this way the groove can be made more lingual and the neck be able to be acutely inclined labially without labial perforation. How-ever, the necks will have to be greatly inclined thus making it necessary to countersink the posts on the labial side. Even reduction rather than spot reduction is often more practical for the totally edentulous knife-edge ridge. Even reduction permits better visualization of prospective implant sites and better access during surgery. Furthermore, almost the entire ridge will be occupied by the blades needed for adequate support. The ridge is gradually leveled by working around the entire arch (12) until adequately wide sites appear.

Caution: Although extensively reducing the ridge might produce a wider table, it also brings vital landmarks nearer the crest and limits the choice of implant. Reduce only enough to safely widen the ridge to accept the deepest-bodied bladevent appropriate to the site.

When an adequately wide table has been established, the sharp edge (13) of the ridge carefully may be rounded with a bur or stone to reduce trauma to the soft tissues that will overlie the altered bone.

An atypical drilling technique is recommended in fragile knife-edge ridges to make the socket in as few steps as is possible. The 700 XL bur is centered on the reduced ridge (14) and the groove is made angled slightly toward the lingual to take advantage of harder lingual bone and to avoid the typical labial concavity. The operator places his fingers (15) on each side of the site. These will brace the ridge and feel the proximity of the running bur to the labial and lingual plates. The bur is driven straight down to the entire intended depth of the socket (16).

The bur is then slightly retracted (17) to back its shank slightly out of the bone, and then run inside the ridge, making the major portion of the socket and firmly establishing its direction in one sweep. One more pass of the bur, initiated at the original insertion site, is usually adequate to complete the socket (18). The finger (19) is kept on the ridge to sense the bur's progress.

Caution: Progress the bur evenly (20). Do not drag or advance (21.) its tip. This will distort the socket's shape and very likely perforate the labial plate.

Caution: Running the bur back and forth in a narrow ridge, trying to gradually create the socket, increases the opportunity of over-enlarging the channel or fracturing or perforating the bone.

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