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Extended-Length Implants for Reconstruction of the Edentulous Maxilla

Prosthetic treatment planning for the edentulous maxilla may reveal bone in the posterior region that is insufficient for placement of standard endosseous implants. Patients who have been edentulous for extended periods may manifest a pneumatized posterior maxilla that is not amenable to placement of osseointegrated implants without sinus augmentation. Although well documented, sinus augmentation with subsequent placement of osseointegrated implants involves the delay of prosthetic phases for up to one year.1,2 While protocols utilizing simultaneous implant placement in augmented maxillae have also shown promise, maxillary alveolar bone heights that approach 8 mm are not frequently present to adequately stabilize the implants.3 Potential donor site morbidity has also discouraged these approaches.

Threaded titanium zygomatic implants can be used as an alternative to avoid bone grafting. The diameter of these implants gradually increases from 3.75 mm to 4 mm, and they are available in lengths up to 50 mm.4 The use of the zygomatic fixture has been reported with up to 10 years of evaluation in a conservative number of patients; he has even greater numbers over 5 years in function.5 The patient population treated included edentulous maxillary and maxillectomy cases after tumor ablative surgery, and the reported success rate is in excess of 96%.5 Since the majority of anchorage for the zygomatic implant is within the zygomatic process and the bone quality in this region is significantly different from that found in the maxillary or mandibular regions, implant success may be better compared to implants actually placed in the craniofacial skeleton.5

The currently recommended protocol includes placement of two zygomatic implants (one on each side of the maxilla) in combination with two to four auxiliary, root-form, anteriorly placed, standard length endosseous implants. Following six months of integration to the zygomatic bone, the implants are uncovered, and a provisional rigid bar is fabricated to connect the  zygomatic implants to the auxiliary root-form implants. This is necessary to stabilize the zygomatic fixtures throughout the definitive fabrication process. An implant bar-supported, full-arch fixed, or fixed-detachable unit can be subsequently used as the definitive prosthesis.

This procedure does not attempt to replace the traditional method of sinus grafting with implant placement, but serves as an alternative for treatment of patients that are not amenable to grafting procedures or extended treatment periods. Surgical delivery of these extended-length implants is best performed under general anesthesia, and care should be taken to visualize the exit site of the zygomatic fixture to avoid a significant palatal trajectory. Three-dimensional treatment planning may involve the use of CAT technology to predict any obstacles during placement. Modifications of the current protocol are currently under review and may be published when more data become available. Additional application of these fixtures for intraoral and extraoral maxillofacial treatment (eg, resective or tumor ablative surgery) are exciting alternatives to traditional care.

*Assistant Professor, Department of Otolaryngology, University of Nebraska Medical Center, Omaha, Nebraska.

 

References:

  1. Watzek G, Weber R, Bernhart T, et al. Treatment of patients with extreme maxillary atrophy using sinus floor augmentation and implants: Preliminary results. J Oral Maxillofac Surg 1998;27(6):428-434.
  2. Blomqvist JE, Alberius P, Isaksson S. Two-stage maxillary sinus reconstruction with endosseous implants: A prospective study. Int J Oral Maxillofac Impl 1998;13(6):758-766.
  3. Kent JN, Block MS. Simultaneous maxillary sinus floor bone grafting and placement of hydroxylapatite-coated implants. J Oral Maxillofac Surg 1989;47(3):238-242.
  4. Salinas T, Sadan A, Peterson T, et al. Zygomaticus implants: A new treatment for the edentulous maxilla. Quint Dent Tech 2001;24:171-180.
  5. Petruson B. The reaction of the maxillary sinus mucosa to titanium implants [thesis]. Göteborg, Sweden: Sahlgrenska University Hospital; 1999.
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