A four year old male child was referred from the diagnostic service of the Universidad Mayor to the Dr. Luis Calvo Mackenna Paediatric Hospital for evaluation of an increase in volume in the right mandibular area, asymptomatic and of undetermined evolution. The mother reported that she had not noticed the increase in volume until the time of referral, and that the child never complained of pain or functional impotence.
The patient had no relevant morbid or surgical history.
Extraoral examination revealed an enlargement involving the body and right mandibular ramus, firm and painless on palpation, with no skin involvement. There were no adenopathies. There was also no associated sensory involvement and the mandibular functional examination was normal.

On intraoral examination, the patient had complete primary dentition and a large increase in volume involving the body and the right side ramus, the mucosa covering it was undamaged, painless on palpation and hard in consistency.

In the panoramic Cone Beam view, an extensive well-defined unilocular radiolucent lesion could be observed, with variable content of radiopacities similar to dental structures, extending from the distal root of the second temporal molar to the upper area of the right mandibular ramus, equivalent to 45mm in the mesiodistal direction, 30mm in the vestibulo-lingual direction and 35mm in the cephalo-caudal direction. The lesion produced displacement towards the basilar edge of the first permanent molar germ, while the second permanent molar was not observed. The anterior border of the ramus, the alveolar ridge and the basilar border were involved. In the coronal section, the expansion of the vestibular bone table and the inferior displacement of the lower dental canal were particularly visible.

An incisional biopsy of the lesion was performed. Histopathological examination with haematoxylin-eosin staining showed fibrous connective tissue with areas of dental tissue with varying degrees of calcification similar to dentine or dentinoid tissue, all in relation to odontogenic epithelium. In addition, areas similar to dental papilla were observed with epithelial proliferation arranged in cords and islets with periphery similar to ameloblasts, and towards the centre tissue reminiscent of stellate reticulum. The histopathological diagnosis was FOA.

With this diagnosis, definitive surgery was planned. Under general anaesthesia, the approach was performed at the level of the anterior border of the right mandibular ramus. Bone exposure showed a significant expansion of the mandibular vestibular bone table, over which an osteotomy was performed to allow access and subsequent complete enucleation, followed by conditioning of the cavity and suturing with Vycril 4.0.

Postoperative management of the patient involved antibiotic therapy and conventional analgesia in conjunction with revulsives and a soft diet. The latter was prolonged for one month.
The patient is maintained with periodic controls in the immediate and late postoperative period and, currently, after one year postoperatively, he is in very good condition.