基于纳米晶包覆及强磁场织构的新型口腔科修复全瓷基底材料

The introduction of partially stabilised zirconia ceramics to the dental all-ceramic restorative framework has increased the reliability of all ceramic crown and bridge restorations due to the high bending strength and fracture toughness. But the quality and clinical longevity of zirconia all-ceramic restorations are decreased because of the low thermal conductivity, high coefficient of linear expansion, prone to crack when adjusted by dental technicians owing to friction heat and low binding force to veneer. Especially its sintered compact is hard to machine because of its high hardness. The compromising method is to machine the incomplete sintered compact before complete sintering, which can bring about 30% volume shrinkage and irregular morphological changes. Then the precision of the restoration is affected and production cycle is prolonged. In this project submicron-sized zirconia grain is evenly coated by nano-sized alumina(toughening phase） and boron nitride(machining phase), then anisotropic toughness can be aquired by strong magnetic field alignment which can increase the fracture toughness of the restorations along the direction of biting force. Air pressure sintering is changed to hot pressure sintering. Discolor owing to deoxidization in hot pressure sintering can be avoided as a result of higher standard free energy of formation for alumina than zirconia and positive reaction of boron nitride forming in nitrogen. The design make it possible that composite ceramic with better mechanical properties, excellent machinability and pleasing appearance can be fabricated and applied to dental field with less problem.

氧化锆陶瓷因其优异的机械学性能，被广泛应用于口腔全瓷修复基底。但其热导率低，线胀系数高，修形操作时易导致摩擦热诱导的裂纹形成，且与外层饰瓷结合不理想，降低了修复体的质量和寿命；特别是其硬度高，烧结体的机加工难度大，目前均采用先部分烧结加工成需要形态再完全烧结的成型方式，此过程有约30%的体收缩及不规则形态变化，影响修复体精度、延长了制作周期。本项目通过纳米晶包覆将纳米级氧化铝(增韧相)和氮化硼（加工相）均匀包裹于亚微米级氧化锆晶粒周围，通过强磁场织构的方法,使块体材料在咬合力破坏方向上的断裂韧性进一步提高。同时改常压烧结为热压烧结，利用氧化铝比氧化锆的标准生成自由能高以及氮气保护下氮化硼的生成为正向反应，克服热压烧结过程中的脱氧变色问题。项目拟从基材微观设计的层面探索获得高强高韧兼具良好加工性能氧化锆系陶瓷的可行性及其机理，同时使材料色彩符合牙科美观的要求，且能与外层饰瓷获得化学结合。

目前应用于口腔全瓷修复基底的氧化锆陶瓷材料有着机加工难度大、二次烧结后发生不规则收缩形变以及和饰瓷结合能力不理想等缺点，影响了修复体的精度、延长了治疗周期、增加了成本。本课题通过在微纳米级氧化锆晶粒周围包覆纳米级氧化铝（增韧相）和氮化硼（加工相），离心筛选法控制m-ZrO2晶粒的粒径并以TEM检测，球磨法混合8Y-TZP。非匀相沉淀法包裹氧化铝，反应烧结法包裹氮化硼，完成粉体的初步制备。使粉体分散于聚乙烯亚胺中，置于闭路10T强磁场中诱导，同时进行电泳沉降；强磁场诱导后的粉体过筛以热压烧结方式烧结成瓷块，通过对比不同热压烧结的保温时间和压力下烧结体的微观结构与力学性能、可加工性能，研究较为合适的热压烧结工艺。利用透光性检测试验、疲劳试验进一步检测新型陶瓷材料的物理性能和力学性能；通过细胞学实验和动物实验验证新型材料的生物相容性，并通过招募临床志愿者进行临床试验。