Unusual fusion of a distomolar with a third molar assessed by cone-beam computed tomography

Supernumerary teeth are teeth that occur in addition to the normal series. They can be observed in all quadrants of the jaw, with highest incidence in the maxilla. When a supernumerary tooth is distal to the most posterior molar, it is called a distomolar. Distomolars are more common unilaterally, in the maxilla and in black people and affect 2.2% of the population. In contrast, fusion is the result of the union of two separate tooth germs, forming a single tooth joined by dentin and/ or enamel, and fusion of a permanent tooth with a supernumerary accounts for fewer than 0.1% of cases, usually involving anterior maxillary teeth. Periapical radiographs are routinely used for endodontic diagnosis and preoperative planning, for transoperative guidance and for postoperative follow-up. However, the two-dimensional nature of this imaging technique can impose limitations on the ability to determine the anatomy of root canals in teeth with anatomical variations. The objective of this case report is to describe a rare case of fusion of a distomolar with a third molar, assessed using cone-beam computed tomography (CBCT)