Finite element analysis of stresses in endodontically treated, dowel-restored teeth

Statement of problem

Endodontically-treated, dowel-restored teeth may experience fracture, but investigations of variables related to fracture are often inconclusive and occasionally contradictory.

Purpose

The finite element method was used to analyze the stresses in dowel-restored teeth. The variables studied were material, shape, bonding, modulus of elasticity, diameter, and length of the dowel.

Material and methods

The model of the dowel-restored tooth involved dentin, ligament, cortical and trabecular bone, gingiva, and gutta-percha. The dowels were made of glass fiber, titanium, or zirconia and modeled as an approximation of the brands ParaPost Fiber White, ParaPost XH, and Cerapost, respectively. The dowel was cemented with zinc-phosphate cement or with bonded or nonbonded resin luting agents, and an approximation of the material properties of these 2 materials were used in the modeling. The restoration included a composite resin core and a gold crown. Other variables included taper versus parallel-sided posts, modulus of elasticity, diameter, and length of post. The model was axisymmetrical in 3 dimensions. A load of 100 N was applied to the crown at an angle of 45 degrees, and tensile, shear, and von Mises stresses were calculated.

Results

The generated stresses decreased with respect to the dowel material in the following order: glass fiber, titanium, and zirconia. Stresses were in general higher with tapered than with parallel-sided dowels. Stresses were reduced by bonding and with an increasing modulus of elasticity, increasing diameter, and increasing length of the dowel.

Conclusions

Within the limitations of this study, it was found that all investigated dowel-related factors influenced the stress field generated in dowel-restored teeth.