in its bucco-lingual and mesio-distal width to incorporate a sturdy anchorage device. The mechanism may be a figure-eight female attachment (1) or an internally, vertically threaded screw system device (2). The interlocking male (3) -female (4) attachments are more desirable because the screw system is less sturdy, requires a bulkier restoration, and the screw looks unesthetic occlusally. As reinforcement against lateral thrust, the pioneer unilateral pterygoid extension implant splint with an internally threaded screw system had a finger-like extension over the hard palate. This feature has been discarded because of difficulties in maintaining a tight elastic soft tissue cuff around the extension.

In many cases, pterygoid extension implants are bilateral, and inserted simultaneously. However, if the pterygoid extension implant is unilateral and bladevents are to be used on the other side of the arch, the bladevents are inserted first. They will be included in the splint to which the pterygoid extension implant attaches.

As does any form of dental implant that fits over the bone, the pterygoid extension implant must be fabricated from a direct impression of the exposed intended sites. The incision begins in the hamular notch area (5) , great care being taken to avoid the greater palatine foramen (6) and the tendinous strap (7) stretched across the pterygoid hamulus. The incision progresses anteriorly along the crest and terminates interproximally between the two anterior teeth (8) that border the span.

If a presurgical interocclusal record has not been taken for determining tissue thickness, tissue depth is measured before the tissues are retracted or become swollen. A periodontal probe (9) is used along the entire span, from the cantilevered anchorage de-vice site (10) to the distal end of the tuberosity (11). These measurements tell the laboratory where to place the horizontal bar so that it lies outside the soft tissues.

The tissues are pushed away from the ridge with a periosteal

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