污染对氧化锆陶瓷剪切强度影响的研究

目的：研究污染对氧化锆陶瓷剪切强度的影响．以及清除这种污染的方法。方法：40个Al2O3颗粒喷砂处理过的氧化锆陶瓷片．分成5组,每组8个。其中一组不经任何处理为对照组,其余四组经唾液浸泡以及使用硅橡胶指示剂后．分别用75％乙醇冲洗、37％磷酸冲洗、水冲洗和喷砂的清洁方法处理。使用X射线能谱仪对各组陶瓷片进行表面化学分析。使用Fuji plus黏结材料与各组氧化锆陶瓷片黏结,水浴24h后测试其黏结剪切强度。结果：喷砂组的污染被有效清除．磷酸有一定的清除唾液污染的作用,而乙醇和水不能清除陶瓷表面的这两种污染。结论：在氧化锆陶瓷修复体的试戴过程中。污染显著地降低了氧化锆陶瓷与树脂类黏结剂的剪切强度,而进行喷砂处理是最有效的去除污染的方法。     

5种表面处理方法对锆-锆界面黏结强度的影响

目的 检测氧化锆-氧化锆界面经5种不同处理后之间的黏结强度,研究适用于口腔中氧化锆陶瓷表面的处理方式.方法 将未烧结的氧化锆陶瓷制作成剪切力样本100个.烧结后根据对其表面的处理方式不同分为以下5组:A、B、C、D、E组.将所有试件用超级黏结剂Super-bond黏结,比较各组剪切黏结强度.结果 4个实验组的剪切黏度强度值均明显高于对照组(P < 0.05).在各组之间两两比较中,除了B组与C组,D组与E组差异无统计学意义外,其他各组之间差异均具有统计学意义.结论 喷砂+30%硅溶胶+硅烷偶联剂或喷砂+30%硅溶胶+磷酸单体是最适合牙科氧化锆陶瓷的表面处理方法.     

硅烷偶联剂对陶瓷托槽与瓷面粘接性能的影响

目的研究硅烷偶联剂（CP）对陶瓷托槽与瓷面粘接性能的影响。方法120个烤瓷试件按不同瓷面处理随机分为3组：A组氧化铝喷砂处理;B组金刚砂车针打磨;C组9.6%氢氟酸酸蚀2min。再根据是否使用CP各分2小组,粘接剂为Trans-bondXT（3M）。托槽粘接后在37℃水浴条件下24h后冷热循环500次（5℃和55℃）,使用材料实验机检测粘接剪切强度,并统计粘接剂残留指数（ARI）。结果喷砂组和打磨组使用CP后平均抗剪切强度与未使用CP组比较差别无统计学意义（P〉0.05）;HF酸蚀＋CP＋3MUniteTM釉质粘接剂组的粘接剪切强度最高,与其余组比较有显著性差异（P〈0.05）。结论用金刚砂车针打磨或喷砂处理瓷面后,使用CP来粘接陶瓷托槽,黏接强度不确切;氢氟酸酸蚀瓷面后,再使用CP,同时结合LED光照下用光固化粘接剂,可获得陶瓷托槽与瓷面间满意的粘接强度,但瓷面破损的几率增加。     

氧化锆全瓷冠的实验研究进展

氧化锆全瓷材料因其良好的生物性能及力学性能在口腔中的应用快速增长。为达到好的美学效果常在其上进行饰瓷，然而强度较弱的饰面瓷及其与氧化锆的粘结界面是临床失败的主要部位，因而也成为近期的研究热点。近年的研究在模拟临床条件和失败模式方面取得了很大的进步，作者对其进行综述。     

金瓷修复体的制作工艺对其颜色的影响

金瓷修复体因其兼具金属全冠的强度和瓷全冠的美观,而且还具有耐磨耗、菌斑不易附着、抗腐蚀性强的特点,是一种较为理想的修复体.但其颜色有时未能完全反映天然牙颜色而影响修复效果.影响金瓷修复体颜色的因素很多,其中制作工艺对修复体颜色会有明显影响.制作过程中,遮色瓷和体瓷厚度、瓷表面粗糙度、烧结次数等制作工艺均对其颜色有影响,现就制作工艺对金瓷修复体颜色影响的研究现况做一综述.     

陶瓷托槽与瓷面粘接实验研究

目的:研究三种不同釉质粘接剂对陶瓷托槽与瓷修复体粘接剪切强度的影响.方法:使用氢氟酸酸蚀结合硅烷偶联剂处理瓷面,再分别采用三种不同釉质粘接剂粘接陶瓷托槽,在37 ℃水浴24 h后冷热循环500次(5 ℃-55 ℃),测量其粘接剪切强度,并统计粘接剂残留指数.结果:粘接剂种类对粘接剪切强度有影响,光固化和双糊剂型化学固化粘接剂粘接强度优于非混合型化学固化粘接剂.结论:三种粘接剂在此种瓷表面处理方式下均可用于陶瓷托槽与瓷面的粘接.     

Ni-Cr合金烤瓷冠桥崩瓷后树脂修补的研究

目的:探讨崩瓷树脂修复中,ClearfilTMSE BOND~和Lute粘结剂的剪切粘结强度的差异。方法:镍铬(Ni-Cr)合金试件、烤瓷试件、新鲜离体上中切牙、烤瓷熔附金属全冠共60例,分6组,每组10例。1组:Ni-Cr合金 Clearfil SE BOND 复合树脂;2组:烤瓷 Clearfi SE BOND 复合树脂;3组:Ni-Cr合金 Lute 复合树脂;4组:烤瓷 Lute 复合树脂;5组:牙釉质 Durafill Bond 复合树脂;6组:烤瓷熔附Ni-Cr合金。1~5组修复材料均为Durafill vs口腔光固化复合树脂。镍铬合金和烤瓷试件表面分别用ClearfilTMSE BOND~、Lute粘结剂粘结复合树脂,离体牙牙釉质用常规粘结剂粘结复合树脂,粘结剂按产品说明书使用,复合树脂用Durafill vs。经37℃恒温水浴24h后做剪切实验,进行统计分析。结果:ClearfilTMSE BOND~对镍铬合金与树脂的剪切粘结强度明显高于Lute粘结剂(P<0.05),对烤瓷的剪切粘结强度两者差异无统计学意义(P>0.05),且这3组和离体牙釉质与树脂的剪切粘结强度差异无统计学意义(P>0.05)。结论:无需酸蚀或喷砂,ClearfilTMSE BOND~粘结剂对镍铬合金与树脂的粘结牢固有效。     

不同处理方法对金属与复合树脂粘结强度影响的研究

目的研究不同处理方法对镍铬合金与树脂修复材料粘结强雅的影响。方法镍铬合金试件40个,随机分为4组。分别用不同方法进行粘结并做剪切强度测试。结果alloy primer组与激光组处理后,强度显著高于对照组（9P〈0.05）;而喷砂组所获得的剪切强度与对照组差异无统计学意义（P〉0.05）;alloy primer组和激光组之间差异无统计学意义（P〉0.05）。20倍OPTON体视显微镜下观察到alloy primer组和激光组各有2例试件呈现混合性破坏。结论采用alloy primer和激光对镍铬合金进行处理,可增加金属与复合树脂间的剪切强度。     

CePO4包覆Mg-PSZ复合粉体的制备

氧化锆陶瓷体系因其突出的力学和生物学性能,开始成为国内外口腔生物材料开发的热点瓷材。但是,为了满足临床需求,烧结体难加工问题是其中之一。由于氧化锆陶瓷极高的抗弯强度和断裂韧性,无法直接采用口腔CAD/CAM系统对其进行磨削加工,目前,临床应用的主要是二步烧结的氧化锆陶瓷。二步烧结的氧化锆陶瓷虽然同时满足了加工工艺与理化性能的需求,但是从氧化锆原材料到最终氧化锆陶瓷修复体的生产加工工艺非常复杂,而且需要解决烧结收缩的问题[2,3]。本研究通过将软相磷酸铈包覆在高强度、高韧性的氧化锆表面,解决陶瓷材料的难加工问题,试图探索即能满足口腔临床要求又可以直接用于口腔CAD/CAM系统的、一次烧结牙科陶瓷材料的制备方法,为氧化锆基全瓷材料在口腔临床的广泛应用打下基础。     

不同表面处理方式对氧化锆与树脂水门汀粘接强度的影响研究

目的分析不同表面处理方式之间氧化锆与树脂水门汀之间粘接强度的差异性。方法制作60个氧化锆陶瓷试件,随机分为3组,分别进行金刚砂车针打磨联合硅烷耦联剂(即Ⅰ组)、Er:YAG激光蚀刻联合硅烷耦联剂(即Ⅱ组)以及硅涂层联合硅烷耦联剂(即Ⅲ组),每组选取15个试件经过Rely XTM Unicem粘固后测试剪切粘接强度,另外5个利用利用电子显微镜观察表面破坏形式。结果Ⅲ组剪切粘结强度(6.79±0.98MPa)显著高于Ⅰ组(4.23±0.67MPa)和Ⅱ组(5.07±0.85MPa),P<0.05,存在明显差异;各组均以界面破坏为主,Ⅱ组兼有内聚破坏,Ⅲ组各种破坏均可见。结论表面处理方式能够影响氧化锆与树脂水门汀的粘接强度,优化表面处理方式极为重要。     

New nano-sized Al2O3-BN coating 3Y-TZP ceramic composites for CAD/CAM–produced all-ceramic dental restorations. Part I. Fabrication of powders

Partially sintered 3 mol % yttria-stabilized tetragonal zirconium dioxide (ZrO₂, zirconia) polycrystal (3Y-TZP) ceramics are used in dental posterior restorations with computer-aided design–computer-aided manufacturing (CAD/CAM) techniques. High strength is acquired after sintering, but shape distortion of preshaped compacts during their sintering is inevitable. The aim of this study is to fabricate new machinable ceramic composites with strong mechanical properties that are fit for all-ceramic dental restorations. Aluminum oxide (Al₂O₃)-coated 3Y-TZP powders were first prepared by the heterogeneous precipitation method starting with 3Y-TZP, Al(NO₃)₃ · 9H₂O, and ammonia, then amorphous boron nitride (BN) was produced and the as-received composite powders were coated via in situ reaction with boric acid and urea. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to analyze the status of Al₂O₃-BN on the surface of the 3Y-TZP particles. TEM micrographs show an abundance of Al₂O₃ particles and amorphous BN appearing uniformly on the surface of the 3Y-TZP particles after the coating process. The size of the Al₂O₃ particles is about 20 nm. The XRD pattern shows clearly the peak of amorphous BN among the peaks of ZrO₂.     

Shde-eye-EX测量颜色时稳定性研究

目的研究用松风Shde-eye-EX电脑比色仪测量比色板颜色时的稳定性.方法用松风Shde-eye-EX电脑比色仪测量Vintage Hal0(松风)、VITA及Vita 3D-master比色板的每个比色片,每片测量9次,分别用松风Shade-eye-EX自然牙及瓷牙测量模式测量,3人次每人重复完成一次.结果(1)瓷牙测量模式测量时,Shade-eye-EX对Vita 3D-master、VITA及Vintage Hal0(松风)比色板测量结果绝大多数表现为同一数字结果.(2)测量比色板时Shade-eye-EX应用瓷牙测量模式较自然牙测量模式准确率高.(3)在两种模式测量比色板下,同一次测量的三次按键时,测量头位置保持不动,结果显示数字的同一性较高;测量头位置每次都动时,结果显示数字变动性较大;(4)无论采取任何方式,三种比色板的结果总会有一些结果显示不同.结论松风Shde-eye-EX电脑比色仪测量颜色时,测量模式与需测量对象相符,否则,结果会有很大的差异,甚至比色失败.     

Internalization and distribution of three α1-adrenoceptor subtypes in HEK293A cells before and after agonist stimulation

AIM: To examine the subcellular distribution of the 3 alpha1-adrenoceptor (alpha1-AR) subtypes and their internalization and trafficking upon agonist stimulation in human embryonic kidney 293A cells. METHODS: Confocal real-time imaging, enzyme linked immunosorbent assay (ELISA) and whole cell [3H]-prazosin binding assay were applied to detect the distribution and localization of the 3 alpha1-AR subtypes. RESULTS: alpha1A-AR was found both on the cell surface and in the cytoplasm; alpha1BAR, however, was predominantly detected on the cell surface, while alpha1D-AR was detected mainly in the intracellular compartments. After stimulation with phenylephrine, localization changes were detected by confocal microscopy for alpha1A- and alpha1B-AR,but the localization of alpha1D-AR were unaffected. Phenylephrine stimulation promoted a more rapid internalization of alpha1B-AR than alpha1A-AR. alpha1D-AR internalization was detected only by ELISA. Whole cell [3H]-prazosin binding assay showed that alpha1A-AR functional receptors were detected both on the cell surface and in the cytoplasm; alpha1B-AR, however, were detected predominantly on the cell surface, while alpha1D-AR were detected mainly in intracellular compartments. Phenylephrine stimulation promoted internalization of alpha1A- and alpha1B-AR. CONCLUSION: Phenylephrine stimulation induced changes in the localization of the 3 alpha1-AR.     

Real-time detection of α1A-AR movement stimulated by phenylephrine in single living cells

Aim： To investigate the movement of α1A-adrenergic receptors（α1A-AR） stimulated by agonist, phenylephrine （PE）, and the dynamics of receptor movement in real time in single living cells with millisecond resolution. Methods： We labeled α1A-AR using the monoclonal, anti-FLAG （a kind of tag） antibody and Cy3-conju- gated goat anti-mouse IgG and recorded the trajectory of their transport process in living HEK293A cells stimulated by agonist, PE, and then analyzed their dynamic properties. Results： The specific detection of α1A-AR on the surface of living HEK293A-α1A cells was achieved, α1A-AR internalize under the stimulation of PE. After the cells were stimulated with PE for 20min, apparent colocalization was found between α1A-AR and F-actins. After 40 rain stimulation of PE, trajectories of approximate linear motion in HEK293A-α1A cells were recorded, and their velocity was calculated. Conclusion： The specific labeling method on the living cell surface provides a convenient means of real-time detection of the behavior of surface receptors. By this method we were able to specifically detect α1A-AR and record the behavior of individual particles of receptors with 50 ms exposure time in real time in single living cells.     

Selective blockade and recovery of cell surface alpha 2-adrenergic receptors in human erythroleukemia (HEL) cells. Studies with the irreversible antagonist benextramine

alpha 2-Adrenergic receptors are present on human erythroleukemia (HEL) cells, both on the cell surface and in a sequestered compartment. In the current study we show that benextramine, a hydrophilic irreversible antagonist, can be used to investigate alpha 2-adrenergic receptor compartmentation in these cells. In membranes prepared from HEL cells, benextramine competed for all alpha 2-adrenergic receptors ( [3H]yohimbine sites). In intact cells, at 4 degrees, benextramine exhibited a biphasic competition curve for alpha 2-adrenergic receptors, with EC50 values of approximately 10 microM and greater than 1 mM for the high and low affinity components, respectively. We propose that the alpha 2-adrenergic receptors preferentially blocked by benextramine are those on the surface of the cell, whereas those with low affinity are sequestered receptors because: 1) only epinephrine-accessible sites [i.e., cell surface sites; McKernan et al., Mol. Pharmacol. 32:258-265 (1987)] are removed by prior treatment of cells with benextramine, 2) a preparation enriched with surface membranes is also enriched in receptors with a high affinity for benextramine; and 3) after blockade of cell surface receptors (54 +/- 6% of total sites, n = 7) by benextramine, the ability of the alpha 2-adrenergic agonists epinephrine and UK-14,304 to inhibit forskolin-stimulated cAMP accumulation is lost. The latter result implies that only cell surface and not sequestered receptors are functionally coupled to adenylate cyclase. The return of receptors from the sequestered compartment to the cell surface and the recovery of alpha 2-adrenergic receptor function were measured after HEL cells were treated with benextramine (50 microM for 1 hr at 4 degrees). The recovery of receptor binding (t1/2 = 25 min) was somewhat slower than the recovery of function (t1/2 approximately 8 min). This is consistent with the existence of "spare receptors" and also suggests that the sequestered compartment of alpha 2-adrenergic receptors can rapidly exchange with those on the surface. When all alpha 2-adrenergic receptors were blocked by incubation of HEL cells with benextramine for 1 hr at 37 degrees, repopulation of surface and sequestered receptors was much slower (t1/2 = 9 hr for recovery of total receptors). Surface receptors recovered even more slowly than did total cellular receptors consistent with the idea that alpha 2-adrenergic receptors must traverse through intracellular locations before insertion into the cell surface.(ABSTRACT TRUNCATED AT 400 WORDS)     

Human xenoreactivity is reduced in mice bearing porcine antisense alpha(1,3) galactosyltransferase cDNA.

AIM: To explore the effect of antisense alpha(1,3) galactosyltransferase alpha(1,3) GT cDNA on production of Gal alpha(1,3) Gal (Gal epitope) xenoantigen in vivo. METHODS: Transgenic mice bearing the porcine antisense alpha(1,3) GT cDNA (nt 1alpha-640) were generated by pronuclei microinjection method. The integration of transgene was identified by PCR and Southern-blot analysis. The expression of murine alpha(1,3) GT was characterized by RT-PCR. Morphology of the spleen was examined by histological technique. Gal epitope was detected by immunofluorescent analysis. Binding of human natural xenoantibodies (IgM and IgG) and complement (C3c) to cells from mice was determined by flow cytometric assay. RESULTS: Transgenic mice bearing the porcine antisense alpha(1,3) GT cDNA were born healthy and developed normally. However, necrosis occurred in the spleen of some mice heterozygous for transgene. Cell surface Gal epitope in transgenic heterozygotes was evidently reduced. Substantially less (30 % - 60 %) xenoantibodies in human serum bound to cells from a variety of tissues of transgenic heterozygotes compared with wild-type controls. Consequentially, human complement activation on cells from these mice was reduced by 40 % - 50 %. CONCLUSION: Human xenoreactivity could be effectively reduced by inhibiting the expression of alpha(1,3) galactosyltransferase with an antisense gene.     

Macromolecular prodrugs. VIII. Synthesis of polymer-gemfibrozil conjugates

Gemfibrozil is covalently linked to two similar polymers: poly[alpha,beta-(N-2-hydroxyethyl-DL-aspartamide)] and poly[alpha,beta-(N-3-hydroxypropyl-DL-aspartamide)]. The synthesised polymer drug conjugates differ in average molecular mass, type of covalent bonding, length of spacer, drug-loading and solubility.     

Characterization of cAMP accumulation mediated by three α1—adrenoceptor subtypes in HEK293 cells

AIM:To investigate the characterization of cAMP response mediated by α1-adrenoceptor (α1-AR) subtypes in HEK293 cells. METHODS:(1) Full-length cDNA encoding three α1-AR subtypes were transfected into HEK293 cells by the calcium phosphate precipitation method, respectively. (2) The densities of α1-AR subtypes expressed in HEK293 cells were measured by radioligand binding assay. (3)cAMP accumulation was measured by [^3H] adenine prelabeling method. RESULTS: (1)Activation of each of three subtypes resulted in an increase of cAMP accumulation in HEK293 cells in a dose-dependent manner, which was inhibited by selective α1-AR antagonist prazosin. (2) Comparing the pharmacological property, the maximal responses of α1A-AR to agonists were the most potent, while the sensitivity of α1-AR subtypes to norepinephrine(NE) was the highest. CONCLUSION: Each of three α1-AR subtypes can mediate cAMP accumulation in HEK293 cell line, and there are differences in pharmacological property.     

Interaction between antidepressants and alpha 1-adrenergic receptor antagonists on the binding to alpha 1-acid glycoprotein

alpha 1-Receptor antagonists and antidepressant agents are basic (cationic) drugs that are known to bind to alpha 1-acid glycoprotein (AAG). Since these drugs are frequently co-administered and since they bind to the same protein, this investigation was designed to evaluate the "in vitro" ability of antidepressants, alpha 1-receptor antagonists, and propranolol to displace [3H]imipramine and [3H]prazosin from the AAG binding site(s). Equilibrium dialysis was employed. Of the drugs studied, the following order of potency in displacing [3H]prazosin was found: trazodone greater than prazosin greater than doxazosin greater than propranolol greater than doxepin = amoxapine = trimazosin = amitriptyline greater than imipramine greater than nortriptyline = desipramine = nomifensine greater than bupropion = maprotiline. [3H]lmipramine binding from AAG was displaced with the following potency order: prazosin greater than imipramine greater than propranolol greater than doxazosin greater than nortriptyline greater than desipramine greater than trimazosin. Tricyclic antidepressants produced similar degrees of displacement of both [3H]imipramine and [3H]prazosin from AAG; whereas, alpha 1-receptor antagonists were more effective displacers of [3H]prazosin than of [3H]imipramine. Furthermore, the demethylated metabolites of imipramine and amitriptyline were less potent displacers than their parent compounds. These results suggest that more than a single binding site may be available for binding to AAG and that hydrophobic bonding is important in the binding of drugs to AAG.     

Alpha 1-adrenoceptor subtypes in bovine prostate.

The object of this study was to examine the existence and characteristics of alpha 1-adrenoceptor subtypes in the bovine prostate using the radioligand binding assay method. [3H]Prazosin was used as the radioligand and its binding sites in bovine prostate were classified into two subtypes. One subtype showed a high affinity (alpha 1High, Kd: 101.1 pM and Bmax: 11.8 fmol (mg protein)-1) and the other had a low affinity (alpha 1Low, Kd: 3371.4 pM and Bmax: 50.5 fmol (mg protein)-1). Although the same pKi values of clorethylclonidine, p-aminoclonidine, benoxathian and dibenamine to both alpha 1High and alpha 1Low binding sites in bovine prostate tissue were observed, other alpha 1 antagonists used in this study had different pKi values for the two alpha 1-adrenoceptor subtypes. The existence and binding characteristics of alpha 1-adrenoceptor subtypes in bovine prostate were clarified. It is possible that agents selective for one site may contribute to the development of better drugs for the treatment of bladder outlet obstructions of men with benign prostatic hyperplasia.