Initial situation

Fifty-five years old healthy female who is not taking any medication and never smoked. She complained about her mouth aesthetic aspect, deficient function, oral bleeding and tooth mobility both at maxilla and mandible (Fig. 1). Her oral hygiene was considered good. She wore an unstable full arch PFM (Porcelain Fused to Metal) restoration at the upper jaw. Several mandibular teeth were missing.

The panoramic X-ray confirmed an extensive bone loss at maxilla and mandible with some remaining teeth which were all considered hopeless (Fig. 2).

Treatment planning

The lack of bone and the wish of the patient to benefit of a straight-forward rehabilitation solution oriented our decision making towards the insertion of a combination of conventional and zygomatic implants. Particularly the Straumann® Zygomatic implants (Institut Straumann, Basel, Switzerland) present some advantages comparatively to others available on the market as follows:

• a rough surface at the apical end,
• a non-threaded smooth surface in the medial part,
• a small diameter tip (2,6 mm),
• a choice between two different types, ZT (Zygo round) and ZC (Zygo flat) offering versatility to address different clinical situations,
• a prosthetic armamentarium compatible with Straumann® conventional implants.

Due to the specificity of the above Straumann® Zygomatic implants and depending on the clinical situation it was foreseen to proceed according to ZAGA 0 class on the right side and to ZAGA 3-4 on the left side of the patient.

It was decided to set up the surgical treatment in three successive phases:

1. Teeth extraction, immediate placement, immediate loading of a screw-retained full arch temporary restoration at the mandible, in order to restore an accurate occlusal plane (insertion of 4 Anthogyr® Axiom REG, diameter 4 mm, length 12 mm implants with multi-unit abutments, Anthogyr SAS, Straumann Group, Sallanches, France).

2. Teeth extraction, immediate placement and immediate loading of a screw-retained full arch temporary bridge on 4 implants (Anthogyr® Axiom PX implants, diameter 3.4 mm, length 12 mm, Anthogyr SAS, Straumann Group, Sallanches, France) at the maxillary, in order to restore aesthetic and function and foster tissues healing particularly on the left side. All four implants reached a primary stability which was judged suitable for immediate loading.

3. Two months later, placement of 2 Straumann® Zygomatic implants under the maxillary sinuses. The purpose of inserting these was clearly to avoid the presence of any cantilevers (Fig. 3-4) on the final restoration.  The delayed placement enabled to take advantage of a fully regenerated gingival tissue facilitating its management at the cervical part of the implants.

Four months after the last surgical procedure, 2 screw-retained full arch CAD-CAM titanium bridges with composite teeth were inserted.

Surgical procedure

Two months after maxillary implants placement the temporary bridge was removed and the soft tissues healing at posterior palate checked out (Fig 5). A good gingival health around the zygomatic implants emerging heads guaranties the absence of complications.

On the first quadrant, a large flap was raised with an oblique incision starting from  the tuberosity followed by a straight incision on the palatal side of the remaining crest (in order to place keratinized tissue around the future abutment) and a vertical incision from the distal area of the distal implant up to the ridge of the nasal fossae. This flap design has the advantage of some free space to place a retractor into the fronto-zygomatic notch without tearing the soft tissues. A small bony window was prepared at the upper distal part of the anterior sinus wall to visualize the lower aspect of the zygomatic bone. An excellent bone exposure and access is mandatory to start with the first drilling away from the buccal part of the sinus wall. A round bur was used to drill through the palatal bone and to engage the zygomatic bone. Then, the final drill went through the zygoma. It is imperative to evidence the emergence of the drill for 2 reasons as follows:

• stay away from the orbital cavity and the temporal fossae.
• control that at the end of the insertion phase, the zygomatic implant apical end slightly emerges from the zygomatic bone and that the cervical end of the implant becomes positioned as close as possible to the residual alveolar ridge.

At drilling completion, a gauge was used to choose the implant size (Fig. 6).

In this clinical situation where the body of the implant is totally intra-sinus (ZAGA 0) a Zygo-Tunnel (ZT) implant, diameter 4.3 mm, length 40 mm (Institut Straumann, Basel, Switzerland) was selected to engage the palatal bone with its threaded part (Fig. 7). The implant was inserted manually with a dedicated screwdriver, the final insertion torque reached 55 Ncm.

Before removing the implant mount, the screwdriver helps the surgeon to properly position the implant head by slight rotations, in order to be as close as possible to the prosthetic corridor. The implant head was 55° angulated and a straight screw retained abutment of 1,5 mm height (Institut Straumann, Basel, Switzerland) was placed and tightened up to 35 Ncm (Fig 8).

The last part of the surgical procedure is decisive as the implant shall be surrounded by keratinized gingiva, to create a safe biological environment. Most of the complications consist in mucositis, generally followed by sinus complications due to oro-antral communication (Fig 9). This case demonstrates how the initial flap design contributed to a large presence of keratinized tissue retracted from the palate. Sutures were placed buccally.

In the present case, it was decided not to connect the implant to the temporary bridge.

On the left side, the anatomical situation was different. The buccal aspect of the maxillary bone was concave, and the remaining crest was very thin (ZAGA3 class). A large bed was prepared to place the implant as close as possible to a suitable prosthetic emergence positioned in a load bearing palatal bone (Fig. 10).

In order not to place the head of the implant and the abutment directly in the sinus, it was decided to use a longer implant and to place the abutment at palatal bone level (Fig. 11).

In this clinical situation, in order to facilitate the gingival healing and decrease the tension on the flap, a Zygo Channel (ZC) implant, diameter 4.3 mm, length 42.5 mm (Institut Straumann, Basel, Switzerland), with a flat non threaded buccal part is used.

After 4 months of healing, the temporary bridge was removed, the tightness of each abutment (Straumann® screw retained abutment, diameter 4.6 mm, height 1,5 mm) checked (35 Ncm) and the prosthetic procedure started.

Prosthetic procedure

An analog impression with plaster was done. The stone model with copings in place was used to mill a titanium frame by CAD-CAM. Composite teeth and acrylic gingiva were disposed on the metallic structure.

Treatment outcomes

The final restoration was screwed on the abutments at 15 Ncm torque and the occlusion adjusted (Fig. 12).

Furthermore, we made sure that the design of the prosthesis provides enough space to facilitate dental oral hygiene procedures (inter-dental brushes).

Finally, X- rays follow-ups by means of OPG and CBCT were performed at the end of the treatment (Fig 13, 14 & 15).

Conclusion

The present report is an element more to confirm that the use of Straumann® zygomatic implants avoids any grafting procedures reducing the whole treatment time. Beside the relatively short-term follow-up reported here this contributes to a high level of patient satisfaction.

The present case demonstrates more specifically that the implemented zygomatic implants- based procedure avoids the use of bilateral cantilevers.

It can be expected that a more even loading allocation on conventional and zygomatic implants will ensure full maxillary arch rehabilitation stability and consequently increases the long-term prognosis.

It has to be outlined that the success of zygomatic procedures is also directly related to the quality of the surgery and most of the time the failures are the consequences of an inappropriate prosthetic restoration.

Acknowledgements

The author sincerely thanks Dr Maureen Thiel for his active role during the treatment phase (clinical follow up and aesthetic try-in) and Mr. Gilles Giordanengo (Pro Lab, Toulon, France) for manufacturing the prosthesis.

We also thank Dr Ed Bedrossian for teaching us the technic and sharing his knowledge.