Endodontic Retreatment of Tooth 2.6: Locating a Missed MB2 Canal in the Presence of Fiber Posts

A 60-year-old patient was referred for evaluation of tooth 2.6 (upper left first molar). The existing endodontic treatment was deemed inadequate, with a high clinical suspicion of an untreated mesio-buccal second canal (MB2). Two carbon fiber posts were also present, complicating access to the root canal system. The case was managed in a single session. Pre-operative Assessment Radiographic and clinical examination confirmed the presence of a previous root canal treatment with two carbon fiber posts placed in the mesio-buccal (MB) and palatal (P) canals. The pre-operative X-ray raised clear concern over the MB root, suggesting a missed MB2 canal — a frequent finding in upper first molars, where the MB2 prevalence can exceed 70–80% of cases. Pre-operative X-ray of tooth…