labial aspect of the neck and shoulder (7).

Occasionally, if it is desirable to flare out the posts at a greater angle the countersinking (8) might have to be accomplished by eliminating the interfering bone beneath the labio-gingival aspect of each post (8a). A supporting finger (9) is mandatory in this situation during tapping. Care must be taken not to let the denser bone in the center of the implant act as a fulcrum for see-sawing the implant as it is tapped to the proper depth. The double-headed inserting instrument usually prevents this. If the single-headed (10) or pointed seating instrument must be used, a finger is needed to hold down the untapped post (11) .

Open-Socket Bladevent

As its name implies, originally the open-socket bladevent was designed for use immediately after an extraction. In such a situation, its recessed central shoulder should be buried at least 2-3 mm below the floor of the socket with its mesio-distal shoulders in the denser bone on each side of the socket and its posts touching the crest.

In cases of limited bone height, it is frequently necessary to postpone implantation until the socket remodels.

In some situations an open socket is not deep after extraction. For example, incisors so seriously periodontally involved that they can be "unscrewed" by hand may be immediately replaced by an open-socket bladevent. There is usually enough bone beneath the apices of these anterior teeth to bury the bladevent correctly.

In addition to its original purpose, the open-socket bladevent has come to have even wider applications. A ridge may be very

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