dictates of the site, with atypical bending and countersinking of the posts not unusual.

The need for two anterior abutments may be fulfilled more easily with two single blades than with one long double-posted blade. Two separate bladevents are often more practical, particularly when there are undercuts to avoid or when the ridge is narrow. Each blade may be set to its best advantage (14,15), usually without the extreme oblique angling or bending of their bodies often needed for a double-posted blade in the same situation. Exaggerated bending of the necks can also either be avoided with two blades, or at least perhaps limited to only one implant.

Caution: Avoid the temptation to insert the implants so that the posts are set at the same height. Differences in occlusal level are easily adjusted in the prosthesis. Improperly seating an implant (16) is the major cause of implant failure.

A double-posted implant is advisable only when there are no undercuts or other problems with the ridge. Seating the implant so that both its posts touch the crest of the ridge may set it oblique (17) to the occlusal plane (18) .

Caution: It is far more important to encase the shoulders firmly in bone than to position the implant parallel with the dental arch (19). The base of both posts must touch the crest.

The posts are adjusted after the socket has been prepared, and after the bladevent has been curved to fit the groove. If very acute angling is needed to adjust the posts, some adjustment can be done by grinding (20) outside the mouth to create a new taper (21). When exaggerated angling is predictable and if time permits, it might be more practical to order a custom-made bladevent with the posts already angled.

In most cases, the need for countersinking will become obvious as the implant approaches the crest. Countersinking is more easily accomplished with the implant in its socket.

Most adjustments in the necks of the posts should be made out-side the mouth, prior to final seating. However, when a double-posted bladevent is used in firm bone, minor adjustments can be made in the mouth. After the implant has been almost seated to its proper depth—i.e., only the posts and their necks protrude above the crest—one cone socket pliers stabilizes one post for use as a brace (22), while another pliers adjusts the second post (23) by bending its neck, using the shoulder as the fulcrum.

78