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Assessment of the middle mesial canals of mandibular first molars using cone-beam computed tomography: an in vivo study.

OBJECTIVE
For a successful root canal therapy, it is necessary to locate all the canals debride and seal them with an inert filling material. The clinician must be aware of the internal morphology and variations in a permanent tooth. Mandibular first molars are widely studied to identify variations in the anatomy of the pulp space. In this study, the primary objective was to measure the distance between the mesiobuccal (MB) and mesiolingual (ML) canals in patients with and without a middle mesial canal (MMC) using cone-beam computed tomography (CBCT). The secondary objectives were to assess the tapering degree of the mesial root and to measure the dentinal thickness in relation to the danger-zone area in patients with and without an MMC.


MATERIALS AND METHODS
A total of 200 CBCT scans were evaluated for the presence of an MMC. Two observers performed the observations, and the results obtained were subject to statistical analyses.


RESULTS
The results revealed the prevalence of MMC was 5%. The average distance between the MB and ML canals was higher when there was an MMC [M(SD) = 3.61 (0.6) vs. 2.69 (0.66)]. However, there were no differences between the groups in the distance to the danger-zone area and the tapering degree of the mesial root. On CBCT images, the MMC was clearly visible 3 mm apical to the level of the cementoenamel junction; beyond 3 mm, the MMC could not be traced.


CONCLUSIONS
Based upon the results of this study, the average distance between the MB and ML canals was higher when there was an MMC. A lesser degree of taper would be preferred to prepare the MMC than to prepare the other canals. It is recommended that careful examination of the canal 3 mm apical to the cementoenamel junction should be carried out when attempting to detect an MMC.