齿科氧化锆陶瓷水热稳定性研究进展

近年来, 齿科氧化锆陶瓷凭借高强韧性、良好生物相容性和美观自然色泽而成为牙齿临床修复的首选对象, 可用于修复、固定局部义齿和种植牙。然而, 在低温潮湿环境中氧化锆陶瓷易发生t-m相变老化, 服役寿命显著缩短, 严重影响其临床稳定性。本文综述了氧化锆陶瓷低温老化的特点、机制及其老化动力学规律, 并介绍了表征氧化锆低温老化现象的常规技术手段以及光学相干断层扫描、聚焦离子束等新方法; 总结了低温老化行为的主要影响因素以及抗老化措施, 具体可通过调整材料体系、改进加工方式等来增强氧化锆的韧性, 解决其存在的低温老化问题。随着齿科氧化锆陶瓷抗老化性能的提高以及健康功能化的未来需求, 其在齿科修复领域的应用将会越来越广泛。     

Biocompatibility of Dental Alloys

Modern dental alloys have been used for 50 years to produce prosthetic dental restorations. Generally, the crowns and frames of a prosthesis are prepared in dental alloys, and then veneered by feldspar ceramics or composites. In use, the alloys are exposed to the corrosive influence of saliva and bacteria. Metallic dental materials can be classified as precious and non‐precious alloys. Precious alloys consist of gold, platinum, and small amounts of non‐precious components such as copper, tin, or zinc. The non‐precious alloys are based on either nickel or cobalt, alloyed with chrome, molybdenum, manganese, etc. Titanium is used as Grade 2 quality for dental purposes. As well as the dental casting alloys, high purity electroplated gold (99.8 wt.‐%) is used in dental technology. This review discusses the corrosion behavior of metallic dental materials with saliva in “in vitro” tests and the influence of alloy components on bacteria (Lactobacillus casei and Streptococcus mutans). The test results show that alloys with high gold content, cobalt‐based alloys, titanium, and electroplated gold are suitable for use as dental materials.     

Viscoelasticity of Dental Hard Tissues

Strength of Materials - The results of a study of the mechanical properties of dental hard tissues by nanoindentation are presented. With quasi-static nanoindentation, the analysis of the Berkovich...     

Failure Analysis of Titanium-Based Dental Implant

Metallic materials designed for applications in orthopedic or dental surgical implants must show a group of properties, including biocompatibility, mechanical strength and resistance to degradation (by wear or corrosion) outstand. In order to assure that the properties are achieved, the implant materials must fulfill certain requirements, usually specified in standards. The standards also include chemical composition, microstructure and even macrographic aspects. The main aim of this work was to perform a failure analysis on a titanium-based dental implant and connect the possible causes of failure with the associated material requirements which were previously mentioned. Evaluation techniques included metallographic analysis by optical microscopy and fractographic analysis by scanning electron microscopy (SEM). The results of the examinations suggested that, in spite of their adequate microstructures, the implants fractured due to the overload generated by stress raisers which were found in the implants.     

牙体材料的摩擦学研究进展

摩擦学研究正逐渐深入到各个学科领域,牙齿作为一类特殊的摩擦副有着与其它摩擦副不同的特点。而仿生牙体材料作为一种特殊的功能材料,除了它的机械力学性能、生物相容性、防腐耐蚀等性能外,它的摩擦磨损特性正引起越来越多的的国内外材料科学家的重视。为了促进我国牙体材料健康有序地快速发展,本文介绍了牙齿摩擦副的摩擦磨损特点和国外对牙体材料的摩擦磨损特性研究进展;并就我国牙体材料及其摩擦学研究的发展方向提出了几点     

加成型室温硫化硅橡胶口腔印模材料

加成型室温硫化硅橡胶印模材料可以用于口腔外科整形如假牙修复、烤瓷等整形术.其主要成分是乙烯基聚二甲基硅氧烷,故也称乙烯基聚二甲基硅氧烷(Vinyl Polydimethyl Siloxane,以下简称VPS)印模材料.其突出特点是印模精度高、尺寸稳定性好.概括介绍了VPS印模材料的物理和化学性能及其最新研究进展.     

Dental Age Estimation Based on X-ray Images

Chronological age estimation using panoramic dental X-ray images is an essential task in forensic sciences. Various statistical approaches have proposed by considering the teeth and mandible. However, building automated dental age estimation based on machine learning techniques needs more research efforts. In this paper, an automated dental age estimation is proposed using transfer learning. In the proposed approach, features are extracted using two deep neural networks namely, AlexNet and ResNet. Several classifiers are proposed to perform the classification task including decision tree, k-nearest neighbor, linear discriminant, and support vector machine. The proposed approach is evaluated using a number of suitable performance metrics using a dataset that contains 1429 dental X-ray images. The obtained results show that the proposed approach has a promising performance.     

齿科用氧化锆陶瓷韧性研究进展

氧化锆陶瓷具有高强度、高韧性、高硬度、耐磨损、生物相容性好等优点, 广泛应用于齿科修复。但氧化锆陶瓷相变增韧会缩短其服役寿命, 尤其在极潮湿的口腔唾液等复杂的生物化学条件下, 因承受咀嚼力、温度的频繁变化, 而导致其失效断裂。本文概述了氧化锆陶瓷在齿科修复领域的应用研究进展, 总结了氧化锆陶瓷的增韧机理以及常用齿科氧化锆陶瓷的研究现状, 并对临床服役中氧化锆陶瓷的韧性老化现象进行分析, 总结了韧性老化机理及其预防措施和方法。随着齿科氧化锆陶瓷综合力学性能的提高以及健康功能化的未来需求, 其在生物医用领域的应用将会越来越广泛。     

氧化铝改性钾长石牙科陶瓷的研究

利用氧化铝的颗粒增强作用, 采用常规烧结法制备了氧化铝改性钾长石牙科陶瓷. 通过实验确定了钾长石复合陶瓷的最佳烧结工艺, 分析了工艺条件对烧结效果、可加工性、显微硬度和抗弯强度等性能的影响. 用XRD、SEM对钾长石复合材料进行了表征. 研究表明: 添加氧化铝可以提高钾长石的烧结温度, 当Al₂O₃添加量为20wt%时, 其最佳烧结温度为1200℃, 相对密度达97.9%. 此外, 添加氧化铝可以显著改善钾长石陶瓷的性能, 当Al₂O₃添加量为5wt%时, 钾长石瓷的磨削率达到最大, 当Al₂O₃添加量为20wt%时, 钾长石瓷的显微硬度提高了26.9%. 并且随着氧化铝添加量的增加, 钾长石陶瓷的抗弯强度逐渐增强.     

白榴石增强的牙科饰面瓷研究现状

回顾了白榴石微晶玻璃在制备方法、热稳定性和力学性能3个方面的研究进展。与传统的玻璃析晶法相比,先制备白榴石晶体,然后将其与低软化点玻璃混合烧结,这种方法在控制白榴石晶体尺寸方面更具优势。烤瓷温度和时间会影响微晶玻璃中白榴石晶体的含量,进而影响微晶玻璃的热膨胀系数,因此需要严格控制。微晶玻璃中白榴石晶体的直径应该小于4μm,这样可以将微晶玻璃中微裂纹的影响减少到最小。作者制备的一种白榴石微晶玻璃在950℃保温60 min后析晶完成,并且白榴石晶体的尺寸在1μm左右。     

Zirconium Alloys for Orthopaedic and Dental Applications

Zirconium alloys for biomedical applications are receiving increasing attention due to their two unique properties: 1) the formation of an intrinsic bone‐like apatite layer on their surfaces in body environments, and 2) better compatibility with magnetic resonance imaging (MRI) diagnostics due to their low magnetic susceptibility, as well as their overall excellent biocompatibility, mechanical properties, and bio‐corrosion resistance. In particular, since both of the MRI quality and speed depend on magnetic field strength, there is a compelling drive for use of high magnetic field strength (>3 Tesla) MRI systems. This paper provides a comprehensive review of the characteristics of commercially pure (CP) Zr and Zr‐based alloys as orthopaedic and dental implant materials. These include their 1) phase transformations; 2) unique properties including corrosion resistance, biocompatibility, magnetic susceptibility, shape memory effect, and super‐elasticity; 3) mechanical properties; 4) current orthopaedic and dental applications; and 5) the d‐electron theory for Zr alloy design and novel Zr‐alloys. The mechanical properties of Zr‐based bulk metallic glasses (BMGs) and their application as implant materials are also assessed. Future directions for extending the use of Zr‐alloys as orthopaedic and dental implants are discussed.

     

牙齿形态图像的记录与鉴定

在现代法庭科学中，人体特征识别主要采用下列四种技术：指纹识别、虹膜纹识别、DNA技术和牙齿形态识别。指纹载体是综合性有机物，虹膜是软组织，在重大灾难性案件中，他们极易毁坏，且我国尚未建立非犯罪人口档案库。DNA技术虽然鉴定精确，但成本高，检验周期较长，因此三种技术都有不足之处。相比之下牙齿形态鉴定法效果较好，本文对此作详细介绍。     

Structures of Biological Minerals in Dental Research

Structural features of some calcium phosphates of biological interest are described. Structure of hydroxyapatite (OHAp), considered as the prototype for the inorganic component of bones and teeth is discussed with respect to the kinds and locations of ionic substitutions. Octacalcium phosphate (OCP), is a probable precursor in biological mineralization. OCP has a layer type structure, with one layer quite similar to that of OHAp and the other, a hydrated layer consisting of more widely spaced Ca, and PO₄ ions and the water molecules. The closeness of fit in the apatitic layers of OCP and OHAp accounts for the epitaxial, interlayered mixtures formed by these compounds and the in situ conversion of OCP to OHAp. Possible roles of OCP in biological mineralization are discussed.     

Quality and Delta Dental Plan of Massachusetts

This article on Delta Dental Plan of Massachusetts's total quality management program is the winner of the Coopers & Lybrand/Sloan Management Review Quality Award. Delta Dental Plan's enviable TQM program emphasizes now-standard elements such as teamwork and employee involvement and more cutting-edge elements such as service guarantees. Here's how it's done.     

Dental Y-TZP Ceramics: Local Fracture Resistance

Strength of Materials - The behavior of dental Y-TZP zirconia ceramics (in comparison with technical ones) was studied on Rockwell edge chipping the polished rectangular specimen by the EF (edge...     

Design and Evaluation of Tinidazole Dental Implants

Tinidazole dental implant was formulated, in vitro release, stability and in vivo therapeutic efficacy of these dental implants were evaluated. Tinidazole dental implant had efficient antibacterial activity with 400 times decreased dose.