24/09/2015
KRASNER & RANKOW nine guidelines,
or laws, of pulp chamber anatomy to
help clinicians determine the number
and location of or***ces on the
chamber floor.
Law of centrality: The floor of the
pulp chamber is always located in the
center of the tooth at the level of the
CEJ.
Law of concentricity: The walls of the
pulp chamber are always concentric to
the external surface of the tooth at
the level of the CEJ, that is, the
external root surface anatomy reflects
the internal pulp chamber anatomy.
Law of the CEJ: The distance from the
external surface of the clinical crown
to the wall of the pulp chamber is the
same throughout the circumference of
the tooth at the level of the CEJ,
making the CEJ is the most consistent
repeatable landmark for locating the
position of the pulp chamber.
First law of symmetry: Except for the
maxillary molars, canal or***ces are
equidistant from a line drawn in a
mesiodistal direction through the
center of the pulp chamber floor.
Second law of symmetry: Except for
the maxillary molars, canal or***ces lie
on a line perpendicular to a line drawn
in a mesiodistal direction across the
center of the pulp chamber floor.
Law of color change: The pulp chamber
floor is always darker in color than
the walls.
First law of or***ce location: The
or***ces of the root canals are always
located at the junction of the walls
and the floor.
Second law of or***ce location: The
or***ces of the root canals are always
located at the angles in the floor–wall
junction.
Third law of or***ce location: The
or***ces of the root canals are always
located at the terminus of the roots’
developmental fusion lines.
A, In a mandibular second molar with
two canals, both or***ces are in the
mesiodistal midline. B, If two or***ces
are not directly in the mesiodistal
midline, a search should be made for
another canal on the opposite side,
using Krasner and Rankow's laws of
anatomy in the area of “X.” D, Distal;
M, mesial.
