自制IPS-Empress2铸瓷快速包埋材料的膨胀特性研究

IPS—Empress2铸瓷是国内外广泛应用的全瓷修复系统。为取代昂贵的进口专用包埋材料，国内已自制出与之相配套的快速包埋材料。本文研究的是其最关键的膨胀特性。采用千分尺位移计和热机械分析仪，分别测量了进口专用快速包埋材料和自制快速包埋材料的凝固膨胀及热膨胀性能，进行了统计分析和比较。结果显示，进口专用快速包埋材料的凝固膨胀率、热膨胀率和总膨胀率分别为0．858％、1．11％和1．17％；自制包埋材料的上述指标分别为0．798％、1．09％和1．16％，三项指标均无统计学差异，表明自制快速包埋材料的膨胀性能指标接近IPS—Empress2专用快速包埋材料，能满足IPS—Empress2铸瓷精密铸造的要求。     

松质骨支架的制备及结构特征观察

目的研究猪松质骨支架结构特征。方法采用物理化学方法对猪松质骨进行处理得到猪松质骨支架,采用扫描电子显微镜(SEM)观察材料的结构、图像分析测量孔径,液体静力称重法测量材料的孔隙率,DDW-100型万能实验机进行材料抗压测试。结果猪松质骨支架外观呈乳白色、透光、无异味,维持原有形态并有一定的强度;骨块呈蜂窝状多孔结构,表面孔隙与深层孔隙相连通;扫描电镜观察材料表现为三维多孔网状结构,孔隙均匀且孔隙相互连通;孔径为(387.54±21.60)μm,孔隙率为78.26%±2.01%,最大抗压强度和抗压力分别为25MPa和12N。结论猪松质骨支架具有骨组织工程支架材料结构特征。     

应用三维打印成型技术制备个体化多孔纯钛植入体的研究

三维打印(3DP)成型技术适合成型形状复杂、结构精细的个体化多孔医用生物植入材料,能满足不同患者的不同需求。本文应用3DP成型技术制备直径为25mm×20mm的多孔纯钛植入体生柸,于500℃真空脱粘后,在氩气保护下烧结至1 300℃,利用扫描电镜(SEM)观察其孔径大小介于50～150μm,其孔隙率、体积密度、维氏硬度、抗压强度及弹性模量测试结果分别为(44.26±2.43)%、(2.59±0.81)g/cm3、134.2～151.6、(61.2±3.2)MPa、(3.25±1.08)GPa。结果表明,3DP成型技术在制备个体化多孔纯钛植入体方面有着广阔的应用前景。     

内窥镜活检组织包埋方法的改良

内窥镜目前在我国各级医院较为普及 ,作内窥镜检查的人也不断增加 ,我院每年作病检的内窥镜的例次占全年总病检例次的 2 6 9%～ 32 5 % ,最多者为胃镜 ,由于取材方法及部位较固定的特点 ,我们对传统包埋方法进行了改良 ,使用镶嵌法及一片法包埋和切片 ,使用 8年多以来 ,效果较好 ,现介绍如下。1　材料与方法1.1　材料　纤维内窥镜取材为芝麻大小至米粒大小的活检组织。熔点为 5 6℃～ 5 8℃的生物切片石蜡。1.2　方法1.2 .1　包埋前先将融化的石蜡液倒入包埋框 ,然后以 0 5ｃｍ的间距 ,插入较薄的金属片 ,待石蜡冷却凝固后 ,即成为可使用…     

可塑型生物活性骨修复材料的制备及性能表征

背景：国外研制的可注射性硫酸钙骨替代材料具有操作简便、生物相容性好、能够注射入骨缺损处、原位固化、适应骨缺损进行塑形等优点,但价格昂贵。 目的：研究以α-半水硫酸钙为主要成分可塑型骨修复材料的最佳制备参数,并对其性能进行研究和表征。 方法：使用汽热法制备粉末,将α-半水硫酸钙粉末与透明质酸钠固化液分别按液固比0.2,0.25,0.3,0.35,0.4 mL/g混合,制备可注射人工骨材料,检测其注射性能、凝固时间和抗压强度;根据检测结果选择最佳液固比0.3 mL/g,在α-半水硫酸钙粉末中分别加入质量分数为1%,2%,3%的二水硫酸钙粉末,制备可注射人工骨材料,检测其注射性能、凝固时间和抗压强度,同时检测可注射骨材料的生物安全性。将液固比为     0.3 mL/g并加入2%二水硫酸钙制备的可注射人工骨材料植入巴马小型猪胸骨缺损模型,植入后8,16,24周进行组织学观察。 结果与结论：α-半水硫酸钙粉末与透明质酸钠固化液液固比为0.3 mL/g,加入质量分数2%二水硫酸钙粉末制备的可注射人工骨材料,初凝时间为4.0-5.0 min,终凝时间为8.0-9.0 min,抗压强度(8.93±0.23) MPa,具备良好的注射性能,符合临床要求的凝固时间及作为非负重骨缺损修复要求的抗压强度,并具有良好的生物安全性。动物植入实验表明可注射人工骨材料通过自身降解,可为新生骨的爬行替代提供空间,具有一定的成骨活性。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

三维打印制备钛/羟基磷灰石复合体及功能梯度材料CSCD

背景:传统压模成形法制备的钛/羟基磷灰石复合材料结构简单,自动化程度较低,难以控制材料的孔隙率及孔径,不能满足多样化需求。目的:评价三维打印成型技术制备钛/羟基磷灰石复合体及功能梯度材料的可行性。方法:设计钛/羟基磷灰石复合体为直径25mm、高度15mm的圆柱体,功能梯度材料为直径25mm,上层5mm的钛粉末层,下层5mm钛/羟基磷灰石粉末层的圆柱体CAD模型。利用三维打印技术制备钛/羟基磷灰石复合体及功能梯度材料并进行烧结。观察烧结完成后钛/羟基磷灰石复合体和钛/羟基磷灰石功能梯度材料的显微结构,并行X射线衍射分析和抗压强度检测。结果与结论:烧结后的钛/羟基磷灰石复合体及功能梯度材料试件均匀无收缩和变形。钛/羟基磷灰石复合体形成紧密结晶体,孔径为50-150μm。钛和羟基磷灰石在烧结中发生了化学反应,生成物包含Ca3(PO4)2、CaTiO3、TiO2和CaO,其抗压强度为(184.3±27.1)MPa。烧结后钛/羟基磷灰石功能梯度材料在微观结构下可见不同材料间较为清晰的分界线,具有梯度结构。表明三维打印技术制备钛/羟基磷灰石复合体及功能梯度材料的微观结构和力学性能可满足医用生物植入材料的要求。     

冷冻干燥法制备聚乳酸多孔支架

冷冻干燥法制备聚乳酸(polylactic acid,PLA)多孔支架材料。将0.5 g PLA干燥24 h后加入到4 mL有机溶剂(1,4-二氧六环/二氯甲烷,v/v)中,按体积比分为3组(n=5)(A组,95:5;B组,90:10;C组:85:15)混合。冷冻干燥箱内冷冻干燥24 h,对其表面形貌、孔隙率、抗压强度以及细胞毒性进行检测。扫描电镜显示PLA支架内部孔隙分布均匀,孔隙率在(68.97±0.12)%～(73.75±0.48)%之间,差异有统计学意义(P0.05);抗压强度在(2.90±0.53)～(4.11±0.05) MPa之间,差异有统计学意义(P0.05);体外细胞毒性检测结果显示,材料浸提液不影响细胞的增值,表现出良好的细胞相容性。冷冻干燥法能制备出符合骨组织要求的PLA多孔支架材料。     

不同烧结温度下三维打印成型多孔钛植入体的实验研究

目的 评价三维打印成型技术(3DP)用于多孔钛植入体制备的可行性,研究不同烧结温度对其组织结构和力学性能的影响.方法 设计试件大小为25×20 mm圆柱体,设定每层的黏结面积为80％.选择纯度98.5％、颗粒直径约75 μm的钛粉为原料,聚乙烯醇粉作为黏结剂,聚乙烯吡咯烷酮粉作为辅助黏结剂.通过三维打印获得多孔钛植入体试件初胚,在氩气保护下,将试件分别烧结至1 200、1 300、1 400℃;对烧结完成的试件进行性能检测,包括孔隙率、显微硬度、扫描电镜观察试件的显微结构、抗压强度及弹性模量.结果 最终获得的多孔钛植入体试件,其收缩均匀、无明显变形、细节清晰、肉眼可见排列整齐的微孔结构、表面无裂纹,呈现金属光泽.在1 200、1 300、1 400℃的烧结温度下,孔隙率分别为(65.01±1.03)％、(46.73±0.73)％、(41.06±0.31)％,显微硬度为115.2±0.6、148.6±1.1、182.8±2.1,弹性模量为(5.9±0.5)、(16.2±0.9)、(34.8±1.5) GPa,抗压强度为(81.3±4.3)、(135.4±8.5)、(218.6±7.1)MPa.扫描电镜观察其孔隙相互连通成三维网状结构.结论 证实了应用三维打印成型技术制备多孔钛植入体的可行性,得到的多孔钛植入体具有与骨组织相匹配的良好的生物力学相容性.     

钙磷生物陶瓷多孔骨修复材料的制备*

以适量的Mg(H2PO4)2-(NaPO3)6为粘结剂,HA和-TCP粉末为原料,用有机泡沫浸渍法制备钙磷多孔生物陶瓷坯体,并在850℃烧成,探索在较低烧结温度下制备钙磷多孔生物陶瓷的工艺。采用X射线衍射(XRD)、扫描电镜(SEM)、能谱(EDS)等方法对多孔生物陶瓷的物相组成、显微结构、物理性能进行了分析。烧成后的钙磷生物陶瓷多孔支架主要由-TCP、-Ca2P2O7和CaO-MgO-Na2O-P2O5磷酸盐玻璃组成。烧结过程中,HA发生了向-TCP的转化,部分-TCP转化为-Ca2P2O7。多孔支架具有良好三维连通性的孔隙结构,孔径为200～500m,孔隙率达81%,抗压强度为1.1～1.5MPa。     

Demineralized bone matrix/polylactic acid produced through supercritical carbon dioxide and its properties

目的:以聚乳酸(PLA)为塑型剂,通过超临界二氧化碳(SC-CC2)合成法,将脱矿骨基质(DBM)构建成三维多孔组织工程骨材料,并选取最适复合分子量及最适复合比例,为骨库大量骨皮质不能被有效利用提供一种有效的解决办法.方法:取不同重均分子量的PLA,利用SC-CO2合成法制备多孔材料,通过孔隙率、生物力学性能评价,筛选出与DBM复合的最适分子量;将DBM与PLA按1/9、2/8、3/7、4/6、5/5、6/4、7/3质量比均匀混合,相同方法制备一系列复合多孔材料,通过孔隙率、生物力学性能、体外细胞毒性、扫描电镜观察,选择最适的DBM/PLA复合比例.结果:5万、10万、50万重均分子量PLA支架材料孔隙率分别为65.39％、76.46％、85.52％,10万重均分子量PLA支架材料抗压强度及弹性模量为264.03及49.71MPa,优于5万及50万重均分子量PLA; DBM与PLA不同比例复合,随着DBM含量的增加材料孔隙率逐渐变大,力学性能逐步下降,细胞毒性逐渐降低,当DBM含量为60％时,材料的孔隙率为79.71％,抗压强度及弹性模量为108.72及13.82MPa,细胞毒性为0级或1级,扫描电镜观察材料混合均匀,结合致密,材料孔隙分布均匀.结论:10万重均分子量的PLA更适合与DBM进行复合;6/4为DBM/PLA的最佳复合比例.     

Study of a hydraulic dicalcium phosphate dihydrate/calcium oxide-based cement for dental applications

By mixing CaHPO(4) x 2H(2)O (DCPD) and CaO with water or sodium phosphate buffers as liquid phase, a calcium phosphate cement was obtained. Its physical and mechanical properties, such as compressive strength, initial and final setting times, cohesion time, dough time, swelling time, dimensional and thermal behavior, and injectability were investigated by varying different parameters such as liquid to powder (L/P) ratio (0.35-0.7 ml g(-1)), molar calcium to phosphate (Ca/P) ratio (1.67-2.5) and the pH (4, 7, and 9) and the concentration (0-1 M) of the sodium phosphate buffer. The best results were obtained with the pH 7 sodium phosphate buffer at the concentration of 0.75 M. With this liquid phase, physical and mechanical properties depended on the Ca/P and L/P ratios, varying from 3 to 11 MPa (compressive strength), 6 to 10 min (initial setting time), 11 to 15 min (final setting time), 15 to 30 min (swelling time), 7 to 20 min (time of 100% injectability). The dough or working time was over 16 min. This cement expanded during its setting (1.2-5 % according to Ca/P and L/P ratios); this would allow a tight filling. Given the mechanical and rheological properties of this new DCPD/CaO-based cement, its use as root canal sealing material can be considered as classical calcium hydroxide or ZnO/eugenol-based pastes, without or with a gutta-percha point.     

Effect of added gelatin on the properties of calcium phosphate cement

This study investigates the effect of gelatin on the setting time, compressive strength, phase evolution and microstructure of calcium phosphate cement. The composite cement powder (about 18 wt% gelatin, and 82 wt% alpha-tricalcium phosphate) was prepared from the solid compound obtained by casting a gelatin aqueous solution containing alpha-tricalcium phosphate. 5 wt% of CaHPO(4) x 2H(2)O were added to the powder before mixing with the liquid phase. Two cement formulations were prepared using two different liquid/powder ratios, and their properties compared with those of control samples, prepared without gelatin. The final setting time increases from 10 min to more than 45 min when the L/P ratio increases from 0.3 to 0.4 ml/g. The presence of gelatin accelerates the setting reaction, and improves the mechanical properties of the cements. The compressive strength increases with the setting reaction up to 10.7-14.0 MPa for the gelatin cements, whereas the control samples exhibit much lower values. The improved mechanical properties of the composite cements with respect to the controls can be related to their reduced total porosity and more compact microstructure.     

Microarchitectural and mechanical characterization of oriented porous polymer scaffolds

Biodegradable porous polymer scaffolds are widely used in tissue engineering to provide a structural template for cell seeding and extracellular matrix formation. Scaffolds must often possess sufficient structural integrity to temporarily withstand functional loading in vivo or cell traction forces in vitro. Both the mechanical and biological properties of porous scaffolds are determined in part by the local microarchitecture. Quantification of scaffold structure-function relationships is therefore critical for optimizing mechanical and biological performance. In this study, porous poly(L-lactide-co-DL-lactide) scaffolds with axially oriented macroporosity and random microporosity were produced using a solution coating and porogen decomposition method. Microarchitectural parameters were quantified as a function of porogen concentration using microcomputed tomography (micro-CT) analysis and related to compressive mechanical properties. With increasing porogen concentration, volume fraction decreased consistently due to microarchitectural changes in average strut thickness, spacing, and density. The three-dimensional interconnectivity of the scaffold porosity was greater than 99% for all porogen concentration levels tested. Over a porosity range of 58-80%, the average compressive modulus and ultimate strength of the scaffolds ranged from 43.5-168.3 MPa and 2.7-11.0 MPa, respectively. Thus, biodegradable porous polymer scaffolds have been produced with oriented microarchitectural features designed to facilitate vascular invasion and cellular attachment and with initial mechanical properties comparable to those of trabecular bone.     

Variation of the mechanical properties of PMMA to suit osteoporotic cancellous bone

Poly(methyl methacrylate) (PMMA) is by far the most frequently used bone substitute material for vertebroplasty. However, there are serious complications, such as cement leakage and an increased fracture rate of the adjacent vertebral bodies. The latter may be related to the mechanical properties of the augmented segment within the osteoporotic spine. A possible counter-measure is prophylactic augmentation at additional levels, but this aggravates the risk for the patient. Introduction of pores is a possible method to reduce the inherent high stiffness of PMMA. This study investigates the effect of porosity on the mechanical properties of PMMA bone cement. Different fractions of a highly viscous liquid were mixed into the PMMA during preparation. An open-porous material with adjustable mechanical properties resulted after removal of the aqueous phase. Different radiopacifiers were admixed to investigate their suitability for vertebroplasty. The final material was characterized mechanically by compressive testing, microscopically and radiologically. In addition, the monomer release subsequent to hardening was measured by means of gas chromatography. The Young's modulus in compression could be varied between 2800 +/- 70 MPa and 120 +/- 150 MPa, and the compression ultimate strength between 170 +/- 5 MPa and 8 +/- 9 MPa for aqueous fractions ranging between 0 and 50% of volume. Only a slight decrease of the Young's modulus and small changes of ultimate strength were found when the mixing time was increased. An organic hydrophilic and lipophilic radiopacifier led to a higher Young's modulus of the porous material; however, the ultimate strength was not significantly affected by adding different radiopacifiers to the porous cement. The radiopacity was lost after washing the aqueous phase out of the pores. No separation occurred between the aqueous and the PMMA phase during injection into an open porous ceramic material. The monomer released was found to increase for increasing aqueous fractions, but remained comparable in magnitude to standard PMMA. This study demonstrates that a conventional PMMA can be modified to obtain a range of mechanical properties, including those of osteoporotic bone.     

磷酸钙骨水泥承载头孢哌酮钠后对其理化特性的影响

分析不同复合比例的头孢哌酮钠 磷酸钙骨水泥复合体的理化特性。其方法为制备含头孢哌酮钠与磷酸钙骨水泥质量比分别为 0 %、2 9%、4 8%、7 4%的复合材料 ,观察固化时间 ,用材料万能试验机测试抗压极限强度 ,用扫描电镜观察和分析超微结构等。结果表明 :磷酸钙骨水泥承载头孢哌酮钠后 ,随着所承载药物量的增加 ,固化时间和孔隙率的变化不显著 ;而抗压极限强度逐渐降低 ,四组抗压极限强度分别为 2 1 98± 1 0 6、2 1 38± 0 95、19 2 2± 1 11、13 5± 1 6 5MPa。磷酸钙骨水泥承载头孢哌酮钠药量在 0 % 4 8%之间对其理化特性无显著影响 ,复合体存在自然孔隙 ,具有较强的抗压性能 ,有望成为感染性骨缺损的理想修复材料。     

Comparative study of bone cements prepared with either HA or alpha-TCP and functionalized methacrylates

The properties of bone cements prepared with both hydroxyapatite (HA) and alpha-tricalcium phosphate (alpha-TCP) and methacrylates containing acidic or basic groups are the main interest of this article. The presence of methacrylic acid or diethyl amino ethyl methacrylate as comonomers in the bone cement and both ceramic types as filler were found not to affect the amount of residual monomer, which was generally less than 4.5 wt%. In contrast, setting times, maximum temperature, and glass transition temperature were found to be composition dependent. For samples with acidic comonomer, a faster setting time, a higher maximum temperature, and higher glass transition temperatures were observed compared to those with the basic comonomer. The presence of the fillers slightly increased the setting time but did not affect the other parameters. The mechanical properties of the filled bone cements depended mainly on composition and type of testing. Both HA or alpha-TCP filled systems fulfilled the minimum compressive strength required for bone cement application, although a significantly lower value was observed for the alkaline comonomer systems. The minimum bending strength was not satisfied by any of these formulations. The tensile and shear strength of these composites ranged from 20 to 37.9 and from 18 to 27 MPa, respectively. In all cases it was higher for bone cements containing methacrylic acid. The results of this study suggest that the properties of dry unfilled bone cements prepared with MAA are comparable to CMW 3 in mechanical terms but inferior in their setting properties.     

Mechanical and thermal properties of novel polymerized NDGA-gelatin hydrogels

Nordihydroguaiaretic acid (NDGA), an antioxidant with two functional ortho-catechols from the creosote bush, has been shown to increase the mechanical properties of synthetic collagen fibers, producing biologically based, biocompatible fibers with material properties in uniaxial tensile tests to failure that are comparable to those of native tendon (Koob and Hernandez, Biomaterials 23 (2002) 203; Koob et al., J Biomed Mater Res, 56 (2001) 31; 56 (2001) 40). The NDGA polymerization scheme was applied to gelatin hydrogels to determine whether it could provide a viable approach for producing gelatin based biological materials with advantageous mechanical and thermal properties. NDGA treatment eliminated gelatin solubilization from hydrogels in chaotropic agents and increased the thermal stability of gelatin hydrogels from less than 37 degrees C to over 80 degrees C. NDGA caused a dose dependent increase in the compressive stiffness and fracture load of gels ranging in concentration from 2.5% to 40% gelatin in uniaxial, unconfined compression tests to failure. Maximum fracture load averaged 0.5+/-0.1MPa and the compressive modulus averaged 4.4+/-1.4MPa for all gelatin concentrations, however, the concentration of NDGA that produced maximum strength and stiffness varied inversely with gelatin concentration. The compressive strength and stiffness of 5% gelatin hydrogels treated with NDGA were independent of temperature up to 52 degrees C. These results indicate that NDGA polymerization renders gelatin hydrogels thermally and mechanically stable and thereby potentially useful for surgical procedures that would benefit from biocompatible, stable and mechanically competent gelatin-based biomaterials.     

Injectable PLGA microsphere/calcium phosphate cements: physical properties and degradation characteristics

Calcium phosphate (CaP) cements show an excellent biocompatibility and often have a high mechanical strength, but in general degrade relatively slow. To increase degradation rates, macropores can be introduced into the cement, e.g., by the inclusion of biodegradable microspheres into the cement. The aim of this research is to develop an injectable PLGA microsphere/CaP cement with sufficient setting/cohesive properties and good mechanical and physical properties. PLGA microspheres were prepared using a water-in-oil-in-water double-emulsion technique. The CaP-cement used was Calcibon, a commercially available hydroxyapatite-based cement. 10:90 and 20:80 dry wt% PLGA microsphere/CaP cylindrical scaffolds were prepared as well as microporous cement (reference material). Injectability, setting time, cohesive properties and porosity were determined. Also, a 12-week degradation study in PBS (37 degree C) was performed. Results showed that injectability decreased with an increase in PLGA microsphere content. Initial and final setting time of the PLGA/CaP samples was higher than the microporous sample. Porosity of the different formulations was 40.8% (microporous), 60.2% (10:90) and 69.3% (20:80). The degradation study showed distinct mass loss and a pH decrease of the surrounding medium starting from week 6 with the 10:90 and 20:80 formulations, indicating PLGA erosion. Compression strength of the PLGA microsphere/CaP samples decreased siginificantly in time, the microporous sample remained constant. After 12 weeks both PLGA/CaP samples showed a structure of spherical micropores and had a compressive strength of 12.2 MPa (10:90) and 4.3 MPa (20:80). Signs of cement degradation were also found with the 20:80 formulation. In conclusion, all physical parameters were well within workable ranges with both 10:90 and 20:80 PLGA microsphere/CaP cements. After 12 weeks the PLGA was totally degraded and a highly porous, but strong scaffold remained.     

Brushite-collagen composites for bone regeneration

Brushite-based biomaterials are of special interest in bone regeneration due to their biocompatibility and biodegradability; on the other hand, collagen is a well-known osteoconductive biomaterial. In the present study a new brushite-collagen composite biomaterial is reported. This new biomaterial was prepared by combining citric acid/collagen type I solutions with a brushite cement powder. The obtained biomaterial was a cement paste, with improved handling properties. The effect of collagen on the setting reaction of brushite cement was studied, and was found to speed up the cement setting reaction. The cement paste set into a hard ceramic material within 18.5+/-2.1min and had compressive strength similar to that of spongeous bone (48.9+/-5.9MPa in dry conditions and 12.7+/-1.5MPa in humid conditions). The combination of collagen with citric acid revealed an interesting synergistic effect on the compressive strength of the composite material. Moreover, this new biomaterial had excellent cohesion properties (ninefold better than brushite cement), and high cellular adhesion capacity (threefold higher than brushite cement). The composite biomaterial described in this study combines good handling properties, compressive strength, cohesion and cell adhesion capacity, along with the osteoconductive and biodegradable properties inherent in brushite and in collagen-based biomaterials.