Three-Dimensional Finite Element And Experimental Analysis For The All-Ceramic Crowns

All-ceramic crown is one of the perspective restorative dental materials because of its aesthetics and safety for human, but the brittleness of the material limits its wide application in clinic. Then it is very important to study the mechanics properties of the all-ceramic crown.Combining the finite element method with experimental measuring technique, the effects of luting cement type, cement thickness and the sorts of all-ceramic crown on the stress and its distribution within all-ceramic crowns are investigated in this thesis. The 3D finite element model of all-ceramic crown is developed. And two adhesive systems, such as Panavia F and Variolink II, are considered to design the finite element model of all-ceramic crown with thickness of 60μm, 90μm, 120μm, and 150μm. The models are subjected to four loading conditions, and the stress and its distribution in all parts of all-ceramic crowns are obtained. The maximum stresses of five kinds of all-ceramic crowns are evaluated under two load conditions. The sectioned flat-layered ceramic specimens were prepared, and Hertzian contact test is used to study the effects of luting cement type and thickness on the fracture load, and to obtain the fracture loads of all-ceramic crowns. Analyzing the numerical and experimental results, we have the following conclusions:1. From the results of three-dimensional finite element analysis, the stress distributions in the all-ceramic crowns with double layer structure are the same approximately under the same load; the tensile stresses are appeared in the vicinity of contact zone at the out surface of the veneer and at the lower surface of the core under the contact point; and the larger tensile and shear stresses exist at the shoulder of the all-ceramic crown. Under the different loads, there are apparent different stress distributions in the all-ceramic crowns, and this indicates that the types of clinical loads play an important role in the stress distribution.2. The thickness of the cement agent has influences on the stress distribution in the all-ceramic crown. There is an optimal thickness, which is 90μm. The different type of cement will obtain the different stress level in all-ceramic crowns. Cement with larger Young's modulus is believed to help reducing the stress in the crowns effectively. The experimental results of Hertzian contact tests show good agreement with the numerical ones of finite element analysis.3. The stress distribution of the all-ceramic crown is affected by the type of the all-ceramic crown, and the all-ceramic crown should have its own range of application. The results of finite element and experimental analysis show that, in clinic as the tensile stress strength of the dental ceramic system increasing as Young's modulus decreasing to the best of one's abilities, then the all-ceramic crown which wears well can be designed.This thesis has illustrated effective research methods and provided referenced numerical and experimental results for the clinical application of all-ceramic crowns.