Use of zygomatic implants to deal with resorbed posterior maxillae.

For some 40 years, osseointegration has been clinically applied in both the maxilla and the mandible. With a high predictability for some systems (19), increased applications have been developed for compromised patients. Unfortunately, restrictions have appeared in the use of oral implants. One of them is the lack of sufficient bone volume, especially in the posterior maxilla. This insufficient bone volume can be due to bone resorption as well as to pneumatization of the sinus or to a combination of both. In any case, insertion of implants in this region remains extremely unpredictable. According to some clinical reports, the minimal bone height for a standard implant in the posterior region should be at least 10 mm (33) to ensure acceptable success rate. This is confirmed by a retrospective study of 660 implants using the Brånemark system in the posterior maxilla followed for 5– 12 years showing a cumulative success rate of 94.4% but with a loss of 10 implants on 49 implants with a length of 7 mm and a diameter of 3.75 mm (22). With the introduction of wide implants 5 and 6 mm in diameter (17, 18) the contact surface between implant and bone is increased and assumes a cortical anchorage with an initial stability in bone type IV even if the bone height is no greater than 6 mm. Implants of wide diameter limit the biomechanical complications in the treatment of the posterior maxillas. Pterygomaxillary implants have also been proposed for posterior anchorage in totally edentulous patients (3). Although wide implants could be a solution for crestal heights up to 6 mm, many patients present a maxillary height of 0.8–6 mm (39). For these cases, several solutions have been proposed to augment the volume of bone in this region, such as onlay/inlay bone grafting (33). Although autologous bone grafting remains the gold standard, different types of grafting materials have been proposed for these procedures: demineralized bone from human cadavers, bovine bone and synthetic materials. Although many have claimed good clinical results, there is insufficient long-term data from histologic and histomorphometric investigations to provide real guidelines for these procedures. Contraindications for sinus lifting (33), such as Caldwell Luc operations, Underwood’s septae, severe sinus floor convolutions and narrow sinuses, limit the use of this clinical technique. Perforation of the Schneidarian membrane could also jeopardize the final result. The gold standard for sinus-lifting procedures uses autogenous bone (25) but bone harvesting is most often performed under general anesthesia and, as in a majority of these cases these procedures necessitate a two-stage since surgery, since the implants are not inserted at the moment of the bone grafting. Complications like sinusitis or loss of grafts have also been described with the sinus graft technique. Final results (15) show a success rate of up to 75% for the sinus-lifting procedure together with simultaneous insertion of implants and it is recommended to avoid this one-stage procedure.