A rare case of fusion between a third molar and a distomolar: case report

Fusion between a tooth and a supernumerary one that involves the union of two distinct tooth germs into a single with an enlarged dental structure. This case reports the endodontic treatment of a fusion involving a third molar and a supernumerary tooth (distomolar) in the left mandibular region of a 46-year-old female. This condition presented significant diagnostic and clinical challenges due to its atypical crown anatomy, two distinct pulp chambers, and morphological complexities that complicate traditional access and preparation. The diagnosis relied on comprehensive clinical examination and conventional radiographic analysis and the cone beam computed tomography, emphasizing the clinician’s skill in interpreting subtle findings. Non-surgical endodontic therapy was planned, executed in two sessions, with the use of the Logic 2 (25.05) nickel-titanium rotary instruments and an extensive irrigation protocol using 5.25% sodium hypochlorite and 17% EDTA under active ultrasonic agitation. A key element of success was the consistent use of an operating microscope (20x magnification), which was instrumental in refining access, navigating complex anatomy, and ultimately confirming the presence of five distinct root canals. Tri-dimensional canal sealing was achieved with Tagger’s Hybrid technique. This meticulous approach resulted in the functional maintenance of the tooth for over five years, showing that despite rare and complex morphological variations, advanced technological aids and thorough clinical expertise are paramount for achieving successful, long-term outcomes in endodontic treatment.