The primary goal of endodontic treatment is to ensure the long-term masticatory and aesthetic function of the tooth, whose irreversible and pathologically changed pulp tissue had to be removed from the endodontic space due to the harmful effects of various agents. A condition for the survival of such a tooth in the oral cavity is the successful implementation of root canal treatment, the role of which is to prevent the spread of inflammation into the periapical tissues or to provide conditions for the healing of the periapical lesion in teeth in which the inflammation has already reached the periapical tissues. Factors affecting the outcome of endodontic treatment are divided into preoperative, intraoperative and postoperative. Preoperative factors include the patient's age and systemic health, the variability of the anatomy of the endodontic space, and the preoperative condition of the pulp and periapex. Intraoperative factors refer to the quality of endodontic procedure implementation and include the knowledge and experience of the operator, adequate access cavity preparation, isolation of the teeth and achievement of a dry working field, control of the working length, sufficient chemomechanical preparation of the canals and adequate filling of the root canals which guarantees good apical sealing. Postoperative factors concern the postendodontic supply of the treated tooth and refer to the quantity and quality of the remaining tooth tissue, the type of permanent restoration, the time elapsed from the filling of the canal to the fabrication of the permanent restoration, the quality of the coronary sealing of the permanent restoration, and the occlusion. Endodontic treatment is a procedure that involves many interdependent steps. For optimal success, not only individual factors must be considered, but also any interaction between them.