Three essential steps in root canal therapy are proper instrumentation, irrigation and obturation of the root canal. Elimination or significant reduction of irritants and prevention of recontamination of the root canal after treatment are essential elements for successful outcomes. The comman belief that inadequate obturation is the major cause of endodontic failure has been proven to be fallacious as obturation reflects the adequacy of cleaning and shaping. The primary endodontic treatment goal must thus be to optimize root canal disinfection and to prevent reinfection.