350 Theories and techniques of oral implantology

9-48). After fusing the pins together, the prosthesis was then cemented with hard cement (Fig. 9-49). An x-ray shows the bridge set over the two types of implants, which seem to complement one another (Fig. 9-50) .

Case 6

Unilateral posterior free-end saddle restoration using a prefabricated prosthesis and the

hollow-mill technique

The construction of a four-unit prefabricated fixed partial denture replacing two missing mandibular molars and secured by two bicuspids and two posterior vent-plants will be described. Here a bone plug will be placed inside the vent-plants as an autogenous transplant. The plug acts as a matrix for the speedier deposition of new bone. Eventually the plug is re-placed by new bone or collagenous tissue.

As a preliminary procedure, an intraoral roentgenogram was made of the implant region and the anterior abutment teeth. At the first operative visit, the two bicuspid teeth were prepared for full crowns and compound tube impressions were made of them. A wax interocclusal record of centric relation was taken. Because the tube impressions were used, an alginate (irreversible hydrocolloid) impression of the teeth in the opposing dental arch and a plaster index of the prepared teeth were included.

At the second visit, the two veneer castings, or metal copings for porcelain, were tried on their respective prepared teeth, and all necessary occlusal and gingival adjustments were made. The shade of the teeth was selected, and a wax interocclusal record of centric relation and a plaster index including the edentulous region were taken.

At the third visit, the four-unit veneer fixed partial denture had been completed (Fig. 9-51). It was tried in the mouth to check for occlusal and gingival fit. All necessary adjustments of the inter-proximal contacts and gingival contour were made prior to inserting the implants.

The restoration was removed from the mouth, and the mucosa over the alveolar crest was marked with an indelible pencil in the exact area where, according to the roentgenograms, the implants were to be inserted (Fig. 9-52). The fixed partial denture was once more seated firmly and removed, with the indelible pencil markings transferred to the basal surface of the molar pontics (Fig. 9-53) . Holes deeper and larger in diameter than the implant shafts were drilled inside the pontics with large burs.

A No. 6 round bur was positioned over the first

Fig. 9-51. A, A four-unit gold occlusal, acrylic veneer type bridge is prefabricated prior to implant insertions. B, The undersurface of the bridge. (From Linkow, L. I.: Prefabricated mandibular prostheses for intra-osseous implants, J. Prosth. Dent. 20 [4] :365-375, 1968.)

Fig. 9-52. Indelible pencil markings indicate the location for the implants. (From Linkow, L. I.: Prefabricated mandibular prostheses for intraosseous implants, J. Prosth. Dent. 20 [4] :365-375, 1968.)

marked spot on the mucoperiosteum and drilled about 5 nun. into the bone, parallel with the preparations on the two anterior abutment teeth. The round bur was left in the mouth as a guide for drilling the second hole parallel to the first one. Another No. 6 round bur was then employed to drill the second hole at the other point marked with indelible pencil (Fig. 9-54). Roentgenograms were made after each bur was drilled into position.