牙科可切削氧化锆/磷酸镧复相陶瓷的制备及烧结[英文]

Preparation and sintering of dental machinable zirconia/La-monazite diphase ceramic

背景:陶瓷本身质地较脆,抗弯强度较小,在一定程度上限制了其在口腔修复中的应用。氧化锆陶瓷通过其相变增韧,具有较高的抗弯强度和断裂韧性,这一特点可以弥补传统全瓷修复体所存在的脆性问题。目的:利用纳米氧化锆粉体和磷酸镧复合,初步探索制备新型可切削氧化锆陶瓷。探索牙科可切削氧化锆/磷酸镧复相陶瓷制备烧结特性。设计:实验通过调整原料的成分、配比、采用不同的工艺路线、不同的烧结方法,确定工艺参数,探索最佳的工艺方式。单位:上海交通大学医学院附属第九人民医院口腔医学院口腔修复科;上海大学材料科学与工程学院先进无机材料制备工艺实验室。材料:3Y-TZP(3mol钇稳定的四方相氧化锆),一次粒径≤50nm,纯度99.99%,由宜兴新兴锆业有限公司提供。磷酸镧,纯度99.99%,由包头稀土研究院湿法冶金部提供。方法:实验于2004-01/2006-12在上海交通大学医学院附属第九人民医院口腔修复科完成。预初实验发现磷酸镧含量低于15%强度较高不易加工,而磷酸镧含量高于20%强度明显下降,故将体积百分数分别为15%,18%,20%的磷酸镧加入3Y-TZP(钇稳定四方相氧化锆),采用冷等静压成型(200MPa),在空气气氛中烧结,采用1560℃,1580℃,1600℃烧结温度,制得不同烧结温度下陶瓷样品。主要观察指标:用阿基米德法测试各温度下陶瓷体积密度、表观气孔率;用EZ-100万能试验机测试三点弯曲强度。结果:①瓷体体积密度和表观气孔率:随着烧结温度升高,15%,18%和20%磷酸镧含量的氧化锆/磷酸镧复相陶瓷的体积密度都随之升高,在1600℃时达到最高,分别为5.77,5.42,5.39g/cm3。表观气孔率则随温度升高而下降,在1600℃时达到最低,分别为0.88%,1.21%,1.49%。表明瓷块的致密性逐步提高,3种烧结温度烧结的样品体积密度比较,差异无显著性意义(P>0.05)。②抗弯强度:18%和20%磷酸镧含量的氧化锆/磷酸镧复相陶瓷样品在烧结温度为1580℃前,抗弯强度随烧结温度增加而增加;烧结温度为1580℃时达到最高,分别(772.22±43.43)MPa,(216.03±25.20)MPa和(157.21±9.79)MPa;在1600℃时抗弯强度反而下降。结论:采用冷等静压(200MPa)成型,空气中常压在1580℃烧结,可以得到致密的复合陶瓷。

BACKGROUND： The brittleness and low flexural strength of ceramic material hinder, to a certain extent, its application in prosthodontic dentistry. Zirconia is enhanced in its flexural strength and toughness by the transformation toughening mechanism, which makes up for the brittleness of the traditional all-ceramic material. OBJECTIVE： To preliminarily explore a new machinable zirconia ceramic material and investigate sintering properties of dental machinable zirconia/La-monazite diphase ceramics with nano-zirconia/La-monazite diphase ceramics. DESIGN： By adjusting the composition and ratio of raw materials, and by adopting different preparation and sintering method, this study was intended to measure the related parameters and to explore the best preparation and sintering method. SETTING： Department of Prosthodontics, College of Stomatology Shanghai Ninth People＇s Hospital Affiliated to Shanghai Jiao Tong University; Lab of Advanced Inorganic Material Technology, School of Material Science and Engineering, Shanghai University. MATERIALS： There were 3 mol yttria-containing tetragonal zirconia polycrystals （3Y-TZP） （size≤50 nm, purity 99.99%, Yixing Xinxing Zirconia-products Co., Ltd.） and Laonazite （purity 99.99%, Baotou Rare-earth Phosphate Institution）. METHODS： Experiments were performed at the Department of Prosthodontics, College of Stomatology Shanghai Ninth People＇s Hospital Affiliated to Shanghai Jiao Tong University from January 2004 to December 2006. The pilot experiments found that the zirconia with less than 15% of lanthanum phosphate was high in strength but poor in machinability while more than 20% of lanthanum phosphate was decreased significantly in its strength. Therefore, 15%, 18% and 20% （volume percentage） of la-monazite was added to 3Y-TZP. The green bodies of the three groups were compacted by cold isostatic pressing （200 MPa） and were sintered in air atmosphere at different temperatures： 1 560 ℃, 1 580 ℃ and 1 600℃ to make the ceramic samples. MAIN OUTCOME MEASURES： The volume density, porous rate （Archimedes method） and three-point bending strength （EZ- 100 universal testing machine） were tested of all the ceramic samples. RESULTS： （1）With the increase of sintering temperature, zirconia/La-monazite ceramics with 15%, 18% and 20% lanthanum phosphate was increased in its bulk and density. The density was the highest for 1 600 ℃ and the respective density of the three groups were 5.77 g/cm^3, 5.42 g/cm^3 and 5.39 g/cm^3. The porous rate decreased with the increasing temperature and was the lowest at 1 600℃ （0.88%, 1.21%, 1.49% respectively）. There was no significant difference in volume and density at different temperatures （P 〉 0.05）. （2）The flexure strength of diphase ceramic with 18% and 20% lanthanum phosphate increased with the temperature increasing to 1 580 ℃. At 1 580℃, the flexural strength reached the highest level, respectively （772.22±43.43） MPa, （216.03±25.20） MPa and （157.21±9.79） MPa. When the temperature reaches 1 600 ℃, the strength was decreased. CONCLUSION： Zirconia/La-monazite diphase ceramics can be prepared by adopting cold isostatic pressing （200 MPa） and sintering at 1 580℃.