A theoretical model was developed to analyze the influence of various cement bases on temperature distribution and heat flow in restored teeth. A physical model of a molar was developed to simulate different thermal processes by simple parameter variation. The time-dependent temperature field was calculated using the finite element method (FEM). The values for material properties and thermal load were chosen from the dental literature. The results are in good agreement with clinical experimental research as published by Trowbridge et al. It is concluded that the model is a valid tool for further research with regard to the influence of restorative materials and cavity design on the thermal behavior of restored teeth.

Using the finite element method, we analyzed the temperature distribution and heat flow patterns in an axisymmetric tooth model. The models of an unrestored tooth and three teeth restored with different restorative materials were evaluated comparatively. The insulating ability of a calcium hydroxide cement base (Ca(OH)2) is low, which is inherent in its insufficient thermal and poor mechanical properties. In the given conditions, the Ca(OH)2 base reduces the temperature increase at the cement-dentin interface by 12.5% with respect to a restoration of amalgam only. By using a double base (Ca(OH)2 + polymer-modified zinc oxide-eugenol), the reduction is 21.9%. With respect to a sound tooth model, the presence of a double base in the restored tooth caused a temperature increase of only 0.1 degree C at the pulpo-dentinal junction. The thermal conductivity coefficient (lambda) of amalgam does not have any influence on the results of the calculations. The heat transfer coefficient (alpha) turned out to be an essential parameter in this mathematical model.

Two methods for determining internal stresses in tooth structures were compared under a specific load condition. The numerical method of the finite element method has a definite number of advantages over the experimental photoelastic method. The numerical results obtained by the first method are in reasonable conformity with those obtained by the latter. In addition the sensitivity of the finite element method towards variation of a number of relevant parameters has been studied.

In this study, two different cavity designs were compared from a mechanical point of view: (a) an axisymmetric model of a conventional class 1 cavity preparation and restoration; and (b) an axisymmetric model of a modified cavity design. The modified design was characterized by a cavo-surface angle (c.s.a.) of approximately 90° and a stepped cavity wall. Using a mathematical model, stresses were calculated by finite element analysis to compare the force distribution. It is concluded that the clinical superiority of the modified cavity design, with respect to the marginal breakdown of the amalgam restoration, can be supported by stress calculations.

Refractory ceramics used as kiln furniture are designed to operate at elevated temperatures with a high thermal shock resistance. In practice, however, the material fails due to thermal fatigue after a limited number of cycles. To predict this failure behaviour, it is generally not possible to use linear elastic fracture mechanics due to the fact that the coarse grained, porous material shows a dissipative mechanical behaviour. Differently sized specimens are tested to determine the size effect associated with this material. Four different finite element models widely used for concrete modelling are investigated on their ability to describe this nonlinear failure behaviour, in particular the associated size effect phenomenon. The results of the initially promising Nonlocal Continuum Damage Mechanics (CDM) model indicate that this approach cannot properly describe the observed size effect. The other three models (Adapted Local CDM, Fictitious Crack and Smeared Crack), however, give comparable results with a good description of the observed size effect phenomenon.