复合树脂类材料耐者化性能的研究（二）拉伸疲劳老化对复合树脂充填材料耐磨耗性能的影响

实验中通过对圆柱形试件施加径向压缩载荷，使试件内部承受位伸疲劳作用．疲劳试验后，将试件加工成磨耗试件，通过磨耗试验检测评价材料的耐老化性能。研究结果发现，低应力拉伸疲劳对复合树脂充填材料的耐磨耗性能无明显降低作用，个别材料甚至有被增强的趋势。     

牙科复合树脂的磨损及测试方法的研究

本研究设计了一台磨耗试验机。它以三体磨损为特点,并尽量模拟复合树脂在口腔内发生磨耗的主要条件。四个圆柱形试块(高5毫米,直径15毫米)同时安装在机器上,对磨偶件(磨轮)为布轮(高25毫米,直径150毫米),转速74转/分钟,试块承受正负荷1500克(应力0.85公斤/厘米~2)。冲量0.0729牛顿·秒。磨料为320目方解石粉与水(1:1重量比)配成的泥浆。磨耗时间5小时,每种材料重复试验三次。 用该磨耗试验机对五种材料进行了磨损率的测试,它们的磨损率顺序是:无填料丙烯酸树脂>微细填料树脂“Isopast”>牙科银汞合金>传统型复合树脂“Adaptic”。同时测定了材料经过冲击老化之后磨损率的改变,其磨损率的顺序为:无填料丙烯酸树脂>Isopast>牙科银汞合金=Adaptic。 用扫描电子显微镜(SEM)观察磨损后的材料表面,发现材料在本磨耗试验机上磨5小时后的表面微观结构与在患者口腔内实际使用一年后的磨耗状态是十分相似的。     

氧化锆及4种全冠修复材料磨耗性能的对比

背景：氧化锆陶瓷是近年来新兴的一种口腔修复材料,因其美观性及生物相容性好而受到患者的欢迎,但目前关于其与对颌天然牙磨耗性能方面的研究较少。 目的：观察氧化锆与其他4种临床常用的全冠修复材料与滑石瓷对磨时对其造成的体积损失量,并与天然牙比较,研究氧化锆及另外4种修复材料的磨耗差异。 方法：将氧化锆陶瓷,vita陶瓷,金钯合金,镍铬合金,钴铬合金及对照组天然牙釉质作为上试件,分别安装于磨耗机上部夹具中,将滑石瓷作为下试件,分别安装于磨耗机下部夹具中,在人工唾液环境下进行加载磨耗实验,计算上下试件的体积损失量;使用纤维硬度测试仪对上述试件进行硬度测试;扫描电镜下观察试件表面磨耗形态。 结果与结论：5种材料所致的滑石瓷体积损失量均大于对照组滑石瓷体积损失量    (P < 0.05);氧化锆陶瓷硬度值最高,自身及对磨滑石瓷体积损失量最大;金钯合金硬度值最小,自身及对磨滑石瓷体积损失量最接近天然牙;5种材料的硬度与其导致的对磨滑石瓷体积损失量呈显著正相关 (P < 0.05)。氧化锆及vita陶瓷主要为磨粒磨损,表面沟裂突起样结构明显、磨耗犁沟深、形态不规则,磨耗面可见散在气孔结构。钴铬合金磨耗面相对光滑,表面磨耗犁沟较浅,磨耗面散在金属磨粒;镍铬合金磨耗犁沟深而宽,磨耗面存在大量金属磨粒;金钯合金磨耗犁沟均匀分布,偶见剥脱斑块,斑块内金属磨粒附着。表明氧化锆陶瓷在临床中容易造成对颌天然牙的过度磨耗,永久黏固前应对其进行精细抛光;金钯合金的磨耗性能与天然牙最接近且最优,是较好的后牙区全冠修复材料;口腔修复材料的硬度值不能代表其磨耗性能大小,应综合考虑材料表面的微观结构等因素,采取措施发挥各种材料优势。     

复合树脂的填料尺寸分布与磨损率的相关性

本文报道体外研究13种实验复合树脂填料尺寸分布和磨损率之间的关系。用SA—CP_2—20型粒子尺寸分析仪测定了填料的尺寸分布,并用SEM进行验证。13种填料分别用KH—570(γ—甲基丙烯酸丙脂基三甲氧基硅烷)处理,并与合成的环氧丙烯酸脂配制成13种复合树脂试样。用北京医学院徐恒昌等人研制的磨耗试验机测出试样磨损率。最后用SEM观察复合树脂磨损后的表面微观结构。     

复合树脂类材料耐老化性能的研究：（二）拉伸疲劳老化对复…

实验中通过对圆柱形试件施加径向压缩载荷，使试件内部承受位伸疲劳作用。疲劳试验后，将试件加工成磨耗试件，通过磨耗试验检测评价材料的耐老化性能。研究结果发现，低应力拉伸疲劳对复合树脂充填材料的耐磨耗性能无明显降低作用，个别材料甚至有被增强的趋势。     

用于牙科复合树脂的具有固位力外形的无机填料的研究

本文介绍了一类微细的复合式无机填料。由于具有特殊的表面结构，这类填料与复合树脂中的树脂基质之间有良好的结合力，因此称之为“具有固位力外形的无机填料”。用此类填料配制的试验性复合树脂，不仅其磨耗性能有明显的改善，而且其它机械性能也有不同程度的提高。     

前牙混合型复合树脂的8年临床行为评价

复合树脂是过去几十年中牙科材料的一种重要进展。早期复合树脂采用直径1～100μm无机石英(quartz)或玻璃填料颗粒,属于巨型填料类(macrofiller),临床上可用于替代硅酸盐粘固剂或银汞合金,该材料耐磨性较好,但是抛光性能较差,时间久后因表面粗糙而影响美观,并可磨损对颌牙。显微填料树脂含有直径0.04～0.06μm亚微颗粒,通常由氧化硅和预聚合的有机树脂构成。该材料表面抛光性能优于前述传统型,但是缺乏用于载荷区所需要的强度,由于含无机填料比例低,材料的吸水较大,弹性模量和线性TEC较高。为了克服上述两类树脂的不足而开发出混合型(hybr…     

齿科复合树脂单体转化率的影响因素

齿科修复用复合树脂是目前牙体缺损常用的修复材料。研究发现,树脂残余单体对材料的机械、化学及生物学性能具有不可忽视的影响。本文阐述了牙科复合树脂残留单体的危害,分析了树脂基质、无机填料的类型、含量,以及引发体系、光照、二期处理等因素对复合树脂单体转化率的影响,讨论了提高单体转化率的有效措施和方法,指出了复合树脂发展方向,为研制更为理想的复合树脂和临床应用提供一定的理论依据。     

复合树脂充填材料修复牙体缺损的应用价值及临床评价

背景：各种复合树脂充填材料已成为牙体缺损修复治疗必不可少的重要材料,与合金修复材料并驾齐驱,但目前复合树脂的耐磨性能尚不够理想。 目的：就近年来研究应用的各种复合树脂充填材料的特点进行总结及对比,为牙体缺损的生物材料和组织工程修补手段提供理论基础。 方法：由第一作者于2010-12应用计算机检索PubMed数据库、万方数据库和维普数据库有关口腔复合树脂材料修复牙体缺损的文献。英文资料的检索时间为1999-01/2010-12,中文资料的检索时间为2000/2010-10;英文检索词为“composite resin,visible-light cured dental,detal adhesive materials,compatibility”,中文检索词为“复合树脂,口腔充填材料,固化性能,生物相容性,口腔修复,纳米材料”。排除较陈旧文献及重复研究。阅读标题和摘要进行筛选,共纳入28篇进行分析。 结果与结论：复合树脂是有机树脂基质经过表面处理的无机填料以及引发体系组合而成的牙体修复材料,作为牙色充填材料,具有可接受的物理机械性能,美观以及操作方便、易于修补等优点,在口腔修复领域使用越来越广泛。但复合树脂也存在聚合收缩、不耐磨、变色等缺点,尤其是其耐磨性能的不足,可导致修复物表面体积减小,以及修复体和边缘的破坏。随着纳米技术在生物医学领域的发展,复合树脂的纳米技术极大地丰富了口腔材料科学的研究领域,有望在牙齿修补领域带来更好的应用前景。     

Bis-GMA／（SiO2-ZrO2）纳米复合树脂的制备与性能研究

目的：通过添加纳米无机填料对树脂基质进行增强增韧改性,来满足修复性牙科材料的要求,解决树脂基质耐磨性较差、强度低的问题,制备出合适的临床牙科修复材料。方法：采用原位分散法,双酚A-甲基丙烯酸缩水甘油酯（Bis-GMA）和双甲基丙烯酸二缩三乙二醇酯（TEGDMA）共同作为树脂基质,混合加入经过硅烷偶联剂（KH-570）表面处理的纳米氧化硅（SiO2）和二氧化锆（ZrO2）制备新型复合树脂,同时使用高速搅拌和超声分散等制备工艺来改善纳米填料分散体系,运用X射线衍射（XRD）、扫描电子显微镜（SEM）等实验手段对Bis—GMA纳米复合树脂材料进行性能测试及结构表征。结果：使用高速搅拌和超声分散技术可使经过表面处理的纳米SiO2和ZrO2均匀分散在树脂基质中,达到了纳米级原生粒子分散效果,发挥了不同无机填料间的相互作用,能够有效的提高复合树脂材料的机械性能。结论：该方法制备出的高性能Bis—GMA／nano（SiO2-ZrO2）复合树脂牙科材料,能充分满足临床牙科修复学需要。     

Structure and properties of methacrylate based dental restorative materials

The chemistry and structure of the dimethacrylate resins and the nature of the filler systems in dental composite resins are reviewed in relation to their influence on the setting behaviour, dimensional stability, aesthetics, fracture behaviour and adhesive potential. It is clear that a deeper understanding of the structure of the polymeric matrix and the mechanism of clinical wear is required. As a result of ongoing research in this area and with the development of dentine adhesives, the future prospects of composite resins are encouraging.     

Experimental and computational approach for evaluating the mechanical characteristics of dental composite resins with various filler sizes

This study aimed to investigate the influence of particle size of fillers on flexural properties of dental composite resins by laboratory testing with computational analysis validation. Four kinds of silica fillers with mean particle sizes of 3.3, 4.3, 7.9, and 15.5 μm were used. Filler content was kept constant at 70 mass% (or 53.8 vol.%). The three-point bending test was performed with a constant loading speed of 1.0 mm/min, and a span length of 20 mm using an Instron machine, in order to measure flexural strength and modulus of composite resins with various particle sizes. Test specimens were 2-mm wide, 2-mm thick, and 25-mm long rectangular bars. Furthermore, a numerical simulation using three-dimensional finite element (FE) analysis was performed to investigate stress distribution in composite resins under loading. As a result, flexural strength decreased with increasing particle size of the filler of the composite resins (p < 0.05). On the other hand, there was no significant difference in Young’s modulus among composite resins with various filler sizes (p > 0.05). Moreover, FE analysis indicated that stress concentration increased with increasing particle size in agreement with experimental results of flexural strength. In conclusion, within the limitations of this investigation, we confirmed that flexural strength of composite resins decreased with increasing filler particle size. In addition, FE analysis was effective for evaluating stress distributions of dental composite resins with various filler sizes.     

一种非线性呼吸力学模型及其参数估计

本文报道了一个非线性呼吸力学模型,该模型可以反映深呼吸过程中呼吸气体流率、跨肺压力及肺容积变化之间的动态关系。模型参数分别反映气道阻力状态及肺弹性特性。敏感度分析表明,该模型肺弹性参数估计值的准确度高于气道阻力。实验测定了10名被试者的呼吸气体流率、食道压力及肺容积。参数估计结果表明,动、静态肺弹性参数之间存在显著差异(P<0.01)。我们认为肺组织及肺泡表面活性物质的应力松驰机制是造成这种差异的主要原因。     

齿科修复材料耐磨性及硬度与天然牙齿的比较

背景：天然牙与牙科修复材料之间存在摩擦现象,为了防止天然牙过度磨损,同时延长修复体使用寿命,有必要了解天然牙与牙科修复材料间的摩擦学特性,选取相匹配的修复材料。 目的：比较天然牙和各种牙科修复材料的摩擦学性能及硬度。 方法：由第一作者检索2000/2010 PubMed数据(http://www.ncbi.nlm.nih.gov/PubMed)及万方数据库(http://www. wanfangdata.com.cn)有关天然牙的磨耗以及各种牙科修复材料磨耗等方面的文献,英文检索词为“enamel,dental restorative material,zirconia, wear resistance,hardness”,中文检索词为“牙釉质,口腔修复材料,氧化锆,耐磨性,硬度”。计算机初检得到46篇文献,根据纳入标准保留30篇进一步归纳总结。 结果与结论：牙釉质具有非常优良的摩擦学性能,耐磨性好,牙本质的耐磨性较差,天然牙齿在磨损过程中,牙本质一旦暴露,磨损将会加快。因此,选择耐磨性与天然牙齿相匹配的牙科修复材料至关重要。牙釉质的耐磨性明显高于复合树脂,复合树脂材料对天然牙的磨损较小,但自身耐磨性较差。随着新型树脂材料物理性能的不断提高,有些树脂材料的耐磨性已接近牙釉质。拜尔牙、热固塑料、铜基合金、钛及钛合金是较为理想的牙科修复材料。氧化锆陶瓷属于生物惰性陶瓷,具有很好的生物相容性、高强度和韧性等特点,是一种新型的牙科修复材料。     

Mechanical properties of new composite restorative materials

OBJECTIVE: Determination of flexural strength, flexural modulus, fracture toughness, Vickers hardness, and wear resistance of condensable composites (Solitaire, Surefil, Alert) and an ormocer (Definite) in comparison with a hybrid composite (Tetric Ceram) and an ion-releasing composite (Ariston pHc). METHODS: Flexural strength, flexural modulus, and fracture toughness were determined in 3-point bending. Single-edge notched-bend specimens were used to evaluate fracture toughness. Microhardness was measured with a Vickers indenter. Wear was determined in a pin-on-block-design with a Degusit antagonist at 50 N load and quantified by a replica technique after 6000, 10000, 30000, and 50000 load cycles using a 3D-laser scanner. All results were statistically analyzed with ANOVA and post hoc Tukey HSD tests. RESULTS: Alert exhibited the highest flexural modulus, K(IC), and hardness, but lowest wear resistance. Solitaire presented the highest wear resistance, but significantly lower flexural strength, flexural modulus, K(IC), and hardness than all other materials. No significant correlation could be detected between hardness and wear of the tested composites with Pearson's correlation coefficient. SIGNIFICANCE: The condensable composites differed significantly in their mechanical properties. This study suggested that, besides the filler content level and filler size, other factors like matrix-filler interactions highly influence the fracture and wear behavior of the materials.     

Slow crack propagation in composite restorative materials

The double-torsion test technique was used to study slow crack propagation in a set of dental composite resins including two glass-filled and two microfilled materials. The microstructure within each pair was the same but one of the resins was selfcured and the other photocured. The fracture behavior was dependent on the filler concentration and the presence of absorbed water. Wet materials fractured by slow crack growth in the range of crack velocity studied (10(-7) to 10(-3) m/s), and the microfilled composites, which contain a lower concentration of inorganic filler, had lower stress intensity factors (K1c) than the glass-filled composites tested. Dry specimens of the microfilled materials and the selfcured, glass-filled composite also showed unstable, stick-slip fracture behavior indicative of a crack blunting mechanism which leads to an elevation of the stress intensity factor for crack initiation over K1c for stable crack growth. The plasticizing effect of water increased the viscoelastic response of the materials measured by the slope of curves of slow crack growth. Analysis of fracture surfaces showed that cracks propagated at low velocities (10(-7) to 10(-5) m/s) by the apparent failure of the filler/matrix interfacial bond, and absorbed water affected the strength or fracture resistance of the interface. At high crack velocities the properties of the composite depend on the properties of the polymeric matrix, the filler, and the filler volume fraction, but at low velocities the interface is the controlling factor in the durability of these composites exposed to an aqueous environment.     

Three body wear studies of five dental composites preconditioned in food simulating media

Progressive three body wear up to 30 min for five dental composites (Concise, Heliomolar, Occlusin, P-30, Profile, TPH) stored for 9 months at 37 degrees C in citrate, lactate and PBS buffers, 25 and 75% ethanol media, has been measured using a wear tester. Particle size of the filler and the storage media are found to play dominant roles in determining the extent of wear. Heliomolar, which is a microfilled composite, shows maximum wear whereas wear is least in composites containing filler particles of conventional and hybrid size such as P-30 (> 1 micron). The storage media is found to attack and degrade glass filler particles compared to composites having quartz fillers.     

人体步行运动的关节力学研究

利用角度传感器和步态测力板,本文观察了人体的步行运动,采用Fourier数字滤波拟合出各关节的运动规律,依据多刚体动力变分原理建立了适合作实时计算和模型修改的人体步行动力学方程。对于步行中双脚着地时出现的闭环结构,作者借助测力板测出的脚底反力曲线,提出了由力——位移组成的混合求解法。用文中计算方法编制的软件可用于人体下肢疾病的临床医学诊断。     

Mechanical properties and three-body wear of veneering composites and their matrices

Fatigue as one of the major factors affecting three-body wear of resin composites is influenced by mechanical properties of the resin matrix. The aim of this in vitro study was to determine three-body wear (ACTA methodology), fracture strength, and Young's modulus of four veneering composites (Artglass old and new formula, Vita Zeta LC Composite, Targis) and one direct restorative composite (Z 100). Furthermore, three-body wear of the pure matrices of the materials was tested. The wear results were compared to Amalgam as reference material. It should be computed whether there exists a correlation between the wear results of resin composite and matrix alone. Wear of the veneering composites was significantly higher than of Z100 (13 microm) and Amalgam (14 microm; p < 0.01, Mann-Whitney U-test). Mean fracture strengths of indirect composites ranged from 127.5 MPa (Targis) to 71.6 MPa (Vita Zeta LC). The elastic moduli of the composites were between 2.9 and 12.8 GPa. The matrix wear rates did not differ significantly. Three-body wear results of complex resin composites are highly influenced by their filler content, filler particle size distribution, kind of filler particles, shape, and their silanization to the matrix. Due to this fact, three-body wear testing is an essential testing method and cannot be replaced by testing single material components.