Discuss that the coronal seal is more important than the apical seal for endodontic success.

One of the main principles for successful root canal treatment is the prevention of microorganisms and toxins from the oral flora penetrating through the root canal system into the periapical tissues (1). This is achieved by obturating the root canal system completely, including the coronal and apical ends. Inadequate obturation of the root canal system has been found to be the most frequent cause of failure after endodontic treatment (2). A number of studies have indicated that leakage, whether from a coronal or apical direction, adversely affects the success of root canal treatment (3-7). The significance of the coronal seal has been increasingly recognized in the dental literature (4, 5, 8, 9) and in more recent times, it has been suggested that apical leakage may not be the most important factor leading to the failure of endodontic treatment--but that coronal leakage is far more likely to be the major determinant of clinical success or failure (10). This paper will discuss aspects of: endodontic success and failure; the use of leakage studies to assess the quality of the seal; the significance of both apical and coronal leakage; followed by a review of the literature.