This study aimed to evaluate the stress and strain at the interface between zirconia crowns and prepared tooth abutments, with or without a shoulder finish line. The main objective was to determine which of the two types of preparations provides a more favorable long-term prognosis, particularly in the case of single-unit crowns. The Finite Element Analysis (FEA) method was employed to assess the mechanical response of both zirconia and dentin under occlusal forces of 200 N, simulating physiological occlusion. Values from the literature for Young’s modulus, Poisson’s ratio, and Bulk modulus were introduced into the simulations for zirconia and tooth abutments. The simulations demonstrated that zirconia crowns, regardless of the preparation type, experienced higher stress than the tooth abutments. However, preparations with a shoulder finish line demonstrated superior biomechanical behavior. This study provides a detailed biomechanical analysis of zirconia crowns cemented onto tooth abutments prepared with or without a shoulder finish line, highlighting the importance of FEA in optimizing prosthetic design and material selection.