[The importance of apical and coronal leakage in the success or failure of endodontic treatment].

The present paper reviews the literature and gives the evidence that apical and coronal leakage of the root canals may lead to failures of the root-canal therapy. It becomes clear that none of the present-day root canal sealers may hermetically seal "the root canal wall--gutta-percha filling interface". In this respect the importance of perfectly sealing coronal restorations (both temporary and permanent) is emphasized.