Cone-beam computed tomography investigation of middle mesial canals and isthmuses in mandibular first molars in a Chinese population

摘要

Measurement of isthmus length using Carestream Software’s built-in measuring tool. The red line in figure ( ) corresponds to the level of figure ( ), the red line in figure ( ) corresponds to the level of figure ( ). ( ) The first cross-sectional picture exhibiting the isthmus in coronal-apical direction, which corresponds to the upper edge of isthmus. linear distance of the upper edge of isthmus to the root canal orifice is 4.60 mm. The first cross-sectional picture where the isthmus disappears in coronal-apical direction, which corresponds to the lower edge of isthmus. linear distance of the lower edge of the isthmus to the root canal orifice is 8.57 mm. Thus length of the isthmus = linear distance of the lower edge of the isthmus to the root canal orifice - linear distance of the upper edge of the isthmus to the root canal orifice, which means 3.97 mm = 8.57 mm - 4.60 mm