结构陶瓷中心 国家重点实验室 特邀学术报告

　　Zirconia as a Dental Material

　　Speaker：Prof. Dr. Yu Zhang

　　Department of Biomaterials & Biomimetics

　　New York University，College of Dentistry

　　报告时间：2015年元月6日（星期二）下午13:30

　　报告地点：2号楼6楼607会议室

　　联 系 人：曾宇平研究员，江东亮院士

　　Dr. Yu Zhang received his Ph.D. in Materials Science and Engineering from Monash University, Australia in 2002. From 2002 to 2005, he worked as a Postdoctoral fellow at the Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, MD under Dr. Brian R. Lawn’s supervision. In February 2005, Dr. Zhang of Biomaterials and Biomimetics at New York University Collegejoined the Department of Dentistry as an Assistant Professor, where he was promoted to Associate Professor with tenure in July 2011. His research interests include the development of functionally graded ceramics for damage resistance, aesthetics and bioactivities; and mechanical reliability, fatigue damage assessment and lifetime prediction for biomechanical structures—all-ceramic dental crowns and ceramic hip components. Dr. Zhang received three R01 grants from the United States National Institutes of Health (NIH) in 2007 and 2012, respectively, and a research grant from the United States National Science Foundation (NSF) in 2008. He is the recipient of the Arthur R. Frechette Award from the Prosthodontic society of International Association of Dental Research in 2007. Dr. Zhang has published over 70 journal articles and book chapters. He also holds 5 US patent applications.

　　ABSTRAT: More than a decade of clinical trials recording survival rates for all-ceramic dental crowns and bridges indicate vulnerabilities to various failure modes. The trend in circumventing this problem has been toward a strong and tough yttria tetragonal zirconia polycrystal core veneered with an aesthetic porcelain. Such bilayer systems have a major drawback in veneer chipping and fracture. The obvious way to circumvent this drawback is to replace the veneer/core bilayer with a monolithic ceramic. This has not been straightforward, because the microstructural qualities that confer good mechanical properties do not lend themselves to good aesthetics. Recent advances in theoretical and experimental work from our laboratory and elsewhere have demonstrated that damage resistance of ceramic prostheses can be substantially improved by controlled gradients of elastic modulus at the ceramic surface. This is because the gradient diminishes the intensity of tensile stresses and simultaneously transfers these stresses from the ceramic surface into the interior, away from the source of failure-inducing surface flaws. The materials science has been validated by sound fracture mechanics theory, finite element analysis and experimental work. It is interesting to note that biological systems (e.g., teeth, bone, shells) often employ layered and specifically oriented architectures to produce extremely damage-tolerant and fracture-resistant structures. For example, tooth enamel has strong gradients in elastic and other mechanical properties, arguably a contributing factor in the survivability of natural dentition. Although our findings are examined in the context of possible applications for next-generation dental ceramic prostheses, implications of our studies have broad impact on civil, structural, and an array of other engineering applications.

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