The typical tuberosity is markedly undercut on its palatal side, where the groove for the vessels lies (8), and slightly con-cave on the buccal surface (9). The guiding diameter is the width of the narrowest portion of the ridge, above the concavities (10). Caution: Because of proximity to the vessels (11), reshaping the ridge to reduce the palatal undercut is inadvisable.

A tuberosity implant — one of the mesio-distally shorter blade-vents — can be inserted mesio-distally (12), or bucco-palatally (13), or angled across the arch (14), or curved (15) to fit the remaining bone.

Starting the socket in the center (16) of the ridge and then working outward (17) will give the operator a better feel of the bone's density. The cancellous bone in the center should offer minimal resistance. Depending upon the bone's fragility, the socket may or may not be drilled to its maximum depth.

The posterior region is one of the few sites where it is in-advisable to angle the bur and socket palatally. The bur should remain almost perpendicular to the occlusal plane to avoid the blood vessels and nerves.

The bur may be driven straight up (18) — if the sinus has left a fairly wide vertical column of bone — or angled posteriorly (19).

To check the alignment of its posts with that of other abutments, the blade is tried in. When a specially-designed bucco-palatal (BP) blade is used, post adjustments are minimal. The post is manufactured so that its broader face (20) is at a right angle to the broader face of the body (21) . Only when the socket is inclined (22), or when it is diagonal to the arch line (23), are adjustments necessary.

The single-headed inserting instrument is usually appropriate for a bucco-palatal blade unless the socket is acutely inclined. A few taps should sink the implant to its proper depth. Counter-sinking may be necessary.

Problem Ridge:

The Pterygoid Extension Subperiosteal Implant

The posterior portion of the maxillary arch may be almost flat (1), with only a few millimeters of bone separating the sinus

21

20

113