Interradicular Root Canals in Mandibular First Molars: A Literature Review and Ex Vivo Study

Successful endodontic treatment vastly depends to a high degree on an accurate knowledge of root canal system morphology. It is a prerequisite to be aware of all possible reservoirs where bacteria and/or toxins can persist, compromising the surrounding tissues; such knowledge results in endodontic success.The presence of interradicular canals and diverticula between the pulp chamber floor and the bifurcation area surface of 117 mandibular first molars was investigated. Access cavities were prepared, the teeth were embedded in plastic, and the pulp chambers were flooded with methylene blue and then centrifuged. An average of 4.2 (0.145 ± 0.03 mm thickness) slices per tooth were obtained by means of a diamond band saw. The presence of interradicular canals and diverticula was investigated using a light microscope (125×).Interradicular canals were observed in 9 teeth. Seven teeth had 1 interradicular canal, and 2 teeth had 2 interradicular canals. Diverticula (blind interradicular canals) were observed in 11 teeth originating either on the pulp chamber floor or the bifurcation side. The number of diverticula per tooth varied between 1 and 5 and originated in 3 teeth in the pulp chamber floor and 8 teeth in the bifurcation area. Two teeth had both 1 interradicular canal and 3 diverticula. Of the 117 mandibular molars investigated, 18 had either 1 or 2 interradicular canals, 1 to 5 diverticula, or an interradicular canal and 3 diverticula.Based on the results obtained with this ex vivo study and because of the difficulties involved in the clinical performance of mechanical cleaning of possibly existing interradicular canals, it is highly recommended to perform thorough chemical cleaning and disinfection of the pulp chamber floor area in order to enhance the sealing possibility of such structures and minimize treatment failure.