| Any material used for internal application of the human body must be biologically inert,that is,once it enters the human body,it cannot show cytotoxicity or immune rejection,and can withstand the effects of various host systems in the static and dynamic changes of the body,and maintain relatively stable without being rejected and destroyed.Zirconia ceramic is a typical biological inert ceramic with high chemical stability in human body and good biocompatibility in physiological environment.Due to its high bending strength,fracture toughness and wear resistance,zirconia（Zr O2）can reduce the wear between the sizes of medical and surgical implants,and with its good biological inertia,it has a wide range of applications in biomedical fields such as dental crowns,intervertebral fusion cages,femoral joints,valves,etc.However,zirconia ceramics have high hardness and brittleness,high production cost and long production cycle in traditional processing methods,and it is difficult to prepare complex part shapes that meet practical applications.In order to solve the preparation difficulties mentioned above,based on the digital light processing（DLP）molding technology,starting from the preparation of light-cured zirconia ceramic paste,this paper studied the problems encountered in the preparation of ceramic paste and provided theoretical support for the subsequent process research.Secondly,zirconia ceramics with excellent mechanical properties were prepared by improving the light curing parameters and optimizing the degreasing sintering process.Finally,a systematic biological evaluation of zirconia ceramics prepared by UV curing was carried out.The main research work and conclusions are as follows:（1）Preparation and research of light-cured zirconia ceramic paste.The viscosity of zirconia ceramic paste was controlled by different amount of dispersant,and the dispersion mechanism of the paste was analyzed.The research shows that the special group of dispersant Solsperse can play a good role in the dispersion of zirconia particles in the resin.When the addition amount is 2.5wt.%,the prepared zirconia ceramic slurry has the best flow performance.By optimizing the solid content of the slurry,the zirconia ceramic slurry meeting the requirements of DLP photocurable printing was obtained.The fitting results were in line with the Krieger-Dougherty model.Finally,the slurry with a solid content of 46 vol% and a shear rate of 2478 m Pa·s at 30 s-1was prepared.（2）By adjusting the exposure time,the change rule of the single-layer curing depth of the slurry was studied,and the critical parameters of the slurry were calculated according to the Beer-Lambert equation.The optimum exposure time of the slurry in vacuum was determined to be 5s,which provided a theoretical basis for analyzing the curing parameters.By studying the influence of slice thickness on bending strength and relative density,the optimal layer thickness parameter for printing is determined as 25μm。The degreasing and sintering systems were optimized to improve the cracking problem in the manufacture of light-curing additives,and the zirconia ceramic samples with high density and no crack defects were prepared.The results show that the relative density of horizontally printed zirconia ceramics is 98.64%,the average shrinkage is 24.25%,the bending strength is 1041MPa,the Vickers hardness is 12.75 GPa,and the fracture toughness is 7.12 MPa·m1/2.（3）In vitro evaluation of biological safety.Based on the method and evaluation system in the national standard GB 30367-2013,this paper uses the extract of mouse fibroblast L929 to detect the proliferation and damage of cells,and evaluates the biocompatibility of zirconia ceramics prepared by DLP light curing from four different cell level experiments.From the cellular level,the zirconia bioceramics prepared by DLP light curing have no cytotoxicity,and thus will not affect the normal adhesion,growth,proliferation and apoptosis of cells.It is preliminarily verified that it has certain extrabiological safety. |
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