Flora in Obturated Root Canals

It is generally acknowledged that persistence of disease is most commonly due to difficulties that occur during initial endodontic treatment. Inadequate aseptic control, poor access cavity design, missed canals, inadequate instrumentation, and breakdown of temporary or permanent restorations are examples of procedural pitfalls that may result in persistence of endodontic disease.

The reasons for disease persistence in well-treated root-filled teeth have been poorly characterized. Using block biopsy material from non-healed periapical tissues by correlative light and electron microscopy showed that there were four factors that may have contributed to persistence of periapical radiolucency after treatment. The factors were:

i) intraradicular infection;

ii) extraradicular infection by bacteria of the species Actinomyces israelii and Propionibacterium propionicum;

iii) foreign body reaction; and

iv) cysts, especially those containing cholesterol crystals.

Of all these factors, it is generally acknowledged that the major cause of posttreatment disease is the persistence of micro-organisms in the apical part of rootfilled teeth.

Persistent endodontic disease, or apical periodontitis associated with a root-filled tooth, can continue for many years and may become apparent only when a tooth requires a new restoration or is detected on a routine radiograph.

The bacterial genera most frequently recovered from filled root canals were Enterococcus faecalis (most common) and streptococci. Other species found in higher proportions in individual studies are lactobacilli, Actinomyces species, peptostreptococci, Pseudoramibacter alactolyticus, Propionibacterium propionicum, Dialister pneumosintes, Filifactor alocis and Candida albicans.