Spreading Infections: Etiology

Infections spreading beyond that of local abscess formation are relatively rare in endodontics. When the balance between the root canal infection and the hosts defence system errs in favour of the infection, a local spreading of the infection occurs. This may either take place spontaneously before any treatment has been started, or in connection with the instrumentation of the canal. It is important to understand that over-instrumentation is not a prerequisite for a flare-up after treatment start as some canal contents are usually introduced into the periapical area, despite correct cleaning and shaping procedures. Only occasionally does a flare-up develop into an infection spreading to the tissues. Spreading endodontic infections are usually caused by a mixed anaerobic infection with some facultative bacteria also present. Fusobacteria and peptostreptococci are typical members of the flora.