Discuss the factors that affect the outcome of endodontic treatment.

Factors affecting the outcome of endodontic treatment are discussed from the theoretical viewpoint (microbes, foreign bodies and epithelium) and from a clinical aspect (preoperative factors, intraoperative factors and miscellaneous factors). The following conditions favour endodontic success significantly: the absence of a periapical infection, a well-condensed root filling, the root filling extending to 2 mm within the radiographic apex and not beyond, a satisfactory coronal restoration, use of a rubber dam during treatment and cases involving primary root canal treatment as opposed to retreatment. Other factors have the potential to affect success rates, but these have not yet been quantified. Although there is an array of potential factors that influence the outcome of endodontic treatment, success is most significantly dependent upon the elimination of root canal infection present when treatment starts and the prevention of contamination during treatment.