the hard palate or eliminating the hard palate completely appear to have minimized the problems.

Extending bilaterally from the premaxillary framework of cur-rent designs is a long, posterior palatal arm. This is a broad, flat piece (15). It buttresses the framework. The posterior palatal arm can extend into the first molar region (16) but further posterior extension places it in close proximity to the foramen (17) of the greater palatine vessels. The palatal arm is positioned under firmly attached soft tissue.

The anterior framework also gives rise to labial struts (18). These pass over the crest, preferably in the cuspid region, and continue high on the labial face of the ridge, where each strut bifurcates into lateral arms. The labial struts further secure the implant against dislodging forces, principally torque. The lateral arms, or wings, are slightly reflected back toward the crest in a "roll bar" effect. The arms can extend anteriorly toward the midline (19), posteriorly (20), or in both directions (21), whichever option best utilizes bony prominences. Ideally, the arms will be approximately symmetrical, and perpendicular to the post to offset rocking. Today all arms join beneath the anterior nasal spine.

The toroplant can be designed for a great many totally edentulous arches utilizing them as they present. However, in a significant number of cases, it may be necessary to slightly remodel the ridge to accommodate the labial struts. A resorbed maxillary ridge often has a pronounced concavity that makes accurate impression-taking difficult and seating a rigid toroplant without damaging the bone almost impossible. The cuspid area, noted for its thick, dense bone, is the ideal site for the strut, morphologically and prosthodontically. It can be easily modified to accept the strut by cutting a groove perpendicular (22) to the plane of insertion. This alteration may be necessary bilaterally (23) or unilaterally, depending upon the patient. It works equally well for the partially edentulous (24), as well as for the totally edentulous, arch. This minimal re-modeling simplifies both insertion procedures and implant design by eliminating the undercut in limited but vital areas.

The first toroplants incorporated anterior bladevents. These were to provide additional stability and in principle are a sound idea. However, in practice the bladevent-toroplant combination often proves risky because of the time lag between bladevent insertion and seating of the subperiosteal toroplant.

Although it is the sturdiest of all endosteal implant designs, the bladevent — no matter how accurately inserted — can be un-

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