Printed in U.S.A. VOL. 30, NO. 1, JANUARY 2004
Anatomy of the Pulp-Chamber Floor
Paul Krasner, DDS, and Henry J. Rankow, DDS
Locating the number and position of orifices on pulp-chamber floors can be difficult. This is especially true when the tooth being treated is heavily restored, malposed, orcalcified. After evaluating 500 pulp chambers of extracted teeth, new laws for finding pulp chambers and root-canal orifices are proposed. The use of these laws can aid in the determination of the pulp-chamber position and the exact location and number of root canals in any individual tooth.
therefore, with greater certainty. This could aid in a rational approach to root-canal therapy. MATERIALS ANDMETHODS A total of 500 extracted, permanent, human teeth were used. The teeth were equally distributed between maxillary and mandibular anteriors, premolars, and molars. The teeth had a wide variety of crown conditions: virgin crowns, small restorations, large restorations, metal and porcelain crowns, and caries. A total of 400 teeth had their crowns cut off horizontally at the level of the CEJ sothat the outline of the pulp chamber relative to the external surface of the tooth could be observed. Fifty teeth were sectioned in a buccolingual direction through the crown and the roots. Fifty teeth were sectioned in a mesiodistal direction through the crown and the roots. Each cut section was irrigated with water, dried, and examined. Two observers examined each specimen independently andrecorded all observed anatomical relationships. These relationships included orifice location, size, color, and shape. These observations were then correlated and any consistent patterns were listed. Lines were drawn on horizontal sections to observe the relationships more easily. RESULTS Two categories of anatomic patterns were observed: relationships of the pulp chamber to the clinical crown andrelationships of orifices on the pulp-chamber floor. Relationships of the Pulp Chamber to the Clinical Crown The following observations were noted: 1. The pulp chamber was always in the center of the tooth at the level of the CEJ (Figs. 1–3). 2. The walls of the pulp chamber were always concentric to the external surface of the crown at the level of the CEJ (Fig. 2). 3. The distance from the externalsurface of the clinical crown to the wall of the pulp chamber was the same throughout the circumference of the tooth at the level of the CEJ (Fig. 3). These observations were consistent enough that several anatomic laws could be formulated: Law of centrality: the floor of the pulp chamber is always located in the center of the tooth at the level of the CEJ (Figs. 1–3). Law of concentricity: thewalls of the pulp chamber are always
Endodontic therapy is essentially a surgical procedure, a microneurologic surgical procedure. Because the fundamental foundation on which all surgical procedures are performed is an intimate knowledge of anatomy, any attempt to perform endodontic therapy must be preceded with a thorough understanding of the anatomy of both the pulp chamber and theroot-canal system. Attempting to treat the root-canal system without detailed anatomic description would be the equivalent of a physician looking for an appendix without ever having read Gray’s Anatomy. Literature describing pulp-chamber anatomy in the past has been very general and offered little specificity for determining orifice number and location. Discussions, in print and in the classroom,typically present generalizations about the average number of canals in different teeth. However, the average number of canals in a tooth is of no value when dealing with an individual tooth. Likewise, the description of the location of canal orifices has often been presented in a nonsystematic manner. Essentially, most advice has been to make an access in an appropriate position in the clinical crown...