Background: Knowledge of root canal anatomy is essential for the success of endodontic treatment. The introduction of Conebeam computed tomography (CBCT) to dentistry has led to increase the accuracy of internal anatomy assessment. The aim of this study was to evaluate the validity and reliability of CBCT imaging technique to assessing mesial root canal type in mandibular first molars. Material and methods: 64 mandibular first molars were chosen and fixed in a base plaster model mixed with Sawdust then scanned by CBCT. A radiologist and an endodontist independently assessed the mesial canals morphology, this assessment was repeated seven days later. The canal configurations were categorized using Vertucci's classification and compared to the same teeth after making them transparent and examined by a blind evaluator under stereomicroscope. The results from of endodontist and radiologist’s observation in both evaluation were compared to each other and to the gold standard (stereomicroscope data) using the weighted kappa test. Results: Endodontist’s evaluations were both strongly correlated with the gold standard data (spearman correlation coefficient=0.7 and 0.9 for first and second evaluation respectively, p<0.001), likewise the radiologist’s evaluations had similar results (spearman correlation coefficient=0.8 and 0.9 for first and second evaluation respectively, p<0.001). Intra-observer reliability was excellent for both endodontist (k=0.79) and radiologist (k=0.80). Conclusions: The validity of CBCT to explore the morphology of mesial root canals of mandibular first molars has been proved in this article.
