Endodontology is related to processes that take place in, or originate from, contents of the pulpal chamber. Under normal conditions, the pulp is protected by the hard tissues of the tooth and an intact periodontium. Kakehashi et al.1 showed that when the dental pulps in germ-free rats were exposed, reactionary dentine was formed. However, surgical exposure of teeth in rats kept in a conventional microbial environment resulted in the development of pulpal necrosis and apical periodontitis. Therefore, micro-organisms (such as those associated with the caries process) and their by-products may gain access to the pulp and stimulate an inflammatory response. The pulp may maintain its function, but continued stimulation will result in its irreversible destruction and complete breakdown. A necrotic pulp does not have a defence mechanism, and the enclosed environment of the pulp chamber is a favourable medium in which anaerobic bacteria may proliferate. This inflammatory process may then spread beyond the confines of the pulp chamber and into the periapical tissues with consequent tissue damage and resorption of periapical bone. Early signs may be seen on a radiograph as loss of apical lamina dura, more extensive destruction of the periapical tissues may result in stimulation of epithelial cells in the apical region, which can then cause formation of a cyst.

Therefore, treatment of the irreversibly damaged or necrotic pulp should be by removal of the damaged tissue and its replacement with a root filling, the overall aim being to control the intra-canal infection. The canal system is cleaned with files and antimicrobial irrigating solutions before being filled with an inert material (root filling) to prevent further microbial ingress. It is also necessary to have excellent moisture control, so that the canal system can be dried when required, and also to ensure that contamination of the canal system with salivary bacteria does not occur: airway protection is also required owing to the risk of dropping the small instruments. To achieve these objectives, placement of a rubber dam is essential.

The response to endodontic treatment is measured in terms of clinical signs and symptoms and radiographic evidence of healing. If healing is not satisfactory it is necessary to make a decision as to whether the tooth should be re-treated, treated via a surgical approach or extracted.

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