Preparation And Properties Of ZrO₂ And ZrO₂-Al₂O₃ Bioceramics By Additive Manufacturing

The application of digital technology has promoted the development of stomatology in the direction of individuation,precision and minitrauma,but traditional CAD/CAM technology has problems such as difficult machining,easy to result in poor performance for the phase transition from t-ZrO₂ to m-ZrO₂ and material waste when fabricating ZrO₂restorations.Additive manufacturing technology has unique advantages in preparing parts with complex and personalized structures.In this paper,ZrO₂ and ZrO₂-Al₂O₃ were used as main raw materials to prepare restorations by selective laser sintering（SLS）and stereo lithography（SL）,and the properties were studied to explore new ways to prepare personalized restorations with multi-surface complex structures.The conclusions are as follows:（1）ZrO₂ bioceramics were prepared by SLS technology.The density of ZrO₂ green samples prepared under the optimum SLS parameters was significantly increased after cold isostatic pressing,and the linear shrinkage in the height direction was larger than that in the horizontal direction.The main phase composition of ZrO₂ ceramics was t-ZrO₂ and c-ZrO₂after sintering.As the sintering temperature increased,the diffraction peak intensity of m-ZrO₂ gradually increased,the average grain size gradually increased and the grains became tighter and tighter.The relative density and flexural strength of ZrO₂ ceramics had a maximum of 86.65%and 279.50 MPa respectively at 1500℃.（2）ZrO₂ bioceramics were prepared by SL technology,which had a higher relative density than ZrO₂ ceramics prepared by SLS technology.As a monomer with two functional groups,HDDA was used as the photosensitive resin monomer.ZrO₂ slurry suitable for SL could be obtained when the dispersant concentration was 5 wt%and the solid loading was42 vol%.The phase composition of ZrO₂ ceramics was t-ZrO₂ and c-ZrO₂ after sintering.When the sintering temperature increased from 1450℃to 1600℃,the ZrO₂ grains gradually grew,Vickers hardness and fracture toughness reached the maximum of 14.87 GPa and 6.73MPa·m^1/2 respectively at 1500℃,when linear shrinkage and relative density were 23.42%and 97.32%respectively.The results of in vitro biological experiments showed that the surface of ZrO₂ bioceramics prepared by SL technology was suitable for the proliferation,adhesion and migration of rat bone marrow mesenchymal stem cells（r BMSCs）,indicating good biocompatibility.（3）ZrO₂-Al₂O₃ bioceramics were prepared by SL technology,which further improved the mechanical properties of the restorations.The addition of Al₂O₃ was 20 wt%.ZrO₂-Al₂O₃ slurry suitable for SL could be obtained when the dispersant concentration was 4 wt%and the solid loading was 45 vol%.The phase composition of ZrO₂-Al₂O₃ ceramics was t-ZrO₂,c-ZrO₂ and Al₂O₃ after sintering at 1450-1600℃.Relative density,Vickers hardness and fracture toughness all reached their maximum of 99.09%,16.66 GPa and 6.88 MPa·m^1/2respectively at 1600℃.In vitro biological experiments confirmed that r BMSCs could adhere on the surface of ZrO₂-Al₂O₃ ceramics uniformly and had good proliferation and migration ability.In this paper,additive manufacturing technologies had been used to prepare ZrO₂ and ZrO₂-Al₂O₃bioceramics with good properties successfully,which could provide a new way to prepare personalized restorations with multi-surface complex structure,and it is beneficial to promote the application of additive manufacturing technologies in the field of stomatology.