磷酸钙骨水泥临床应用类型选择及微结构观察

根据磷酸钙骨水泥（CPBCs)的基本性能选择符合临床适用的类型,并观察适用类型CPBC固化体超微结构。制备五种CPBCs粉末,即磷酸八钙－沉淀性羟基磷灰石（OCP－PHA）、磷酸八钙－羟基磷灰石（OCP－HA）、磷酸八钙（OCP）、缺钙性羟基磷灰石（CDHA）、羟基磷灰石（HA).调和液为去离子水和0．25M Na2HPO4/NaH2OPO4等摩尔浓度缓冲液。采用Gillmore双针法测定凝结时间,采用TS－14单颗粒压缩强度自动测量仪－Ⅱ测定压缩强度,按照Ginebra临床应用标准选择适用类型,并用扫描电镜观察适用类型CPBC固化体浸泡仿生液体前后的超微结构。结果表明：5种CPBCs中以OCP－PHA型和CDHA型CPBCs的凝结时间和压缩强度符合Ginebra临床应用标准。SEM观察两种CPBCs固化体为多孔结构,并随浸泡仿生液体中时间的延长而溶解或溶合。OCP－PHA型和CDHA型CPBCs适合于非承重骨的修复,其固化体为多孔结构,利于纤维组织长入及纤维血管化。     

真空烧结粉末冶金法制作的钛合金试件的显微结构观察

目的 研究真空烧结粉末冶金制作的钛合金试件的显微结构。方法 采用机械模压成形和真空电阻炉烧结的粉末冶金方法制作钛合金试件,观察其微观结构。结果 镀铜、镀锡组的烧结体仙孔隙数量少于未镀铜镀锡组,孔隙也较小。结论 对钛粉进行化学镀铜镀锡处理是改善钛粉的压制性能、烧结性能,减少烧结体孔隙度的理想方法。     

Metallurgical characterization of experimental Ag-based soldering alloys

AimTo characterize microstructure, hardness and thermal properties of experimental Ag-based soldering alloys for dental applications.Materials and methodsAg12Ga (AgGa) and Ag10Ga5Sn (AgGaSn) were fabricated by induction melting. Six samples were prepared for each alloy and microstructure, hardness and their melting range were determined by, scanning electron microscopy, energy dispersive X-ray (EDX) microanalysis, X-ray diffraction (XRD), Vickers hardness testing and differential scanning calorimetry (DSC).ResultsBoth alloys demonstrated a gross dendritic microstructure while according to XRD results both materials consisted predominately of a Ag-rich face centered cubic phase The hardness of AgGa (61 ± 2) was statistically lower than that of AgGaSn (84 ± 2) while the alloys tested showed similar melting range of 627–762 °C for AgGa and 631–756 °C for AgGaSn.ConclusionThe experimental alloys tested demonstrated similar microstructures and melting ranges. Ga and Sn might be used as alternative to Cu and Zn to modify the selected properties of Ag based soldering alloys.     

骨质疏松骨折基础和临床研究方法进展

骨质疏松是一种常见的代谢性骨病,其最严重的危害在于发生骨折.骨质疏松骨折与骨量减少和骨组织微结构退行性改变有关.对骨微结构、微损伤的基础研究有助于揭示骨折机制,而临床运用影像学手段可检测骨结构变化,结合有限元分析可预测骨折危险性.独立于骨结构的代谢途径标志物及骨折风险评估工具对骨折的早期防治也起了积极作用,关注已骨折患者的生命质量可降低再骨折风险.这些研究方法将为骨质疏松骨折危险性分析、药效检测等提供新的研究方向和思路.     

绞股蓝对高脂血症兔动脉粥样硬化超微结构和显微结构的影响

目的观察绞股蓝对高脂血症兔动脉粥样硬化(AS)超微结构和显微结构的影响。方法40只日本大耳白兔随机分为A组、B组、C组、D组,分别喂饲高脂饲料(标准饲料92.5%+2%胆固醇+2%蛋黄+3.5%猪油)+绞股蓝5 g/kg、高脂饲料+辛伐他汀5 mg/kg、高脂饲料、标准饲料。实验前和实验后6 w、9 w耳中动脉采血检测血脂:甘油三酯(TG)、胆固醇(TC)、低密度脂蛋白胆固醇(LDL-C)、高密度脂蛋白胆固醇(HDL-C)。光镜、电镜对比观察主动脉病理学形态。结果①血脂:E组饲养前后血脂比较无显著差异,A组、B组、C组饲养后TG、TC、LDL-C显著升高(P<0.05~0.01),A组、B组HDL-C显著升高(P<0.01),A组和B组TG、TC、LDL-C低于C组(P<0.05~0.01),A组和B组HDL-C高于C组(P<0.01);②病理学:A组、B组、C组、D组的斑块/内膜面积比分别为(30.91±5.21)%、(31.55±6.13)%、(59.89±8.91)%、0,A组、B组与C组间比较有显著差异(P<0.01);A组、B组、C组、D组的内膜/中膜厚度比分别为(40.13±15.56)%、(40.89±14.97)%、(70.17±12.12)%、0,A组、B组与C组间比较有显著差异(P<0.01);电镜下主动脉超微结构观察显示:C组血管内皮细胞及中膜平滑肌细胞质内大量脂滴空泡,甚至形成脂囊;A组和B组AS病变较C组轻,血管内皮细胞质内偶见小脂滴空泡,各种细胞器存在,内弹力膜存在,中层平滑肌细胞质内无脂滴空泡。结论绞股蓝能调节高脂饲料饲养兔血脂代谢,对AS显微和超微病变有明显的抑制作用。     

骨质疏松髋部骨折区骨微结构变化研究

目的 分析骨质疏松髋部骨折区张力侧骨小梁微结构的变化。方法 实验组选择16例低能量创伤致股骨颈骨折需要行髋关节置换的老年患者,术前行健侧髋部骨密度检测。因活体取材困难,故选取5根青年同种异体股骨为对照组。在实验组与对照组股骨颈张力侧骨小梁中,切取5mm×5mm×10mm的松质骨,行Micro-CT扫描分析微结构参数。分析两组之间微结构参数的差异及实验组患者微结构参数与骨密度之间关系。结果 实验组微结构：骨体积分数(BV/TV) 0.0645±0.0259,骨小梁数量(Tb.N) (0.8078±0.2212) mm-1,骨小梁厚度(Tb.Th ) (0.0836±0.0212) mm, 骨小梁距离(Tb.Sp) (1.2197±0.4492) mm,连接密度(Conn.D) 1.8577±1.0217, 结构模型指数(SMI) 1.7780±0.5168。对照组微结构：BV/TV 0.1470±0.0633,Tb.N (1.2692±0.1376)mm－1,Tb.Th (0.1201±0.0414) mm,Tb.Sp (0.6810±0.1129) mm,Conn.D 3.3585±1.7851,SMI 0.8781±0.6665。与对照组相比,实验组髋部张力侧松质骨小梁显著破坏,各微结构指标均有明显的改变,差异有统计学意义（P＜0.05）。实验组微结构参数与骨密度之间无相关性（P＞0.05）。结论 骨质疏松髋部骨折区张力侧骨小梁明显破坏,这可能是髋部骨折发生的重要原因之一。     

Microfabricated polymeric vessel mimetics for 3-D cancer cell culture

Modeling tumor growth in vitro is essential for cost-effective testing of hypotheses in preclinical cancer research. 3-D cell culture offers an improvement over monolayer culture for studying cellular processes in cancer biology because of the preservation of cell–cell and cell-ECM interactions. Oxygen transport poses a major barrier to mimicking in vivo environments and is not replicated in conventional cell culture systems. We hypothesized that we can better mimic the tumor microenvironment using a bioreactor system for controlling gas exchange in cancer cell cultures with silicone hydrogel synthetic vessels. Soft-lithography techniques were used to fabricate oxygen-permeable silicone hydrogel membranes containing arrays of micropillars. These membranes were inserted into a bioreactor and surrounded by basement membrane extract (BME) within which fluorescent ovarian cancer (OVCAR8) cells were cultured. Cell clusters oxygenated by synthetic vessels showed a ∼100μm drop-off to anoxia, consistent with in vivo studies of tumor nodules fed by the microvasculature. Oxygen transport in the bioreactor system was characterized by experimental testing with a dissolved oxygen probe and finite element modeling of convective flow. Our study demonstrates differing growth patterns associated with controlling gas distributions to better mimic in vivo conditions.     

Novel speed sintered zirconia by microwave technology

ObjectiveContinuous efforts have been made to hasten the zirconia densification process without compromising properties. This study evaluated the long-term structural durability of microwave speed-sintered zirconia (MWZ) relative to a conventionally sintered zirconia (CZ).MethodsAs-machined dental 3Y-TZP discs (Ø12 × 1.2 mm) were speed sintered at 1450 °C for 15 min using an industrial microwave oven, while conventional sintering was conducted in a standard dental furnace at 1530 °C for 2 h. Both were followed by natural cooling. The total sintering time was 105 min for MWZ and 600 min for CZ. Groups were compared regarding density, grain size, phase composition, and fracture resistance. Structural durability was investigated employing two fatigue protocols, step-stress and dynamic fatigue.ResultsCompared to CZ, MWZ exhibited a slightly lower density (MWZ = 5.98 g/cm³, CZ = 6.03 g/cm³), but significantly smaller grain sizes (MWZ = 0.53 ± 0.09 μm, CZ = 0.89 ± 0.10 μm), lower cubic-zirconia contents (MWZ = 15.3%, CZ = 22.7%), and poorer translucency properties (TP) (MWZ = 13 ± 1, CZ = 29 ± 0.8). However, the two materials showed similar flexural strength (MWZ = 978 ± 112 MPa, CZ = 1044 ± 161 MPa). Additionally, step-stress testing failed to capture the fatigue effect in 3Y-TZP, whereas dynamic fatigue revealed structural degradation due to moisture-assisted slow-crack-growth (SCG). Finally, MWZ possessed a slightly higher Weibull modulus (MWZ = 7.9, CZ = 6.7) but similar resistance to SCG (MWZ = 27.5, CZ = 24.1) relative to CZ.SignificanceDental 3Y-TZP with similar structural durability can be fabricated six-times faster by microwave than conventional sintering.     

Microstructures in shells of the freshwater gastropod Viviparus viviparus: A potential sensor for temperature change?

Mollusk shells contain a plethora of information on past climate variability. However, only a limited toolkit is currently available to reconstruct such data from the shells. The environmental data of some proxies (e.g. Sr/Ca ratios) is obscured by physiological effects, whereas other proxies, such as δ¹⁸O, simultaneously provide information on two or more different environmental variables. The present study investigates whether microstructures of the freshwater gastropod Viviparus viviparus provide an alternative means to reconstruct past water temperature. Cold and highly variable temperature regimes resulted in the precipitation of highly unordered first-order lamellae of simple crossed-lamellar (XLM) structures if new shell formed from scratch. However, during stable and warm conditions, well-ordered first-order lamellae were laid down irrespective of pre-existing shell material. Homogeneous first-order lamellae also formed during times of cold and highly variable temperatures if the new shell was deposited onto existing shell material with well-ordered first-order lamellae. The growth front seems to contain instructions for building specific microstructure variants, irrespective of environmental conditions. However, if this template is missing, the animal forms a deviating microstructure. Under extremely stressful situations (e.g. removal from habitat, calcein staining, extreme temperature shifts), the gastropod precipitates an evolutionarily older microstructure (irregular simple prisms) rather than XLM structures. These shell portions were macroscopically described as disturbance lines. In addition, repetitive, presumably periodic growth patterns were observed, which consisted of gradually changing third-order lamellae between consecutive faint, organic-rich growth lines. These growth patterns were probably controlled by intrinsic biological clocks and exhibited a two-daily periodicity. The results of this study may provide the basis for using changes in the microstructure of shell sections as a new sensor (environmental proxy) for past water temperature.