Ductility and structure of some cobalt-base dental casting alloys

The shape of the clasps on removable partial dentures often has to be adjusted by bending. Occasionally they fracture during the small plastic deformation that takes place during the adjustment The tendency to brittle failure of three Co-Cr-Mo alloys for prosthetic use with different carbon and chromium contents was investigated by tensile testing. The total elongation which can be used as a measure of the ductility was observed to vary from 4–17% for the investigated alloys. The reasons for these differences have been sought fay studying the structures of the alloys and analysing the fracture mechanisms. The fractures are basically brittle and seem to be initiated during straining by cracking of particles. Microprobe analyses showed that many of the particles were agglomerations of constituents which in all cases were substantially enriched in C, Cr and Ma Each of these constituents may contain phases too small to be resolved by SEM and by the electron beam in the microproba TEM investigations showed that many of the constituents were eutectic with alternating lamellae of Co-rich FCC structure and M₂₃C₆. The crack propagates rapidly either by following the interface between the matrix and the particles or by running inside the particles. Cleavage along stacking faults in FCC Co-rich grains in the matrix takes place when the distance between neighbouring particles increases. The ductility of the alloys is clearly improved by decreasing amounts of particles and thus by a reduction of the C content     

Electrochemical study of corrosion in NiCr dental alloys

The anodic behaviour of Ni-Cr dental alloys used as porcelain substrates has been investigated in both as-cast and thermal treated conditions. Polarization curves and scratching at constant potentials in synthetic salivas have shown that breakdown potentials are not influenced by the elimination of passive films covering the samples. Thermal treatments used to reproduce the microstructure of the alloys in dental crowns have not shown detectable effects on the electrochemical behaviour. Selective corrosion occurs by dissolution of Ni-rich interdendritic regions formed during solidification.     

The effect of zinc on the biocompatibility of dental amalgams in vitro

When freshly triturated, two zinc-containing amalgams, Velvalloy and Dispersalloy, were more cytotoxic in vitro than two zinc-free amalgams Amalcap and Sybraloy. The high copper amalgam, Sybraloy, was only slightly irritant: similarly the presence of copper in Dispersalloy did not increase its toxicity over Velvalloy. All four amalgams retained some degree of toxicity up to one month after setting which is in marked contrast to most other dental materials investigated previously. This was greatest with the zinc-containing amalgams and was accompanied by the continued release of zinc over this period.     

In vitro and in vivo evaluation of a nanoparticulate bioceramic paste for dental pulp repair

Bioactive materials play an important role in facilitating dental pulp repair when living dental pulp is exposed after injuries. Mineral trioxide aggregate is the currently recommended material of choice for pulp repair procedures though has several disadvantages, especially the inconvenience of handling. Little information is yet available about the early events and molecular mechanisms involved in bioceramic-mediated dental pulp repair. We aimed to characterize and determine the apatite-forming ability of the novel ready-to-use nanoparticulate bioceramic iRoot BP Plus, and investigate its effects on the in vitro recruitment of human dental pulp stem cells (DPSCs), as well as its capacity to induce dentin bridge formation in an in vivo model of pulp repair. It was found that iRoot BP Plus was nanosized and had excellent apatite-forming ability in vitro. Treatment with iRoot BP Plus extracts promoted the adhesion, migration and attachment of DPSCs, and optimized focal adhesion formation (Vinculin, p-Paxillin and p-Focal adhesion kinase) and stress fibre assembly. Consistent with the in vitro results, we observed the formation of a homogeneous dentin bridge and the expression of odontogenic (dentin sialoprotein, dentin matrix protein 1) and focal adhesion molecules (Vinculin, p-Paxillin) at the injury site of pulp repair model by iRoot BP Plus. Our findings provide valuable insights into the mechanism of bioceramic-mediated dental pulp repair, and the novel revolutionary ready-to-use nanoparticulate bioceramic paste shows promising therapeutic potential in dental pulp repair application.     

In vitro and in vivo biological responses of plasma-sprayed hydroxyapatite coatings with posthydrothermal treatment

This study was undertaken to evaluate the effect of post-hydrothermal treatment on the biological responses of the plasma-sprayed hydroxyapatite (HA)-coated Ti-6Al-4V implant system both in vitro and in vivo. After hydrothermal treatment, the HA coating (HAC) shows the high mechanical strength and indices-of-crystallinity, denser microstructure, lower concentrations of amorphous and impurity phases, when compared with the as-sprayed HAC. The in vitro cell-culture studies, using UMR106 osteoblast-like cell, demonstrated no signifiacnt cell growth on both surface of as-sprayed and hydrothermal-treated HACs during 10-day culture. The in vivo studies, using the transcortical implant model in the femora of goats, evaluated the histological responses of two coatings. After 6 week of implantation, using backscattered electron images, no substantial histological variations in the extents of new bone apposition and new bone healing between the two HACs were observed. However, the as-sprayed HAC, owing to the dissolution induced the granular particles dissociated from the HAC, showed the statically lower extent of new bone apposition than hydrothermal-treated HAC at 12 weeks. The results suggest that hydrothermal treatment could be used to improve the mechanical strength, crystallinity, and phase composition of HAC, which are important factors of long-term fixation and stability of implant. Besides, the treated HAC could also achieve the initial fixation of implant in clinical use.     

钛种植体基台和不同合金的体外耐腐蚀性能

背景：各种医用生物材料在应用于口腔环境之前,除了对其机械性能和理、化学性能予以严格的考察之外,还需要进行口腔环境耐腐蚀性实验,以保证材料的生物相容性。目的：分析钛种植体基台和不同钛合金的体外耐腐蚀性能。方法：构建体外人工唾液腐蚀环境,pH=6.0,温度(37±0.5) ℃,利用动电位极化技术、扫描电镜、X射线衍射等方式评估钛合金、金合金、镍铬合金及钛种植体基台在人工唾液中浸泡24 h的耐腐蚀性能。结果与结论：不同合金的稳态电位不同,其中金合金钝化区范围最大,其次为钛种植体基台和钛合金,镍铬合金钝化区范围最小。经过24 h的人工唾液浸泡后,不同材料的表面均开始出现钝化膜,扫描电镜显示,镍铬合金表面可见明显的腐蚀痕迹,出现大量直径较大的深点蚀坑,其余3种合金均未出现明显腐蚀现象;镍铬合金表面铬、钼、铝含量均出现减少现象,镍、氧含量增加,其余合金表面未出现明显改变;镍铬合金表面生成 Cr₂O₃,钛种植体基台及钛合金表面均生成TiO₂,金合金表面仍为Au、Pt单相存在,未生成化合物。表明钛合金与钛种植体基台具有相似的耐腐蚀性能,且差于金合金,但优于镍铬合金。 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     

In vitro and in vivo corrosion measurements of magnesium alloys

The in vivo corrosion of magnesium alloys might provide a new mechanism which would allow degradable metal implants to be applied in musculo-skeletal surgery. This would particularly be true if magnesium alloys with controlled in vivo corrosion rates could be developed. Since the magnesium corrosion process depends on its corrosive environment, the corrosion rates of magnesium alloys under standard in vitro environmental conditions were compared to corrosion rates in an in vivo animal model. Two gravity-cast magnesium alloys (AZ91D, LAE442) were used in these investigations. Standardized immersion and electrochemical tests according to ASTM norms were performed. The in vivo corrosion tests were carried out by intramedullar implantation of sample rods of the magnesium alloys in guinea pig femura. The reduction in implant volume was determined by synchrotron-radiation-based microtomography. We found that in vivo corrosion was about four orders of magnitude lower than in vitro corrosion of the tested alloys. Furthermore, the tendency of the corrosion rates obtained from in vitro corrosion tests were in the opposite direction as those obtained from the in vivo study. The results of this study suggest, that the conclusions drawn from current ASTM standard in vitro corrosion tests cannot be used to predict in vivo corrosion rates of magnesium alloys.     

In vitro and in vivo assays of isopropanol for mutagenicity

To assess the mutagenic potential of isopropanol, an in vitro Chinese hamster ovary (CHO) cell/HGPRT gene mutation assay and a bone marrow micronucleus study in mice were conducted. In the CHO/HGPRT assay, concentration levels ranged from 0.5 to 5.0 mg/ml. No elevated mutant frequencies attributable to treatment were observed in the test under either activated or non-activated conditions. In the micronucleus assay, mice were injected intraperitoneally (IP) with either 350, 1,173, or 2,500 mg/kg of isopropanol at constant volumes of 10 ml/kg. No increased incidence of micronuclei was observed in bone marrow polychromatic erythrocytes (PCEs) harvested at 24, 48, or 72 hr post-dosing. In both assays, negative and positive control mutant frequencies were within historical control ranges. These results, in conjunction with previously published data, clearly demonstrate that isopropanol is not a mutagen. © 1993 Wiley-Liss, Inc.     

可降解金属Mg-Nd-Zn-Zr镁合金的降解行为

背景：添加合金元素是改变镁合金微观结构和控制镁合金降解行为的有效方法。 目的：探讨Mg-Nd-Zn-Zr镁合金体内外的降解行为。 方法：①体外静态浸泡实验：在(37.0±0.5) ℃条件下,将Mg-Nd-Zn-Zr镁合金和纯镁各6个样品分别浸入 250 mL模拟体液中,浸泡过程中不搅拌振荡。静态浸泡第3,7,30天后从模拟体液中取出试样,扫描电镜及能谱分析分析Mg-Nd-Zn-Zr镁合金在模拟体液中的降解行为。②体内植入实验：在成年新西兰兔左侧股骨钻孔,实验组植入Mg-Nd-Zn-Zr镁合金,对照组植入钛合金,空白对照组不植入任何内植物。植入后1,2,4,8周,通过X射线观察内植物的位置及降解行为;植入后4,8周,通过扫描电镜观察Mg-Nd-Zn-Zr镁合金表面腐蚀产物,通过元素能谱分析腐蚀产物的成分,并计算材料降解速率。 结果与结论：①Mg-Nd-Zn-Zr镁合金浸泡于模拟体液中不同时间点的降解速率均低于纯镁组;浸泡30 d后,沉积于Mg-Nd-Zn-Zr镁合金表面的腐蚀产物主要是氧、碳、钠、镁、钙、磷和氯,去除腐蚀产物后Mg-Nd-Zn-Zr镁合金和纯镁表面均有腐蚀坑,但Mg-Nd-Zn-Zr镁合金表面腐蚀坑体积更小,分布更均匀,表明Mg-Nd-Zn-Zr镁合金和纯镁存在不同的腐蚀形式。②Mg-Nd-Zn-Zr镁合金植入动物体内后随时间延长逐渐降解,材料表面腐蚀产物及成分类似于体外浸泡实验。     

动态力学信号对人骨髓基质细胞、骨膜细胞生长和成骨表达的作用

目的 探讨动态力学信号对体外分离培养的人骨髓基质细胞、骨膜细胞生长与分化特征的生物学效应。方法 使用Flexcell应力系统，将频率为1Hz、振幅为5％变形、正弦波状力学信号作用于体外分离培养的正常人骨髓基质细胞和骨膜细胞，在不同时间段检测其对细胞DNA、总蛋白合成、碱性磷酸酶（ALP）表达和骨钙素分泌量的影响。结果 动态力学刺激对人骨髓基质细胞、骨膜细胞蛋白与DNA合成无明显作用。接受力学刺激信号后骨膜细胞受维生素D3刺激后分泌骨钙素显著增加，而骨髓基质细胞则显著下降。结论 动态力学信号能够促进人骨膜细胞向成骨细胞分化，这可能是其对骨的生物学作用的机制之一。     

In vitro responses to known in vivo genotoxic agents in mouse germ cells

Genotoxic compounds have induced DNA damage in male germ cells and have been associated with adverse clinical outcomes including enhanced risks for maternal, paternal and offspring health. DNA strand breaks represent a great threat to the genomic integrity of germ cells. Such integrity is essential to maintain spermatogenesis and prevent reproduction failure. The Comet assay results revealed that the incubation of isolated germ cells with n‐ethyl‐n‐nitrosourea (ENU), 6‐mercaptopurine (6‐MP) and methyl methanesulphonate (MMS) led to increase in length of Olive tail moment and % tail DNA when compared with the untreated control cells and these effects were concentration‐dependent. All compounds were significantly genotoxic in cultured germ cells. Exposure of isolated germ cells to ENU produced the highest concentration‐related increase in both DNA damage and gene expression changes in spermatogonia. Spermatocytes were most sensitive to 6‐MP, with DNA damage and gene expression changes while spermatids were particularly susceptible to MMS. Real‐time PCR results showed that the mRNA level expression of p53 increased and bcl‐2 decreased significantly with the increasing ENU, 6‐MP and MMS concentrations in spermatogonia, spermatocytes and spermatids respectively for 24 hr. Both are gene targets for DNA damage response and apoptosis. These observations may help explain the cell alterations caused by ENU, 6‐MP and MMS in spermatogonia, spermatocytes and spermatids. Taken together, ENU, 6‐MP and MMS induced DNA damage and decreased apoptosis associated gene expression in the germ cells in vitro. Environ. Mol. Mutagen. 58:99–107, 2017. © 2017 Wiley Periodicals, Inc.     

纯镁膜体外腐蚀及体内的生物安全性

文题释义： 引导骨再生技术：是指在骨缺损处覆盖上一层生物膜作为屏障,确保阻止来自周围软组织的成纤维细胞,让骨面处的成骨细胞有足够的时间增殖,最终达到组织再生、定向修复的目的。 生物降解镁基金属：是指镁基植入物在辅助并完成生物组织修复的过程中,在生物体内逐渐腐蚀直至完全降解,同时材料的腐蚀产物对生物体不会产生或产生轻微的宿主反应。    背景：镁及其合金具有良好的机械性能、生物相容性及可降解性等,有望在引导骨再生技术中作为引导骨再生膜应用于临床。 目的：分析可降解高纯镁膜的体外腐蚀规律及体内生物安全性。 方法：将纯镁样品、纯钛样品分别浸泡于人工唾液中,7,14 d后取出样品,观察样品表面腐蚀情况,检测样品失重率、平均腐蚀速率与人工唾液内的pH值。取6只健康杂种犬(由锦州医科大学实验动物中心提供),建立双侧下颌骨缺损模型,左侧植入纯镁膜,右侧植入纯钛膜,术后12周取下颌骨实验区标本,分别进行大体观察、X射线显微镜检测,同时进行主要脏器病理组织学观察。实验方案经锦州医科大学伦理委员会批准。 结果与结论：①体外浸泡实验：纯镁样品表面先是出现点腐蚀,随着浸泡时间的延长腐蚀降解越来越严重,浸泡14 d后表现为面腐蚀;纯钛膜无明显腐蚀现象。浸泡纯镁膜溶液的pH值不断升高,在7 d后基本趋于平衡,保持在10左右;纯钛膜pH值相对稳定,且略低于纯镁膜,维持在8.6左右。纯镁膜浸泡14 d的失重率较7 d时增加(P < 0.05),平均腐蚀速率较7 d时降低(P < 0.05);纯钛膜并无明显降解行为出现,各时间点基本无质量损失。②体内植入实验：纯镁膜组膜材料全部降解,骨小梁排列较紧密,形成立体网状结构,部分骨组织已改建为成熟骨,但仍有骨缺损;纯钛组植骨区新生骨组织充满缺损区,新生骨小梁数量增多,骨小梁较为粗大,排列尚为有序、紧密;纯镁膜组骨缺损区骨体积分数与骨孔隙体积分数均高于纯钛膜组(P < 0.05)。实验犬的肝、肾结构均未见异常,未见炎细胞浸润。③结果表明：纯镁膜可促进犬下颌骨骨缺损区的骨愈合,并且生物安全性良好,但其耐腐蚀性有待进一步提高。ORCID: 0000-0002-1870-2946(孙溪饶) 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     

In vivo and in vitro techniques to determine the biological activity of food allergens.

Methods for determination of the biological activity of food allergens comprise both determination of the allergenic potency, i.e. the capability to elicit an allergic reaction in an already sensitized individual, and the allergenic potential, i.e. the risk for sensitizing a hitherto non-allergic individual. Several methods are discussed for determination of potency including the double-blinded placebo-controlled food challenge, skin testing, in vitro effector cell assays such as basophil histamine release, and IgE-based techniques such as RAST and RAST inhibition. No reliable methods have yet been developed which can predict the allergenic potential of a food or a food allergen. The progress in the areas of stability studies and animal models for food allergy are discussed.     

Flavobacterium meningosepticum ventriculitis: In vivo and in vitro results with the combinations rifampicin-erythromycin and mezlocillin-cefoxitin

A case ofFlavobacterium meningosepticum ventriculitis is described in which the failure of therapy with a combination of rifampicin and erythromycin is attributed to inadequate antibiotic levels in cerebrospinal fluid. The successful eradication of the organism was achieved with the use of mezlocillin and cefoxitin given by the intravenous and intraventricular route. In vitro sensitivity tests of recently isolated strains ofFlavobacterium meningosepticum suggested that the combination mezlocillin and cefoxitin is more often synergistic than rifampicin and erythromycin.     

In vivo and in vitro responses to tumor-associated antigens: apparent absence of T cell participation

The tumor-associated antigens of the murine tumors B16, SAD2 and C3HBA readily induced antibody production in vivo, but produced little transplantation immunity. These tumors grew better in normal syngeneic hosts than they did in lethally irradiated or thymectomized lethally irradiated, marrow reconstituted hosts, where they grew equally well. When blood or spleen cells were reacted with anti-H-2 sera directed against the responder cells or with anti-Θ C3H sera and complement and then cultured with irradiated syngeneic tumor cells or extracts of these tumors, the responses to the tumor-associated antigens and to two thymus-independent antigens were not impaired; however, the same treatment greatly reduced the responses to allogeneic tumor or spleen cells and to two thymus-dependent antigens. The observations suggested that the tumor-associated antigens under study primarily stimulated B rather than T cells.     

In vitro and in vivo production of pectolytic enzymes by some phytopathogenic fungi

Five fungal plant pathogens were investigated for their in vitro and in vivo ability to produce pectolytic enzymes. Only Fusarium solani did not produce any appreciable amount of enzymes in vivo and in vitro. Alternaria solani, Collectotrichum truncatum, Colletotrichum capsici and Curvularia pallescens produced pectolytic enzymes in vitro which were detected after ten-fold concentration of the cultures by ammonium sulphate precipitation. These same four fungi produced pectolytic enzymes in vivo which were detected after twenty-fold concentration of blended infected host tissue. The pH values of peak enzyme activity of 3.0 and 5.0 indicate that the enzymes produced were polygalacturanaes. The monogalacturonide end-product of sodium polypectate and cell wall degradation indicate that exopolygalacturonases were produced by the pathogens. The low concentration of these enzymes in infected host plant tissues and the slow pectate-splitting action of the exopolygalacturonases produced may account for the slow development and the dry necrotic nature of the disease these fungi cause.     

Selective dissolution of AuCu and AuAg alloys in vitro and in vivo

AuCu and AuAg alloys (30 at.% Au) have been immersed in aqueous solutions of chloride and sulphide with additions of protein (mucin). The surfaces of the alloys were subsequently analysed by means of ESCA and compared with previous and similar tests without addition of mucin. No noticeable effect of the mucin addition was observed on the surface composition of the alloys after exposure to the various solutions. Cu in contrast to Ag was found to be selectively dissolved from the 2 or 3 uppermost atomic layers in chloride as well as sulphide solutions (pS > 4), both with and without additions of mucin, leaving behind a surface enriched from 10 to 25 at.% in Au. Testing of the same alloys in vivo for 8 d revealed the same tendencies to selective dissolution of Cu. The AuAg alloy was tarnished in the sulphide solutions and in vivo.     

PIKA佐剂在体内外诱导小鼠免疫应答的探讨

目的：探讨PIKA佐剂在体内外诱导小鼠的免疫应答。方法：体外将小鼠脾淋巴细胞与不同浓度PIKA佐剂培养后，ELISA检测细胞因子IFN-γ、IL-12p40的产生，FACS检测细胞的增殖及活化。体内将PIKA佐剂经小鼠腹腔注射后，检测不同时间点血清中IFN-γ、IL-12pao、IL-6、TNF-α等细胞因子的产生。结果：PIKA佐剂体外呈剂量依赖性诱导小鼠脾细胞产生IFN-γ和IL-12p40。细胞亚群分析的结果表明，PIKA可显著刺激B细胞和NK细胞活化、增殖。体内注射PIKA佐剂后可诱导细胞因子IFN-γ、IL-12pao、IL-6、TNF-α的产生，但产生的时间点不同。结论：PIKA佐剂体内外直接通过诱导细胞因子的产生，B细胞和NK细胞的活化和增殖，而促进免疫应答反应。