凝胶注模固化及真空干燥优化ZTA牙科陶瓷的性能

目的:研究影响氧化锆增韧氧化铝(ZTA)牙科陶瓷性能的凝胶注模成型固化反应过程和真空干燥条件,探索优化可应用于全瓷牙冠制备的工艺.方法:采用凝胶注模成型制备ZTA:①在不同固化温度下分别制备样品,检测各组试样在固化过程中表面相对硬度变化；烧结各组试件,测试其抗弯强度、线收缩率;确定最佳制备参数.②采用前期得到最佳参数制备、固化样品,再置于不同温度及真空度进行干燥,检测各时点素坯相对含水率,及烧结后各组试件的强度和收缩率.结果:①40 ～ 70℃的升温条件能加速凝胶固化速率,而高于80℃的高温度段将会造成陶瓷性能下降.②升温真空环境能极大缩短凝胶陶瓷干燥时间,但失衡的温度-真空度配比将会导致陶瓷毁灭性破坏.结论:凝胶注模成型的ZTA陶瓷在50 ～ 60℃进行凝胶化反应,20 min完全固化,再于0.08 ～ 0.09 MPa的真空度下,70 ～80 ℃干燥,2.5h凝胶湿坯即可干燥完全.该ZTA陶瓷成型固化及干燥的制备工艺具有在口腔全瓷牙冠修复临床应用的前景.

Optimizing of curing and vacuum drying on dental zirconia-toughened alumina ceramics formed by gel-casting

Objective: To investigate the effects of process parameters in curing polymerization and vacuum drying process of gelcast zirconia-toughened alumina(ZTA) ceramics,and the gel-casting route was optimized for dental all-ceramic restoration applications.Methods: The ZTA composite gel system was prepared by gelcasting.①Samples were prepared respectively under different polymerizing temperature.Change of relative surface hardness on solidifying course was measured.The strength and shrinkage of ceramic green bodies were tested before and after sintering.②On the basis of previous studies,all the samples were dried under different allocation of temperature and vacuum degree.Their relative moisture content at each time point was characterized,and ceramic performance was estimated by means of three-point bending strength,linear shrinkage rate while sintered.Results: ①The temperature area between 40 ℃ to 70 ℃ could improve the gel reaction rate,while ceramic performance degraded at the temperature of 80 ℃.②Vacuum with warming environment could shorten gel ceramic drying time vastly,however,unbalanced proportion of temperature and vacuum degree may lead to tremendous damage of ceramics.Conclusion: ZTA gel system requires only 20 min for fully curing reaction at 50～60 ℃.In condition of 70～80 ℃ heating and 0.08～0.09 MPa of vacuum degree,wet ceramic matrix were completely dried within 2.5 h.Furthermore,the specimen showed a unbroken surface,with little defect and deformation in structure.This technological process has the promising for dental all-ceramic applications and may merit further research.