2021, Number 3
Zygomatic implants. An alternative treatment in atrophic maxilla. Clinical case report
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ABSTRACT
Establishing an ideal treatment plan in patients with severe maxillary atrophy has become a real challenge. Prosthodontists and maxillofacial surgeons should interdisciplinary work to integrally rehabilitate the patient. Anterior alveolar resorption and maxillary sinus pneumatization reduce the possibility of endosseous implant placement by conventional surgery. Therefore, multiple surgical approaches have been devised for residual ridge augmentation. However, alveolar reconstruction fails to improve bone conditions, or simply due to the severity of resorption, multiple surgeries must be performed, or long waiting periods must be endured. In 1990, Branemark introduced a new alternative to rehabilitate patients with severe maxillary atrophy by placing zygomatic implants without prior grafting. A clinical case is presented of an edentulous patient with severe maxillary atrophy, rehabilitated with four zygomatic implants in the maxilla and conventional implants in the mandible ("All-on-Four") at the Implantology Clinic of the UNAM, DEPeI.INTRODUCTION
More than forty years ago, osseointegration began, and today the use of endosseous implants continues as the ideal treatment to rehabilitate and replace missing teeth. It is a viable, predictable, and standard option in general and specialized dental practice.1 For patients with severe maxillary atrophy in which is impossible to insert conventional implants, multiple treatments have been devised to achieve the quality and quantity of bone for a conventional implant, such as extraoral iliac crest grafts, sinus membrane lift, block grafts for crest augmentation. However, these treatments increase the waiting time for definitive rehabilitation and morbidity.1,2
In 1990, Branemark designed a treatment protocol for patients with severe maxillary atrophy and described the zygomatic implant placement, which the main anchorage is in the zygomatic body, which presents dense bone tissue of adequate quality and volume, in addition to providing multiple location possibilities for maxillary reconstruction.2,3 These implants allow good retention and support of a fixed prosthesis without previous grafts. Initially, zygomatic implants were used in patients with sequelae of facial trauma, congenital disabilities, or partial or total maxillectomies. In patients who do not have enough bone and wish to undergo rehabilitation with a fixed prosthesis, zygomatic implants are an excellent option.3,4 The success rate for zygomatic implants is 95 to 96% in studies with a 10-year follow-up, similar to that for conventional endosseous implants.3
Patient selection is essential in planning treatment with zygomatic implants. A systematic medical analysis should be performed to rule out pathologies that may contraindicate the treatment and avoid future complications.4 Radiographic and tomographic evaluations are essential to achieve an adequate diagnosis and predictable final treatment.5 Bedrossian describes a classification for atrophic maxilla in a panoramic radiograph, considering three zones: zone 1 when bone is in the anterior zone of the maxilla; zone 2, when bone is in premolars; zone 3 when absent bone in the posterior region of the maxilla (Figure 1).4
Depending on the amount of bone in each area, the type of surgical-prosthetic treatment is established:
- 1. Presence of bone in zones 1 and 2: inclined implants placement, the concept "All-on-Four".
- 2. Presence of bone in Zone 1: placement of two zygomatic and two conventional implants in the anterior zone.
- 3. Absent bone in the three areas: placement of four zygomatic implants.4
Computed tomography is a diagnostic tool to plan the placement of the implants together with computerized programs. It is a way to obtain the length, diameter, and angulation where they should be placed (Figure 2A).1,5,6 Mainly indications for zygomatic implants placement are severe maxillary atrophy, reconstruction of neoplastic defects (maxillectomies), patients with cleft lip and palate sequelae, failure of ridge augmentation.7 Significant advantages are offered when placing zygomatic implants in severe maxillary atrophy since procedures such as extraoral grafts are eliminated, which increases morbidity by having two surgical sites and bone block grafts with which integration time and osteogenesis are increased.8
Transoperative complications typical of surgery have been reported, such as hemorrhage caused by damage to the infraorbital and posterior alveolar arteries and invasion of the orbit and/or temporal fossa.9,7 To avoid these complications, it is necessary to know the adjacent anatomical structures. One of the most frequently reported postoperative complications is sinusitis, especially in intrasinus implant cases. Aparicio10 reported sinusitis in patients up to 27 months after surgery. Nerve lesions in a smaller percentage, such as paresthesia and dysesthesia of the infraorbital and zygomatic nerve. The loss of an implant has been reported after prosthetic rehabilitation due to biomechanical complications.
Surgical protocolThe technique described by Branemark intrasinus implants was initially placed, which involved sinus complications. Then, due to the emergence of the implant platforms towards the palate, prosthetic and phonation complications took place.7
Extrasinus placement was subsequently reported, eliminating sinus complications and improving platform emergence.11 However, depending on each patient's anatomy, they could be intrasinus implants or extrasinus implants.12
Prosthetic rehabilitationZygomatic implants can be loaded immediately because their length allows bone anchorage of one or more cortices and, therefore, more significant bone contact with the implant surface and stability.13,14 The provisional screw-retained prosthesis is intraoperatively placed immediately, and the time for placement of the definitive prosthesis is 6-8 weeks after placement, although six months are recommended to achieve implant integration. In cases where the prosthesis is not intraoperatively placed, it can be placed deferred as early loading. The prosthetic rehabilitation options will depend on the implant conditions, the peri-implant tissue, mainly on the patient's smile line, and the bone resorption grades. Options include hybrid prosthesis with splinted implants or overdenture.14-16
CLINICAL CASE
A clinical case of a 57-year-old completely edentulous female patient (Figure 3A) (maxilla and mandible) is presented (Figure 4A and 4B). No relevant pathology data to the current condition. The patient attended the implantology service (Clínica de Implantología del Postgrado de Odontología de la Universidad Nacional Autónoma de México) for evaluation and treatment. The clinical, radiographic, and tomographic evaluations were carried out, and the diagnosis of severe maxillary atrophy was obtained (Figure 2B). For rehabilitation, the placement of four zygomatic implants with a hybrid fixed prosthesis was proposed. The procedure was performed without complications under general anesthesia following the protocol for patients requiring hospitalization. It was decided to carry out early loading (one week later) with the immediate prosthesis previously made.
Four intrasinus zygomatic implants were placed through a full-thickness linear incision; the foramen and infraorbital nerve were located, a sinus window was designed, and the drilling protocol was started. Beginning with a ball drill, the zygomatic implants were placed, obtaining 35 Ncm torque. Subsequently, the Multi-Unit implants were placed, and immediate loading would be at ten days after surgery (early loading). After 10 days, the patient was provisionally rehabilitated (Figure 4C-4E). To complement the treatment in the mandible, it was decided to place four implants ("All on Four"). The orthopantomography revealed implants in position and fulfilling function (Figure 4F). At the time of the prosthesis placement, a considerable change in patient's physical appearance was observed (Figure 3B).
DISCUSSION
Restoring phonation, masticatory function, comfort, and quality of life has become a challenge for prosthetic treatment. Conventional implants changed the perspective of rehabilitation. In cases where there is insufficient bone to place conventional endosseous implants, the treatment alternative with zygomatic implants was devised in patients with severe maxillary atrophy. This predictable technique rehabilitates the patient in a short time.17-19 Clinical and imaging planning is essential for a successful treatment.19
CONCLUSIONS
Zygomatic implants are a predictable alternative to rehabilitate patients with severe maxillary atrophy. A specific and detailed protocol is required for a proper diagnosis and to establish that zygomatic implants are ideal for edentulous patients with severe maxillary atrophy.
REFERENCES
AFFILIATIONS
1 Profesor adscrito al Servicio de Cirugía Oral y Maxilofacial, DEPeI, FO, UNAM. México.
2 Coordinador del Programa de Alta Especialización en Implantología Quirúrgica y Protésica, DEPeI, FO, UNAM. México.
3 Profesor adscrito al Programa de Prótesis, ULA. México.
CORRESPONDENCE
Dayanira Lorelay Hernández Nava. E-mail: cmfdayanira@fo.odonto.unam.mxReceived: Diciembre 2020. Accepted: Febrero 2021.