A 28-year-old male patient came to our department presenting with left hemimandibular pain and fever. He had no pathological history of interest. Physical examination showed no specific signs, but there was pain on palpation of the pericoronary tissues of the lower left third molar. A blood test was carried out in the emergency department showing a slight increase in the number of leukocytes, with no other notable alterations. The orthopantomography (OPG) showed both third molars included, in mesioangular position, with follicular sacs, the right one being larger.

With the suspicion of a possible infection of odontogenic cause (pericoronaritis) antibiotic treatment was started, with complete resolution of the symptoms. Exodontia of both lower wisdom teeth was recommended. Histological examination confirmed the presence of a follicular sac associated with the wisdom tooth, formed by non-keratinised polystratified epithelium. After the extraction of the lower left third molar, the patient did not return to complete the treatment. After 20 months he consulted again for pain at the level of the lower right third molar. The OPG showed a large radiolucent image around the crown of the right lower third molar.

With the diagnostic suspicion of a dentigerous cyst associated with the third molar, surgery was performed with exodontia of the tooth and cystectomy. The anatomopathological study confirmed the presumptive diagnosis as a lesion with a connective tissue wall lined on the inside by a stratified epithelium of keratinised ciliated cells and cells with abundant mucin. At the three-month check-up, the residual cavity created by the cyst was found to have undergone active ossification (with the formation of bone trabeculae).