Current implant techniques—an overview 15

B

D

Fig. 1-40. A, At the next visit the final prosthesis is tried in position. B, The porcelain-fusedto-metal bridge in position. All occlusal adjustments are made before final cementation. C, Interocclusal relationship of bridge with opposing teeth. D, Final radiograph.

If the work is to be performed in the mandible, the superior wall of the mandibular canal must be demonstrated.

When the optimal sites for the tripod pins have been determined, the operator inserts the first pin, drilling through soft tissue and bone and penetrating the crest of the alveolar ridge at an acute angle (Fig. 1-41) . Roentgenograms are taken to check the pin's depth and direction to ensure that it does not encroach upon any of the anatomic landmarks (Fig. 1-42). If the pin appears to be going in the wrong position, it is merely backed out slightly and then driven in at a different angle.

The second pin is then inserted in the same manner, near the same point of entrance as the first one but at a different angle (Fig. 1-43) ; another x-ray is then taken (Fig. 1-44). The third tripod pin is then drilled into position between the first two pins and from the same point of entrance, but extending either lingually or buccally from the alveolar ridge (Fig. 1-45), and a third x-ray is taken (Fig. 1-46). The protruding ends of the three tripod pins are then trimmed to the desired length, using either shears, an abrasive disk, or a fissure bur.

It is desirable to plan the placement of each pin

so that their protruding ends do not emerge from the bone too close together. By leaving plenty of room for blood circulation, osseous breakdown is reduced. Care must be taken, however, to plan the insertions so that the heads of the pins do not form too broad an angle. They should be as far apart as

Fig. 1-41. The first pin that will be part of a tripod implant abutment is seen attached to a slow running contra-angle with a special chuck attachment.