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thus appears to have lost little bone, maintaining its original post-extraction shape. With this observation, certain prosthodontists congratulate themselves upon the excellent fit of their conventional denture, inaccurately assuming that a correctly fitted denture retards bone loss. Although a poorly fitting denture hastens bone loss, a correctly fitted denture can be credited with retarding bone loss only in that it doesn't traumatize bone.

Eventually bone is markedly lost from the crest, as well as from the lateral walls. During this process, the ridge may maintain its deceptive padding (19) or gradually assume the near-"classic" recession pattern, moving the crest (20) toward the midline. It is important to recognize, for progress in both implant design and conventional restorative procedures, the varying trends in ridge resorption. Surface pressure, particularly directed on the crest of a knife-edge ridge, will encourage resorption of the ridge into the undistinguished flat plane that is the scourge of removable prosthesis design and fit.

The maxillary tissues' tendency towards thickening has several implications. A thick, firm distinct ridge is useful as a base for a conventional removable appliance. If the epithelium of such a ridge is heavily keratinized, and thus toughened against surface pressure, the situation is considered ideal by the prosthodontist. However, if the epithelium is poorly keratinized, yet rigidly bound

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