252 Theories and techniques of oral implantology

The edentulous mandible

There are usually far more opportunities for using implants in the mandible than in the maxilla. The horseshoe-shaped mandible is easier to fit, does not contain large sinuses, and has no gravity problems. Instead of being suspended from the jaw, as is the case with the maxillary restoration, a mandibular prosthesis sits on it.

When the mandibular alveolar bone has resorbed to such an extent that only basal bone remains (Fig. 6-60), a subperiosteal implant should be used. Some-times, however, both inferior alveolar nerves as well

as their mental branches are completely exposed as a result of the dehiscencies of the mandibular canals and mental foramina (Fig. 6-61). In such situations it may be advisable to contraindicate a subperiosteal implant. The implant may press on the nerves, at best leaving the patient with a unilateral or bilateral paresthesia that can never be eliminated. However, because the patient cannot function with a conventional denture, the operator may wish to attempt a subperiosteal design that will avoid the exposed neurovascular bundles. This should not be attempted if the patient has a full complement of upper teeth.

Fig. 6-61. When dehiscencies have occurred, a subperiosteal implant may be contraindicated.

Fig. 6-62. An ideal mandible for endosseous implants. There is deep dense alveolar bone around the entire arch.