Abstract
Understanding of microbial ecology of the pulp-dentine complex is important because it provides a rational basis for disease prevention and treatment. Endodontic microorganisms can be acquired via traumatic damage, failing pulpal restorations, the apical foramen and a multitude of dentinal tubules and accessory/lateral canals. Survival within the endodontium is determined by the microenvironment; for example, Eh, pH, absence of sugars, other microbes and host defences. Compared with other sites in the mouth, the endodontium is a highly selective environment so that the flora differs from that seen in other sites in the oral cavity. Very little is known presently of effects of localised endodontic microenvironments on specific species. The endodontic flora affects other environments such as the periodontium and leads to periapical and more far-reaching infection. Treatment is designed to render the root canal and surrounding dentine less hospitable to infecting microorganisms. Some species are closely associated with endodontic infection, e.g. Mitsuokella dentalis, P. endodontalis, P. nigrescens. However these particular species are not always present by any means. Other bacteria have been associated with endodontic disease features, including P. melaninogenica and Peptostreptococcus micros with pain and swelling. In refractory cases, other species may achieve importance in the altered environment of the treated dental root canal; the facultative and highly chemically resistant bacterium Enterococcus faecalis is one such microorganism.