A case of dentigerous cyst originating from an impacted supernumerary tooth with a dens in dente deformity

Dentigerous cysts are relatively common lesions in the maxillomandibular region. However, it is difficult to distinguish them from odontogenic tumors when the lesion involves a malformed tooth. In this report, we describe a rare case of an odontogenic cyst involving a supernumerary tooth with a dens in dente deformity in the mandibular region. The patient was a 15-year-old boy. At the time of his initial examination, there was mild bony swelling on the 7 buccal side. Panoramic radiography showed a cyst-like radiolucent image in the right mandible from the 7 to the middle of the mandibular ramus, and opaque images with internal transparency to its anterior and posterior. The pathological diagnosis via biopsy was cyst-like lesion. The cyst-like lesion and hard tissue lesion were removed under general anesthesia. The cyst-like lesion was relatively thick, and the pathological diagnosis was dentigerous cyst. One of the hard tissues was a supernumerary tooth with a dens in dente deformity, grayish-white in color, and bullet-shaped. This is a valuable case, since dentigerous cysts originating from a supernumerary tooth with a dens in dente deformity in the mandibular wisdom tooth region are rare, and few cases have been reported in Japan.