Guided and Navigation Techniques for Zygomatic Implants

Key points

  • The application of surgical navigation in complex craniomaxillofacial procedures has become helpful in transferring the surgical plan to the patient and in avoiding pertinent anatomic injuries.

  • In quad approach, the potential risks of surgical complications are minimized by navigation.

  • It is recommended to use individualized fiducial configuration in zygomatic implants placement for patient with maxillectomy defect.

  • Errors in zygomatic implant navigation do occur that the surgeon should be aware of.

With the continuous improvement of medical devices, the use of dynamic navigation systems in dental implants is gradually increasing worldwide. The ideal implant position can be determined in advance with dynamic navigation system software, and the preoperative design can be accurately transferred to the operation with guidance, especially in the esthetic area of the anterior teeth and in patients with complex anatomic conditions in the operation area.

For patients who suffer from severe maxillary atrophy, guidance systems have also been gradually used in zygomatic implant surgery, which is considered a reliable and promising approach for the rehabilitation of oral function. The following 2 cases show the use of real-time navigation in classic zygomatic implant surgery for an atrophic maxillary edentulous patient and triple zygomatic implant insertion for the rehabilitation of a patient with maxillary bone defect.

Case 1

A 65-year-old female patient, healthy and a nonsmoker, requested a fixed prosthesis for edentulous jaws. The patient had been diagnosed with severe generalized periodontitis and had maxillary anterior teeth extracted 2 weeks before implant consultation. Clinical examination revealed moderate to severe atrophy of the edentulous maxilla and mandible ( Fig. 1 ). Initial soft tissue healing was achieved in the extraction sockets of anterior maxilla ( Fig. 2 ). Panoramic and cephalometric image analysis showed pneumatization of maxillary sinuses and severe bone resorption in the posterior maxilla and mandible ( Fig. 3 ).

Fig. 1
( A ) Frontal view of the patient pretreatment. ( B ) Lateral view of the patient pretreatment.

Fig. 2
Initial healing 2 weeks after extraction of maxillary anterior teeth.

Fig. 3
( A ) Preoperative panoramic radiograph: pneumatization of the maxillary sinuses and severe bone resorption in posterior maxilla; adequate bone height in anterior maxilla. ( B ) Preoperative cephalometric radiograph: insufficient bone width of anterior maxilla; severe resorption of mandible and posterior maxilla.

A cone beam computed tomographic (CBCT) scan was taken. Severe vertical bone loss was observed in regions of maxillary right central and lateral incisor. Although adequate bone height was present in the anterior region of the maxilla, inadequate bone width limited conventional implant placement ( Fig. 4 ). Based on the division of the edentulous maxilla into 3 radiographic zones, by Bedrossian and colleagues, insufficient bone volume for the installation of the implants was observed in zones 1, 2, and 3 without extensive bone grafting.

Fig. 4
Preoperative CBCT: ( A ) limited bone height of 4 mm to 5 mm in right premolar area; ( B ) severe vertical bone loss in right central and lateral incisor areas; ( C , D ) inadequate bone width in bilateral incisor and canine areas.

Digital Imaging and Communication in Medicine (DICOM) data were imported into the Nobel Clinician (Nobel Biocare AB, Göteborg, Sweden) implant planning software. Preliminary planning for zygomatic implants using quad approach was also conducted at this stage.

Placement of the zygomatic implants was performed using a dynamic navigation system. On the day of surgery, bone-anchored mini titanium screws were used as fiducial markers and were broadly spread in a polygon arrangement across the maxilla ( Fig. 5 ). An intraoperative CBCT scan was performed with fiducial markers fixated, and the data were imported to the planning software for the navigation surgery (iPlan Navigator, BrainLAB AG, Munich, Germany). The data from the initial plan, containing information about the positions of implants, were exported as an STL file and overlapped with the new DICOM file in the navigation surgery software.

Fig. 5
On the day of the surgery, registration bone-anchored mini pins were inserted in the residual bone covering as much of the maxilla as possible.

The skull reference base was rigidly secured within the hairline with a single self-tapping titanium screw ( Fig. 6 ) under general anesthesia. The navigation system (VectorVision2, BrainLAB AG, Munich, Germany) was registered by using a navigation probe to contact the surface cavity of the mini screws ( Fig. 7 ). A custom-made rigid bracket integrating the reference array was connected to the zygoma drilling handpiece, enabling constant visualization of the drill on the screen in real time. During this procedure, the position of the bur was actively followed on the display with a 3D image of the patient, allowing the surgeon to adjust the position and angulation of the tool. A midcrestal incision and vertical releasing incisions at the maxillary tuberosity region were made. The lateral sinus wall and a part of the zygomatic complex were exposed, a window of 5 × 10 mm was made in the lateral aspect of the sinus wall, and the sinus mucosa was reflected. Zygomatic implants (Brånemark System Zygoma, Nobel Biocare, Göteborg, Sweden) were placed with the guidance of the navigation system, and complete drilling procedure followed the trajectories from the entrance point to the exit point, as planned. In zygomatic drill-path preparation, calibration had to be executed before the initial drilling and later, every time the drill was changed; then the direction vector of the drill, relative to the coordinate system of the reference frame, could be obtained ( Figs. 8–11 ).

Fig. 6
A view of a real-time navigation system used in zygomatic implant surgery: the skull reference base with reflected spheres as the tracking device of the head and the reflected spheres for the tracking of the handpiece.

Fig. 7
( A ) During the operation, the registration procedure was performed by individually contacting the registration points (on one of the registration mini screws anchored in the middle of the palatal line) with a probe, from which a connection between the virtual image and the patient was established. ( B ) The starting of registration procedure on the screen. ( C ) The screen showed the same procedure of registration simultaneously as ( A ).

Fig. 8
( A ) Set the start point with the round bur. ( B ) Position of the round bur was actively followed on a display with the three-dimensional image of the patient, allowing the surgeon to adjust the position and angulation of the tool.

Fig. 9
( A ) For the calibration of the axis of the surgical drill, the drill was inserted into the prefabricated axial hole. ( B ) The calibration procedure showed on the screen.

Fig. 10
( A ) The drilling was conducted with the guidance of the navigation system for the right anterior zygomatic implant. ( B ) The surgical drill (yellow column) displayed on the screen, combining with the image and planned trajectories (pink column). The tip of the drill was close to the base of the zygomatic bone.

Nov 5, 2021 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Guided and Navigation Techniques for Zygomatic Implants
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