occlusal angles estimated. The bladevent is withdrawn, and the posts bent appropriately, taking care not to distort the curve bent into the blade's body.

Many operators working near the canal prefer to blunt the leading edge (17) of the blade, so that if it should accidentally intrude into the canal, it will not pierce the nerve or arterial membrane. If the leading edge of the bladevent should intrude into the canal, it might only push the neurovascular bundle away from it without tearing or crushing it. However, this too, is not desirable.

Because the ridge has undergone considerable recession, the posts will probably be bent away from the axial inclination of the socket. The pointed seating instrument (18) should be used to sink the implant to its proper depth. A finger holds the post over the untapped shoulder to prevent the implant from being rocked up and down in its socket (19) .

Caution: Gentle taps are essential. Hard whacks can break through the bone into the canal (20) , as can neglecting to secure the distal post (21) with a finger.

The leading edge of the implant will break a few remaining bony bridges directly under the implant's legs as it is correctly seated. If the situation and amount of remaining bone were correctly appraised, the bladevent should be secured in the small amount of bone remaining above the canal.

Problem Ridge: Irregular Alveolar Crest

In an adult who lost numerous teeth in the arch, especially due to over-retained periodontally involved teeth, thus causing extreme resorbtion of the labial and buccal plates of bone, the ridge is left with numerous uneven concavities and loss of bone. The alveolar crest height may therefore drop down anteriorly (1), posteriorly (2) , or in the middle (3) .

The goal in selecting an implant is to place as much implant in bone as possible. Thus many designed implants both in height and width as well as single posted or double posted varieties must be used to give the maximum amount of metal to the minimum amount of bone that exists as well as proper interspacial arrangements of

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