COF tends to have a female-to-male predominance of 3:1, with peak incidence in the 2nd to 4th decades. Svirsky et al.  analyzed 15 cases of COF and reported that 80% occurred in the mandible. In a study carried out by Handlers et al. , of the 39 cases of COF found, 56% were reported to have occurred in the maxilla and 44% in the mandible. The most recent review of the literature by Ramer et al.  reported a similar incidence in the maxilla and mandible.
Clinical, Histopathological, and Radiographic Appearance
Clinically, COF tends to manifest as an asymptomatic swelling, although it can appear in a more aggressive way, provoking dental displacement and rhizolysis . The current patient’s lesion was central in the jaws and exhibited a slow persistent growth that resulted in painless cortical expansion. COF is usually a painless mass. The tumor occurs more frequently in the anterior maxilla and may result in a distinctive palatal cleft or depression, which is considered characteristic of this tumor. Large lesions may affect adjacent structures, move teeth (as evident in our case), or even cause root resorption . Specimens are usually encapsulated, firm, smooth masses. Surgeons may describe the lesion as “shelled out” or hollowed out .
Histologically, COF is defined as a fibroplastic neoplastic lesion that contains inactive odontogenic epithelium and variable quantities of calcified material. COF may be associated with the crown of an included tooth or the roots of erupted teeth. The maxilla shows a predilection for the front part of the mouth, whereas in the mandible there is a predilection for the posterior regions . Due to its non-exclusive histological features, this lesion may be confused with other entities, such as hyperplastic dental follicles, odontogenic myxomas, and desmoplastic fibromas, highlighting the importance of clinicopathological correlation in the diagnosis of COF . Careful diagnosis is crucial.
There is a wide variety of histologic appearances, ranging from densely hyalinized and cellular, to loose and myxomatous, to nearly acellular (see Fig. 2). Delicate collagen fibers are occasionally identified, along with fibromyxoid stroma. It is this variation that has resulted in the historical separation of COF into two types: the epithelium-poor type (formally referred to as the simple type) or the epithelium-rich type (formally referred to as the WHO type). Features of odontogenic fibromas include inactive-looking odontogenic epithelium that, when present, may appear proliferative or form irregular islands and cords. Calcifications may or may not be present, simulating cementum, osteoid, or dentin. A rare granular cell odontogenic fibroma variant also exists .
Radiologically, COF manifests as a unilocular or multilocular lesion with well-defined margins and surrounded by a sclerotic halo. The multilocular radiotransparent form is more frequently associated with complications such as severe resorption of the roots of adjacent teeth, displacement of neighboring teeth, or inclusion of some tooth tissue . Severe effects on the surrounding bone trabeculae are often seen, even if the borders are well defined on radiographic images. Kaffe et al.  stated that a differential diagnosis of COF should be considered for all abnormal radiolucencies in the jaws, as a diagnosis of COF can be difficult for a variety of reasons. Ikeshima and Utsumomiya  attempted to show specific characteristics of fibromas for differential diagnosis, such as boundaries, root resorption and calcification. Other reports have noted that COFs are multilocular, radiolucent, slowly growing neoplasms of bone with no tendency to recur after surgical enucleation and have a variety of radiographic and histopathological characteristics.
Wesley et al. in 1975  suggested a set of criteria for diagnosing COF:
1) Clinically, the lesion is central in the jaws and has a slow, persistent growth that results in painless cortical expansion.
2) Radiologically, the appearance of the lesion varies, but like ameloblastoma and odontogenic myxoma, most are multilocular radiolucent lesions that involve relatively large portions of the jaws in the later stages. In some instances, they may be associated with unerupted and/or displaced teeth.
3) Histopathologically, the most consistent feature is a tumor composed predominantly of mature collagen fibers with numerous interspersed fibroblasts. The presence of small nests and/or strands of inactive odontogenic epithelium is a variable feature.
4) The lesion is benign and responds well to surgical enucleation, with no tendency to undergo malignant transformation.
Gardner  attempted further clarification of lesions previously described as odontogenic fibroma and classified them into three different, yet probably related, lesions:
1) The hyperplastic dental follicle.
2) A fibrous neoplasm with varying collagenous fibrous connective tissue containing nests of odontogenic epithelium (simple type).
3) A more complicated lesion with features of dysplastic dentin or cementum-like tissue and varying amounts of odontogenic epithelium (WHO type). As this group is similar to the calcifying odontogenic tumor described by Pindborg in a WHO publication in 1971 [2, 12], Gardner designated it as odontogenic fibroma (WHO type) . The two lesions can be distinguished by the fact that, the calcifying odontogenic tumor stains positive with amyloid stains, but the odontogenic fibroma (WHO type) does not.
According to Marx and Stern , most COFs require an incisional biopsy, because their presentation suggests more aggressive disease. After a diagnosis is established, a panoramic radiograph is sufficient for treatment planning.
Mohanty et al.  reported on the rare occurrence of unilocular intrabony pathology in the mandibular anterior teeth, similar to our case. Of 17 cases found in a 10-year review of records, nine different pathologies were seen, although clinical and radiographic signs and symptoms were similar: ameloblastoma, adenomatoid odontogenic tumor, odontogenic keratocyst, two ossifying fibroma, idiopathic bone cavity, dentigerous cyst, radicular cyst, central giant cell granuloma, and calcifying odontogenic cyst. Careful histologic examination would therefore appear to be essential to a correct diagnosis.
Sheikhi et al.  observed a lesion in a 37-year-old patient’s maxilla, and a range of clinical and radiographic (intraoral, panoramic, cone beam computed tomography) did not provide a diagnosis. The differential diagnosis included chondrosarcoma or osteosarcoma, fibrous dysplasia, odontogenic cyst, squamous cell carcinoma, calcifying odontogenic cyst (Gorlin cyst), and calcifying epithelial odontogenic tumor (Pindborg tumor). The well-defined border of what they termed a “central cementifying fibroma” helped differentiate it from the aggressive sarcomas and carcinomas.
Scholl et al.  reviewed cysts and cystic lesions of the mandible. They noted that many nonodontogenic lesions can mimic odontogenic lesions, including benign fibro-osseous lesions (conventional or juvenile ossifying fibroma, focal or periapical cemento-osseous dysplasia, florid osseous dysplasia), traumatic bone cyst, lingual salivary gland inclusion defect, central giant cell granuloma, brown tumor of hyperparathyroidism, arteriovenous malformation, and mucoepidermoid carcinoma. Like Mohanty et al. , Scholl et al. concluded that “microscopic tissue evaluation is generally necessary to accurately identify the lesion”.
TREATMENT AND RECURRENCE
The treatment of COF involves conservative surgery through enucleation of the lesion and the use of a curette to heal the remaining cavity. These lesions readily separate from their bony crypt and show no evidence of bony infiltration. The resultant bony cavity is closed at the mucosal level without the need for drains or packing .
In spite of the frequent ease of removal of COF, because it does not adhere to bone or tooth structures, uncommon recurrences have been attributed to insufficient curettage. Due to its benign, slow growth, a clinical identification of recurrent or residual disease might not be identified until several years later. Dunlap and Barker  presented two cases of maxillary COF treated by curettage with follow-up of 9 years and 10 years, respectively, with no evidence of recurrence. However, some recurrent cases have been reported. Heimdal et al.  in 1980 reported a recurrence 9 years after surgical removal. In 1986 Svirsky et al.  reported a 13% (2 out of 15 cases) rate of recurrence. Jones et al.  reported a case that recurred 16 months after surgery. According to Marx and Stern , if a recurrence is observed, the original pathological specimen, as well as a biopsy specimen, should be reviewed. Despite the low recurrence rate, postoperative monitoring should be carried out for at least 5 years after surgical removal.