442 Theories and techniques of oral implantology

cause of frictional grip (Fig. 10-211) . Although such a template may be successful, its shape tends to obscure the outline of the bone and make implant insertion tricky. Also, it is unnaturally wide buccolingually.

THE EDENTULOUS MAXILLA

Only one other type of implantation   the single tooth restoration—has given more problems than a full arch of implants for the edentulous maxilla. The difference in long-terns stability between restorations for the completely edentulous maxilla and those for the maxilla with as few as one or two remaining teeth has been great. The inclusion of some type of stress-distributing support, such as a connecting bar or template, has improved the prognosis.

The rehabilitation of the maxillary dental arch may be accomplished with the use of one type of implant, such as the vent-plant, spiral-screw, or blade, or by the combination of triplants with post type implants. Triplants alone will not work for more than a short while. The final prosthesis can be either a complete full arch fixed splint or a palateless removable denture with some form of internal clip bar, Gerber type attachments, or Ceka attachments.

The choice of implants can be determined through a careful radiographic examination of the bone available in relation to anatomic obstructions, such as the nasal vestibulum and the maxillary sinuses. For example, if the nasal vestibulum is dropped very low and extends distally close to the anterior wall of the maxillary sinus on both sides, then the only osseous structure available for utilization in the anterior region would be the nasal septum, which is usually quite thin. In this area a narrow vent-plant with a hollow threaded shaft or a combination of single pin implants could be used. Posteriorly, either triplants are used to circumvent the maxillary sinus or, preferably, blades are used distal to a low-flaring sinus in the maxillary tuberosity. Wherever possible the pin implants should be used in conjunction with a metallic template. However, when not enough alveolar bone is available, implants must be contraindicated.

The factors determining the choice of a fixed or removable appliance should be considered carefully. The most important one is the amount of bone resorption, especially in the area of the anterior labial plate. If a profile view of the patient reveals a great deal of labial plate resorption, making the anterior portion of the lower jaw with or without teeth

appear more protrusive, it would be impractical to construct a fixed bridge unless it is fabricated to a Class III relationship. Otherwise too much torque would result from the extreme flaring of the anterior teeth of a fixed restoration. If this is ignored and the incisal edges are fabricated to contact those of the lower incisal teeth and the gingival tissue-bearing surfaces would contact the resorbed labial and alveolar crest surfaces of tine maxilla, the teeth would create a tremendous amount of torque on the underlying implants as a result of the extreme labial flare. In such situations, a removable, palateless type denture should be used. Some other factors influencing the choice of a removable or fixed denture are the presence of a full complement of mandibular teeth and possible detrimental habits, such as bruxism, tongue thrusts, and pencil or pipe biting.

A fixed full arch denture for a completely edentulous maxilla should be fabricated whenever possible of all-acrylic fused to thin gold copings so that the overall weight of the prosthesis is as light as possible. The acrylic also minimizes trauma. A porcelainbaked-to-metal fixed denture or an acrylic veneer crown fixed denture may be used, providing there is enough deep, dense bone to adequately place and secure enough implants. A lower partial or full denture opposing the maxillary restorations, rather than a full complement of natural teeth, also influences the choice of material for restoring the maxillary arch. The importance of good articulation, especially when using a fixed restoration, cannot ever be overemphasized.

In order to establish the rationale for present-day procedures, the first few cases will involve failures and the reasons for them.

Case 22

A full arch removable palateless denture for the endentulous maxilla using triplants with Teflon cylinders

Triplants alone were used in this case. After intraoral and extraoral radiographs were taken to evaluate the sites, an elastic impression of the entire maxilla and an alginate (irreversible hydrocolloid) impression of the opposing jaw were taken. A denture base plate with a wax rim was fabricated from the maxillary cast. It was muscle trimmed with compound material and lined with Opotow. The wax rim was softened, and a wax interocclusal record of centric relation and vertical dimension was made.

A complete wax-up palateless denture was fabricated from the articulated casts and tried in the