Liquid-phase esterification of methacrylic acid with methanol catalyzed by cation-exchange resin in a fixed bed reactor:Experimental and kinetic studies

The kinetic behavior of esterification between methacrylic acid and methanol catalyzed by NKC-9 resin was studied in a fixed bed reactor.The reaction was conducted in the temperature range of 323.15 to 368.15 K with the molar ratio of reactants from 0.8 to 1.4 under certain pressure.The measurement data were regression with the pseudo-homogeneous(P-H),Eley-Rideal(E-R),and Langmuir-Hinshelwood(L-H)heterogeneous kinetic models.Independent adsorption experiments were implemented to gain the adsorption equilibrium constants of four components.Among the above three models,the L-H model exhibited the best fitting results.The stability of NKC-9 was evaluated by long-term running with the yield of methyl methacrylate no decrease during 3000 h operation.The structure and physicochemical properties of the new and used catalyst were performed by several characterizations including thermogravimetric analysis(TG),scanning electron microscope(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FT-IR)and so on.

The Effect of the Light Intensity and Light Distances of LED and QTH Curing Devices on the Hardness of Two Light-Cured Nano-Resin Composites

Background: Effective polymerization of the composite resin is essential to obtain long term clinical success and has a great importance obtaining improved mechanical properties. The purpose of this study was to measure the effect of the light intensity of LED and QTH curing devices in relation to the light distances, on the hardness (KHN) of two light cure nano-resin composite. Material and Methods: The top and bottom surfaces of the two nanofill composite specimens were evaluated. Two LED and two QTH light curing devices were used at nine different distances. Light intensity was measured with two radiometers placed at these same distances from the curing tip. 360 pvc dies were prepared with circular cavity 3 mm in diameter and 2 mm thick. The tested materials were placed in each cavity. The different light curing distances were standardized by adding pvc spacers dies at different height matching the different distances. Top and bottom surface microhardness were evaluated with a Micro Hardness Tester in knoop hardness numbers (Kg/mm2). Data were statistically analyzed using: Three-way ANOVA, Tukey and Pearsons test. Results: It was revealed that there was a statistically significant difference in microhardness between the composites (p < 0.001), between the nine distances (p < 0.001) and between the four light curing devices (p < 0.001). Increasing the distance of the light source from composite resin, the light intensity and the microhardness values at the top and bottom surface decrease. LED light curing devices produced a greater microhardness results at the bottom surface of the specimens. The Filtek Ultimate nanocomposite (3 m) showed highest microhardness values on the top and bottom surfaces, polymerized with all four curing devices and all nine distances compared to Empress Direct nano composite (Ivoclar vivadent). Clinical significant: Even with high power LED curing light, the distance between the tip of the light source and the restoration surface should be as close as possible. In this study, Filtek Ultimate showed better results (highest microhardness values) than Empress Direct.

Simulation of Cefoselis hydrochloride adsorption on macroporous resin in a fixed-bed column using orthogonal collocation

Adsorption operation is of great importance for separation and purification of semi-synthetic cephalosporin compounds in pharmaceutical industry. The adsorption dynamics of Cefoselis hydrochloride(CFH) on XR 920 C adsorbent in fixed bed was predicted by the model of modified film-pore diffusion(MFPD). The intraparticle diffusion equation and mass balance equation in fixed bed are discretized into two ordinary differential equations(ODEs) using the method of orthogonal collocation which largely improves the calculation accuracy. The MFPD model parameters including the pore diffusion coefficient(Dp), external mass-transfer coefficient(kf), and the axial dispersion(DL) were estimated. The kfvalue was calculated by the Carberry equation, in which the effective diffusion coefficient Dewas fitted based on Crank Model through experimental data. Moreover, three key operating parameters(i.e., initial adsorbate concentration; flow rate of import feed, and bed height of adsorbent) and the corresponded breakthrough curves were systematically studied and optimized. Therefore,this research not only provides valuable experimental data, but also a successfully mathematical model for designing the continuous chromatographic adsorption process of CFH.

改良everStick C&B纤维树脂粘接桥在老年切牙缺失修复中的疗效观察

目的:评价改良everStick C&B纤维树脂粘接桥在老年切牙缺失修复中的临床疗效。方法:纳入年龄65岁以上切牙缺失患者32例。其中上颌切牙缺失13例、下颌切牙缺失19例;缺牙1颗13例、缺牙2颗11例、缺牙3颗5例、缺牙4颗3例;基牙松动24例、基牙无松动8例。对所有患者均采取改良everStick C&B纤维树脂粘接桥修复治疗。分别于修复完成后6、 12、 18个月复查,复查内容包括修复体脱粘接、折断、颜色变化、缺损以及基牙松动、牙周组织炎症等6项指标。修复完成后6个月对患者进行满意度调查,调查内容包括治疗过程是否舒适、美观效果是否满意、修复后发音、咀嚼是否舒适等3项指标。结果:32位老年患者修复完成后6个月,6项指标均为A级。12个月,出现1例修复体缺损B级,2例基牙牙周组织炎症B级,其余均为A级。18个月,出现1例修复体缺损B级,3例基牙牙周组织炎症B级,其余均为A级。2例修复体缺损B级经过树脂充填后均达到A级。5例基牙牙周组织炎症B级经过牙周洁治后5~7 d均达到A级。患者满意度调查3项指标均为A级。结论:改良everStick C&B纤维树脂粘接桥在老年切牙缺失修复中临床疗效良好。

二硅酸锂基玻璃陶瓷单端树脂粘接桥修复个别前牙缺失的临床应用

目的探讨二硅酸锂基玻璃陶瓷单端树脂粘接桥修复个别前牙缺失的临床效果,为个别前牙缺失修复方式的选择提供参考。方法本研究已通过单位伦理委员会审查批准,并获得患者知情同意。选取42例单颌前牙缺失数量在两颗内的患者,采用二硅酸锂基玻璃陶瓷单端树脂粘接桥修复,修复后6个月、1年、2年、3年进行随访,评价美学、功能修复效果及牙周健康状况,并采用视觉模拟评分量表(VAS)调查患者的满意度。结果观察期间,42例二硅酸锂基玻璃陶瓷单端树脂粘接桥修复的患者中有1例3个月内连接体发生断裂,1例2年内发生脱粘;美学修复效果的等级均评定为A级;修复后牙周健康状况良好,基牙及桥体下的软硬组织无临床吸收现象,评价指标均为A级;患者总满意率为100%。结论对于个别前牙缺失,二硅酸锂基玻璃陶瓷单端树脂粘接桥可达到微创、固位牢靠、美观舒适和生物相容性好的修复效果,患者满意度高,在临床中可以考虑作为一种理想的修复方式。

Properties of a New Dental Photocurable Resin based on the Expanding Monomer and Threecomponent Photoinitiator System

The purpose of this study was to use. a three-component photoinitiation system comprising 1wt% CQ （camphorquinone）, 2wt% DMAEMA （2-（dimethylamino） ethyl meth acrylate） and 2wt% ph^2I^＋PF6^- （diphenyliodonium hexafluorophosphate） to initiate the copolymerization of the matrix resins which combine bisphenol-S-bis （3-methacrylate-2-hydroxy propyl） ether （BisS-GMA） with the expanding monomer unsaturated spiro orthoesters 2-methylene-l,4,6-tdspiro[4,4] nonane （MTOSN）, for minimizing the volumetric shrinkage that generally occurs during polymerization. It was hypothesized that MTOSN would expand volumetrically during polymerization under the three-component photoinitiator system and further reductions in volumetric shrinkage would be obtained. The performance study which consists of degree of conversion and condition of the ring-opening reactions of MTOSN, volumetric shrinkage and mechanical properties including tensile bond strength, compressive strength and Vicker＇s hardness were carried out respectively by Fourier transfer infrared, the dilatometer and the universal testing machine. The results supported that the dental composites based on the expanding monomer and three-component photoinitiator system engendered a greater decrease of volumetric shrinkage and better mechanieal properties.

Priming the tooth surface with chlorhexidine and antibacterial activity of resin cement

AIM: To evaluate the effect of priming the tooth surface with 2% chlorhexidine gluconate on antibacteria activity of resin cement. METHODS: Ten patients in whom a single missing tooth was present on both the right and left side in the upper or lower arch were selected. Two fixed partia dentures(FPDs) in each patient on the right and left side were planned. Each FPD was assigned either to the control or test group. In the control group, FPD was luted with resin cement and in the test group, the tooth surface was primed with 2% chlorhexidine gluconate before luting with resin cement. Bacteriological samples were collected at base line level, as the patient came to the outpatient department before the start of any treatment, 5 wk prior to cementation of FPD and at 13 wk(8wk after final cementation). Microbiological processing of all samples was done and the results were statistically analyzed. RESULTS: In the test group, a predominance of aerobic/facultative gram positive cocci rod was seen which indicates a healthy periodontal site, whereas in thecontrol group, a predominance of anaerobic gram negative rods was present which indicates an unhealthy periodontal condition. This is evident by the fact that the anaerobic bacteria percentage in the control sample is 57% and 15% in the test sample after 13 wk, whereas the aerobic/facultative bacteria percentage is 43% in the control sample and 85% in the test sample after 13 wk. The percentage of gram negative bacteria in the control sample is 61% and in the test sample is 20% after 13 wk, whereas the percentage of gram positive bacteria in the control sample is 39% and in the test sample is 80% after 13 wk. The shift from anaerobic gram negative bacteria to aerobic gram positive bacteria is clearly seen from the control to test sample after 13 wk. CONCLUSION: The present study demonstrated that priming the tooth surface with 2% chlorhexidine gluconate may enhance antibacterial activity of the resin cement.

ADSORPTION OF GOLD ON TBP EXTRACTING RESIN FROM HCI SOLUTION

Adsorption of gold on TBP extracting resin from HCI solution was researched. All the effects of factors, such as solution acidity, TBP content,tempo)uture, etc. , on adsorption equilibrium were discussed and the equilibrium equation was formulated. The breakthough time of adsorption process withfixed bed uns studied through experiment.

环氧树脂改性多异氰酸酯微胶囊的制备及其防砂性能

为提高疏松油田的采油率,研发高性能防砂是必须要采取的工艺措施,本论文通过二苯基甲烷二异氰酸酯多聚体(MDIP)与环氧树脂(E-51)反应,制备环氧树脂改性多异氰酸酯(EMP).通过物理化学法中复相乳液法对EMP进行微胶囊化.进行红外、核磁、扫描电镜等结构表征,证明EMP的成功制备.同时EMP微胶囊固砂液平均粒径为0.1359μm和动力学稳定指数(TSI)为0.468,表明该微胶囊的粒径分布均一,且体系稳定.在达到油井粉细砂固结要求的同时最环保和节约成本条件下,得到最佳固砂配方和条件下固结砂柱的抗压强度为6.563 MPa,渗透率为1476 mD,出砂量为6 mg,出砂率为0.006%,同时还具备良好的耐酸、耐盐、耐氧化性,显著提高油井采油率.

纳米银树脂粘结剂在牙齿畸形矫治中的抗菌效果及粘接性能分析

为探究纳米银树脂粘结剂在正畸固定矫治器使用中抗菌效用及粘接性能。以2-乙基己酸银为原料,适量添加至甲基丙烯酸叔丁基氨基乙酯(TBAEMA),制备质量分数为8%的银源溶液,然后将TBAEMA加入Clearfil SE Bond(CSB)树脂粘结剂,获得3组的纳米银树脂粘结剂,质量分数分别为0%、0.1%、0.2%Ag,采用1000 mW/cm 2强度光进行20 s照射,制作为6 mm×1 mm正畸固定矫正器试件。在无菌人工唾液中对试件进行浸泡,分别于浸泡后1、8、12周进行抗菌活性检测,观察表面细菌生物膜形成情况,计算聚合度,对比各组纳米银树脂粘结剂与牙本质的粘接强度。纳米银树脂粘结剂在正畸固定矫治器粘接使用中能够产生良好的长期抗菌效用,且对粘接性、聚合度影响不大,可在正畸固定矫治器粘接材料中应用。

树脂基陶瓷光学性能影响因素的研究进展

树脂基陶瓷是一种由大量无机填料及少量树脂基质组成的新型可切削材料,其结合了树脂的韧性及陶瓷的硬度,有着独特的机械性能,近些年来在口腔固定修复中的应用越来越广泛。树脂基陶瓷可分为树脂纳米陶瓷和树脂渗透陶瓷。不同类型的树脂基陶瓷由于材料组成及结构的区别,颜色和透光率有着较大的差异。在实际应用中树脂基陶瓷的光学性能还会受到多种因素例如:修复体厚度、表面处理方式、粘接剂颜色、基牙颜色、抛光及上釉等因素的影响。随着人们对口腔修复美学需求的日益增长,修复体的光学性能越来越受到重视,深入了解树脂基陶瓷的光学性能对于临床工作有着重要的意义。本文将根据现有文献分析树脂基陶瓷光学性能的影响因素,为临床工作提供一定的指导。

固定义齿修复后食物嵌塞的原因分析及扩隙树脂修复治疗

目的探讨固定义齿修复后食物嵌塞的原因,并对保留固定义齿扩隙树脂修复治疗的效果进行分析。方法选择100例固定义齿修复后出现食物嵌塞的病例,分析食物嵌塞的原因并采取相应的处理方法,对由于与健康邻牙接触不良而导致食物嵌塞者,采用保留固定义齿扩隙树脂修复法进行治疗。结果固定义齿与健康邻牙间接触不良是食物嵌塞的主要原因(70%)。随访3年,100例固定义齿修复后食物嵌塞患者的治疗有效率为100%。结论扩隙树脂修复法是固定义齿与健康邻牙接触不良的一种有效治疗方法。

前牙玻璃纤维强化复合树脂粘结桥的强度

目的 对前牙玻璃纤维强化复合树脂粘结桥的力学性能进行初步的探讨。方法 通过预制铜制标准模型 ,保证固位翼三维恒定的情况下 ,以Sinfony复合树脂制作不加纤维和加纤维的上中切牙粘结桥共 2 6例 ,在37± 1℃的蒸馏水中保存 10天后 ,在万能力学试验机上分别从切端顺牙长轴方向和舌侧垂直于牙长轴方向以1mm/min的速度加压 ,得出折裂力值。结果 由切端顺牙长轴方向垂直加力时 ,经纤维强化的粘结桥的折裂力值较未经强化的粘结桥的折裂力值出现了显著的提高 ,达到 4 97.4± 90 .3N ;舌侧垂直加力时 ,两组的折裂力值无显著性差别。结论 前牙玻璃纤维强化复合树脂粘结桥承受轴向力的能力显著增强 。

玻璃纤维强化复合树脂前牙粘结桥临床应用初探

目的 :探讨前牙玻璃纤维强化复合树脂粘结桥 (GFRC RBFPD)修复方法和评价短期临床效果。方法 :收集修复门诊 3 0名前牙缺失病例 ,缺失 1颗牙者 2 7例 ,缺失 2颗牙者 3例。其中基牙不需牙体预备的 16例 ,少量牙体预备的 14例。采用STICK预浸透玻璃纤维强化的Sinfony复合树脂制作粘结桥。应用All Bond 2树脂粘结材料粘结修复体。临床进行定期检查 ,全面评价使用效果。结果 :2 6例 6个月后临床复查 ,2 3例 (88.5 % )GFRC RBFPD不松动 ,修复体完好 ,无折断、缺损或过度磨耗 ,无明显着色 ,固位体边缘与粘结剂界面临床观察结合良好。 2例 (7.7% )在使用中出现脱粘 ,1例 (3 .8% )折断。 2 4例 18个月后临床复查 ,其中 3例 (12 .5 % )脱粘 ,3例 (12 .5 % )折断 ;基牙的探诊出血与对照牙比较均有显著性差别 (P <0 .0 5 )。结论 :GFRC RBFPD是一种微介入、无金属的固定修复方法 ,向患者提供了传统固定桥以外另一种固定修复方式。其支架强度和粘结强度需进一步提高 ,临床应用效果应长期观察。

口腔氧化锆陶瓷的粘接方法

背景:氧化锆陶瓷因具有良好的理化性能和生物相容性在口腔修复重建领域被广泛应用,但如何对氧化锆陶瓷表面进行改性,以提高修复体与牙体组织的粘接强度成为目前临床工作中的难点。目的:综述口腔氧化锆陶瓷的粘接方法。方法:应用计算机检索Pub Med数据库,检索关键词为"zirconia,silane coupling agent,resin cement,bonding"。结果与结论:通过化学摩擦硅涂层系统结合新型混合非功能性硅烷偶联剂对氧化锆瓷进行表面处理,利用小粒径(50μm)的含硅颗粒氧化铝粉末对氧化锆进行喷砂,形成含硅粒子的粗糙覆盖表层,此系统可降低传统喷砂对瓷边缘薄弱部位的损伤,提高修复体边缘密合度;新型混合非功能性硅烷偶联剂与陶瓷表面可形成稳定且高强度的硅氧烷键,其水解稳定性远高于传统的硅烷偶联剂,利用硅氧烷在界面处与聚合物交联形成的互穿网络体系,可更有效地将树脂共价接枝到硅烷表面,有效提高氧化锆陶瓷与树脂的粘接强度,为修复体提供足够的固位力,提高临床修复成功率。

酸碱树脂两步催化含酸油脂制备生物柴油

设计催化酯化脂肪酸和催化转酯化甘油三酯连续制备生物柴油过程,分别考察NKC-9催化酯化脂肪酸的能力及D261催化转酯化甘油三酯的能力,并利用模型化合物在固定床中依次进行酯化、转酯化,实现连续反应。实验表明:酯化与转酯化反应在理想条件下,转化率均高于95%,应用于连续制备效果较好,且可多次再生并重复利用。

复合树脂粘结桥支架优化设计研究

以基于STL的网格实体建模方法,设计了修复体、基牙、牙周膜、骨皮质,骨松质和牙槽骨的三维几何模型。借助有限元分析,将力学模型简化为弯扭变形,确定了初步支架设计方案。同时通过施加真实口腔载荷,对支架结构进行了进一步的验证和优化,得到基于传统支架的改良设计方案Ⅱ-M和创新支架设计方案Ⅲ-M。计算表明较纯树脂粘接桥,对危险域里的应力值,方案Ⅱ-M能平均降低22.50%,方案Ⅲ-M则可达到37.80%。证明优化后的支架加强效果明显,对修复体能起到很好的保护作用。

改良式固定型马里兰桥修复老年前牙缺失的临床效果观察

目的探讨运用改良式固定型马里兰桥修复老年患者前牙缺失的可行性,并对修复的方法设计、修复体制作过程及适应证进行总结。方法选择个别前牙缺失,存在不同程度邻牙松动、牙龈萎缩、牙根暴露等体征的老年患者24例,运用改良式固定型马里兰桥修复缺失牙,并对完成修复的病例随访3～5年。结果修复成功率为87.5%。24例患者有3例修复体脱落,需重新粘接;其余修复体未见明显松动。基牙无松动,桥体下方牙龈无明显红肿,患者对修复体的使用与外观效果均感满意。12例患者存在不同程度牙结石;2例患者存在舌侧轻度异物感,经过对症处理后效果满意。结论改良式固定型马里兰桥修复老年前牙缺失具有磨牙少、效果美观,并能同时固定松动牙邻牙等优点,修复效果可靠。但其远期效果有待进一步观察。

改良式烤瓷粘接桥的临床研究

目的研究改良式烤瓷粘接桥的修复效果。方法2000—2001年选择100例前牙或单个后牙缺失的患者,采取改良式烤瓷粘接桥修复。结果120个修复体中,15个松动脱落,5个有继发龋,8个有基牙变色。结论改良式烤瓷粘接桥是一种较好的修复方式,应严格选择适应证,合理设计修复体。

激光扫描结合逆向工程技术建立粘结桥的三维有限元模型

目的:建立一套简便、低成本的口腔修复体及相关牙体、牙周组织、骨组织的三维有限元建模方法。方法:制作包括双侧基牙和修复体桥体的石膏模型,采用线激光扫描仪扫描石膏模型,在逆向工程CAD软件Geomagic5.0中完成对扫描数据拼合,完成石膏模型的数字化过程,生成基础三维几何模型。在I-DEAS10NXSeries软件和Geomagic中对基牙及修复体三维模型设计后,在Geomagic5.0中,构建牙周组织及基牙对应区域牙槽骨结构,完成三维几何模型。在MSC.MarcMentat2003有限元分析软件中进行网格划分,并确定边界条件。将模型提交到Msc.Marc2003,对模型进行试计算。结果:建立了右下第二前磨牙、右下第一磨牙玻璃纤维强化复合树脂粘结桥(GFRC-RBFPD)及相关组织的三维几何模型与三维有限元模型。模型分为4个部分:粘结桥、基牙、牙周膜、牙槽骨(区分了骨硬板、皮质骨、松质骨3部分结构)。结论:基于三维激光扫描、逆向工程技术建立几何模型、利用有限元软件进行网格划分生成修复体及相关结构的三维有限元模型的方法是可行的,并极大的提高模型的几何相似性。