Evaluating the implant candidate 257

teeth in the restoration helps stabilize them. When-ever practical or possible, a full arch fixed prosthesis is Linkow's choice.

The posteriorly edentulous mandible (unilateral or bilateral)

When enough alveolar bone exists posteriorly (Fig. 6-69), blades, screws, and even pin implants can be used successfully. Sometimes more bone exists posteriorly on one side of the arch than on the other (Fig. 6-70). In the area containing the deeper bone, blades, screws, or pins may be used, but in the shallower area only a shallow type blade is appropriate.

Occasionally very little, if any, alveolar bone exists above the mandibular canals posteriorly (Fig. 6-71). In these situations only a partial subperiosteal implant or a universal subperiosteal implant with its usual four protruding posts can be used. In the latter

case the remaining anterior teeth are included as part of the superstructure.

In cases where very little bone exists posteriorly and the anterior teeth are supported by dense bone, Linkow has sometimes tapped blade implants directly into the external oblique ridges buccal to the canal, thereby enabling a blade to go fairly deep into the bone without involving the mandibular nerve.

It may be difficult in borderline cases to deter-mine whether a subperiosteal or an endosseous implant should be used (Fig. 6-72). If it appears that there is just enough bone to accept a shallow blade, the density of the bone is the deciding factor. If the bone looks dense, a unilateral subperiosteal implant might be preferable. If the bone looks rather on the porous side, a narrow long blade often serves the purpose successfully. Under no circumstances should screws or pins be used in such an area.

Fig. 6-72. A borderline case. The decision whether to use a shallow blade or a subperiosteal implant depends upon the bone's density.

Fig. 6-73. There is enough bone in this long span to more than adequately accept an endosseous implant. Not only will the implant help support the fixed denture, it may help preserve weakened teeth.