In this study, stress distribution in a maxillary central incisor that was subjected to endodontic treatment and various post and core applications was determined by using a three-dimensional finite-element method. Cast gold post and gold core and different combinations of prefabricated stainless-steel post, or a prefabricated titanium post with amalgam or composite cores were considered. In all cases, the tooth was assumed to have a porcelain crown. The primary purpose of the study was to evaluate the stress distribution due to simulated biting forces and thus investigate the reliability of different post and core applications. It was found that, within the limitations of the study, the cast gold post and gold core application yielded the best result. The second purpose of the study was to highlight the importance of using a unique stress value, which contains the effects of all the possible stress components existing upon loading in the determination of a possible failure. A resultant stress value and all the constituent components were shown in detail, and it was proved that an estimation independently based on an individual component might lead to erroneous results.