Abstract
Purpose: It is pointed out that the Castable Ceramics Crown is excellent in the aesthetic aspect but poor in strength. Therefore, we compared the differences in internal stresses between a natural toothmodel and the Castable Ceramics Crown model (Cosmic® Crown model), in the mandibular first molarpart.
Methods: We prepared a natural tooth model and the Casmic® Crown model. We compared andexamined the differences in the internal stresses exerted on the crown, the anchor tooth, and theperipheral tissues, for various load points and load directions, by the three-dimensional finite elementmethod.
Results: For centric occlusion, the Casmic® Crown model showed a larger value than the natural toothmodel in each of equivalent stress, tensile stress, and compressive stress. For the eccentric position, the natural tooth model showed the largest value under the load on the summit of the cusp in thedirection of the tooth axis, in equivalent stress and compressive stress. The Casmic® Crown modelshowed the largest value under the load on the external incline in the direction of the tooth axis, intensile stress. The natural tooth model showed tensile stress distribution in the periphery of the loadpoint on the surface layer. The Cosmic® Crown model showed tensile stress distribution in theperiphery of the load point on the external layer, and in the inner surface of the crown.
Conclusions: The Casmic® Crown model showed the largest tensile stress value under the load on theexternal incline in the direction of the tooth axis. The aspect of its stress distribution was notedbetween the periphery of the load point on the external layer of the crown and the inner surface of thecrown. It suggested that this loading condition is likely to cause fracture.
