Stress Analysis of Molar All-Ceramics Crown Using the Three-Dimensional Finite Element Method

Purpose: Fracture of an all-ceramics crown is a serious problem in fixed prosthodontics restoration. The purpose of this study was to clarify the stress distribution at a fissure caused by the difference in occlusal surface forms of molar all-ceramic crowns. Methods: The distal half area of the mandibular right first molar was generated in this analysis model. The three-dimensional finite element method was used for the analysis. The model was changed factors of the tooth form such as fissure radius, the thickness of ceramics, and the cusp angle for computing. The load condition was a circular loading area assumed to be taking foods. The load was applied on the central fossa. Analyzing model at fissures concentrated stress. Therefore their areas meshed in detail for exact calculation of stress. For the material of ceramics crown and abutment tooth authors assumed Olympus Castable Ceramics and dentin. The above matters were analyzed by ANSYS 5.5 (ANSYS Inc.). Results: The results were that great tensile stress appeared at the fissure and when compression load was applied. This stress increased according to a decreasing fissure radius and an expanding cusp angle. Tensile stress was found at the boundary of the ceramics crown and the abutment tooth. This stress increased with decreasing occlusal thickness of the crown. Conclusions: Reducing the risk of a ceramics fracture is effective for increasing the fissure radius and equalizing the thickness of ceramics