Characterisation of the Mesial Root and Middle Mesial Canal Morphology in Mandibular First Molars: An Ex Vivo Micro-CT Study

This ex vivo study characterised the mesial root morphology of mandibular first molars with a middle mesial canal (MMC) using micro-CT. Among 469 scanned molars, 42 (8.96%) presented an MMC. Morphological parameters analysed included canal configuration, chamber orifice features, dentine thickness, isthmus type, and aspect ratio. Twenty-four configurations were found, with the confluent type most prevalent (90.48%). Three separate orifices occurred in 64.29% of teeth, and MMCs were mainly in the coronal and middle thirds. Fully independent MMCs were rare (2.38%). Mean dentine thickness 2 mm below the furcation was 1.31 mm (MB), 1.03 mm (MMC) and 1.28 mm (ML). The mean aspect ratio was 2.90. Accessory canals appeared in 28.58%, and an independent MMC foramen in 38.09%, mainly on the mesial wall. Type III isthmus predominated (52.38%). Mesial roots with MMCs exhibit marked anatomical variability, with thin dentine around the MMC requiring careful endodontic management.