| The main clinical practice of restorative dentistry is to prepare all kinds of dentures and maxillofacial falses. The materials to prepare denture base include two main categories: metal and resin, the latter is widely used in clinical practice in China for its fine color, good elasticity, easy repairing and low costs. To improve the mechanic properties of resin denture base of removable denture has long been the main research for restorative dentistry. With the development of science and technology, the improvement methods for the mechanic properties of resin denture base have greatly changed with the increasing overflow of new methods. However, these new methods still cannot fully meet the demands of mechanic properties of resin denture base. In the course of denture application,various causes will result in fractures and fissures of resin denture base. Although many scholars have adopted various methods to strengthen resin denture base, each of these methods has manifested some defects such as high costs, expensive instruments, complex operation, lacking of affiliated instruments for the clinical application, liability to form local stress concentration, defect of denture base color or difficulty of local relief of denture base, poor cohesion between intensified products and resin matrices and irritation symptoms of fibers to mucus with the consequences of inapplicability in clinical practices.The methods to improve the mechanic properties of resin in industry consist of surface modification and whole modification. Surface modification is only applied to the resin surface, mainly to change some properties of resin surface without the modification to the entirety of resin as a result of limitations in applicability.The discovery of high-energy ionized radiation to cause the reaction of crosslinking concentration of polyethylene in 50s of 20th century led to the high development of radiation chemistry with the radiation techniques widely used not only in developing new materials but also mainly in the research of the modification of the original materials. The high-molecule radiation crosslinking technique is to use high energy or ionized radiation to cause ionization and excitation of polymers with the result of occurrences of some sub-reactions to lead in further chemical reactions for the purpose of formations of crosslinking network among high molecules, which is one of the main effective methods for the polymers to modify the new materials. The advantages of radiation crosslinking modification are that this modification does not acquirecrosslinking agents and can be prepared in room temperature. Therefore, the products can be crosslinked after they are molded and this modification can also maintain the original form of the resin products. This study, based on the analysis on effects of preparation technology to the mechanic properties and quality of resin denture base, uses high-energy radiation techniques to study PMMA resin materials with radiation crosslinking methods and some experiments are carried out on the effects of radiation dose volume and radiation time on the mechanic properties of PMMA resin materials after radiation crosslinking, with the purpose to find out a new way to modify the properties of PMMA resin denture base and to point out the proper dose volume and time of radiation to PMMA resin.The experimental research has found out the results as follows:1.The increase of content of monomer, PMMA leads to the lowering of modulus of elasticity and Brinell hardness; and the decrease of content of monomer, PMMA leads to the increase of impact strength and decrease of bending strength.2.PMMA filled during stringy stage shows the decrease of bending strength and impact strength and PMMA filled after doughlike stage shows the increase of impact strength. The suggestion is that filling stage should be arranged after the doughlike stage in clinic to obtain the better mechanic properties.3.The heat treatment of PMMA in the warm water of 70 C for 9 hours or directly in the water of 100 C...
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