6 Theories and techniques of oral implantology

one hand while he maintains, with a finger of the other hand, a vertical pressure on its head to ensure that the tap is engaged in the prepared hole. This manual drilling proceeds much more slowly than drilling with a power tool; however, it permits greater control and finer adjustment.

When the tap has been screwed between one-third to one-half of the depth of the prepared hole, another x-ray film is taken to determine whether or not the tap is parallel to the anterior abutment and to ascertain the actual depth to which it has penetrated. If the tap is out of line, adjustment can be made as the tap is set deeper into the alveolar bone. When the insertion of the tap has been completed, another x-ray film is taken as a final check (Fig. 1-10) . The remaining helical bur is removed, and the other narrow tap is then screwed into the pre-pared hole in the same manner (Fig. 1-11). The ratchet is then reset and turned counterclockwise and either of the taps is extracted.

A wider tap, with the exact diameter of the implant spires, is substituted for the narrower one. This wider tap penetrates the same hole, with x-ray films being taken as the tap approaches the pre-determined depth. When the wide tap is in place, the narrow tap in the other prepared hole is re-moved and a wide tap substituted in the same way, using the first wide tap as a guide. When both wide taps are in place (Fig. 1-12), their placement and alignment are checked by intraoral radiographs. If the placement is correct, both taps are withdrawn and replaced by implants. These implants are inserted by means of the hexagonal prolongator, one end of which fits into the dental ratchet while the other engages the square neck of the implant.

Prior to being inserted into a tap hole, the base of each implant is coated with cortisone ointment in order to obviate pain, infection, or swelling and to promote healing. The implant must be eased into the tap hole carefully, with special care being taken to avoid using undue pressure, because there is a chance of fracturing the implant (Fig. 1-13). The final position of the implant is determined by x-ray films, using the remaining tap as a guide. When finally situated, the implant post should be parallel to the remaining tap and to the prepared abutment teeth (Fig. 1-14). In addition, it should not encroach too closely upon the mandibular canal. How-ever, it should be buried deep enough so that no soft tissues can invaginate its uppermost threads. A good portion of the solid shaft of the implant should always be buried in bone.

Fig. 1-14. The implant shaft is parallel to the remaining tap.

Fig. 1-15. A, Both implants are in place. They are in the correct positions—parallel to each other and to the anterior tooth preparations. B, The implants are in their osseous "seats."