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Case Study
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Reconstruction of the Posterior Maxilla Following Total Loss of Crestal Bone Support

A 45-year-old white male patient presented with an edentulous posterior left maxilla (Figure 1). The patient was a nonsmoker and in good health. The medical history of the patient did not demonstrate any contraindications but revealed that he had undergone questionable extraction of the maxillary left premolars, molars, and all supporting alveolar substructures. As a result of this treatment, the patient exhibited an exposed sinus cavity, covered only by the mucoperiosteal flap. No prospect for satisfactory prosthetic rehabilitation was evident.

The patient desired the fabrication of a fixed prosthesis that would restore posterior function, aesthetics, and health. The treatment plan mandated diagnostic evaluation that included radiographs, models, and laboratory waxups. The surgical and restorative plans required the staging of the clinical procedures. The initial phase necessitated a surgical reconstruction of the posterior maxilla with a bone graft. The placement of implants was scheduled for the second surgical phase. The third phase of the treatment included the exposure of the implant fixtures, soft tissue management, and the initiation of the restorative procedures.

 

Phase I

In the initial phase of the clinical procedure, full mucoperiosteal flaps were elevated, revealing the crestal opening in the sinus cavity. The Schneiderian membrane was also elevated (Figure 2). A resorbable membrane was placed onto the Schneiderian epithelium to prevent trauma during the placement of the bone graft (Figure 3). A monocortical bone block was harvested from the patient’s symphysis. In addition, a particulate autogenous bone graft and 2 cc of demineralized freeze-dried bone (DFDB) (500 µm to 1000 µm), were utilized as bone grafting materials. The bone grafts were placed in layers into the sinus cavity. The DFDB mixture was placed into the remote regions of the sinus cavity where no implant placement was planned. The partic­ulate autogenous bone was placed into the anticipated implant sites, and the monocortical bone block was wedged into the crestal bone defect (Figure 4). The complete grafted site was covered with a nonresorbable expanded polytetrafluoroethylene membrane to allow for stabilization of the blood clot around the bone graft, to prevent resorption of the bone graft, and prevent soft tissue cells from invading the site (Figure 5).

 

Phase II

Following an uneventful healing period of 8 months (Figure 6), the site was reopened and the membrane was removed. Once full-thickness buccal flap elevation and membrane removal were accomplished, complete incorporation of the bone graft was noted and the closure of the crestal bone defect was observed (Figure 7). Radiographic analysis revealed sufficient bone height and density to support 3 titanium standard screw type dental implants of 13-mm length. The implants were placed, utilizing a modified surgical procedure that included the use of a smaller (2.85 mm) twist drill, no tapping of the bone site, and a 3.75-mm standard titanium implant (Figure 8). While the quality of the bone density was determined to be type III to IV, adequate implant stability was achieved (> 20 N/cm).

 

Phase III

Following a 6-month uneventful healing period, abutment connection surgery was planned. A periapical radiograph taken at the conclusion of the healing period indicated good bone density, maintenance of crestal bone level, and no radiolucencies around the implant fixtures (Figure 9). A split-thickness flap was elevated toward the buccal aspect to increase the quantity of keratinized attached tissue surrounding the implants (Figure 10). The healing abutments were connected, and the soft tissue was permitted to heal undisturbed for 2 months.

Following the completion of soft tissue maturation, attached keratinized tissue was observed surrounding the 3 implants (Figure 11), and the restorative phase was initiated. Once implant impression taking, bite registration, and abutment selection was completed, three individual copings were fabricated and placed onto the implants (Figure 12). A metal superstructure was subsequently fabricated and fitted and adjusted to the individual copings intraorally (Figure 13). The one-piece metal substructure was subsequently finished with porcelain and cemented to the individual copings (Figure 14). No screw access holes were evident on the occlusal aspect, and the definitive restoration demonstrated an optimal emergence profile and satisfactory aesthetic and functional results (Figure 15).

The prosthesis was in function for 1 year, at which time the patient was recalled for follow-up evaluation. Periapical radiographs demonstrated the restoration of the posterior maxilla and normal density of the bone surrounding the implants and in the sinus cavity (Figure 16).

 

Conclusion

Implant placement may be performed in challenging intraoral sites. In treatment sites (eg, the posterior mandible) that do not demonstrate suitable hard and soft tissue support for implant placement, the clinician may augment the existing tissue with bone grafts, guided bone regeneration, soft tissue management, or a combination of these treatment modalities. In addition, moderate bone quality requires a modified implant surgical procedure to enhance implant stability. These procedures offer a technique-sensitive, yet efficacious, means of restoring tissue for suitable implant restoration. When the clinician adheres to clinical parameters based on biological principles such as a sufficient blood supply, selective proliferation of cells, and appropriate bone graft and barrier membrane, and an uneventful healing period, these restorative treatments may be utilized to effectively rehabilitate partially and fully edentulous patients.

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