Key Clinical Message

Radix entomolaris (RE) characterized by an extra root in mandibular molars is a rare phenotype. When this condition occurs simultaneously with complex root canal curvatures or S-shaped canals, root canal therapy (RCT) challenges arise\RL. The present study presents three cases of RE + complex root curvatures. The challenges of RCT and case management of this study are in the framework of paying attention to the access cavity according to the extra root, instrumentation with the crown down technique, sufficient irrigation, using nickel-titanium rotary systems, dense obturation with warm vertical technique and patient follow-up. Also, in the last case, the management of two broken files by loop and bypass techniques is described. \RL Adequate knowledge of the root canal system’s morphology and the use of appropriate techniques and materials for root canal therapy is the background for successful RCT.