A Fatigue Research On SHOFU Feldspathic Ceramic

Purpose: To evaluate the fatigue characters of dental feldspathic ceramic and establish an evaluation system for fatigue characters of dental ceramics with the help of fatigue theory and techniques.Methods: To measure the dynamic fatigue parameter and Weibull modular of Shofu Vintage feldspathic ceramic in artificial saliva by 3-point bending test. To illustrate the fatigue lifetime of the material with dynamic fatigue lifetime diagrams and SPT diagrams. To observe and analyze the crack surface using SEM and fractal dimension method. To estimate the cyclic fatigue lifetime and S-N curve using mathematic method. To test the surface contact fatigue characters of the material on hydro-servo fretting wear machine (DELTALAB-PLANT, France) in a manner of Hertzian sliding contact. Results: 1. fatigue and sub-critical crack propagation of dental feldspathic ceramic can be well described by Paris law and 3-point bending test is fit for the test of dynamic fatigue. Dynamic fatigue parameter and S-N curve are basic parameters to describe the fatigue character of dental ceramics. 2. The dynamic parameter n of Shofu Vintage ceramic in artificial saliva are: procelain for body n=32±9.5; porcelain for incisor n=35.8±4.46; porcelain for transparency n=23.5±3.4; Weibull modular and character strength of different materials in artificial saliva is: porcelain for body m=17.345, σ~*=77.636MPa; porcelain for transparency m=16.072, σ~*=75.546MPa; porcelain for incisor m=16.527,a*=76.022MPa o 3. Fractoanalysis of fracture surface can provide many details of prosthesis' destroy. 4. A contact cyclic stress of less than 80% of fracture strength is safety for the material. But, the influence of the surface cracks and rapture high stress under functional condition can not be ignored. 5. Surface cracks from surface sliding contact fatigue are the most dangerous defects for dental PFM prosthesis. Under cyclic masticatory strength, these cracks may propagate and leads to a disaster destroy. Conclusion: Dynamic parameter n and character strength c* of dental ceramic can well describe the mechanical characters of the material in functional environment. In point of fatigue, a high n value may be more important than high fracture strength for dental ceramics. Fractoanalysis is helpful for realizing the fracture detail of destroyed prosthesis. Ordinary masticatory tresses are safety but abrupt stress and surface cracks are dangerous. Surface fatigue cracks from surface sliding contact fatigue are the most dangerous defects for dental ceramic prostnesis.