The Use of Prefabricated Titanium Tissue Abutments for the Construction of a Maxillary Subperiosteal Implant

In cases where bone is deficient in some areas of the arch and severe bone atrophy, narrow bone width, or inadequate bone height is encountered over the mandibular canal or below the maxillary sinus, the clinician may have to consider alternative plans.1–11 Surgical solutions6,12,13 or combined implant modalities13–19 should be considered. In cases where surgical compensatory procedures such as onlay or sandwich bone grafts, sinus-lifting procedures, or bone-spreading augmentations are used, the loading period is lengthened as much as twice the regular osteointegration period. The technique described in this article decreases the healing period before prosthetic loading.

A 60-year-old fully edentulous man presented to our prosthodontics clinic for implant-supported prosthodontic rehabil-itation (Figure 1). He was 174 cm tall and weighed 75 kg. His chief complaint was that he was unable to wear and use his complete dentures. His ortopantomography showed no evidence of bone pathology or impacted teeth, and his vital signs and medical history did not contraindicate implant therapy. He lost his teeth 10 years earlier because of rapidly progressive periodontal infection and bone loss. Multiple attempts at complete dentures were unsuccessful, and he now desired implant-supported dentures.

In the first attempt at treatment, 2 implants were positioned immediately anterior to the mental foramen on each side of the mandible, and 2 implants were positioned bilaterally at the level of the maxillary tuberosities. It was not possible to position any endosteal implants (EOIs) on the anterior maxilla because of the knife-edge shape of the alveolar process. A bar-and-clips-retained complete denture was fabricated for the lower jaw. Posterior O-rings retained a complete denture for the edentulous maxilla. The patient used the prostheses for 2 years but was not satisfied with the maxillary denture, for the anterior part was not stable and dropped during function. At the end of the second year, the implant at the level of mandibular left second premolar failed and was removed. An anterior partial-arch subperiosteal implant (SPI) was planned for the anterior maxilla with 4 posterior EOIs to support full-arch crown and bridge restorations.

After a midcrestal incision, the maxillary arch was fully exposed from the deepest portion of the vestibular sulcus to 2 cm palatally. Heavy bodied silicone material, sterilized with ethylene oxide, was used to obtain an exact bone impression. The surface of the silicone impression was painted lightly with Vaseline. A model of polysiloxane condensation silicone (Speedex putty, Coltène, Switzerland) was obtained by forcing the material into the impression (Figure 2).

An SPI was designed with self-curing resin on the silicone model. The vestibular major connector, palatal major connector, and fixation sections for the miniscrews were fabricated with the self-curing resin. Tissue abutments (Figure 3) were used as anterior posts.

The internally threaded end was positioned toward the oral cavity. Next, the titanium tissue abutments were positioned in the self-curing resin at the desired levels for the posts. Labial and palatal major connectors, minor connectors supporting the posts, and fixation rings on the buccal major connector were all sculpted in self-curing acrylic (Figures 4 and 5). The resin pattern was cast in titanium and then sandblasted (Figure 6). Only the tissue abutments were finely polished. After sterilization, the SPI was fixed in the mouth with 2-mm diameter miniscrews (Figures 7 and 8).

Two weeks later, the impression pins were positioned (Figure 9) and the impression was taken with silicon material. After the metal try-in, the ceramic try-in, and the necessary occlusal adjustments, the full-arch fixed bridge was glazed and screwed in situ over the maxillary implants (Figure 10). A bar-supported mandibular removable partial denture was constructed over the mandibular implants.

It is apparent that the indications for an SPI begin where the indications for an EOI end. In this case it was possible to rehabilitate the patient with implant-supported crown-and-bridge restorations over his partial-arch SPI with internally threaded tissue abutments. Laser welding the tissue abutments to the titanium casting to eliminate further abutment detachments from the casting should be considered as a precautionary measure.