Also, one of the basic rules of implantology is that the simpler the implant design and the faster its insertion, usually the better. Several-stage implantation procedures and the time lapses between them almost invite complications. Unless the combination bladevent-pterygoid extension implant can be rapidly inserted and stabi-

lized as a unit, hopefully within 24 hours, the one-piece version with its greater simplicity is recommended. Furthermore, the prognosis for a bladevent-assisted pterygoid extension implant is vastly improved if the anterior ridge is deep and thick, with plenty of bone to be left labial to the bladevent to counteract a tendency toward labial displacement. The obvious advantage of strong endosteal anterior support may prove very worthwhile when conditions are favorable.

The bladevent-pterygoid combination implant differs from the single-unit pterygoid mainly anteriorly. Those struts crossing the ridge palato-labially are modified into copings to include the blade-vents. In the one-piece pterygoid extension implant, they incorporate the abutment posts themselves.

All portions of the pterygoid extension implant are fabricated from a direct bone impression. Therefore, they are inserted first, carefully into the anterior portion of the maxilla, in front of the menial extent of the sinuses (1) and below the nasal vestibulum. As much anterior bladevent support as is possible is desirable. There may be one abutment (2) on each side of the midline, or two provided by a double-posted bladevent (3) or two single-posted bladevents (4, 5).

To insure minimally traumatic insertion of the subperiosteal portion of the implant, it is extremely important to adjust the bladevent posts so that they are parallel with one another and perpendicular to the occlusal plane. Also, the anterior bladevent sites cannot be too severely undercut (6), or it will be difficult to fit the long, inflexible, one-piece implant (7) over the undercut bone. No matter how tall and thick the ridge, notching and using the one-piece, totally subperiosteal pterygoid may be preferable for an undercut ridge.

Initially to insert the bladevents, it is necessary only to expose the anterior portion of the upper arch. After bladevent insertion, the tissues are further reflected to get an adequate impression of the areas to be included in the pterygoid extension implant.

To facilitate laboratory procedures, prefabricated plastic copings (8) are slipped over the protruding bladevent posts prior to

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