Methods: 3-D models of posterior teeth were created: intact teeth; unrestored teeth with class II cavity preparations with different tapers (between 0 and 10 degree); the same teeth restored with ceramic inlays. The geometries of the teeth were constructed by 3D scaning using a manufactured device. Files were imported in LeiosMesh (Enhanced Geometry Solutions Corporations, Italy), where the point clouds from the teeth surfaces were cleaned and assembled, and then merged to create a complete model. NURBS surfaces were built and imported in Rhinoceros (McNeel North America) modeling program. The 3D teeth models were used as a support for inlay modeling. These were exported in ANSYS finite element analysis software (Ansys Inc., Philadelphia, USA), to be used for structural simulations. Each model was subjected to a force of 200 N directed to the occlusal surface. Stresses were calculated in the tested inlays, and tooth tissues.
Results: In teeth restored with ceramic inlays, the von Mises equivalent stress values were higher than in intact teeth. High stresses were located at the junction of the butt joint margin inlay and enamel. The values depend on the preparation shape and decrease with the increase of the taper.
Conclusions: The finite element study provides a biomechanical explanation for inlays restored teeth. Within the limitations of this method, it resulted that ceramic inlays do not restore the original strength of the teeth, and the preparation shape is decisive for the stress values and distribution. (ID_1264)