【作者】 逯宜；

【导师】 姚月玲；

【作者基本信息】 第四军医大学 ， 口腔临床医学， 2004， 博士

【摘要】 口腔修复学临床工作主要是为患者制作各种义齿及颌面赝复体等。用于义齿基托制作的材料有金属和树脂两大类，树脂基托具有颜色好、易成型、易修理、价格便宜等特点，目前在我国仍广泛应用于临床。改进可摘义齿树脂基托材料力学性能一直是修复专业的主要研究方向。随着科学技术的进步，树脂基托性能改进方法也发生了巨大变化，新的方法不断涌现，但目前这些新技术仍不能完全满足树脂基托力学性能的要求。在义齿的使用过程中，会因各种原因造成树脂基托的折裂，虽然许多学者采用各种方法加强树脂基托的强度，但每种方法都有不同程度的缺陷，如成本过高、设备昂贵、操作复杂、没有适于临床应用的配套设备、易形成局部应力集中、影响基托色泽以及基托局部难以缓冲、加强物与树脂基质粘结不好、纤维外露对粘膜有激惹症状等，这些都限制了临床的应用。 工业上树脂改性的方法包括表面改性及整体改性。表面改性仅作用于树脂的表面，主要是改变树脂表面的一些特性，不能对树脂的整体性能加以改进，因此应用有一定局限。 自20世纪50年代发现高能电离辐射可以引发聚乙烯交联聚合第四军医大学博士学位论文反应以来，辐射化学急速发展起来，辐射技术不仅应用于开发新的材料，目前更多的是应用于对原有材料的改性研究。高分子辐射交联技术就是利用高能或电离辐射引发聚合物电离与激发，从而产生一些次级反应，进一步引起化学反应，实现高分子间交联网络的形成，是聚合物改性制备新型材料的有效手段之一。辐射交联改性的优点在于穿透力强，不用交联剂，可在室温下进行，所以可在制品成型后进行交联，并保证树脂制品不发生变形。因此本研究在分析制作工艺对义齿树脂基托力学性能及质量影响的基础上利用高能辐射技术对PMMA材料进行辐射交联改性研究，并就辐射剂量和辐射时间对PMMA材料辐射交联后力学性能的影响进行实验，探索出一种新的改进PMMA基托性能的方法，提出适合PMMA树脂辐照的剂量和时间。 本实验研究可得到如下结果:1 .PMMA单体含量增加，材料的弹性模量和布氏硬度降低;单体含量减少，冲击强度增加，弯曲强度降低。2.丝状期充填的PMMA，弯曲强度和冲击强度均降低;面团后期充填的PMMA，冲击强度提高。建议临床应用时将充填时期调整为面团后期，以获得更好的力学性能。3.热处理时若将PMMA直接置入70℃温水中恒温9h，或直接置入100℃沸水中，均会造成材料的力学性能降低。由此提示技工操作时应采用长时间低温处理(70℃温水中恒温1一Zh)并升温至100℃，维持0.5一lh，以获得质量优良的义齿。4.PMMA热处理完成后出盒温度应控制在40℃或40℃以下，才能获得良好的义齿基托力学性能。5，影响义齿基托适合性的因素有:粉液比过大过小、长时间低温处理未经100℃高温处理或仅经100℃高温处理未经长时间低温处理以及高于40℃出盒。第四军医大学博士学位论文6.单体含量过低、充填过早、热处理升温过快、出盒温度过高均能使义齿树脂基托材料颜色发生改变，提示操作过程中，应严格遵守操作规程，粉液比例适当、缓慢升温及冷却，即可保证义齿树脂基托的颜色稳定性。7.单体含量降低、丝状期充填和未经高温处理均可增加PMMA表面粗糙度。8.限氧辐照可以抑制QC一20PMMA的降解反应。9.辐照可以对PMMA的力学性能进行改进，在50一lookGy的剂量范围内， Qc一20 PMMA的冲击强度、弯曲强度、弹性模量和布氏硬度随辐射剂量的增加可分别提高19%、7%、巧.6%、50%。10.辐照时间影响PMMA的力学性能，在6一12h范围内，QC一20PMMA的冲击强度、弯曲强度、弹性模量和布氏硬度随辐照时间的增加可分别提高19%、7%、巧.6%、50%。更多还原

【Abstract】 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更多还原