The aim of this finite element method (FEM) study was to test two different restorative techniques used for construction of severely damaged endodontically treated premolar teeth using Finite Element Stress Analysis Method. In this study, four types of three-dimensional (3-D) FEM mathematical models simulating (1) a sound lower single rooted premolar tooth with supporting structures; (2) a root-filled lower premolar tooth without lingual cusp, restored with resin composite; (3) a root-filled lower premolar tooth without lingual cusp restored with resin composite in combination with a polyethylene fiber which is placed circumferentially to help to create a composite lingual wall; (4) a root-filled lower premolar tooth without lingual cusp restored with resin composite in combination with a glass fiber post, were modeled. A 300-N static vertical occlusal load was applied on the node at the center of occlusal surface of the tooth to calculate stress distributions. Solidworks/Cosmosworks structural analysis programs were used for FEM analysis. The analysis of the von Mises stress values revealed that maximum stress concentrations were located at loading areas for all models. Root dentine tissue, lingual cortical bone, and apical bone structures were other stress concentration regions. There were stress concentration differences among the models at root dentine tissue. Although the distribution pattern was similar with composite resin restored tooth model, highest stress values were observed at root dentine in the model restored with post-and-core. Post structure accumulated more stress on its own body. Stress distribution patterns of sound tooth and fiber-reinforced restoration models were found as similar. The present study showed that the use of post material increased the stress values at root dentine structure while reinforcing the restoration with a fiber decreases stress transmission. Fiber-reinforced restoration provided stress distributions similar to sound tooth. © 2010 Springer-Verlag.