Validation of finite element analysis in dental ceramics research

In vitro dental materials strength testing of ceramic restorations primarily has involved mechanical evaluations of simplified models. The finite element method (FEM) provides a mathematic analysis to predict strength values, but neither methodology is without the potential for errors.

The purpose of this study was to demonstrate the advantages of combining mechanical testing results and FEM data to determine the strengths of a layered ceramic beam when the layered materials and positions are varied.

Eight finite element 5 x 20 x 1-mm layered beams were modeled. Four of the modeled beams were of the same layered arrangements as physical specimens from a previously published study. The remaining 4 modeled beams provided intermediate layered arrangements not evaluated in the earlier study. A force in newtons was applied in the center of the top layer of each beam until fracture. finite element analysis was performed, and the data were compared with mechanical strength test results from the earlier study.

The FEM data of the 8 models demonstrated a linear decrease in load-bearing capacity as the layer thickness of the core material decreased and the layer thickness of the veneer material increased. The progressively decreasing values for the FEM beams were 170, 144, 140, 134, 72, 43, 34, and 27 N. The mean load-bearing capacities of 3 of the 4 mechanically tested beams compared favorably with the FEM data. The strength of the fourth mechanically tested beam, a veneer/core layered arrangement, was 110 N, which was lower than the corresponding FEM value (140 N). The 110 N value fell outside the decreasing linear progression for load, indicating that the FEM data were more accurate and reliable than the mechanical data.

No one perfect method exists for testing the strength of dental materials. The best approach is to use the results from both mechanical testing and finite element analysis, which together may provide more reliable and valid data than either method alone.