Effect of punch and orifice base sizes in different push-out test setups: stress distribution analysis

This study evaluated the influence of punch and base orifice diameters on push-out test results by means of finite element analysis (FEA).

FEA was performed using 3D models of the push-out test with 3 base orifice diameters (2.5, 3.0, and 3.5 mm) and 3 punch diameters (0.5, 1.0, and 1.5 mm) using MARC/MENTAT (MSC.Software). The image of a cervical slice from a root restored with a fiberglass post was used to construct the models. The mechanical properties of dentin, post, and resin cement were obtained from the literature. Bases and punches were constructed as rigid bodies. A 10-N force was applied by the punch in the center of the post in a nonlinear contact analysis. Modified von Mises stress, maximum principal stress, as well as shear and normal stress components were calculated.

Both punch and base orifice sizes influenced the stress distribution of the push-out test. Bases with larger diameters and punches with smaller diameters caused higher stress in dentin and at the dentin/cement interface.

FEA showed that the diameter of the orifice base had a more significant influence on the stress distribution than did the punch diameter. For this reason, both factors should be taken into account during push-out experimental tests.