Four well-distributed zygomatic implants (quad zygoma) is a first-line approach in severe maxillary atrophy or a rescue therapy after implant failure.
Adequate implant stability allows immediate rehabilitation with a fixed bridge or an overdenture.
Zygoma anatomy-guided approach, adapting the placement of implants to different anatomies, is highly recommended.
Successful quad zygoma technique requires advanced surgical skills.
Quad zygoma is not free of complications, including sinus infections, oral-antral fistula, paresthesia, implant apex infection, or tissue retraction.
Introduction and indications
Severe maxillary atrophy is becoming more common because of the aging population ( Fig. 1 ). The use of 4 zygoma implants (quad zygoma), in which 2 implants are placed bilaterally with appropriate anterior and posterior spread and inclination, has been a great advance in the rehabilitation of severe alveolar bone atrophy ( Fig. 2 ). ,
Quad zygoma is indicated as a first-choice treatment in severe maxillary atrophy and as a rescue treatment after bone grafting and implant failure. The indication of using short implants anteriorly combined with a zygoma implant posteriorly remains unclear, and in the authors’ experience it seems advisable to perform a quad zygoma whenever the bone loss anteriorly precludes placement of conventional implants of at least 10 mm in length ( Fig. 3 ). Fixed or removable prostheses can be used for rehabilitation ( Fig. 4 ).
Specific oral contraindications include untreated periodontal disease, poor oral hygiene, restricted mouth opening (<3 cm anterior interarch distance), acute or chronic infection/inflammation in the proposed implant sites, acute or chronic sinusitis with obstruction of the osteomeatal complex, and malar bone abnormalities.
Preoperative prosthetic treatment planning is critical for success. Imaging studies include standard orthopantomography, cone beam computed tomography, and the use of an implant planning software with virtual three-dimensional assessment of the implant lengths and appropriate positioning ( Fig. 5 ).
Details of the surgical procedure of quad zygoma have been previously reported. The operation is performed under intravenous sedation or general anesthesia, with local anesthesia, and administration of antibiotics preoperatively.
Briefly, the main steps include a full-thickness palatal-crestal incision on the alveolar ridge from first molar to first molar, bilateral distal vertical releasing incisions, careful subperiosteal dissection with preservation of the infraorbital neurovascular bundle, pending anatomy and oblique osteotomy in the lateral wall of the maxilla adjacent to the sinus with elevation of the Schneiderian membrane, preparation of the osteotomy site and a drilling sequence according to the manufacturer’s instructions, placement of the implants, placement of the abutments, and flap coaptation to provide a collar of keratinized tissue around the implants.
Abundant irrigation at the crest and the apex of the malar bone is crucial to prevent overheating. Extraoral palpation of the malar bone while drilling the osteotomy is advisable.
In relation to positioning of the zygoma implants, the goal is to place 2 implants into a finite space with appropriate prosthetic emergence and as midcrestal as possible. This placement can be achieved in most cases given the height and width measurements of a typical malar bone. It should be noted that the anterior implants are placed first emerging at the level of the canines or lateral incisors, followed by the posterior implants emerging in the molar or premolar areas. The position of the implants is inside or outside the sinus depending on the patient’s anatomy, specially the curvature of the lateral wall of the maxilla. Crestal implant emergence is highly recommended for the design of the appropriate prosthesis.
Surgical techniques of placement of 4 zygoma implants
The ideal surgical technique has not been established. Minimization of potential sinus complications and tissue retraction at the crest of the ridge as well as improvement of the implant emergence at the alveolar crest without compromising survival rates are the main objectives of the different surgical protocols. The following techniques have been described and can be used to achieve the most appropriate anatomically guided placement of the implants.
Classic Brånemark approach
The implant passes through the maxillary sinus, and the prosthetic platform is on the palatal crest of the alveolus. The lateral antrostomy window perforates through the sinus allowing direct visualization of the sinus roof ( Fig. 6 ).
Sinus slot approach
The implant follows the path of the slot made through the zygomatic buttress, with minimal invasion into the sinus. This approach involves a more crestal position of the prosthetic platform.
Classic exteriorized approach
A spherical drill is used for the osteotomy penetrating the residual ridge near the top of the crest from palatal to buccal. The ridge is then transfixed with the drill emerging in the buccal aspect of the ridge external to the sinus. , A maxillary antrostomy is not always necessary. Drilling continues along the outer aspect of the lateral wall of the sinus until reaching the lateral portion of the zygomatic bone, which is perforated, surpassing the bone’s outer cortex. Implants are placed outside the sinus ( Fig. 7 ).
The lateral wall of the maxilla is prepared by design of a groove to allow burs direct access to the body of the zygoma. , The implant is anchored exclusively in the zygomatic bone and allocated in this groove.
Extended sinus lift
To maintain the integrity of the maxillary sinus membrane during osteotomy preparation, an extended sinus lift is performed in which the bone window is retained. This technique potentially eliminates the risk of sinusitis and may increase implant stability by promoting bone formation adjacent to the elevated sinus membrane and bone window ( Fig. 8 ).