Enterococcus faecalis(E.faecalis) survive and proliferate in very harsh environments. These bacteria have astrong capability for survival and pathogenesis in the biofilm, thus making them an important pathogenic factor in the recurrence of periapical periodontitis. The virulence factors of E.faecalis cause damage healthy tissues and enhance bacterial adhesion. In this study, the E.faecalis detection rate in an untreated root canal is 7.5% and reaches 70% in teeth with failed endodontic treatment. Therefore, E.faecalis in an untreated root canal is not the major pathogenic bacteria. E.faecalis heavily infects the crown of one root canal, whereas minimal infection is found in the middle third and the apical third of another root canal. E.faecalis is also resistant against common preparation methods and disinfection drugs, thus lending difficultyto the clearing of the root canal. Hence, a drug that effectively inhibits or kills E.faecalis should be developed.
