By means of a finite element method (FEM), the present study evaluated the effect of fiber post (FP) placement on the stress distribution occurring in endodontically treated upper first premolars (UFPs) with mesial–occlusal–distal (MOD) nanohybrid composite restorations under subcritical static load. FEM models were created to simulate four different clinical situations involving endodontically treated UFPs with MOD cavities restored with one of the following: composite resin; composite and one FP in the palatal root; composite and one FP in the buccal root; or composite and two FPs. As control, the model of an intact UFP was included. A simulated load of 150 N was applied. Stress distribution was observed on each model surface, on the mid buccal–palatal plane, and on two horizontal planes (at cervical and root-furcation levels); the maximum Von Mises stress values were calculated. All analyses were replicated three times, using the mechanical parameters from three different nanohybrid resin composite restorative materials. In the presence of FPs, the maximum stress values recorded on dentin (in cervical and root-furcation areas) appeared slightly reduced, compared to the endodontically treated tooth restored with no post; in the same areas, the overall Von Mises maps revealed more favorable stress distributions. FPs in maxillary premolars with MOD cavities can lead to a positive redistribution of potentially dangerous stress concentrations away from the cervical and the root-furcation dentin.

In the development of restorative materials, it is important to evaluate the elastic properties of the material in order to achieve good clinical results. The aim of this study was to evaluate the compression behavior of two dental flowable materials (EverX Flow and Flow-Art) using experimental methods and numerical simulation. The Poisson’s ratio was determined using two methods of strain measurement: the electrical strain gauge method (ESG) and digital image correlation (DIC). Material constants determined in experimental studies were implemented in a numerical model, and displacement analysis was conducted using the finite element method (FEM). The tests showed higher compressive strength and modulus of elasticity for EverX Flow compared to Flow-Art. The values of the Poisson’s ratio were similar for both measurement methods, ranging from 0.27 to 0.28 for EverX Flow and from 0.30 to 0.32 for Flow-Art. This demonstrated the feasibility of the DIC method for obtaining the Poisson’s ratio values for this type of composites. Compression test conditions were reproduced in the numerical analysis. The obtained distributions of the displacement field on the surface of the sample from the DIC and numerical analyses were compared. A good match was observed between DIC displacement measurements and displacement values obtained in FEM analysis. The comprehensive approach used in the study allows us to analyze whether the results obtained in the numerical simulation correspond to the material response to the applied load and validate the model.