Thermal Stresses in Various Post and Core Restorative Materials

Objectives: The aim of this study was to evaluate the influence of temperature changes on different combinations of post and core materials of an endodontically treated maxillary central incisor.

Methods: A three-dimensional finite element model of a maxillary central incisor restored with a post, a core, a crown and the supporting tissues were constructed and 3 combinations of post, core and crown were used: (1) zirconium post/composite core/IPS Empress ІІ crown (ZrC) (2) carbon fiber post/composite core/IPS Empress ІІ crown (CFC) and (3) gold post/gold core and IPS Empress ІІ crown (GG). In thermal analysis a cold irritant (0º C) and a hot irritant (60º C) were applied on the outer surface of the model for 7 seconds. Thermal and stress analyses were performed utilizing ANSYS 5.4 finite element software. The analyses were repeated at 1 second intervals from 1 to 7 seconds on each material combination.

Results: The results revealed that the temperature variation at the outer surface of the ceramic crown is more than inside the root. In addition, no significant stress changes were seen in the supporting tissues. GG model showed the least, while the ZC model showed the highest Von Mises stresses in dentin, cement layer, post and core and ceramic crown (15.76, 16.6, 43.86, 36.92 MPa versus 24.8, 22, 70.6, 65.7 MPa) when the cold irritant and (14.02, 20.05, 35.58, 27.97 MPa versus 37.6, 40.3, 74.4, 109.5 MPa) when the hot irritant was applied. Furthermore, thermal stresses were generally higher when hot irritant was applied compared with cold irritant. Stress concentration was usually seen in places where different materials join together

Conclusion: The temperature gradient and thermal stresses in gold post and core are smaller than that of carbon fiber and zirconium post and composite core