implant's post or restoration will not interfere with the ascending ramus. This latter consideration alone contraindicates many cases, requiring the substitution of another type of implant — usually a pterygoid extension implant, with its post fabricated in a more desirable position. The pterygoid extension implant is also prefer-able when anterior support is weak due to the distance between the tuberosity and the anterior abutments.

Because of its location along the posterior aspect of the sinus, the maxillary tuberosity receives mechanical stimulation as force is deflected around the sinus. Its cancellous interior is densest when healthy molars are present. However, after tooth loss the area continues to receive stimulation, which is why more bone may be present in this site than in the molar region.

Even after extensive bone loss, the tuberosity (2) remains wider than the more anterior edentulous portions of the ridge (3) . Its posterior border is defined by hard, compact bone which retains the bulge-shape after the interior cancellous bone has resorbed. For this reason, it is misleading to assume that a wide tuberosity implies minimal resorption. A radiograph may reveal that an ideally wide ridge encloses an air-space — a severely ballooned sinus (4).

Great care must be taken when working in the area of the maxillary tuberosity. The foramina of the greater (5) and lesser (6) palatine vessels exit from the palatal bone near the third molar site (7).

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