In most cases, the maxillary soft tissues change proportionately in regard to the bone and retain the horseshoe shape. The shape, and the type of soft tissues forming it, are of less interest to the implantologist than the amount and type of bone remaining in the flattened ridge.

Even if the dental ridge proper has completely resorbed, there is usually enough bone remaining anteriorly for some type of endosteal implant. "Nondental" cancellous bone in the canine pillar regions and below the nasal atrium may provide several millimeters of suitable bone. Posteriorly, of course, the subsinus region will doubtless be unsuitable. However, behind the sinus there may be enough bone in the maxillary tuberosity to accept an endosteal implant angled across the dental arch line.

As for the type of bone remaining that could support a subperiosteal type implant, there remains principally the hard palate, the palatal surface of the alveolar crest completely around the arch, the palatal and buccal faces of the tuberosity posterior to the sinus, and the hamular notch area, as well as the labial cortex from canine eminence to canine eminence and up to the anterior nasal spine.

After tooth loss, the maxillary socket's alveolar bone reconstructs in much the same way as the mandible's — with one important difference, most markedly in the posterior portion of the maxilla. Here compact bone does not reform at the surface; a thin plate of dense bone does not separate cancellous alveolar bone from the mucoperiosteal tissues! Instead, loosely arranged trabeculae form an irregular surface (photograph). This characteristic feature has two specific implications for the implantologist.

The mucoperiosteal tissues are much more firmly bound to the maxillary crest than they are to the mandibular. The thin fibers that extend from the mucoperiosteum and bind it to bone have a more irregular, latticed surface in which to intertwine. Therefore, cleanly separating the overlying soft tissues from bone is more difficult in the maxilla. It is a painstaking task, with careful attention paid to avoid fracturing the thin trabeculae.

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