| Ceramic restorative material is the best living substitutive material for natural tooth. Besides aesthetics, it also has many other excellent characteristics, such as biocompatibility, chemical durability, good adherence after eroding, low conductivity of heat, transmissible for X-ray, et al, so all-ceramic restorative material has gained extentive acceptance by dentists and patients, After the birth of the first all-ceramic crown at the early stage of 1920s', many studies on these material have been developed, and some type of all-ceramic restorative materials have been recommened into the dental market one after another. On the 1960s', porcelain-fused-to-metal (PFM) restorative technique which combines the intensity of metal with aesthetics of ceramic, has got broad application. But just owing to the substructure of this sort of crown is metal, the light can't permeate, which affects the transmission of light through the whole prosthetics, and makes it lack of vivid performance; moreover, the metal ions in the substructure can not only chang the color of prosthetics, but also make some patients allergic to them. These reasons initiate the deep and detailed research on the all-ceramic restorative material by the dental restorative pursuer. The major reason that restrict the broad clinic use of it is its unperfect mechanical capability. So many investigaters are striving for strengthening these materials using various methods.Glass-cermic is a sort of composite which is comprised of slim crystal (<10μm) and glass, and made by controlled crystallization. Due to its controllable crystallization, the performance of glass-ceramic is regularable in definite range, and it has been used in many field because of outstanding properties. Now glass-ceramic has been applied as biomedical materials as a result of its biocompatible, which carve out a wider investigative field. A protrudent advantage of all-ceramic dental restorative material is admitting light transmitting, and not only the crystal of glass-ceramic is tiny, but also the refractive index of it is regulable to adapt to glass phase, so it is more compatible for use as all-ceramic dental restorative material. At present, the key subject of applying glass-ceramic to dental restoration is how to improve its mechanical properties, considering aesthetics at the same time, aiming at boosting its application in dental restorative clinic work.Based on lithium disilicate glass system, this study used differential thermal analysis, X-ray diffraction analysis, scanning electronic microscopy and some kinds of measures for chemical and physical performances to determine the heat-treated system of lithium disilicate ,studied the effect of different composition on its properties, discussed the effect of different time and temperature of heat-treated on the growth of lithium disilicate crystal.There have been no reports on dental glass-ceramic like this investigation at present.Now some conclusions have been gained as follows:1. Based on lithium disilicate glass system, lithium disilicate glass-ceramic can be obtained by melting processing. The melting temperature is 1500-1550℃ and the tempertaure range of heat-treated is 510-850℃.2. Phosphorus pentoxide is the effective nucleating agent for Li2O-SiO2 system. The crystallization of lithium disilicate changed from surface crystallization to whole crystallization after adding phosphorus pentoxide.3. The content of lithium silicate decreased as a result of increase amount of phosphorus pentoxide, owing to the drop of interface energy which affect the formation of lithium disilicate; When containing 4.5wt% phosphorus pentoxide, the glass-ceramic has main crystal phase of lithium disilicate, and a small quantity of quartz, cristobalite, lithium phosphate, no lithium silicate.4. Because of the change of interface energy between crystal and liquid, the crystal size of lithium disilicate decrease following the increase of phosphorus pentoxide, moreover, the crystal morphology transform from spheric to long and...
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