The effects of post-core and crown material and luting agents on stress distribution in tooth restorations.

STATEMENT OF PROBLEM

Cement microfracture, post-and-core dislodgement, and tooth fracture are related to the mechanical properties and deformation of restorations.

PURPOSE

The purpose of this study was to determine which combinations of post-and-core cements provide the most favorable stress distribution upon loading.

MATERIAL AND METHODS

Three-dimensional models of teeth were created with the ANSYS program to simulate the different materials used for metal ceramic crowns (nickel-chromium, gold-palladium), posts and cores (Ti, Ni-Cr, Au-Pd), and cement (glass ionomer, composite resin, zinc phosphate, polycarboxylate, Panavia). Models were divided into 2 groups according to the alloys used in the crown restorations. A simulated masticatory force of 400 N was applied to the occlusal surface at a 45-degree inclination in the linguolabial direction to the long axis of the tooth, and von Mises equivalent stress values were calculated.

RESULTS

The Ni-Cr metal ceramic crown/Au-Pd post-and-core/glass ionomer cement had the highest residual root von Mises equivalent stress value, whereas the Ni-Cr metal ceramic crown/Ni-Cr post-and-core/glass ionomer cement had the highest post stress value and the Ni-Cr metal ceramic crown/Au-Pd post-and-core/zinc phosphate cement had the highest cement stress value. For each post-and-core alloy, the stress values in the post and core were higher with Au-Pd metal ceramic crowns than with Ni-Cr metal ceramic crowns. The post-and-core material affected the amount of deformation.

CONCLUSIONS

The use of a post-and-core material with a lower elastic modulus and a cement with a higher elastic modulus led to a reduction in deformation in the residual root, cement, and post and core, and a reduction in stress in the post and core. The Ni-Cr metal ceramic crown/Au-Pd post-and-core/zinc phosphate cement or Panavia may therefore be favorable for post-and-core restorations.