The implant site 71

teum from the crest over the socket. The periosteum lays down the bone. When completely healed, such a site appears entirely normal.

Other variations in healing include a lack of formation of a cortical bone plate at the crest of the ridge and the production of very thin, fluffy-looking bone instead of trabeculated bone (Fig. 3-27).

In addition to remodeling of the socket, the bone at the alveolar margins normally undergoes some changes after tooth loss. This bone formerly followed the contours of the tooth. With the tooth gone, it undergoes some resorption. Often the maxillary ridge resorbs to a knife edge, and the mandible resorbs downward and flat, with only the sharp mylohyoid ridge remaining.

Remodeling may be termed incomplete for any of several reasons. A common failure is only partial filling of the socket, with bone in the deeper portions but entirely lacking at the gingival margin (Fig. 3-28). Bone may form at the base of the socket and over the crest but leave a clear space or very scanty bone in the center. Also, the new bone may not resemble the adjacent bone in character or density. The entire original socket or the uppermost portion of it may be replaced by a thin network of very fine bone with a few widely separated trabeculae, or by bone so dense that it looks like a root (Fig. 3-29) .

Fig. 3-29. Instead of normal bone, the socket has been filled by dense bone that looks like a retained root. (From Worth, H. M.: Principles and practice of oral radiologic interpretation. Copyright © 1963, Year Book Medical Publishers, Inc. Used by permission.)

Progress of periodontal disease

Periodontal disease may involve any one or all three of the periodontal tissues: the gingiva, the periodontal ligament, or the alveolar bone. The disease may be localized initially, eventually spreading to involve the other tissues, or it may begin simultaneously in all three tissues, for example, as a result of trauma.

Certain kinds of gingivitis, including inflammatory reactions caused by a temporary imbalance of the sex hormones or a reaction against drugs, do not tend to spread deeper into the tissues. Inflammation of the gingiva resulting from calculus, plaque, poor dental restorations, and other local irritants does spread.

The spread of an inflammatory process from the gingiva toward the apex of the tooth is always accompanied by pocket formation and bone destruction. The condition, called periodontitis, begins with

Fig. 3-30. Pocket formation resulting from calculus. Note resorption of alveolar crest under this suprabony pocket. (From Bhaskar, S. N.: Synopsis of oral pathology, ed. 3, St. Louis, 1969, The C. V. Mosby Co.)

Calculus Pocket