CHAPTER

10 Maxillary endosseous

implant interventions

Maxillary restorations have caused more problems than mandibular ones. The character of the bone and its height can vary a great deal more than in the mandible. In addition to problems arising from the bone's patterns of resorption and porosity, gravity and occlusal forces complicate the picture. Whereas a mandibular restoration sits on the jaw, a maxillary restoration is suspended. This means that the restoration must be firmly anchored not only against movements of the cheeks, tongue, and lips but also against gravity. Because bone resorption may leave little definition of the arch, there may be difficulties in balancing the prosthesis. Also, resorption leaves little bone between the floors of the various sinuses and the crest of the ridge. This means that implant placement may have to be diverted elsewhere, such as to the nasal septum or the tuberosities.

The first implant restorations for the maxillae were unsuccessful for several reasons. A major cause of implant failure was unequal balance and lack of sup-port as a result of an insufficient number of implants. This insufficiency resulted not from poor judgment but from the limited suitability of early implant designs. The redistribution of stress and the better balance provided by the use of a template helped alleviate some problems.

There was also a weight problem. Eliminating excess bulk by carefully designed prostheses, some-times in more than one part, helped. These and other factors contributing to the prognoses of maxillary implants will be discussed in the following cases. In each case reasons for the choice of pros-thesis and implant are presented. Some failures will be included so that the reader may understand the rationale underlying the development of the more successful implantation procedures. All the implants discussed here were either post or pin type implants. Maxillary interventions using the blade-vent will be

discussed in the chapter devoted exclusively to that type of implant.

UNILATERAL RESTORATIONS

The problems encountered when dealing with maxillary posterior free-end saddle areas are very different from those arising in the mandible. The main concerns are anatomic: the porosity of the alveolar bone, the location of the antral floor, and the amount of bone between alveolar crest and the floor of the sinus, as well as the buccopalatal thickness of the residual crest. In some cases there is enough bone for two post type implants; other cases require either the use of triplants or a combination of the two types of implants.

When contemplating a fixed posterior bridge for the maxillae, an intraoral radiograph is taken to determine the types of implants to be used as well as their locations. At least two teeth anterior to the edentulous area are prepared, and impressions for full crown coverage—either porcelain, gold, or acrylic—are taken. If two vertical spiral-post implants are to be used, an alginate or elastic impression of the entire side of the arch, including the prepared abutment teeth and the edentulous area, should be taken. This is needed to fabricate a temporary acrylic splint for immobilizing the posts. If triplants only are to be utilized, the temporary acrylic splint is not necessary. However, if a triplant and post type implant are combined, a temporary splint is necessary to stabilize the post type implant.

Case 1

A unilateral posterior free-end saddle restoration using a triplant and a template

A highly significant factor in the success of a maxillary posterior fixed partial denture is the Linkow scalloped template, which acts as a stress-distributing

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