Mandibular endosseous implant interventions 343

Fig. 9-26. The difference in diameter between the narrower tap as compared to the wider tap is seen in this diagram. (From Chercheve, R.: Les implants endo-osseoux, Paris, 1962, Librairie Maloine.)

Fig. 9-27. The first implant is screwed into either one of the tap holes.

bur and to the prepared crown (Fig. 9-24). Another x-ray was used to check the accuracy of insertion. The second helical bur was substituted by another tap of the same diameter (Fig. 9-25) and x-rayed.

The first set of taps was exchanged for taps of the same diameter as the spiral portion of the implant. Each tap was carefully screwed into the bone with the hand ratchet to maintain sharp and unbroken threads of bone that fit snugly against the implants (Fig. 9-26). Their positions were checked by x-ray. One of the taps was then removed and the depth of the artificial socket checked with a special bone probe. When measurements for both sockets were approved, the implants were ready for insertion.

A hexagonal prolongator was used to unite the shaft portion of the implant with the head of the ratchet, and the spiral-shaft implant was then screwed into the hole made by one of the previously removed taps (Fig. 9-27). Its depth and direction were checked with an x-ray. The remaining tap was then removed, and the second spiral-shaft implant was carefully screwed into the threaded hole (Fig. 9-28). Another x-ray was taken to check the parallelism and depth of both implants.

The gold casting was then fitted over the prepared bicuspid tooth, and gold copings were placed over the protruding implant shafts (Fig. 9-29) . A wax inter-occlusal record of centric relation was made and a plaster index taken (the index included the castings and copings) .

The temporary, prefabricated acrylic splint was then hollowed out sufficiently to generously accept the implant shafts. It was tried over the abutments, both natural and implant, and checked for passive fit. Once proper occlusion had been established, fast-setting acrylic was placed into the hollowed portions that encapsulated the implant shafts, and the splint was placed over the tooth and implants. It was repeatedly removed and replaced to prevent the acrylic from fusing to the implants. After the acrylic set,

Fig. 9-28. Both implants are seen in position parallel to one another and to the anterior abutment preparation.