At the core of the tooth is soft tissue (otherwise known as pulp). The hollow area that houses this soft tissue contains a space towards the top of the tooth called the pulp chamber. This pulp chamber is connected to the root of the tooth via pipe-like canals, giving rise to the term “root canal”. The blood vessels in these canals provide nutrition to the tooth. Occasionally, the internal soft tissue of the tooth becomes infected and can result in a serious infection if left untreated. Root canal treatment should take place before the infection gets too serious.
Cleaning and Disinfecting the Root Canal System
Bacterial contamination of the root canal system is considered the principal etiological factor in the development of pulpal and periapical lesions.Creating a root canal system free of irritants is a major goal of root canal therapy, traditionally achieved through biomechanical instrumentation. Because of the complexity of the root canal system, however, complete elimination of debris resulting in a sterile root canal system is difficult. Also, a smear layer, which covers the instrumented walls of the root canal, is formed during this treatment.
The smear layer
consists of two parts: a superficial layer on the surface of the root canal wall approximately 1 to 2 μm thick and a deeper layer packed into the dentinal tubules to a depth of up to 40 μm. It contains inorganic and organic substances that include microorganisms and necrotic debris.
In addition to possible infection of the smear layer itself, it also can protect the bacteria already present deeper in the dentinal tubules by preventing intracanal disinfection agents from penetrating into the tubules.Pashley
also has postulated that a smear layer containing bacteria or bacterial products might provide a reservoir of irritants. Thus, complete removal of the smear layer would be consistent with elimination of irritants from the root canal system