Friday, September 23, 2011

Endodontics: Part 4 Morphology of the root canal system

Fig. 1  The pulp chamber in the coronal part of the tooth consists of a single cavity with projections (pulp horns) into the cusps of the tooth.
This part may seem at first sight the most boring in the book, yet it could be the most important in improving clinical practice. Both undergraduate students and dentists on postgraduate courses frequently state that the reason they find root canal treatment so difficult, and the reason surveys frequently report inadequate treatment standards, is because they are working  blind . Unless a surgical microscope is available it is impossible to see down the root canal   to visualize exactly what the instruments are doing. An understanding of the architecture of the root canal system is therefore an essential prerequisite for successful root canal treatment (see Part 1, Fig. 1). As long ago as 1925, when Hess and Zurcher first published their study,

it became clear that teeth had complicated root canal systems rather than the simplified canals that had been previously described. 

Sadly their work, and many similar publications, have largely been overlooked and dentists still remain obsessed with the concept of a  root canal , a hollow tube down a root which has to be cleaned and shaped, eventually appearing as a nice white line on the post-operative radiograph. Undergraduate students learn the number of canals in each tooth by rote. However, many teeth have more than one canal, as described in this part. Where two canals exist within the same root, for example the mesial root of a lower molar, lateral communication (anastomosis) in the form of fins or accessory canals, occurs between them. Even roots with a single canal will have lateral and accessory canals leaving the main canal. Unless this concept of an entire root canal system is clearly understood, and a method of cleaning and shaping this system employed to address these anastomoses as well as the main canals, infection will remain in the root canal system, and the treatment may fail.