bone behind the sinus (18) to accept a bladevent set bucco-palatally. Although sinus expansion may eventually make a bladevent intervention in the tuberosity impossible (19) , the compact bone that often flanks the tuberosity, the palatal surface of the alveolar crest just before it blends in with the hard palate and the pterygoid process of the sphenoid bone can be used as a site for a modified subperiosteal implant.

Stress is also directed horizontally via the hard palate, under the sinuses and nasal cavity. Force initiated upon the left molars, for example, will be deflected (20) toward their bilateral counter-parts. When teeth are missing, cancellous bone within the associated portion (21) of the hard palate may resorb. As a result, in some cases, the compact upper and lower plates of the bone may more closely approach one another, causing a thinning of the hard palate. In a few situations, the sinus may invaginate between the plates. Despite these results, the compact bony surface of the hard palate makes it a sturdy subperiosteal implant site. However, the soft tissues covering the palate do not seem to accept any metal frameworks beneath it.

The different adaptation to stress distribution in the maxillae is reflected not only grossly but in the internal structure of the alveolar bone. Maxillary alveolar bone tends to be more irregularly arranged than does its mandibular counterpart. It does not form trajectories along lines of force because stress is almost immediately diverted away from the dental arch by the pathways circumnavigating the sinuses, nasal cavity, and passing back over the zygomatic arch and pterygoid bone toward the base of the skull.

The muscle attachments that also encourage the maintenance of trajectories are fewer in number and strength in the maxillae. In the mandible, with its muscles for swallowing, opening and closing the mouth, speaking, and so on, a significant amount of force is exerted on bone near the dental arch, and the dental arch secondarily benefits from it.

In the maxillae, the main source of osteogenic stimulation is stress caused by mastication. Once the tooth lacks a functional opponent or is lost from the site, the major source of stimulation is lost and the bone reflects this loss.

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