Many operators working near the sinus prefer to blunt the leading edge (15) of the blade, so that if it should accidentally intrude into the sinus, it will not pierce the Schneiderian membrane. This membrane can be easily detached from the sinus floor. If the leading edge of the bladevent should intrude into the sinus, it will push up the membrane without tearing it (16) .

Because the ridge has undergone considerable recession, the posts will probably be bent away from the axial inclination of the socket. The pointed seating instrument (17) should be used to sink the implant to its proper depth. A finger holds the post over the untapped shoulder to prevent the implant from being rocked up and down in its socket (18).

Caution: Gentle taps are essential. Hard whacks can break through the bone into the sinus (19), as can neglecting to secure the distal post (20) with a finger.

The leading edge of the implant will break a few remaining bony bridges directly under the implant's legs as it is correctly seated. If the situation and amount of remaining bone were correctly appraised, the bladevent should be secured in the small amount of bone remaining below the sinus.

Problem Ridge:

Irregular Sinus

In a young adult with a healthy dental situation, a small sinus is tipped toward the teeth. Because sinus expansion is associated with tooth loss, which is usually sequential, the sinus floor in a posterior edentulous situation is often not parallel with the occlusal plane. It may drop, or flare, anteriorly (1) , posteriorly (2), or in the middle (3) .

The goal in selecting an implant is to put as much implant in bone as is possible. Thus, several design variations exist for circumventing irregularly flared sinuses. The same design might serve, reversed, for either an anteriorly (4) or a posteriorly flared sinus (5). In most cases, such a blade makes a more secure posterior abutment if its deeper end is set distally, where more force is applied.

It also may be possible to substitute a shallow blade (6) with a sinus-circumventing blade (7) and therefore utilize more bone.

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