Fig. 9-39. A, The fixed partial denture is tried in the mouth prior to implant insertions. B, The prosthesis in place prior to implant insertions.

Fig. 9-40. The prefabricated bridge is radiographed for the final determination of the implant sites.

Mandibular endosseous implant interventions 347

Fig. 9-41. The vent-plants are set into their proper locations in the bone.

implants were set in position (Fig. 9-41) . The bridge was tried over the protruding implant shafts and checked for interference with its fit. If a bridge sits too high or cannot be easily slipped over the shafts, the holes should be enlarged. Then fine adjustments of the diameter and depth of the holes should be accomplished so that the implant shafts fit snugly within them. To do this, either of two methods may be followed:

1. The holes may be filled with cold cure acrylic. The bridge is taken on and off at 20-second intervals, and the final hardening is allowed to take place outside the mouth. The excess acrylic along the under-surface of the bridge is then trimmed away and the area polished. Or, if the implant shafts are not parallel with each other, before the acrylic finally hardens, the excess is quickly removed and oxyphosphate of zinc cement is placed inside the bicuspid casting. The bridge is placed back into the mouth for its final setting, with the acrylic bound to the implant shafts.

2. Prefabricated gold copings whose outer surfaces have numerous deep undercuts are placed over the protruding implant shafts (Fig. 9-42). The bridge is then placed in position. If there is any impingement, larger holes are made inside the pontics. After the bridge slips on and off easily, the holes are filled with cold cure acrylic and the bridge is seated over the undercut copings and the bicuspid tooth preparation. When the acrylic hardens, the bridge is removed and the gold cores have now become an integral part of the bridge. The excess acrylic around the margins of the gold copings is removed, and the entire tissue-bearing surface of the crown is trimmed and polished (Fig. 9-43) .

As the final operative step, the bridge was ce-