Pre-sinus Bladevents

Here the reference is to that anterior site immediately in front of the sinus. In some partially edentulous cases, there may be enough bone under the sinus in the second bicuspid region to accept a specially designed bladevent with one very shallow end (1) . This bladevent comes in a double-posted design (2), the posts of which minimize occlusal stresses by sharing them, and a single-posted de-sign (3) . Because abutment posts ideally should be centered under the restoration, not fall interproximally (4), the single-posted implant is sometimes prosthodontically more desirable than the double-posted.

The decision to use a pre-sinus bladevent depends upon several factors. Because the design is asymmetrical — with one shallow end — it is not as well-balanced as are symmetrical designs. Furthermore, bone bordering the sinus (5) is more fragile than that in the canine pillar region and in the maxillary tuberosity. Thus the shallow end of the bladevent with less surface for contacting bone is set in an area with fewer and thinner trabeculae.

When the choice exists, it is preferable to set a symmetrical design (6) more anteriorly in firmer bone than to use a pre-sinus bladevent near the sinus principally to balance the bilateral abutment situation.

The main reasons for using a pre-sinus bladevent are the presence of a cuspid limiting space in front of the sinus; defects in more anterior sites that contraindicate their use as implant sites; and the desire to shorten the gap between anterior and posterior abutments.

A pre-sinus bladevent is not advisable for the most posterior abutment unless the bridge includes stable anterior teeth and can be carried around the arch to include the opposite cuspid. The pontics should extend no further posteriorly from the pre-sinus bladevent abutment than the first molar.

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 (1) should be buried below the floor of the socket with its mesio-distal shoulders (2) 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 post-pone implantation until the socket remodels.

In some situations an open socket is not deep after extraction. For example, incisors so seriously periodontally involved that

92