Endodontic treatment of a fused tooth. Report of a case.

Dental fusion, a rare developmental anomaly present in 0.2% of the general population, consists of the union of two teeth originating from two different tooth germs. The irregular coronal morphology and the complex endodontic anatomy, characterized by the partial or total union of the pulp chambers, together with the peculiarity of the root canal systems, make diagnosis, therapy and rehabilitation difficult. The authors describe the endodontic treatment of a permanent lower second molar fused with a third molar and having four root canals.