20 Theories and techniques of oral implantology

mallet is then used until the shoulders of the blade are 1 to 2 mm. below the cortical plate at the alveolar crest. Interrupted sutures are used to close the soft tissues over the implant's shoulders (Fig. 1-51) . The site is either left exposed or, if de-sired, the wound is covered with an intraoral bandage.

Third visit. In about 5 days the tissues should have healed sufficiently to remove the sutures (Fig. 1-52). Impressions are then taken for the final pros-thesis in either of two ways. With a gold coping over the implant post and a veneer crown casting over the abutment tooth, a wax interocclusal record of centric relation and a plaster index picking up the coping and casting may be taken; or a hydro-colloid, silicone, or rubber impression may be made. With either method, an opposing jaw alginate impression is also necessary. The patient is then dismissed.

Fourth visit. One to two weeks later the tissues should have completely healed. The prosthesis is then tried in the mouth, adjusted, and temporarily worn for a few days to check for soft tissue impingement. It is affixed to the abutments with temporary cement inside the natural tooth abutment crown and Vaseline only inside the implant crown.

Fifth visit. Any necessary adjustments are made, and the bridge is permanently affixed with hard cement (Fig. 1-53). A final radiograph is always taken (Fig. 1-54).

SUBPERIOSTEAL IMPLANTS

A subperiosteal implant involves setting a metallic framework that bears abutments to which a dental prosthesis can be attached over dense cortical bone. As the mucoperiosteal tissues heal over the implant, they hold it securely in place. Obviously, the frame-work must fit snugly over the bone, which means that the operator must design it carefully. The fit must be perfect or the implant will fail.

Several steps are required to make a snugly fitting implant. A surgical tray must be made to get an ac-curate bone impression bearing all important anatomic landmarks. A wax bone bite of the area, as well as a measurement of the soft tissue thickness in the area of the four posts and an alginate impression of the opposite jaw, must be supplied to the technician to help him evaluate the height of the abutments. A temporary prosthesis, either the patient's old denture, which has been specially pre-pared, or a new one fashioned by the operator, must be supplied. The implant itself must be held securely in place on the bone in some manner until the tissues heal. Each of these steps must be care-fully plannecl and executed if the implant is to be successful.

Because surgery must be used to reveal the bone, the patient must be thoroughly apprised of the procedures involved. His medical history should be care-fully examined, with care being taken to avoid a patient with a history of allergies, rheumatic fever, diabetes, blood or bone dyscrasias, hypertension, neurotic tendencies, or any other physical or mental predispositions that might make the procedures fail. It is also always a good idea to talk directly with the patient's physician before attempting the implantation. A subperiosteal implant is an ordeal, but one that is well worth the trouble and pain to the patient who wishes a dental restoration that looks and feels like his natural teeth.

Because the subperiosteal implant is successful over a prolonged period only when set on dense cortical bone, it should be attempted only on a manclible whose alveolar bone has resorbed to a great extent. This type of implant should not be attempted on a mandible with superficial alveolar bone, for within 2 to 3 years the alveolar bone will resorb, leaving a badly fitting implant that should be re-moved. A subperiosteal implant should never be at-tempted in the maxilla, because the bone there is primarily of a cancellous, more porous structure. In maxillae and mandibles with alveolar bone, an endosseous implant technique is called for. Suitable endosseous implant techniques for such cases will he discussed in detail in subsequent chapters.

To illustrate the basic steps, all of the procedures for a full lower subperiosteal implant will be explored.

Materials and equipment required

The following equipment is basic to a subperiosteal implant intervention : a scalpel, bone curettes, periostcal elevators, suture thread, suture needles, hemostats, a syringe, local or general anesthetic, and saline solution (intravenous drop technique). Epinephrine and blood-clotting agents should be on hand in case of hemorrhage. Not necessary, but sometimes desirable, is an intraoral bandage to hold tissues in place around the sutures to prevent tearing.

Procedures

First visit. During the first visit, a bone impression must be taken of the area that will bear the