Dealing With a "Pinched Waist "

In some cases, the ridge may have a definite pinched area, or "waist." This feature may be labio-palatally centered in the ridge (1) , or, more typically, offset palatally (2) . The width of the waist and the shape of the bone above the crest and mesial and distal to the waist determine the implant approach.

If the waist is less than 2.5 mm wide and the deeper bone re-mains narrow (3) or is undercut (4), the ridge must be treated as two separate sites. No single bladevent can span the waist.

If the waist is at least 2.5 mm wide and there are no severe undercuts, the site is treated as a narrow ridge site (q.v.). The guiding dimension is the width of the narrowest portion. The groove is centered in this, with the bur directed slightly palatally (5). The length of the groove — and of the bladevent — depends on the character of the mesial and distal portions of the ridge. Undercuts (6) or converging walls (7) may require using a mesiodistally shorter implant (8) .

If the pinched waist is narrower than 2.5 mm, and a single implant site is desirable, it may be possible to reduce the waist (9) until it is wide enough.