such as the mental foramen as in this illustration. Then its shank is backed out and the cutting portion is worked mesially into wider bone (18), then distally (19), or vice versa—operator's preference. Note that this approach is different. Whereas the socket in an evenly wide ridge is initiated at one end and worked toward the other, the groove here is initiated in the narrowest portion for greater control over its direction.

In many narrow-waist situations, particularly when remodeling of the crest is required, the implant cannot be correctly seated without countersinking the posts (20). Bone must be reshaped mesially and distally (21), to properly seat the implant with the bottom of both posts touching the crest (22).

Occasionally the shape of a pinched ridge may require curving the groove (23) counter to the curve of the dental arch. This is an exceedingly delicate situation. A short, shallow bladevent design must be used to avoid perforating the labial or lingual walls. The neck (24) of the implant should be twisted so that the post will follow the normal dental arch (25).

Finding Bone For Two Anterior Abutments

When two anterior abutments are needed and the crest has a relatively long "waist" (1), the approach, as usual, depends upon the morphology. If the ridge's walls diverge below the narrow crest and have no severe undercuts, the crest can be reduced to 2.5 mm wide (2) to prepare the ridge for a single or double-posted blade-vent.

However, attempts to accommodate an implant design should be subservient to morphological considerations. Only a minimal

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