A Transnasal Implant Technique

The placement of zygomatic implants demands a highly skilled surgeon, and depending on the bone available in the body of the zygoma, the variation in the position of the implants can increase the prosthetic compensation and make the prosthetic rehabilitation difficult.^7,8 Placing the second zygomatic implant on either the right or left side (the most superior one) is frequently difficult due to the limited width of the zygoma.⁷ Another issue is that the infraorbital foramen may be too close to the path of the second implant. Sometimes, this implant is well exteriorized, exhibiting several exposed threads due to the concavity of the anterior wall of the maxilla, which can lead to soft-tissue complications. In recent years, research has recommended rehabilitating zygomatic implant patients without grafts and with immediate loading protocols.^1,9

As an alternative to the quad zygoma technique, the transnasal implant technique was developed, in which implants are inserted into the basal bone of the maxilla, across the nasal cavity tangent to the distal wall, and anchored apically in the frontal process of the maxilla (Figure 1 and Figure 2).^4,10,11 Using the nasal cavity walls as anchorage for implants¹² increases bone availability in the anterior region of the maxilla, allowing for the installation of an anterior extra-long conventional implant accompanied by a posterior zygomatic implant (Figure 3). As long as the anatomy of the region is respected and the final positioning of the transnasal implants is appropriately planned, this technique has been shown to achieve a high success rate.¹¹

When virtually planning transnasal implants with cone-beam computed tomography (CBCT) data and CAD software, a minimum bone height of 3 mm is required between the maxillary edge and the nasal cavity. A bone height of less than this may make immediate loading impossible. In addition, at least 3 mm of implant anchorage is required in the frontonasal process of the maxilla, which allows the extra-long implants to be anchored in good-quality bone.

One of the alternatives to grafting for the restoration of severely resorbed maxillae is the installation of implants in the anatomical pillars of the face.¹³ The anatomical pillars of the face comprise a series of dense, bony areas that act as a protective frame for the different craniofacial cavities, including the orbits, nasal fossae, paranasal sinuses, and the oral cavity.⁶ The choice of region is made according to the amount of bone available for the best positioning of the implant. Clinicians should always seek to combine their knowledge of the anatomy of the operated area with a virtual simulation of the case and prototypes so that complications rarely occur¹⁴ and so that they can prepare several strategies for successful resolution of the case prior to the surgery.

Despite the high success rates of all-on-4 zygoma techniques reported in the literature, the use of four zygomatic implants requires greater availability of bone in the body of the zygoma, which often makes the installation of four implants challenging or sometimes impossible—even for professionals with more experience.^15,16 Insufficient bone volume or density for anchoring the apex of a zygomatic implant may result in insufficient initial stability. The position of the infraorbital foramen, which may be in the path of the second zygomatic implant, can also complicate placement.⁷ In patients with a large concavity of the anterior maxillary wall, a large part of the implant body, or even the entire implant platform, may be without bone contact and only covered by soft tissue, especially in cases with little keratinized gingiva.¹⁷

The height of the alveolar ridge, the shape of the nasal cavity, and the availability of implant anchorage in the frontal process of the maxilla should be evaluated to determine if the transnasal technique is indicated, and the use of a prototype permits these criteria to be observed with greater security (Figure 4).¹⁸ The frontomaxillary pillar is found in a region where dense bone normally exists, which allows the placement of long implants with parasinusal angulation.¹⁹ Using these bone pillars as anchorage for dental implants transfixing the nasal cavity¹⁸ increases bone availability in the anterior region of the maxilla.

Patients with extensive nasal cavities that have very distal lateral limits are not indicated for the transnasal technique because the implant may not reach the distal bone wall, making bone reconstruction unfeasible and possibly interfering with respiratory function. In addition, detailed anatomical knowledge of this region is necessary due to the proximity of the internal maxillary artery in the frontozygomatic process, the nasolacrimal duct, and the posterior palatine artery.²⁰

In cases of highly reabsorbed maxillae, the transnasal technique is a viable alternative to the quad zygoma technique when, due to the reduced dimensions of the zygomatic process, it better meets the surgical and prosthetic requirements and will reduce the risk of complications related to the bone, peri-implant soft-tissue, and prosthesis. The transnasal technique permits long implants to be anchored in good-quality bone, even in situations where little bone is available in the anterior alveolar ridge, and facilitates the realization of immediate loading in complex full-arch cases. It can be applied to avoid performing bilateral sinus-lift bone grafts or block grafts as well as the bilateral double zygoma or quad zygoma technique. The transnasal technique can also be a viable option to replace or avoid the installation of a second zygomatic implant bilaterally because it can be used in combination with other bone anchorage solutions, such as the pterygoid implant. Although the initial research indicates that the transnasal technique can provide successful results in cases involving severely atrophic maxillae, further research with longer follow-up periods is needed to better assess the longevity of the treatment.
 

Vanderlim Branco Camargo, DDS
Director, Implant Specialist
CIIPO Network of Dental Clinics
Florianópolis, Santa Catarina, Brazil

João Ricardo Almeida Grossi, MSD, DDS
Professor, Implant Dentistry Residency
Brazilian Association of Dentistry
Guarapuava, Paraná, Brazil

Private Practice
Curitiba, Paraná, Brazil

Eduardo Meurer, DDS, MSD
Department Head
Oral and Maxillofacial Surgery Service
Hospital Regional de São José Dr. Homero de Miranda Gomes
São José, Santa Catarina, Brazil

Fabio Andretti, DDS, MSc, PhD
Assistant Professor
Department of Prosthodontics
School of Dental Medicine
Tufts University
Boston, Massachusetts

Daniel Baptista, DDS, MSc, PhD
Professor
UniSul Universidade
Palhoça, Santa Catarina, Brazil

Private Practice
Florianópolis, Santa Catarina, Brazil

Cesar Augusto Montanari Dalmolin, DDS, MSD
Private Practice
Criciuma, Santa Catarina, Brazil