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grows. The tooth may be pushed upward in its socket and the root disappear.

Although resulting from an infection, a granuloma rarely contains the causative agent. In x-rays it closely resembles an apical abscess or a radicular cyst (Fig. 6-3). Of all periapical lesions, however, it is by far the most common, comprising at least 45% of them.

The patient with a granuloma is usually in his thirties. Clinically the affected tooth, which is usually in the maxilla, is either asymptomatic or slightly painful upon percussion and nonvital. The tooth should be extracted or root canal therapy performed.

Sclerosing osteitis. Sometimes instead of an inflammation's causing rarefaction of bone, it results in the production of new bone (Fig. 6-4). This sclerosing, or condensing, osteitis may result from the same microorganisms that cause bone destruction, and it is not uncommon that rarefaction and sclerosis often occur together, particularly in the mandible. The most common sclerotic sites are between the teeth, at or just below the crest, and around the apex.

Sclerosis results from the appositional deposit of new bone or the thickening of existing trabeculae. Eventually the marrow spaces between the affected trabeculae are almost obliterated and are so small

Fig. 6-5. Multiple enostosis may sometimes be distinguished from sclerosing osteitis by the "cotton-wool" appearance of the lesions. (From Bhaskar, S. N.: Synopsis of oral pathology, ed. 3, St. Louis, 1969, The C. V. Mosby Co.)

that they are indistinguishable in x-rays because of the superimposition of the numerous enlarged trabeculae. Thus the sclerotic area appears as a structure-less, uniform shadow.

Enostosis. Enostosis is characterized by dense lesions that resemble those in sclerosing osteitis (Fig. 6-5). The distinction between the two has been made on the basis that an enostosis is separated from a tooth by a few millimeters of normal bone, whereas the sclerotic lesion abuts the bone. Also, an enostosis has a rounded outline with well-defined margins and looks like a bone "whorl" or cotton-wool. Its characteristic shape may be the only clue to distinguishing the lesion from a sclerotic one in an edentulous jaw.

In enostosis the lesions are usually multiple. They occur more frequently in females and usually after

Fig. 6.6. In eosinophilic granuloma the lesion may be rounded, oval, or irregular in shape. This makes the tooth look as if it is "hanging in air." (From Bhaskar, S. N.: Synopsis of oral pathology, ed. 3, St. Louis, 1969, The C. V. Mosby Co.)