The Use of the Finite Elements Method (FEM) to Determine the Optimal Angle of Force Application in Relation to Grooves Notched into a Zirconia Coping with the Aim of Reducing Load on a Connection with Veneering Ceramic

OBJECTIVE OF STUDY: To investigate, using the FEM, the influence of different notching angles on a zirconium dioxide coping with the aim of establishing the optimal connection conditions with veneering ceramic. MATERIALS AND METHODS: To calculate the stresses in the connection between zirconia coping and veneering ceramic, a model comprising grooves cut perpendicular was adopted. Such a notch profile was used to design the shape and spacing of the grooves on an FEM model simulating a zirconium dioxide coping. For discretization purposes we used twenty-node solid BRICK elements featuring intermediate nodes with three degrees of freedom in each node. The model was divided into 117 745 finished elements and 439 131 nodes. The problem was solved with a GLU type contact. The same load F = 1N divided by the number of nodes on the external surface was applied to each node of the outer surface of the base. In subsequent computing variants the F load changed the orientation by angle α from 0° to 45° every 15°. RESULTS: The highest level of material strain occurs at angle α = 0° σ(red max) =309 MPa and the lowest at angle α = 45° σ(red max) =220 MPa. The highest positive stress pressure occurs at angle α = 0° p(max)=251 MPa, p(min)=-354 MPa and the lowest at angle α = 15°, p(max)=171 MPa, p(min)=-186 MPa. In the case of tangential stresses on the coping-veneering ceramic connection, the highest values were noted at angle α = 15° τ(max)=44,4 MPa and the lowest at angle α = 45° τ(max)=32,7 MPa. CONCLUSIONS: To reduce the load on the zirconia-veneering ceramic connection, the notches should be made at an angle of α = 45°.