Mandibular Implants (published 1977)   Dr. Leonard I. Linkow

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The bone's condition, as well as the height of the ridge, helps determine the implant type. The totally edentulous posterior ridge is very likely to have fragile bone with widely space, narrow trabeculae. This characteristic may suggest using an apically closed bladevent (5), to give a better locking support rather than an open ended implant (6).

A bladevent's innate stability depends upon broad surface con-tact with bone and using the advantageous horizontal dimension. The shallow body of the shallowest type implants is a design disadvantage, and widely spaced, fragile trabeculae even further minimize the essential bone-implant contact.

The shallow mandibular bladevent works most successfully in a dense bone, and is therefore more appropriate above the canal between stable teeth than in a totally edentulous site. It is not recommended as the posterior abutment for a unilateral bridge, although in some situations it can be used in conjunction with a full arch, fixed prosthesis.

When a shallow bladevent design seems suitable in a posterior situation, the ridge must be at least 3.5 mm wide at its narrowest point (7) . This is wider than for a similar anterior situation because of the greater lateral stress on posterior implants during chewing and grinding. When undercuts are present, the ridge usually must be remodeled (8). However, very careful estimates must be made when considering reducing a shallow posterior site. Too much reduction, and even the shallowest bladevent design will not fit. Bone above the canal is too precious for experimental reduction.

The special, shallow double-posted bladevent requires at least 7 mm of bone for properly deep insertion. Its shoulders must be buried in bone—with the bottoms of the posts touching the crest (9) for good retention.

In a shallow implant site there is always the danger of penetrating the canal. Thus the 700 XL bur is used very cautiously. Typi-

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1 Apically closed bladevent dental implant
2 Open ended mandibular bladevent dental implant
3 Undercut of mandibular ridge remodeled for implant placement



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