The removable prosthesis with the Optiloc® yellow retention inserts (medium retention force) was placed on the Straumann mini-implants.

All implants were loaded immediately on the same day (Fig. 9 and 10).

The post-op medication was as follows:

• Amoxicillin/clavulanic acid 1 gr twice a day starting 24 hours before surgery for 8 days
• Pain medication: Ibuprofen 400mg & Paracetamol 1g   alternately in case of pain
• Rinofluimucil Nasal Spray (decongestant), 2 spray in each nostril 3 times per day for 5 days.
• Mouth rinse & Chlorhexidine gel, 3 times a day for 5 days
• 2 ice packs (local application)

The patient was recommended to follow a soft diet during the first 4 months following the surgery.

Final restorative prosthetic procedure

After a five months loading period (Fig. 11), open tray SRA impression copings were placed onto the SRA abutments and final full arch impressions were done with a polyether material (Impregum 3M) to capture both the positions of the implants and soft tissues.

Afterwards, the maxillary cast was controlled with a lab-made verification jig and mounted using the patient’s provisional bridge as a reference.

The final acrylic resin bridge with a CADCAM high-precision milling titanium bar (Createch) was screwed with a passive fit on the implant abutments. (Fig. 12)

In the very atrophied maxilla the emergence profile of the zygomatic implants appeared in a palatal position (Fig. 13). This was initially planned accordingly with localized emergences that can be easily cleaned on the palatal side and which did not bother the patient (Fig. 14).

The contact on the gingival ridge is only with the titanium framework without any concavity that could trap the food (Fig. 15).

At this stage the yellow retention inserts (light retention force) were replaced with green retention inserts (medium retention force) in the mandibular overdenture (Fig. 16).

Treatment outcomes

It is well known that the poor stability of a complete denture is a common problem due to the bone atrophy of the edentulous ridge.

Clinicians own experience added to some scientific evidence reinforce the fact that the quad zygoma approach offers a predictable solution to treat this type of challenging maxillary atrophy.

This approach provides patients with an efficient solution based on the immediate loading of a fixed restoration. 

In the same manner, the rehabilitation with 4 mandibular mini-implants of edentulous patients suffering of extremely resorbed alveolar ridge opens very interesting perspectives. The existing risk-benefit ratio seems to be low when compared to grafting techniques. This rehabilitation approach constitutes a promising option.

The final outcome was a magic moment for this patient who suffered from removable prostheses discomfort during 40 years (Fig. 17 and 18).

Acknowledgements

The author thanks the dental laboratory “Oral Beauty”, Remiremont, France and “3D Printing” by Omar Bouhelal Schirmer, Paris, France for their highly appreciated contributions.