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Microbiologic and pathologic aspects of pulpal and periapical disease.

The greatest cause of endodontic and periapical pathosis is microbial infection of the pulp. Most odontogenic infections are of a polymicrobial nature. With advances in anaerobic isolation and culturing techniques, much has been learned about the presence of pathogenic organisms such as Porphyromonas and Prevotella species (formerly classified as black-pigmented Bacteroides species) in infected root canals. This review provides a summary of recent developments in endodontic microbiology, virulence factors, and host defense systems as they relate to the pathogenesis of pulpal and periapical inflammatory lesions.