212 Theories and techniques of oral implantology

nign tumors, the adenoameloblastoma is of epithelial origin, arising mostly from the lining of a follicular cyst. Unlike them, it is encapsulated and much less aggressive.

The adenoameloblastoma usually occurs while the patient—generally a female—is in her twenties. Almost twice as many lesions occur in the maxillae as in the mandible, and they usually occur in the cuspid area. An impacted tooth is usually associated with the lesion (Fig. 6-17).

Curettage is often sufficient to remove all of this encapsulated lesion. Once the site heals, implantation may be attempted.

Cementoma. A cementoma, also called a periapical fibroosteoma, cementoblastoma, periapical fibrous dysplasia, or periapical osteofibrosis, is a benign odontogenic tumor of mesenchymal origin. Most patients with cementoma are Negroes, usually women, and the most common site by far is in the region of the mandibular incisors. The lesions may be single or multiple. Unlike other, similar lesions in the area that require pulp extirpation or tooth ex-traction, a cementoma is always associated with vital teeth.

Like other benign odontogenic tumors, a cementoma is slow-growing. It begins as bone at or near the apex if a tooth is replaced by fibrous tissue. In radiographs this appears as a radiolucent area surrounded by a rim of slightly denser bone (Fig. 6-18). The lesion may remain in this state or, more typically, the fibrous tissue becomes replaced by bone or

Fig. 6-19. An odontogenic myxoma is usually associated with the crown of an unerupted tooth. (From Bhaskar, S. N.: Synopsis of oral pathology, ed. 3, St. Louis, 1969, The C. V. Mosby Co.)

cementum. This takes place gradually, usually requiring about 6 years to occur. Finally the lesion appears as a dense, rounded, radiopaque area surrounded by a thin radiolucent line. The bone in this area, unlike the normal bone surrounding it, has very loosely packed, thick trabeculae.

A cementoma requires no treatment. Once it has ossified, it does not regress to its fibrous stage. When implants are contemplated in molar areas, the affected incisors are still vital and suitable as natural abutments.

Odontogenic myxoma. Unlike a true myxoma, the odontogenic myxoma is a benign lesion that is slow-growing and easy to cure by curettage. It de-rives from the mesenchyma, and the presence of epithelial cells in tissue sections distinguishes this tumor from the true myxoma.

The odontogenic myxoma usually occurs around or near an impacted wisdom tooth in the maxilla (Fig. 6-19), developing before the age of 35 years. It is usually asymptomatic but may cause jaw expansion. Upon healing of the curetted site, implantation may be possible.

Odontogenic fibroma. The odontogenic fibroma is the most common odontogenic jaw tumor, representing almost one-quarter of this type of lesion. Radiographically it resembles a dentigerous cyst (Fig. 6-20), and it is therefore frequently mistaken

Fig. 6-20. Common sites for an odontogenic fibroma are the third molar or cuspid areas of the mandible. (From Bhaskar, S. N.: Synopsis of oral pathology, ed. 3, St. Louis, 1969, The C. V. Mosby Co.)