Evaluating the implant candidate 251

rous (Fig. 6-58), implants should again be contraindicated, even though enough height exists. The same maxilla may have both porous and dense areas. In such a case, the location of the dense bone is important. If it exists only anteriorly, it would be impossible to provide enough support for a full arch restoration. The edentulous maxilla must provide enough dense bone for strategically placed implants around the arch.

When enough dense bone exists (Fig. 6-59), endosseous implants can be attempted. Currently, after years of experience, Linkow uses only blade implants in an edentulous maxilla. His previous at-tempts with screw type implants and pins eventually

resulted in their loosening because they were unable to resist lateral forces. The combination of screw and pin type implants with metal or plastic templates and a very lightweight, removable prosthesis was successful for a few years or more, but often the pins had to be removed and driven through the template and into the bone in new directions to restabilize the loosening prosthesis.

A warning about interpreting bone density from x-rays: sometimes the buccal, labial, and palatal cortical plates of bone camouflage the true picture of bone density. These may be mistaken for medullary bone, making it appear denser than it actually is.

Fig. 6-59. The maxillary bone in this case is both dense and deep enough for endosseous implants.

Fig. 6-60. Because the alveolar bone in this mandible has extensively resorbed, a subperiosteal implant is indicated.