Analysis of the Internal Anatomy of Distal Root Canals of Mandibular Molars: A Micro‐Computed Tomography Study

ABSTRACT Detailed knowledge of the internal anatomy of the root canal system and its variations is essential for selecting appropriate endodontic treatment protocols. Micro‐computed tomography (micro‐CT) allows for nondestructive, high‐resolution three‐dimensional (3D) analysis of extracted teeth, enabling precise evaluation of root canal morphology. This study evaluated the morphological characteristics of the distal root canal system of mandibular molars using micro‐CT. One hundred distal roots of first and second mandibular molars were scanned using micro‐CT systems. After image reconstruction, three‐dimensional models were generated using CTAn and CTVox software. The canal configuration was evaluated according to the Vertucci classification, as well as canal dimensions (major and minor diameters), cross‐sectional shape, and morphological changes along the root length. The most prevalent configuration was Vertucci Type I (89%), followed by Type V (8%), while Types III (2%), and VII (1%) were less frequent. The first lower molars showed greater morphological variability than the second. At the apical foramen, the major and minor diameters were similar, indicating a predominantly circular morphology. Between 2 and 3 mm from the apex, an increase in the major diameter was observed, characterizing oval or flattened canals in the middle third. Oval canals predominated at all levels, becoming more elongated and flattened toward the cervical third, with morphological variations along the root. It is concluded that, although they generally present a single canal, the distal roots of the lower molars exhibit great anatomical variability, which can hinder biomechanical preparation and reinforces the importance of anatomical knowledge for effective cleaning and disinfection.