These teeth almost always have one canal. When viewed on radiographs the canal appears to be fairly straight and tapering, but labiopalatally the canal will tend to curve either towards the labial or palatal aspect at about the apical third level. One feature to note is the slight narrowing of the lumen at the cervical level, which immediately opens up into the main body of the canal. The inverted-triangular shaped access cavity is cut with its base at the cingulum to give straight line access.