| The ceramic used as a material for the prosthodontic in the dental application has a great biocompatibility. In addition, the ceramic has a good chemical stability, corrosion resistant and work safely in the oral cavity. The thermal conductivity, luster and wear rate of the ceramic are close to the natural teeth. The CAD/CAM technique in dentistry has been dramatically developed in prosthodontic application since it has many advantages, such as, the model of teeth can be obtained by an optical method, operation in visual,,and the restoration can be produced rapidly and precisely. However, the ceramic for CAD/CAM technique is mainly relied on the foreign import currently. Thus, the application of CAD/CAM technique in national dentistry was limited by the costliness of the foreign products. A dental CAD/CAM fluorosilicic mica glass-ceramics was investigated by our hospital cooperated with Tsinghua University. We had got the based formulation and the method for sintering. But since the multiple crystal system of the mica based glass-ceramics, it is sensitive to the temperature. The final microstructure and mechanical properties of the material are directly affected by the heat treatment. In this study, Y-TZP was incorporated with the mica based glass-ceramics, which was fabricated in previous work. Then the ceramic was fabricated, which satisfied the demands of dentistry, by altering the sintering treatments. This study could lay a foundation for the CAD/CAM technique widely applied in the prosthodontic.In the study, the fabrications were based on the K2O-MgO-SiO2-Al2O3-F glass system, which raw materials of SiO2, K2CO3, MgO, MgF2, Al2O3 et al were adopted. The raw materials were melted at 1500℃and synthesized, then water quenched. The based glass powder was made by ball milling. After that, the glass powder, which was added 3.0wt% Y-TZP, was melted again for the further powder. The mica based glass-ceramics was fabricated by isothermal sintering after forming. The nucleation temperature and the crystallization temperature were confirmed by evaluating the resulting DTA-TGA data of the corresponding powder. Then the appropriate nucleation temperature was determined by observing the sintered samples using SEM, which processed at difference nucleation temperatures. Step treatments, which including the heat treated at 680℃for 1 hr, and in the varying temperature range of 1000℃-1200℃with 40℃temperature interval for 2hrs constant soaking time, were carried out on the biscuits. After that, the sintered bodies were examined and analyzed by XRD, SEM, ect. Besides, the flexible strengths and machinable property were measured. Finally, the effects of difference heat treatments on the K2O-MgO-SiO2-Al2O3-F glass system's properties were comprehensively studied. After those, the final sintering schedule was established and the glass-ceramics which satisfied the requirements of the dental CAD/CAM was fabricated. In addition, the machinable property of the mica based glass-ceramics was also measured by the CEREC 2. The biological safety of this martial was evaluated with acute haemolysis test and cytotoxicity test. The results are showed as follows: 1. The fluorosilicic mica was crystallized from the sintered body after sintering at 1020℃. However, the crystalline rate was low. Most of the crystals were semi-euhedral with the distribution non-uniform. Thus the comprehensive properties of the fabricated material were poorer than others.2. The sintered body could be nucleated when it was sintered at 1040℃for 2 hrs after soaking at 700℃for 1 hr. The distribution of the crystals was well uniform and shaped. The effects of difference sintered methods on the microstructure and the mechanical properties were evaluated by sintering at the temperature rang of 1000℃-1200℃for 2 hrs after soaking at 680℃for 1 hr., The results showed that the microstructure and the mechanical properties of the sintered bodies which sintered at the temperature of 1040℃and 1080℃achieved the demands of the mechanical ceramics in dentistry.3. Y-TZP was soluted into the mica glass-ceramics acted as the nucleating agent, which was examined by XRD and BSE.4. The optimal sintering method was obtained according to the previous study, with the current conditions as follows: the body was sintered at 680℃for 1 hr and soaking at 1060℃for 2 hrs. The flexible strength of the sintered body was 126.1±10.9MPa, and the fracture toughness was 1.60±0.06MPa·m1/2.5. The prefabricated mica glass-ceramic has excellent machinability for CEREC 2 was demonstrated by the resulting data.6. It is suggested that the prefabricated mica glass-ceramics has good biocompatibility for the dental clinical applications. |
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