The posts must be bent to the correct angle, and touch the crest on all faces. This usually means that countersinking (8) is necessary.

A double-headed seating instrument can be used to seat an open-socket bladevent in a slightly inclined socket. Or, if the socket has an exaggerated curve, a single-headed instrument can be rotated from post to post to gradually sink the implant. (9) If the posts have been acutely bent away from the socket's inclination, the pointed seating instrument (10) may be used.

Sometimes a very rugged outline remains. This type of ridge may also be complicated by narrowness and undercuts. Small bony spurs (11) should be removed with a bur or rongeurs. The spurs tend to chip off or irritate replaced wounded soft tissues. An angular shelf of bone (12) should be reduced if it forms a narrow prominence (13) in or near the implant site. Such a fragile projection cannot be used as an implant site, and tends to fracture or otherwise interfere with implant insertion.

When only one abutment post is needed in the anterior maxillary quadrant, any of several bladevent designs can be angled into the remaining bone. The chosen design is inserted according to the 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 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) . Both posts must touch the crest!

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