Subperiosteal implants 557

casting may also be fabricated to fit over each thimble. In this manner, the entire processed bridge, including the two cantilevered thimbles, can be immediately cemented into position (Fig. 12-61).

The second surgical stage takes place anywhere from 3 to 4 weeks after the initial surgery. Before inserting the implants the castings are checked for their fit on the master stone model (Fig. 12-62). Some castings, such as the ones used in this case, may contain a small hole in the region of the external oblique ridge. This is for the insertion of a small Vitallium set screw. A hole is made in the bone with a No. 556 fissure bur, and the screw is inserted

Fig. 12-66. Healing around the protruding posts is usually uneventful if the operator follows good surgical and prosthetic principles. (From Linkow, L. I.: Re-evaluation of mandibular unilateral subperiosteal implants: a 12 year report, J. Prosth. Dent. 17:509-514, 1967).

Fig. 12-67. Two bilateral fixed partial dentures are fabricated from the impressions taken of the implants and anterior gold thimbles.

through the implant and into the bone. Usually the screw is not needed because the lingual finger design provides enough retention.

The implants are placed on the exposed bone (Fig. 12-63), and the tissue is sutured (Fig. 12-64). At this time the anterior processed fixed partial denture can be cemented into position, or—as in this case   the temporary anterior acrylic splint is used (Fig. 12-65).

After healing, the temporary splint is removed. The anterior prosthesis is seated, the veneer castings (if done this way) are positioned over the thimbles, and the prefabricated gold copings are placed over the implant abutments. A wax interocclusal record of centric relation and a plaster index to complete the bridges are taken. The bridges are then cemented into position.

There is a simpler method for making the final impression for the two posterior bridges. An elastic impression of the two cantilevered thimbles and the implant post abutments is taken and a one-piece casting for each bridge made (Figs. 12-66 and 12-67). This procedure makes it unnecessary to first cast veneer crowns to fit over the cantilevered copings and to fabricate gold copings to fit over the implant

Fig. 12-68. A, The bridges are cemented into their positions with oxyphosphate of zinc. B and C, Anterior and lateral views. A new maxillary denture with acrylic teeth was made in conjunction with the lower prosthesis.

A

B

C