【作者】 王富；

【导师】 陈吉华；

【作者基本信息】 第四军医大学 ， 口腔临床医学， 2009， 博士

【摘要】 玻璃陶瓷是由基质玻璃在晶化热处理后得到的由晶相和玻璃相组成的多相固体材料,集中了陶瓷和玻璃的优点,在牙科全瓷修复材料中占有重要地位。二硅酸锂晶体具有适宜的热膨胀系数和光折射系数,与玻璃相能够达到良好的热力学和光学匹配,使得二硅酸锂玻璃陶瓷在具备较高机械性能的同时,仍能保持优秀的半透光特性,实现了高强度和美学效果的统一,在全瓷美学修复领域具有广阔的应用前景。本课题的目的是通过分析玻璃成分组成、成核剂含量、晶化热处理程序对玻璃陶瓷微观结构和性能的影响,制备高强度牙科二硅酸锂玻璃陶瓷;并对该实验玻璃陶瓷的热压铸工艺进行初步的研究,筛选最佳热压铸参数,分析热压铸对材料结构和性能的影响,为研发拥有自主知识产权的牙科玻璃陶瓷产品提供实验基础。本课题共分两部分:第一部分二硅酸锂玻璃陶瓷的制备1.基于Li2O-SiO2二元玻璃系统设计了多种玻璃组成,通过对玻璃熔制特性、外观、玻璃陶瓷晶相组成、微观结构和机械性能等方面进行分析筛选,确立了Li2O–SiO2–K2O–Al2O3–ZrO2系统作为本课题基质玻璃系统。P2O5作为本系统玻璃的成核剂,具有良好的促进晶化能力。2.分析了添加不同含量成核剂(P2O5)的基质玻璃在两种晶化热处理制度后的析晶特征,微观结构和机械性能。结果表明P2O5含量和热处理制度对二硅酸锂玻璃陶瓷的微观结构和性能具有显著的影响。成核剂含量为0.5mol.%时,基质玻璃以表面晶化为主,当含量达到1.0mol.%后,主要表现为整体晶化特征。随着成核剂含量的提高,DTA曲线晶化峰温度呈下降趋势,玻璃陶瓷晶化程度提高,析出晶体尺寸减小,从长大的棒状晶形逐渐转变为球形晶和短针形晶体并存的多晶型微观结构。阶梯制晶化热处理可赋予玻璃陶瓷更稳定的微观结构,有利于获得更好的机械性能。P2O5含量为1.0mol.%,采用阶梯制晶化热处理的二硅酸锂玻璃陶瓷具有稳定的微观结构和理想的机械性能。3.分析了晶化热处理温度对Li2O–SiO2–K2O–Al2O3–ZrO2-P2O5系统玻璃陶瓷结构和性能的影响。结果表明:随着晶化温度的提高,析晶度显著增加,Li2Si2O5晶体含量增加,并成为主要晶相;晶体尺寸逐渐增大,晶体间发生融合,从球状晶体为主逐渐转变为棒状晶体为主;弯曲强度和对比度均表现出不同程度的增高趋势。C组晶化热处理程序(650℃(1h)+900℃(1h))制得的二硅酸锂玻璃陶瓷具有最高的弯曲强度和适当的半透明特性。4.对比分析了实验二硅酸锂玻璃陶瓷(ELDC)和IPS e.max Press玻璃陶瓷的晶相组成,微观结构和机械性能,探讨了微观结构与性能的关系,并对牙科二硅酸锂玻璃陶瓷的自增韧机制进行了分析。实验玻璃陶瓷ELDC和e.max Press均以二硅酸锂为主晶相,晶相含量60-70%,棒状二硅酸锂晶体均匀分布,大小为2-5μm,形成互锁微结构。两种二硅酸锂玻璃陶瓷间机械性能无显著性差异。二硅酸锂玻璃陶瓷较高的机械性能与其晶相组成和微观结构紧密相关,高晶相含量、残余应力场和互锁微结构可能在牙科二硅酸锂玻璃陶瓷自增韧机制中发挥重要作用。第二部分实验二硅酸锂玻璃陶瓷应用牙科热压铸工艺的研究5.通过热压铸参数的正交优化设计,分析热压温度和时间对实验二硅酸锂玻璃陶瓷ELDC的铸入百分比、气孔率和强度的影响。结果表明实验玻璃陶瓷可以应用现有的牙科热压铸造设备进行热压成型。热压温度950℃、保温时间15min、热压时间5min,为实验二硅酸锂玻璃陶瓷ELDC的最佳热压铸参数。6.分析热压铸对实验二硅酸锂玻璃陶瓷(ELDC)晶相组成,微观结构和化学稳定性的影响。结果表明:热压铸对实验二硅酸锂玻璃陶瓷的晶相组成和晶体含量无显著影响,热压前后玻璃陶瓷均是以二硅酸锂为主晶相;热压后二硅酸锂晶体尺寸轻度增大,呈现出一定程度的定向排列趋势;热压前后实验二硅酸锂玻璃陶瓷均表现出良好的化学稳定性。7.应用前期制备的二硅酸锂玻璃陶瓷,利用牙科热压铸技术制作全瓷修复体。结果表明:ELDC制作的全瓷基底冠铸造完整,结构致密,无气孔存在,边缘密合;与IPS e.max Ceram饰瓷形成良好的结合,界面致密,无任何裂隙存在;制作的全瓷修复体形态美观,具有良好的半透光特性,符合牙科美学修复材料的要求,展现出理想的应用前景。更多还原

【Abstract】 Glass-ceramics are composed of crystalline phases and a vitreous matrix phase. These materials combine the advantages of glass and ceramic, and play an important role in dental all-ceramic restorations. Oweing to the suitable coefficient of thermal expansion and refractive index of lithium disilicate crystals, lithium disilicate glass-ceramics could obtain high mechanical strength and translucent effect simultaneously, which show a brilliant future in dental aesthetic restorations. The purpose of the study was to investigate the effects of glass composition, content of P2O5 and heat treatment procedures on microstructure and properties of final glass-ceramic products. And the possibility of application of experimental lithium disilicate glass-ceramic in dental heat-pressing technique was also studied. The appropriate heat-pressing parameters were determined and the influence of heat-pressing on microstructure and properties was also analyzed, which could provide valuable information for developing novel dental glass-ceramic with intellectual property.The whole experiments were composed of two parts.Part one: the preparation of lithium disilicate glass-ceramic1. In this experiment, several glasses were designed based on the Li2O-SiO2 binary glass system. After analysis of crystalline composition, microstructure and mechanical properties, Li2O–SiO2–K2O–Al2O3–ZrO2 glass system was selected for following investigations. P2O5 as nucleation agent could promote the crystallization of base glass.2. The effect of P2O5 content and heat treatment on the crystallization, microstructure and properties of glass-ceramic was studied. Results demonstrated that surface crystallization occurred in the glass ceramic with P2O5 content of 0.5mol.%, and glass-ceramics with P2O5 content in the range of 1.0-2.0 mol.% showed obvious volume crystallization characteristics. With an increasing P2O5 content, the crystallization temperature of parent glasses decreased. There appeared a decreasing trend in crystal size and flexural strength as P2O5 content increased. Glass ceramic with P2O5 content of 1.0mol.% after two-stage heat treatment showed the highest flexural strength and stable microstructure.3. The effect of heat treatment temperature on microstructure and properties of glass-ceramic (Li2O–SiO2–K2O–Al2O3–ZrO2-P2O5) was studied. Results demonstrated that as temperature increased, the content of Li2Si2O5 increased and became the main crystallize phase. The crystal size also increased, even from spherical shape into bar shape (2-5μm). Flexural strength and contrast ratio showed an increasing trend followed the increased temperature. Glass-ceramic in group C (650℃(1h)+900℃(1h)) showed the highest flexural strength and suitable translucent characteristics, in which appropriate crystal size and interlocking microstructure were found.4. The crystalline composition, microstructure and mechanical properties of experimental lithium disilicate glass-ceramic (EDLC) and IPS e.max Press were compared. No obvious difference in mechanical properties and crystalline composition was found between these two materials. The high mechanical properties of dental lithium disilicate glass-ceramics were attributed to the relatively high crystalline content, residual stress and the interlocking microstructure.Part two: the application of experimental lithium disilicate glass-ceramic in dental heat-pressing technique5. The effect of different heat-pressing procedures on the porosity and flexural strength was studied. The feasibility of processing ELDC with current dental heat-pressing equipments was verified. The appropriate parameters were determined as follow: heat-pressing temperature-950℃; holding time-15min; pressing time-5min.6. The influence of dental heat-pressing on the crystalline composition, microstructure and chemical stability of ELDC was studied. Dental heat-pressing had no influence on the crystalline composition and content. Lithium disilicate (Li2Si2O5) represented the main crystalline phase for both ELDC glass-ceramics before or after heat-pressing. After pressing, crystal size increased slightly and seemed to align along the direction of pressing. Superior chemical stability was found for both glass-ceramics before or after heat-pressing.7. In this experiment, all-ceramic restoratives were made with experimental lithium disilicate glass-ceramic using dental heat-pressing technique. The cores made from ELDC were intact and showed superior marginal fitness. No gap was found at the interface between ELDC and veneers ceramic. All restoratives showed good appearance and superior translucent characteristics.更多还原