Mandibular Second Molar

Most common configuration of the mandibular second molar tooth is one distal canal and two mesial canals. In general the access cavity preparation is the same for the adjacent mandibular first molar. In certain cases, one mesial canal may be present. This bicanaled variation has a slightly different access preparation, with the trapezoid narrowed to the mesial to be more rectangular. When two mesial canals are present, a Type II configuration is more common than a Type III.

The mandibular second molar may have only a single root with several variants: one single, large canal; two canals that merge or remain separate; or the so-called Cshaped tooth, first described by Cooke and Cox. The tooth looks like a routine second molar when viewed on the pre-operative radiographs. When the access cavity preparation is made, from the occlusal it appears that the orifices configuration of the canals are not individually distinct but there is a C-shaped configuration on the floor of the chamber. If one file is placed in the mesial canal and one in the distal, the radiograph may reveal that both files are in the same canal. The C-shaped configuration refers to a continuous slit between all the canals so that a horizontal section through the root yields a space in the shape of the letter C.

A common condition found in mandibular second molars is the presence of two roots. In the mesial root, Type I, II, or III configurations may be present. In the distal root a Type I canal is dominant, but Types II and III systems also are possible but rare.