Current implant techniques—an overview 3

Fig. 1-2. The preoperative intraoral periapical radiograph should include the natural tooth abutments and the osseous edentulous area that will house the implants.

successful implantation. If soft tissues invaginate the uppermost spirals, the implant may fail.

The diameter of the spiral portion is slightly larger than that of the solid shaft portion. This provides two distinct advantages. First, because the bone must be trephined with a tap having the same diameter as the spiral portion, a narrow space is left around the shaft for any drainage that might take place the first 48 hours after insertion of the implant. The hollow core of the spiral section is an advantage here too. It allows the apical fluids to drain through it into the unoccupied space around the shaft. Second, because the shaft is narrower, the bony tissues that close in around it create a shelf over the spirals that will prevent vertical ex-foliation of the implant.

This type of design has several other advantages. The spirals of the implant, like the spirals of a wood screw, provide a greater surface for retention. The hollow portion permits a free flow of blood around the spirals; consequently, the tissues heal and re-grow relatively fast. The spirals also serve another important function; they help distribute the force of an impact over a larger area, thereby causing little trauma to the site.

Materials and equipment required. The materials and equipment needed to insert a spiral-shaft implant include a slow-speed contra-angle with water attachment; two large (No. 6) round burs or spear-point burs; two heavy-gauge, helical fissure type bone burs; four taps, the diameter of two being exactly the same as that of the bases of the implants, with the other two slightly smaller; the implants themselves, with ready-made interchangeable

copings; a dental ratchet; an anesthetic, general or local; and a tube of corticoid-antibacterial salve.

Procedures. Normally three visits are required for the installation of a fixed splint secured to spiral-shaft implants.

First visit. During the first visit, a periapical x-ray film of the edentulous area that is to house the implants is taken and evaluated to determine the best location for the implants (Fig. 1-2). In the mandible, the location of the superior wall of the mandibular canal must be determined exactly, because the implants should not penetrate that deep. (Implants should never be placed in the area of the mental foramen.) The film must show any teeth anterior to the edentulous area that are to be used as the anterior abutments of the splint. The exact location of such teeth is important, because the implants, when installed, must be parallel to their prepared coronal portions.

In this first visit, the anterior abutment teeth are prepared for full crown restorations (Fig. 1-3), and impressions and bites of them are taken for the preparation of veneer crown castings. An alginate impression of the prepared abutment teeth and the edentulous area and a bite are also made. A stone casting is made from the alginate impression, and a temporary acrylic splint is fabricated for placement over the anterior tooth abutments and the posterior implants immediately after their insertion.

Second visit. At the time of the second visit, the veneer crown castings are fitted over the prepared abutment teeth and equilibrated in the mouth; they are then removed and set aside. The prefabricated temporary acrylic splint is also fitted into position,