An Endodontic Treated tooth with Post operative Apical Periodontitis often is a result of improper BMP, missed canals, fracture of tooth, loose restoration etc. during Root Canal Treatment. There are many causes of failure of Root Canal treatment which are mentioned in this post – Link

Only a small number of species of micro organisms have been found in the root canals of properly endodontically treated teeth which in follow up revealed a persisting Asymptomatic periapical radiolucency’s.

Micro organisms found in failed Root Canal Treated tooth

So in case of a failed Endodontic therapy it is easy to identify the micro organisms based on Culture methods as the number of species to suspect are very few in comparison to an Actively infected tooth. Below are the list of micro organisms which have been isolated from a Re-infected tooth after a failed Root canal treatment with the help of Culture.

The Micro organisms Genera found in Periapical regions of a Failed Endodontic treated tooth are:

  • Actinomyces
  • Enterococcus Fecalis
  • Propioni bacterium (previously called as Arachnia)
  • Yeasts
  • Candida Albicans – Most commonly isolated Fungus

Enterococcus Fecalis – Most common pathogen found in periapical region of failed Root Canal or Endodontic Treated tooth.

Among the enterococcus Species the most commonly found is Enterococcus Fecalis which is given particular interest because it is “Rarely found in Untreated and Infected Root Canals”. This means that Enterococcus Fecalis is found alone in the Root canal and can live without help from other Micro organisms.

Enterococcus Fecalis can grow as a mono infection in treated canals in the absence of Synergistic support from other bacteria.

Therefore E. Fecalis is held to be a Recalcitrant (Stubborn) Microbe among the potential etiologic agents of post treatment apical periodontitis. This needs special treatment protocol to clear the peri apical region of the micro organisms. One such method is the use of TAP or Triple Antibiotic Paste.