Caution: Do not pound down one shoulder, then the other, or allow an unsupported implant to be rocked mesio-distally (42) . Uneven, forceful seating injures the mesio-distal borders of the socket, and working the implant up and down widens the socket.

The sharp-pointed inserting instrument fits easily between the walls of the socket into the point on the blade shoulders, making it possible to sink the implant to its proper depth without traumatizing bone at the crest.

The implant is properly seated when the bottom of its post rests on the alveolar crest (43). It should resist being moved. Upon tapping the protruding post a sharp "thock" should be heard. A dull "thud" indicates a loose implant.

In summary, the better the ridge, the better the prognosis for a long-term, stable bladevent. Even in the best morphological situation, however, it is possible to make surgical errors because of over-confidence. Cautious surgery is essential in every situation, not just the most difficult.

The Double-Posted Bladevent

The double-posted bladevent provides two abutments in a single implant site. It is most commonly used in the posterior portion of the mandible to provide unusually strong support. It is often used anteriorly in between two periodontally involved cuspids or in anterior edentulous areas when only single posted implants can be inserted posteriorly.

A double-posted bladevent is inserted in much the same manner as is a single-posted bladevent. However, a double-posted blade is from one-half to two times longer than a typical single-posted de-sign. Correspondingly, its socket is longer and usually curves to follow the arch.

To provide maximum contact with bone, the largest implant of a suitable design should be selected. Its placement depends for the most part upon the location of the mental foramina as well as the height of bone above them and the amount of bone existing lingual to the nerve bundles.

When the bone is thick labio-lingually, often the groove can start lingual to the mental foramina. Thus its posts could extend into the lateral incisor and first bicuspid regions. If the mental foramen is large or close to the ridge, the groove must remain mesial to it. The

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