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Abstract
The surveys of many terrestrial and aquatic ecosystems indicated that more than 99% of microorganisms living on earth resisted cultivation under laboratory conditions and could only be identified by the use of molecular genetic methods; furhermore about 50% of oral bacteria had not yet been cultivated.
The vital pulp tissue is a sterile tissue as any other connective tissue in the body. Pulpal infection occurred only through any exogenous source of infection caries, impact trauma, or defected tooth structure. When pulpal damage is so severe, pulp inflammation and consequently necrosis occurs.
As aforementioned, in healthy individuals, teeth can undergo pulp necrosis due to many causes; the genetically disordered patients have also the same chance to have affected pulp. Genetic disorders such as Ectodermal dysplasia, and Enamel hypoplasia exhibited several aspects of common clinical, radiographic and histopathotogical features related to each other. Dental abscess formation is considered one of the main symptoms associated with these disorders which might be the main reason for extraction of the affected teeth.
The knowledge of endodontic infections had increased significantly during last 30 years, but in the same time different species of bacteria in the diseased pulp were not cultivated on artificial media and their pathogenicity was not definitely known. Epidemiological studies reveal that more than 200 different microbial species could be found in infected root canals usually in combination of four to seven species per canal. Theoretically, any one of these species would have the potential to be an endodontic pathogen. The endodontic infections had polymicrobial origins. A restricted group of bacterial species could predominate and produced disease.