A unilateral or bilateral posterior crossbite is a common and severe malocclusion characterized by maxillary transversal deficiency. Various expansion appliances are employed to correct this condition. The objective of this study was to evaluate the forces transmitted to the teeth and the deformation of the expander appliance resulting from modifications to the screw arms of a slow maxillary expander with different angles, using finite element analysis. All models were created in SolidWorks and analyzed using ANSYS Workbench. The analysis revealed that the models with different angular configurations of the expander screw arms (0°, 15°, and 30°) exhibited very similar reaction forces on the teeth. However, significant differences in deformation values were observed among the models. The most effective parameter is the force applied to the expander with a rate of 46%, followed by the arm angle with a rate of 44%, while the effect of material type is 10%. The most significant conclusion that can be drawn from these findings is that the arm angle is as important as the force applied to the expander. In situations where the force that can be applied is limited by various factors, it can be demonstrated that altering the arm angle can lead to the achievement of the desired outcome.