Optimization of human tooth crown in terms of stresses occured after firing process

In this study, it has been purposed to determine the more harmonious material pairs in human tooth crowns which are used for prosthetic treatments and constituted from the different substructure and veneering materials in terms of stresses occurred after firing process. It has been used the most preferred material pairs in dentistry at the present time.Firstly, elastic and plastic region behaviors in the high temperatures of three of the investigated metal alloys have been determined by the hot compression tests. The other properties of the investigated materials have been obtained from the literature studies or documents of the producing firms. Also, it has been developed the calculations that the viscoelastic behaviors effects of the porcelain in high temperatures have been included into the elastic properties. the temperature variations of the inner and outer surfaces been measured after the standard firing process, preparing a crown specimen relating to central incisor tooth of human and then the cooling curves of the inner and outer surfaces has been determined. With the assistance of these cooling curves obtained, the equivalent convection coefficients include the effects of radiation and convection together, have been calculated.The three dimensional (3D) model of the test specimen prepared has been constituted, using ABAQUS finite element program. The equivalent convection coefficients calculated from the experiments have been entered into the finite element program, and then the cooling curves obtained from the analyses have been fitted to the experimental cooling curves, making the minor revisions on these coefficients. In this way, the atmosphere in the furnace has been determined exactly in the finite element program.Afterwards, the analyses of thermal stresses which have been constituted during the cooling process have been done for the different material couples. The results have been evaluated in terms of the maximum stresses and the residual stresses.