A complete maxillectomy for neoplastic lesions leads to serious oral dysfunction. Zygomatic implants for fixed bridge support are considered beneficial for maxillary defects after tumor resection.
Materials and Methods
This clinical study examined the management of patients with different maxillary defect types who underwent delayed rehabilitation using zygomatic implants and immediate prosthetic loading. Virtual preoperative planning and intraoperative navigation were performed in all cases.
Five patients were treated with this new method. The total number of zygomatic implants positioned was 17. Four patients had immediate loading of a fixed prosthesis and 1 had delayed loading. One patient had 1 failed implant.
The use of preoperative virtual surgical planning and an intraoperative navigation system allows the surgeon to achieve safer implant positioning in a complex anatomic site. A systematic bone defect classification was created and a specific treatment protocol is proposed for each type of defect.
Oncologic bone resection for neoplastic lesions involving the maxilla leads to serious oral dysfunction with respect to speaking, swallowing, chewing, and quality of life. Defect classification systems enable clinicians to choose the type of rehabilitation and determine a functional prognosis. Since the publication of the study by Ohngren, many classification schemes have been proposed to describe the anatomic boundaries of maxillectomy defects.
A complete maxillectomy produces complex defects of the alveolar bone, palate, paranasal sinuses, and orbital floor. Loss of these anatomic structures has relevant functional and esthetic consequences. Reconstruction of this region should 1) prevent any communication between the oral cavity and the nasopharynx, 2) reconstruct the palatal surface, and 3) achieve facial symmetry and good facial morphology.
Several surgical reconstruction options exist, including nonvascularized grafts, local flaps, and microsurgical reconstruction with bone or soft tissues. However, in many cases, dental implants have been used to obtain functional restoration through mechanical retention of dental prostheses.
Implant placement and subsequent prosthetic rehabilitation are often difficult to obtain after maxillectomy because of a lack of bone alveolar tissue and gingiva. Dental implants can be considered a viable restorative option only when the basal maxillary bone is preserved.
Zygomatic implants are used to rehabilitate patients with insufficient bone volume for “traditional” dental implants. These implants are inserted into the zygomatic bone when alveolar bone is deficient after maxillectomy. However, the application of zygomatic implants in reconstructive surgery is often associated with various problems, including deficiencies of bone tissue and the presence of a reconstructive soft tissue flap.
In this clinical study, the authors examined the management of patients with different maxillary defect types who underwent delayed rehabilitation using zygomatic implants and immediate prosthetic loading. Clinical outcomes were assessed for implant failure and prosthetic loading.
During the preparation of this article, it became clear that none of the classifications addressed maxillary restoration using zygomatic implants. A systematic bone defect classification was considered and a specific treatment protocol is proposed for each type of defect.
Patients were categorized into 3 classes according to the site of the defect, the size of the defect, and residual masticatory function. Class I was defined as bilateral maxillectomy. Class II was defined as unilateral maxillectomy. In this class, 3 subclasses were identified according to the dental status of the unresected side: Class IIA included patients with dentition or partial dentition in the contralateral maxilla; Class IIB included patients without dentition in the residual maxilla; Class IIC included patients without dentition in the healthy maxilla with atrophied alveolar bone; Class III included patients whose anterior maxilla (premaxilla) was resected.
For patients in Class I, the treatment provided 4 zygomatic implants (2 for each zygoma; Fig 1 ). For those in Class IIA, rehabilitation was achieved through the insertion of 1 or 2 zygomatic implants on the resected side and 1 zygomatic implant on the unresected side. This implant was inserted in the contralateral zygomatic bone with a trajectory passing above the dental roots and below the nose ( Fig 2 ). For those in Class IIB, 2 zygomatic implants were inserted on the resected side and traditional implants were inserted in the alveolar bone of the healthy maxilla ( Fig 3 ). If the healthy side did not have sufficient alveolar bone height, then 2 zygomatic implants were inserted in this site instead of traditional implants (Class IIC; Fig 4 ).
For patients in Class III, the treatment provided 4 zygomatic implants for the edentulous patient ( Fig 5 ). Otherwise, the use of standard implants or a dental-supported prosthesis was contemplated.
Materials and Methods
From October 2013 through April 2014, 5 patients with maxillary defects owing to resections of neoplasms were recruited. The hospital's institutional review board approved this study protocol. Written informed consent was obtained from each patient and the study protocol conformed to the ethical guidelines of the World Medical Association Declaration of Helsinki—Ethical Principles for Medical Research Involving Human Subjects.
Patients were scheduled for treatment based on the extent of resection and residual bone. Clinical procedures were performed according to the specific treatment protocol proposed for each type of defect. In 4 patients, zygomatic implant positioning was delayed with respect to the maxillary resection. All patients underwent rehabilitation using zygomatic implants (Southern Implants, Irene, South Africa). Zygomatic implant length ranged from 27.5 to 52.5 mm according to the residual anatomy after resection.
Each patient in the study underwent preoperative computed tomographic (CT) scanning of the maxillofacial region. Digital Imaging and Communications in Medicine (DICOM) data extracted from the CT scan were imported into simulation software (SimPlant O&O; Dentsply Implants, Leuven, Belgium) for preliminary planning. This plan allowed the surgical team to simulate implant placement on a 3-dimensional (3D) model. While considering the anatomic structures and the bone resection performed, the surgical team interactively simulated the position and the length of the implant in each plane. Once the implant was positioned, its angulation could be modified and its dimensions adapted to obtain a better 3D position ( Fig 6 ).
In 3 cases, an intraoperative navigation system was used to control implant positioning. In 2 of these cases, CT data were imported into the navigation system software (ImplaNav, BresMedical, Ingleburn, Australia). A dental-supported reference tool for the passive tracking navigation system was used to connect the patient's position with the navigation system in real time. In 1 case, an active tracking navigation system was used for the intraoperative navigation guide. In this case, an active tracker was placed on the cranial skeleton.
A full-thickness flap was performed in all cases to obtain zygomatic bone exposure. Implant drilling was performed using a straight or angled handle. The fixtures were placed with the handle at 30 rpm at a maximum torque of 50 N-cm or manually.
Zygomatic implants were used when in contact with the skin flap. This kind of zygomatic implant has a machined surface rather than spires in the third coronal portion of the fixture ( Fig 7 ). Figure 8 shows the design of the implant. Standard zygomatic implants were inserted to maintain contact with the oral gingiva and mucosa.
In these cases in which implant placement was performed under a navigation guide, during surgery, there was constant visualization of the drill trajectory in the 3D-reconstructed CT image and in the sagittal, coronal, and axial views ( Fig 9 ).
Deviation from the planned position was detected immediately, and precise implant placement was achieved. Postoperative radiographic evaluation confirmed the placement and angulation of the implant in the remaining zygomatic bone.
In 4 of the 5 cases, right or angled conical abutments were mounted before suturing and not removed. At the time of surgery after the suture pickup, transfers were positioned and splinted with flow composite or resin. An impression was taken with a polyether impression material (Impregum Penta, 3M ESPE, St Paul, MN) using a custom-made tray, reproducing the dental arch, placed in occlusion. Within 72 hours, a screw-retained fixed bridge was delivered ( Fig 10 ).
A new definitive prosthesis could be placed after a 3-month follow-up if the prosthetist deemed it necessary. The definitive prosthesis could be a fixed bridge or an overdenture-retaining bar to facilitate oral hygiene.
After 3 months, the prosthesis was unscrewed and implant stability was tested. Implant stability, pain, and inflammation of the peri-implant soft tissue were the parameters assessed. The same clinical outcomes were evaluated at each subsequent assessment at 6, 12, and 18 months. Postoperative radiographs (orthopantomogram and lateral head radiograph) were taken immediately after surgery, after 6 and 12 months, and then once every year ( Figs 11, 12 ).