Methods: A total of 100 extracted mandibular first molars were randomly collected. Teeth were scanned by using micro-computed tomography device (SkyScan 1074, Aartselaar, Belgium). These images were reconstructed three-dimensionally by using software NRecon (SkyScan 1074, Kontich, Belgium). After constructing, three-dimensional images exhibiting the shape of the roots were analyzed by using 3D-Doctor software programme (v.3.5 Able Software Corp, Lexington,MA). Thereafter, the number of the middle mesial canals were evaluated.
Results: The results of this study indicate that a middle mesial canal present in 12 % of mandibular first molars. In this study, the middle mesial canals merged with the mesiobuccal or mesiolingual canals.
Conclusions: 12% of mandibular first molars had a middle mesial canal which is significantly important from a clinical point of view. The possibility of additional canal in the mesial root should be anticipated in mandibular first molars. Micro-CT is an effective tool for the detection such extra canals in teeth.