Comparative Analysis of Various Cavosurface Margins in Class II Restorations Using 3D Finite Element Method

The primary aim of these analyses was to evaluate the mechanical characteristics of the restored proximal surface of the lower first molar by comparing four different preparation designs: (a) slot preparation, (b) slot preparation with bevel, (c) slot preparation with bevel and rounded proximal box corners (RPBC), and (d) slot preparation with bevel, rounded proximal box corners, and gingival bevel (GB). The finite element method was utilized to assess various load scenarios applied to slot and bevelled restorations prepared using adhesive restorative materials. The numerical analysis revealed higher tensile stresses by up to 15 MPa when normal traction was applied at the interface between enamel and slot preparations than at the interface between enamel and bevelled preparations. However, the beveled restorations showed increased shear stresses in their thin beveled regions. The results imply a risk of separation for slot restorations. Conversely, incorporating a bevel (with or without RPBC and GB) significantly decreased normal stresses on the restoration edge and shifted it predominantly to compressive stresses. Thus, bevelled restorations may be less prone to debonding at their edges under occlusal loads. However, they may still be susceptible to shear debonding when locally loaded on their thin-beveled regions.