[Stress analysis of porcelain laminate veneers. (1)].

The stress distributions in the porcelain laminates under various kinds loading are analysed numberically in order to make clean the reason of their exfoliation or fracture. The two-dimensional finite element method is used to determine the principal stresses developed in the porcelain laminated and the teeth substance of a restored maxillary central incisor. The thicknesses of enamel preparations are assumed to be 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm and 0.8 mm in the analysis. As a result of this analysis, the following points are made clear: 1) The stress concentration are observed at the vicinity of a loading point and in the cervical regions, independently of the loading conditions on its location and direction. 2) In case of the vertical loading, the location of loading point has no effect on the overall stress magnitude and distribution. 3) In the case when the load is applied in the 45 degrees-direction to the vertical axis, the overall stress level is increased, as the location of loading point is far from the supporting regions. 4) In the case when the load is applied normal to the vertical axis at the incisal edge, the high stress is obtained in comparison with other loading conditions.