Structural behaviour of endodontically treated teeth under thermomechanical loading

Choosing the optimal combination of post construction and restorative materials to minimize thermomechanical stresses in endodontically post-restored teeth is a very challenging task. In fact, while thermal properties of metallic alloys used for endodontic posts are rather similar to those of natural dental tissues, composite restorative materials used for constructing post and postcore usually possess better mechanical properties than metallic alloys. This may make it very difficult to evaluate directly thermomechanical stresses in the restored tooth. Therefore, this paper presents a detailed analysis of the structural behaviour of several post-endodontic restorations submitted to different combinations of thermomechanical load. The aim of the study is to compare the relative merits of different restoration concepts. Three-dimensional finite element method (FE) analysis is carried out for an upper incisor restored with composite as well as metallic post systems. Furthermore, customized and standard post constructions are compared. Two loading cases are considered: (a) exposure to cold irritants in absence of mastication; (b) mastication of cold or hot foods. Effects of thermal field inhomogeneity and occlusal force magnitude are also included in the analysis. Because of the transient nature of thermal loads, relative performance of different restorations is investigated as the thermal perturbation spreads through the restored tooth. Results indicate that composite post systems are globally more efficient than restorations including a metallic alloy post when thermal cycles and mastication act together. However, relative performance of different restoration concepts in the absence of mastication may depend strongly on the time of exposure to thermal irritants.