注塑微波法制作树脂基托对义齿精度的影响*

背景：近年来,注塑微波聚合技术在临床应用越来越多,其制作义齿精度方面的研究在国内鲜见报道。 目的：观察注塑微波方法对树脂基托义齿精度的影响。 方法：用注塑微波法和水浴法分别制作上颌全口义齿各10个,然后在上颌第二磨牙远中部位切断义齿基托与标准模型,用数字显微镜测量上颌全口义齿基托组织面与标准模型之间共5个部位的间隙。 结果与结论：注塑微波法制作的义齿5个部位的精度为：(200±32),(76±13),(69±15),(81±16),(187±27) μm,水浴法制作的义齿5个部位的精度为：(243±50),(100±26),(96±30),(109±32),(213±28) μm,两种方法在相同点处差异有显著性意义(P < 0.05)。提示在精度方面,注塑微波法制作的义齿优于水浴法,并且注塑微波法聚合时间较水浴法明显缩短。     

不同聚合方法对热凝基托树脂力学性能的影响

【摘要】 目的：热凝基托树脂经过不同方法聚合,观察比较其力学性能的变化,为临床提供理论依据。方法：分实验对照两组,实验组为热凝基托树脂经过快速方法聚合,对照组为热凝基托树脂标准方法聚合,对两种方法聚合的基托树脂试样在材料试验机上对其冲击强度、弯曲强度、弹性模量和布氏硬度进行测定,并对断面进行电子显微分析。结果：快速聚合基托树脂和标准聚合基托树脂的冲击强度（KJ/mm3）分别为6.73±1.23 ,7.35±0.93 ,弯曲强度（Mpa）为89.93±12.92 ,90.19±6.88 MPa,弹性模量（Gpa）为 2.2±0.2 GPa ,2.4±0.1,,布氏硬度（kg/mm2)为20.70±2.89,19.57±1.05kg/mm2,其各项力学性能无显著性差异（P>0.05）;不同方法聚合的基托树脂断面的微观结构也比较相似。结论：采用快速与标准两种方法进行基托树脂的聚合,其各项力学性能及微观结构无明显差异。但该材料在实际工作中,对于全口义齿及复杂局部义齿等基托比较厚的情况是否与本实验相一致,是否会影响义齿的质量,还须在临床上具体应用,作进一步的长期观察。     

微波热凝后骨骼肌体积及功能的变化

背景：微波利用其热效应在医学领域得到广泛应用，经微波热凝作用后造成局部组织凝固性坏死，坏死部位由纤维组织修复。但是微波热凝是否能产生缩容效果运用于口腔临床，目前经检索国内外尚未见报道。 目的：观察微波热凝骨骼肌后肌肉体积和功能的改变，探讨微波热凝用于骨骼肌体积缩小的可能性。　 方法：20 只新西兰大白兔暴露双侧胫骨前肌，采用2 450 MHz微波治疗仪以70 W微波热凝一侧胫骨前肌20 s，另一侧不做微波热凝作对照。分别于热凝后24，48 h和1，8周，随机各处死5只兔，测量双侧胫前肌体积变化，8周处死动物前，行肌电生理检测双侧胫前肌的肌动力。　 结果与结论：微波热凝后24，48 h骨骼肌体积增大[(5.82±0.93)，(6.04±0.47) mL]，48 h体积最大，1周后肌肉体积开始缩小[(4.90±0.80) mL]，8周后体积[(4.27±0.67) mL]缩小23.6%；肌电生理检测显示对照组与热凝组潜伏期分别为(1.765±0.393)，(1.760±0.394) ms，波宽分别为(6.273±0.808)，(6.259±0.773) ms，两组之间传导速度及波宽差异无显著性意义(P > 0.05)。结果证实微波热凝后48 h内肌肉体积增大，随后体积减小，骨骼肌可保持肌功能。     

四种超硬石膏模型精度及抗弯强度的比较

背景: 在临床上,超硬石膏广泛应用于制作固定义齿、大支架可摘义齿等需精细复制口腔情况的工作模型,其抗弯强度足够抵抗脱模时的力量不会发生模型牙体的折断。但当印模为硬质材料如聚醚橡胶印模等,存在牙体折断现象。 目的：比较4种超硬石膏YCG,丹特纳,贺利氏,穗诚模型的尺寸精度及抗弯强度。 方法:制作三单位固定桥和长方体(50 mm× 10 mm×5 mm)的金属模具,灌注4种超硬石膏模型,分别采用万能工具显微镜和万能试验机测量其尺寸精度及抗弯强度。 结果与结论：YCG、丹特纳、贺利氏、穗诚4种超硬石膏近远中方向尺寸精度均值分别为:15.043,15.034,15.037,15.040 mm,颊舌方向为：7.020,7.015,7.019,7.019 mm,牙体长轴方向为：8.022,8.018,8.019, 8.02 mm。4种超硬石膏模型抗弯强度均值分别为：15.687,13.000,22.521, 18.675 MPa。4种石膏模型尺寸精度差异无显著性意义 (P > 0.05),但抗弯强度差异有高度显著性意义(P < 0.01)。贺利氏石膏抗弯强度显著高于其他3种石膏 (P < 0.01),穗诚石膏抗弯强度显著高于丹特纳(P < 0.01)。说明贺利氏石膏的抗弯强度是4种超硬石膏中最高者,穗诚的抗弯强度高于丹特纳,提示临床上应根据实际情况尽量选择抗弯强度大的石膏材料。     

太极扣附着体覆盖全口义齿修复后的组织相容性评价

背景：太极扣附着体固位的覆盖全口义齿较之传统全口义齿稳定性好、固位力强、咀嚼效率高,但由于基牙覆盖在义齿基托下,缺乏口腔的自洁作用,易发生基牙牙周组织炎症而导致覆盖基牙丧失,义齿修复失败。 目的：评价太极扣附着体覆盖全口义齿修复后对基牙牙周组织的影响。 设计、时间及地点：自身对比观察,于2006-01/2008-12 在郑州大学口腔医学院实验室完成。 对象：选择2006-01/2007-12就诊于郑州大学口腔医学院口腔修复科的牙列缺损患者20例,女13例,男7例;年龄54~78岁;上颌4例,下颌16例。单颌余留1或2颗尖牙、双尖牙或其残根,松动度不超过Ⅰ度,根长大于或等于8 mm,牙槽骨吸收不超过根长的1/2。 方法：按常规桩核冠根管预备要求进行基牙的根管预备,取印模,灌模型,完成太极扣附着体单颌覆盖全口义齿,将带有太极扣的金属根桩粘固于基牙根管内,使义齿在口内就位。 主要观察指标：每例患者分别在义齿修复前、修复后1,6,12个月,4个时间段测定基牙的牙龈指数、菌斑指数,并拍摄全口牙位曲面体层片,比较修复前和修复后12个月基牙的牙槽嵴高度。 结果：修复前和修复后1,6个月的基牙牙龈指数、菌斑指数差异均无显著性意义(P > 0.05);修复后12个月基牙的牙龈指数高于修复前(P < 0.05)。同一个体修复前和修复后12个月基牙的平均牙槽嵴高度差异无显著性意义(P > 0.05)。 结论：太极扣附着体覆盖全口义齿修复后对基牙牙周组织的影响较小,组织相容性较好。     

不同表面处理对Ceramage聚合瓷黏结强度的影响

背景：长期以来修复材料与基牙的黏接技术一直是口腔修复学的研究热点,其中尤为引人关注的是黏结工件的表面处理工艺。 目的：对比观察8种表面处理方法对Ceramage聚合瓷黏结强度的影响,筛选适合Ceramage聚合瓷的表面处理方法。 方法：将Ceramage聚合瓷制成试件80个,随机分成8组,分别采用喷砂,酸蚀,偶联剂,喷砂+酸蚀,喷砂+偶联剂,酸蚀+偶联剂,喷砂+酸蚀+偶联剂处理聚合瓷表面并与树脂黏结剂黏结,对照组不进行任何处理。在37 ℃水浴24 h后测试样本剪切强度,并用扫描电镜观察处理后的聚合瓷表面形貌。 结果与结论：各组的剪切强度值由高到低分别为：喷砂+酸蚀+偶联剂处理组(31.12±2.81) MPa,喷砂+酸蚀组(27.62±1.70) MPa,酸蚀+偶联剂组(27.31±2.18) MPa,喷砂+偶联剂组(26.91±1.97) MPa,喷砂组(24.23±2.03) MPa,偶联剂组(23.50± 2.19) MPa,酸蚀组(17.61±2.14) MPa,对照组(8.13±0.63) MPa,除喷砂组、偶联剂组之间,喷砂+酸蚀组、喷砂+偶联剂组、酸蚀+偶联剂组之间比较差异无显著性意义外(P > 0.05),其余组间比较差异均有显著性意义(P < 0.05)。结果显示7种表面处理方法都提高了黏结强度,喷砂、酸蚀联合硅烷偶联剂处理的聚合瓷黏结强度最高,是适合Ceramage聚合瓷黏结的表面处理方法。     

自制钴铬烤瓷合金的金瓷结合性能

背景：在非贵金属烤瓷合金中,钴铬烤瓷合金在生物相容性、耐腐蚀性以及金属稳定性方面都优于镍铬烤瓷合金和含钛烤瓷合金,被广泛的应用于临床。 目的：通过与德国BEGO钴铬合金对比,评价自制钴铬烤瓷合金的金瓷结合性能。 方法：制作25 mm×3 mm×0.5 mm规格的德国BEGO钴铬合金与自制钴铬烤瓷合金两种合金的金属试条,分别熔附8 mm× 3 mm×1 mm的VITA MK 95瓷粉,采用三点弯曲的方法测试金瓷结合力,利用扫描电镜观察金属氧化界面。 结果与结论：加力后国产和德国BEGO钴铬合金样本随着力量的增加瓷层开裂同时完全脱落,表面成灰黑色氧化膜,无明显瓷残余;自制钴铬烤瓷合金与德国BEGO钴铬合金的金瓷结合力差异无显著性意义[(41.26±2.68), (41.35±2.59) MPa, P > 0.05]。说明自制钴铬烤瓷合金的金瓷结合强度高于ISO所要求的基本值25 MPa,且与德国BEGO钴铬合金相比无差异,可满足临床要求。     

碳酸钙对去卵巢大鼠骨矿盐代谢的影响

目的：研究表明，缺钙是骨质疏松症发生和发展的一个主要原因，分析碳酸钙（CaCO3）对切除双侧卵巢后的大鼠骨矿盐代谢的影响。 方法：实验于2005-07/2006-04在广东医学院生理学教研室完成。①实验材料：普通级4月龄SD雌性大鼠24只。②实验分组：将大鼠随机分成4组：正常对照组，假去卵巢组，去卵巢组，去卵巢+ CaCO3组，每组6只。③实验过程：去卵巢+ CaCO3组大鼠于切除卵巢术后第2 d开始给予CaCO3灌胃[元素钙20 mg/(kg·d)]，持续11周。假去卵巢组动物手术过程及操作同去卵巢组和去卵巢+CaCO3组，但不切除卵巢。④实验评估：第11周末，麻醉状态下动脉放血处死各组大鼠，观察骨干重、骨干重/体质量、骨灰重、骨灰重/体质量、骨灰重/骨干重（%）的变化。实验过程中对动物处置符合动物伦理学标准。 结果：24只大鼠均进入结果分析。①去卵巢对大鼠骨矿盐代谢的影响：去卵巢组大鼠与假去卵巢组大鼠比较，其骨干重、骨干重/体质量、骨灰重、骨灰重/体质量、骨灰重/骨干重（%）等指标均明显减少，差异有显著性(P < 0.01)。假去卵巢组大鼠与正常对照组大鼠比较，各项指标均差异无显著性（P > 0.05）。②CaCO3对去卵巢大鼠骨矿盐代谢的影响：与去卵巢组比较，去卵巢+CaCO3组大鼠骨干重、骨干重/体质量、骨灰重/骨干重(%)均增加 [(504±24)，(545±12) mg；(1.55±0.06)，(1.68±0.04) g/kg；(58.6±0.8)%，(60.7±2.0)%；P < 0.05]，骨灰重、骨灰重/体质量指标亦增加[(293±14)，(332±16) mg；(0.90±0.04)，(1.01±0.04) g/kg；P < 0.01]；与假去卵巢组比较，去卵巢+CaCO3组大鼠骨灰重、骨灰重/体质量、骨灰重/骨干重（%）指标低 (P < 0.01)。 结论：CaCO3可部分纠正去卵巢大鼠的骨矿盐丢失。     

白细胞介素-2及其受体在癫痫患者发作中的变化和对癫痫大鼠的致惊作用

目的探讨白细胞介素-2(interluekin-2, IL-2)及其可溶性受体在癫痫患者发作中的变化和对癫痫大鼠的致惊作用.方法采用ELISA方法检测58例癫痫患儿和23例健康儿血清IL-2及其可溶性受体的浓度,并进行分组比较;观察侧脑室注射IL-2对遗传性癫痫易感大鼠(P77PMC)惊厥发作的影响.结果癫痫组血清IL-2及其可溶性受体浓度[(25.86±5.21) ng/mL和(758.26±78.49) U/mL ]明显高于对照组[(13.78±3.24) ng/mL和(325.67±34.58) U/mL](P<0.01),且发作期[(30.31±6.77) ng/mL和(806.25±112.35) U/mL]高于间歇期[(20.27±4.66) ng/mL和(584.15±57.85) U/mL ](P<0.01),脑电图异常者[(27.18±4.35) ng/mL和(724.48±78.56) U/mL]高于正常者[(20.04±3.55) ng/mL和(621.85±77.45) U/mL],但与发作类型、病程长短及经治疗与否无关;侧脑室注射IL-2(5 000 U/L)5～10 μL后大鼠惊厥评分从26升高到36(P<0.05),惊厥持续时间从32 s延长到65 s(P<0.01),但对潜伏期无影响.结论 IL-2在癫痫患者处于高水平状态,直接侧脑室注射IL-2可加重大鼠惊厥程度,提示其参与癫痫发病过程.     

不同树脂牙耐磨性和硬度的比较研究

目的 通过对7种常用的树脂牙进行硬度和耐磨性的比较研究，为临床修复牙列缺损缺失时人工牙的选择提供理论基础。 方法 选择七种不同树脂牙,它们分别为硬质复色合成树脂牙(A)、复色合成树脂牙(B)、合成树脂牙(C)、ENDURA塑钢牙(D)、三层色合成树脂牙(E)、Optostar四层色合成树脂牙(F)、CosmosHXL(G)。用销-盘式摩擦磨损试验机进行磨耗试验，用磨耗质量损耗及电镜观察比较这七种树脂牙的耐磨性能；采用努氏硬度法测试树脂亚的显微硬度。并研究树脂牙耐磨性和硬度之间的相关性。 结果 通过磨耗前后各树脂牙质量的损耗及电镜观察结果得出不同树脂牙耐磨性从高到低排列为：D>A>G>E>B>F>C；硬度测试结果是A：29.87±0.47 HK，B：22.63±0.70 HK，C：17.43±0.67 HK，D：41.24±1.71 HK，E：23.76±1.14 HK，F：23.02±1.44 HK，G：29.05±1.01 HK。树脂牙磨耗失重和硬度值的相关系数为－0.888（P<0.01）。 结论 材料组成成分、分子量和树脂牙加工工艺的差别可造成不同树脂牙硬度和耐磨性能之间的差异；不同树脂牙的硬度和耐磨性呈正相关。     

Fibrin polymerization and release of fibrinopeptide B by thrombin

Although it is well known that thrombin releases fibrinopeptide A (FPA) more rapidly than fibrinopeptide (FPB) from fibrinogen different opinions have been expressed as to whether fibrin I (FPA release) and II (FPB release) are sequential or simultaneous. Evidence has been presented that FPB release depends on the polymerization of fibrin and the finding that the tetrapeptide gly-pro-arg-pro inhibits fibrin formation provides a new tool to investigate the effect of polymerization. The radioimmunoassay technique which permits the initial rates of the release reactions to be accurately measured at low concentrations of reactants was used to investigate FPB release. In the absence of gly-pro-arg-pro the FPB release pattern showed three phases - an initial slow and a second more rapid phase both of which were at a constant rate and a final phase with decreasing rate as the substrate concentration fell. Gly-pro-arg-pro at appropriate concentrations inhibited fibrin polymerization as indicated by optical density and light scattering techniques as well as by gel filtration on Sephadex G-200. FPA release and the initial rate of FPB release were unaffected. The second phase of rapid FPB release was abolished indicating that this increased rate is entirely dependent on the polymerization of fibrin I. Under one set of specified conditions the initial release rates of FPB by thrombin from different substrates were 15.8 pmol/min (fibrinogen), 14.0 pmol/min (fibrinogen plus gly-pro-arg-pro), 27.4 pmol/min (fibrin I monomer) and 164.4 pmol/min (fibrin I polymer). The data indicate that fibrin I and II formation are not sequential but simultaneous and that it is the more rapid formation of fibrin I which results in the appearance of a sequential reaction. It is suggested that a number of other reactions in the hemostatic system including fibrinolysis which appear to be sequential are also simultaneous.     

Screening for inhibitors of tau polymerization

The histopathological diagnosis of Alzheimer's disease relies on two kinds of proteinaceous aggregates: the extracellular plaques built from filaments of the Abeta-peptide and the intracellular tangles consisting of tau polymerized into Paired Helical Filaments (PHFs). The order of aggregation events is still under debate, but it is well accepted that tau-related changes have an important impact on the viability of neurons. In neurons, early morphological changes are seen in axons which begin to loose and retract synapses. This process is accompanied by an increase of aggregated tau protein. Thus the prevention of tau aggregation seems to be a valuable target for therapy of Alzheimer's disease. Here we present a screening procedure by which we identified inhibitors of tau polymerization. In the primary screen we used a thioflavin-S based assay which detects PHF formation in solution. These initial hits were further analyzed for their capacity to depolymerize preformed PHFs. These results were confirmed by several secondary assays (tryptophan fluorescence, pelleting, filter trapping and electron microscopy). By this approach it is possible to identify small molecule compounds which prevent or reverse the aggregation of tau and thereby might improve the viability of neurons in a therapeutic approach.     

Induction of rate and pathway-length changes in fibrin polymerization.

Factors influencing fibrin monomer clotting time were found to affect either the rate of fibrin polymerization solely, or both the rate and degree of polymerization. In the latter case the polymerization level required for clotting to take place changed and became a variable of great importance. In experiments with dilution of the fibrin containing solution as well as with CaCl₂ addition the rate effect appeared to be the only factor of significance. The CaCl₂-rate effect was not quite uniform at different steps of the clotting process. Shifts of ionic strength altered mainly the polymerization extent; the required polymerization level ascended sharply as ionic strength increased. The rate and pathway effects could be discerned easily by carrying out the relevant medium changes at different stages of fibrin polymerization.     

溶液直接缩聚法合成聚乳酸的特点*

摘要：聚乳酸具有良好的生物相容性、生物降解性和生物可吸收性,它被广泛用作药物缓释、手术缝合线及骨折内固定等生物医用高分子材料。文章探讨了近年来国内外研究溶液直接缩聚法合成聚乳酸的进展情况,概述了乳酸溶液直接缩聚的原理,研究了溶液聚合中影响聚乳酸相对分子质量的因素。开展聚乳酸直接合成方法的研究,具有非常重要的意义,期望能通过对溶液聚合中影响聚乳酸相对分子质量的因素进行研究,改进聚乳酸的直接合成工艺,通过直接合成法得到较高相对分子质量的聚乳酸。     

Effects of acetaldehyde on polymerization of microtubule proteins

The in vitro effects of ethanol and acetaldehyde on polymerization of calf brain microtubular proteins (MTP) were examined. While ethanol up to 100 mM had no effect on the polymerization of MTP, acetaldehyde above 0.5 mM had an inhibitory effect. This effect was not dependent on the presence of microtubule-associated proteins (MAPs), since acetaldehyde had a similar effect on the polymerization of highly purified tubulin. Electron microscopy revealed that the number and the length of microtubules at equilibrium was reduced by the presence of acetaldehyde. Acetaldehyde raised the critical concentration for tubulin assembly and caused greater inhibition at lower tubulin concentrations. Acetaldehyde augmented the depolymerizing effects of Ca2+ on preassembled microtubules. In addition, acetaldehyde itself caused depolymerization of microtubules but only in the absence of MAPs. Long-term (19.5 h) incubation of MTP with acetaldehyde led to significant loss of polymerization ability which could not be reversed by removal of acetaldehyde. This loss of activity was apparently independent of the observed formation of reducible adducts between acetaldehyde and MTP.     

Inhibition of fibrin polymerization by serum amyloid P component and heparin

The effects of serum amyloid P component (SAP) and heparin on the thrombin-catalyzed formation of polymeric fibrin from purified fibrinogen were examined using a turbidometric method to quantify fibrin polymerization. SAP and heparin acted synergistically to inhibit the lateral aggregation of fibrin fibrils, resulting in the formation of fibrils with a smaller mass to length ratio. Heparin did not enhance the incorporation of SAP into fibrin clots, and the effect of heparin and SAP did not seem to be related to inhibition of thrombin or of fibrinopeptide release. The evidence suggests that a soluble complex of SAP and heparin inhibits fibrin polymerization.     

聚对苯二甲酸乙二醇酯表面接枝改性及其血液相容性的研究进展

背景：聚对苯二甲酸乙二醇酯是一种具有优良的力学性能、化学惰性的聚酯材料,但由于聚合材料的血液相容性不高,因此需对其表面进行修饰,改善其血液相容性。 目的：结合凝血机制简要介绍聚对苯二甲酸乙二醇酯材料表面接枝改性方法及其改性后的血液相容性。 方法：检索1990/2009 PubMed、SDOS及CNKI数据库有关凝血发生机制、抗凝血药物的种类和其对凝血发生的影响以及聚对苯二甲酸乙二醇酯材料本体性质、材料表面接枝的方法及其血液相容性评价等方面的文献。 结果与结论：目前聚对苯二甲酸乙二醇酯表面接枝改性的方法局限性在于表面接枝的分子只能改变材料某种特性,而生物材料在人体内所处环境极为复杂,通过单一的改变材料某些性质很难使材料血液相容性得到根本性的改善。因此从仿生学角度通过接枝特殊分子诱导具有生理活性的血管内皮细胞黏附和生长,构建一种类似于天然血管壁模式的材料表面势必成为未来提高生物材料血液相容性的重要方向。     

In vitro polymerization of oxidized tau into filaments

Paired helical filaments (PHF) are abnormal neuronal polymers characteristic of Alzheimer's disease (AD). Although tau appears to be a major constituent of PHF, the mechanism for the polymerization of tau or its integration into PHF remains unknown. Here, we show that the oxidation of bovine tau in vitro induces an apparent dimerization of this protein and polymerization into filaments. These observations suggest that the oxidation of tau in vivo may contribute to the development of PHF in individuals with AD.     

Platelet factor 4 enhances fibrin fiber polymerization

In order to further examine the role of platelet secretory products on fibrin assembly, we have examined the effects of purified platelet factor 4 (PF4) on fibrin formation in vitro. The kinetics of fibrin formation and the structural properties of the resulting fibrin gel are strongly affected by PF4. In the presence of 7.6 ng/mL PF4, the fibrin fiber mass-length ratio increases from 3.5 X 10(12) daltons/cm. These results emphasize the importance of the local microenvironment in clot structure and its subsequent fate at the site of vascular injury.