## 2 Materials and Methods
The stress analysis was performed using the finite element method (FEM), which is well-suited for biological structures due to its ability to model domains with high diversity of materials and complex geometric structures. The finite element platform used was SolidWorks Simulation 2021, where the discretized model was generated, consisting of 9638 nodes and 6217 elements (Figure 3). Figure 1: Visualization of the anatomical model of the mandibular second premolar from five distinct morphological analysis angles [20]. Figure 2: Three-dimensional model of the mandibular second premolar, anatomically described using Rhinoceros 3D software, version 7, presented from the following perspectives: occlusal view, oblique perspective, frontal view, and left lateral view. Following each FEA simulation, the software generated a von Mises stress distribution field, which expressed a scalar equivalent value of mechanical stress by integrating all components of the stress tensor. This type of stress is commonly used for evaluating ductile materials, such as metal alloys and dental composites, and serves as a direct indicator of the risk of plastic deformation. The data were exported in tabular format for each volumetric mesh element, thus providing a detailed foundation for the subsequent analysis of the stress distribution within the restorative mass. This step was essential for identifying areas with high potential for stress concentration, which were susceptible to the formation of microcracks or other forms of structural damage--information with direct relevance to clinical practice. In order to quantitatively assess the overall mechanical behavior of the restoration under functional load, a volumetric integration of the von Mises stresses was performed across the entire volume of the restorative material. This integration was based on the following formula:  
\[\sigma_{\text{average}}=\frac{\sum_{i=1}^{n}(\sigma_{i}\cdot\Delta V_{i})}{ \sum_{i=1}^{n}\Delta V_{i}} \tag{1}\]  
where \(\sigma_{i}\) is the von Mises stress recorded in element \(i\), \(\Delta V_{i}\) is the volume of that element, and \(\sum\Delta V_{i}\) represents the total volume of the restoration. This method provides a global and objective assessment of the stress level experienced by the material, avoiding interpretations based solely on isolated peak values, which may arise as numerical artifacts. The weighted average stress reflects the deformation energy accumulated throughout the entire restorative body and allows for rigorous comparisons between different materials. Figure 3: Meshing of the mandibular second premolar. To determine the structural stability of the restorations, the safety factor (SF) was calculated for each material, defined as the ratio between the material's compressive strength and the maximum von Mises stress obtained from the simulation:  
\[\text{SF}=\frac{\sigma_{\text{resistance}}}{\sigma_{\text{von Mises max}}} \tag{2}\]  
The interpretation of safety factor (SF) values provides important insights into the structural integrity of dental restorations under functional loading. SF values of below 1 indicate a high likelihood of material failure, either through plastic deformation or fracture, suggesting that the restorative material cannot safely withstand the applied stress. SF values of close to 1 reflect a borderline mechanical condition, where even minor variations in loading or material defects could precipitate failure. Conversely, SF values exceeding 1.5 are generally regarded as indicative of a safe operational regime, ensuring adequate mechanical performance and clinical reliability under masticatory forces. The materials used in this analysis, along with their characteristic parameters, were stored in a material library from which they could be accessed. In this specific study, three types of materials were defined: amalgam, dental enamel, and a composite.