氮化钛纳米膜对磁性附着体铁铬钼合金磁力影响的研究

目的研究应用离子束辅助沉积制备氮化钛薄膜后,对磁性附着体磁力的影响.方法应用电子拉伸机测量镀膜前后磁性附着体磁力大小.结果镀膜前后磁性附着体磁力无明显改变,统计学分析无显著性差异(P>0.05).结论磁性附着体铁铬钼合金经表面镀膜后,磁力无改变.可以应用离子束辅助沉积技术对磁性附着体进行表面处理.     

TiN纳米薄膜提高磁性附着体Fe-Cr-Mo合金显微硬度的研究

目的 :研究应用离子束辅助沉积技术 (ionbeamassisteddeposition ,IBAD)制备TiN纳米薄膜提高铁铬钼软磁合金在口腔环境中的耐磨损性能。方法 :测量在模拟口腔环境中 ,电化学腐蚀前后 ,未镀膜及三种不同条件镀TiN纳米薄膜的铁铬钼合金显微硬度值。结果 :无论腐蚀前后 ,镀TiN纳米薄膜均较未镀膜的合金显微硬度值明显提高。统计学分析具有显著性差异 (P <0 .0 1)。其中 ,离子束溅射 4h、厚为 2 μm的镀膜提高最多。 结论 :TiN纳米薄膜显著提高铁铬钼合金的显微硬度值 ,从而提高其耐磨损性能。     

激光焊接铁铬钼合金与钴铬合金的机械性能

目的：测试激光焊接铁铬钼软磁合金与钴铬合金的机械性能，为临床应用提供参考。方法：采用国产Nd：YANG程控激光焊接机焊接铁铬钼软磁合金与钴铬合金，以激光焊接钴铬合金作为对照。利用Instron万能拉仲实验机测试焊接后的拉仲强度、0．2％屈服强度，作断裂口的扫描电镜分析，并分别进行比较。结果：激光焊接铁铬钼软磁合金与钴铬合金的拉伸强度、0．2％屈服强度与对照组无差别。激光焊接铁铬钼合金与钴铬合金的断裂口呈韧性—解理混合型断裂，而激光焊接钴铬合金的断口呈准解理断裂。结论：激光焊接铁铬钼软磁合金与钴铬合金的机械性能可满足临床需要。     

磁性附着体模拟静磁场对人牙周膜成纤维细胞致突变性的研究

目的:探讨磁性附着体静磁场是否对人牙周膜成纤维细胞具有致突变作用。方法:对体外培养的人牙周膜成纤维细胞分别进行12.5、125、250mT静磁场持续加载4d,另设无外加静磁场作用的阴性和阳性对照组,采用微核试验和彗星试验对各组细胞分别进行染色体和DNA损伤检测。结果:各磁场剂量组细胞微核发生率与阴性对照组比较未见明显差异(P>0.05),其彗星细胞拖尾率和尾长亦与阴性对照组无显著差异(P>0.05)。结论:在现设定条件下,磁性附着体静磁场对人牙周膜成纤维细胞染色体和DNA无明显损伤作用。     

磁性固位体耐蚀性能的研究

目的研究3种钕铁硼磁性固位体的外包裹容器不锈钢的耐腐蚀性能.方法将3种磁性固位体分别浸泡于人工唾液中,温度为36.5℃,时间为6个月.实验方法包括恒电位法极化曲线试验与浸泡试验,分析材料的耐腐蚀能力.结果极化曲线中,国产衔铁的自腐蚀电流密度为7.015μA/cm2,国产磁体为0.119μA/cm2.浸泡试验中,国产衔铁的腐蚀速度为3.67×10-5mg/cm2*h,国产磁体的腐蚀速度为1.77×10-5mg/cm2*h.国产磁性固位体与进口同类材料相比,其耐腐蚀性能差异无显著性.结论人工唾液环境会使3种磁性固位体的耐腐蚀能力降低,进而缩短其寿命.     

Cosmopost全瓷桩核的临床应用

目的 探讨Cosmopost全瓷桩核的适应证、制作技术要点与临床效果。方法 为96例患者制作全瓷桩核228件，其外部均为铸造全瓷冠或桥。临床总结该项技术的适应证，记录制作过程，检查瓷桩的密合度及冠桥的颜色。临床复查修复体的松动脱落与折裂折断情况，随访时间0．5～3年。结果 1件全瓷桩核的核切端因过薄，在全瓷冠戴入前折断1．5mm，但未影响最终修复效果；其余227件全瓷桩核均无破损。所有修复体完成后0．5～3年复查，均无松动脱落与折裂折断。全瓷桩核支持的全瓷冠桥修复体有接近自然的美学效果，但其临床应用有严格的适应证。结论 全瓷桩核支持的全瓷冠桥有良好的美学效果和较好的强度，有临床应用价值。     

自制美学镍钛涂层弓丝的耐腐蚀性研究

目的：研究美学镍钛涂层弓丝的耐腐蚀性能。方法：将美学涂层镍钛弓丝与未涂层镍钛弓丝浸泡于人工唾液中,37℃恒温,采用恒电位法测定阳极极化曲线,浸泡实验测定析出镍、铬离子浓度。结果：涂层弓丝的腐蚀电流显著降低,涂层弓丝析出相对低水平的金属离子。结论：美学涂层可降低弓丝合金的腐蚀倾向,提高其耐腐蚀性能。     

不同钴铬合金铸造卡环循环疲劳性能初探

目的 研究不同钴铬合金铸造卡环的固位力在循环疲劳实验中的变化,以期为临床提供依据.方法 制备进入0.25 mm和0.50 mm两种倒凹深度的3种钴铬合金卡环样本(A组:硬质型钴铬合金;B组:Regalloy～(TM);C组:Vera PDN～(TM)),在材料实验机上进行模拟临床摘戴5年的循环疲劳实验,实验过程中进行21次固位力测量.采用单因素方差分析、x～2检验及直线相关分析对实验结果进行统计分析.结果 各组卡环固位力均呈现逐渐下降的变化趋势.对于进入0.50 mm倒凹的卡环,其初始固位力[A、B、C组分别为(8.714±1.104)、(9.072±0.653)和(9.588±1.980)N]与固位力丧失量[分别为(4.408±0.662)、(3.484±0.494)和(3.290±1.484)N]均大于进入0.25 mm倒凹的卡环[初始固位力分别为(7.940±0.357)、(7.834±1.308)、(8.156±1.067)N,固位力丧失最分别为(2.444±0.736)、(2.954±1.048)、(1.832±1.180)N].卡环固位力与循环摘戴次数的对数呈负相关关系.结论 钴铬合金铸造卡环的固位力能满足临床使用5年的需要.     

钴铬合金与金合金铸造三臂卡环的三维有限元对比分析

目的 对比分析两种材料铸造卡环在义齿摘取时的应力，为临床设计提供参考。方法建立前磨牙和不同形态的卡环固位臂的三维有限元模型，施加动态位移栽荷，计算卡环与基牙的接触受力情况。结果所得数据经SPSS10．0统计软件和数理统计方法分析表明：当宽度一定时，随着卡臂尖倒凹深度的增大，钴铬合金铸造卡环固位臂的峰值应力与金合金卡环相比增加得快；金合金铸造卡环在前磨牙上所能放置的最大倒凹深度比钴铬合金卡环大。结论在设计和制作铸造卡环时，选择钴铬合金卡环进入基牙的倒凹深度较金合金卡环要更加慎重。当基牙的倒凹深度较大时，建议设计金合金卡环，以防卡环在使用中发生永久变形。     

两种低贵金属合金的腐蚀性能实验研究

目的　评价两种牙科低贵金属合金的腐蚀性能。方法　运用动电位极化技术评价了Au -Pd -Ag ,Ag -Pd ,两种低贵合金的腐蚀性能并与Co -Cr ,Ni-Cr,Cu -Al以及Au -Pt合金比较。试验介质为fusayama人工唾液 (37 C ,pH =5 ) ,采用电子能谱扫描分析腐蚀产物。结果　自腐蚀电位EocAu-Pd -Ag和EocAg -Pd分别为 - 2 6mv ,40mv远比Ni-Cr合金 (Eoc =- 2 2 3mv)、Co -Cr合金 (Eoc =- 16 5mv)为正 ,但低于传统Au -Pt合金。极化曲线表明电位一定时 (<6 0 0mv)Au -Pd -Ag合金 ,Ag -Pd合金的电流密度比Cu -Al合金与Ni-Cr合金低 ,与传统Au -Pd合金接近。ESCA腐蚀产物拟合结果表明Au -Pd -Ag合金、Ag -Pd合金腐蚀主要以Ag为主 ,而Au、Pd均无化合物形成。结论　两种低贵合金具有良好的耐腐蚀性能 ,低贵合金腐蚀主要以Ag相腐蚀为主     

三种口腔铸造合金耐蚀性及表面氧化膜的比较

目的 探讨3种常用口腔铸造合金模拟烤瓷前后的耐蚀性差异及氧化膜成分,以期为临床合理选择非贵金属合金提供依据.方法 用电感耦合等离子体原子发射光谱法(inductively coupled plasma atomic emission spectroscopy,ICP-AES)检测模拟烤瓷前后3种常用烤瓷非贵金属合金(镍铬合金、钴铬合金、镍钛合金)在达尔伯克改良伊格尔培养液中浸泡30 d后离子析出的种类和含量.同时用X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)对模拟烤瓷后合金表面生成的氧化膜进行分析,扫描电镜(SEM)对合金表面腐蚀形态进行观察.结果 模拟烤瓷前3种合金离子总质量浓度由大到小依次为镍铬合金[(2.829±0.694)mg/L]、钴铬合金[(2.120±0.418)mg/L]、镍钛合金[(1.211±0.101)mg/L];镍铬合金组镍的质量浓度[(1.531±0.392)mg/L]＞镍钛合金组[(0.830±0.052)mg/L],钴和钼离子质量浓度由大到小为钴铬合金组[钴:(0.048±0.011)mg/L;钼:(1.562±0.333)mg/L]、镍铬合金组[钴:(0.034±0.002)mg/L;钼:(1.264±0.302)mg/L]、镍钛合金组[钴:(0.013±0.006)mg/L;钼:(0.151±0.026)mg/L],差异有统计学意义(P＜0.05).模拟烤瓷后3种合金离子析出总量[镍铬合金:(0.861±0.054)mg/L;钴铬合金:(0.695±0.327)mg/L;镍钛合金:(0.892±0.115)mg/L]均比未模拟烤瓷处理的合金离子析出总量少,差异有统计学意义(P＜0.05).XPS分析显示,模拟烤瓷后3种合金表面Cr2O3和钼、镍氧化物的含量增加.结论 3种常用烤瓷铸造合金中镍铬合金的离子析出量最大,耐蚀性最差;烤瓷加热处理可促进这3种合金生成连续的Cr2O3氧化膜,使合金的耐蚀性增强.

Abstract：

Objective To evaluate the types and compositions of oxide films formed during porcelain-fused-to-metal( PFM ) firing on three kinds of dental casting alloys, and to investigate the corrosion property of these alloys in Dulbecco's modification of Eagle's medium( DMEM ) cell culture fluid, before and after PFM firing. Methods Specimens of three dental casting alloys( Ni-Cr, Co-Cr and Ni-Ti) before and after PFM firing were prepared, and were immersed in DMEM cell culture fluid. After 30 days, the type and concentration of released metal ions were measured using inductively coupled plasma atomic emission spectroscopy(ICP-AES). X-ray photoelectron spectroscopy(XPS) and scanning electron microscope( SEM )were used for analysis of oxide film on the alloys. One way-ANOVA was adopted in data analysis. Results The total amount of metal ions released from the three dental alloys was found to be highest in Ni-Cr alloy [(2.829±0.694) mg/L], followed by Co-Cr[(2. 120 ±0.418) mg/L]and Ni-Ti alloy[(1.211 ±0. 101 ) mg/L]. The amount of Ni ions released from Ni-Cr alloys[( 1. 531 ± 0. 392) mg/L]was higher than that from Ni-Ti alloys[(0. 830 ±0. 052) mg/L]. The amount of Cr, Mo ions released from Co-Cr alloy [Cr: (0. 048 ± 0. 011 ) mg/L, Mo: ( 1. 562 ± 0. 333 ) mg/L]was higher than that from Ni-Cr alloy[Cr:(0. 034 ±0. 002) mg/L, Mo: ( 1. 264 ±0. 302) mg/L]and Ni-Ti alloy[Cr: (0. 013 ±0. 006) mg/L, Mo:(0. 151 ±0. 026) mg/L](P ＜0. 05). After PFM firing, the total amount of metal irons released from the three dental alloys decreased[N i-Cr: (0. 861 ± 0. 054 ) mg/L, Co-Cr: (0. 695 ± 0. 327 ) mg/L, Ni-Ti:(0. 892 ±0. 115) mg/L](P ＜ 0. 05). In addition, XPS showed increase of Cr2O3 and Mo-Ni oxide on the surface of all the alloys after PFM firing. Conclusions The amount of ions released from Ni-Cr alloy was the highest among the three dental casting alloys, this means Ni-Cr alloy is prone to corrode. The PFM firing process changed the alloys' surface composition. Increased Ni, Cr and Mo were found in oxide film, and the increase in Cr2O3 can improve the corrosion-resistance of alloys.     

Influence of shape and finishing on the corrosion of palladium-based dental alloys

PURPOSE

The purpose of this study was to evaluate the effects of the surface treatment and shape of the dental alloy on the composition of the prosthetic work and its metallic ion release in a corrosive medium after casting.

MATERIALS AND METHODS

Orion Argos (Pd-Ag) and Orion Vesta (Pd-Cu) were used to cast two crowns and two disks. One of each was polished while the other was not. Two as-received alloys were also studied making a total of 5 specimens per alloy type. The specimens were submersed for 7 days in a lactic acid/sodium chloride solution (ISO standard 10271) and evaluated for surface structure characterization using SEM/EDAX. The solutions were quantitatively analysed for the presence of metal ions using ICP-MS and the results were statistically analysed with one-way ANOVA and a Tukey post-hoc test.

RESULTS

Palladium is released from all specimens studied (range 0.06-7.08 µg·cm^-2·week^-1), with the Pd-Cu alloy releasing the highest amounts. For both types of alloys, ion release of both disk and crown pairs were statistically different from the as-received alloy except for the Pd-Ag polished crown (P>.05). For both alloy type, disk-shaped pairs and unpolished specimens released the highest amounts of Pd ions (range 0.34-7.08 µg·cm^-2·week^-1). Interestingly, in solutions submerged with cast alloys trace amounts of unexpected elements were measured.

CONCLUSION

Shape and surface treatment influence ion release from dental alloys; polishing is a determinant factor. The release rate of cast and polished Pd alloys is between 0.06-0.69 µg·cm^-2·week^-1, which is close to or exceeding the EU Nickel Directive 94/27/EC compensated for the molecular mass of Pd (0.4 µg·cm^-2·week^-1). The composition of the alloy does not represent the element release, therefore we recommend manufacturers to report element release after ISO standard corrosion tests beside the original composition.     

Corrosion behaviour of Ti-15Mo alloy for dental implant applications

The corrosion behaviour of Ti-15Mo alloy in 0.15M NaCl solution containing varying concentrations of fluoride ions (190, 570, 1140 and 9500 ppm) is evaluated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and chronoamperometric/current-time transient (CTT) studies to ascertain its suitability for dental implant applications. The study reveals that there is a strong dependence of the corrosion resistance of Ti-15Mo alloy on the concentration of fluoride ions in the electrolyte medium. Increase in fluoride ion concentration from 0 to 9500 ppm shifts the corrosion potential (E(corr)) from -275 to -457 mV vs. SCE, increases the corrosion current density (i(corr)) from 0.31 to 2.30 microA/cm(2), the passive current density (i(pass)) from 0.07 to 7.32 mA/cm(2) and the double-layer capacitance (C(dl)) from 9.63 x 10(-5) to 1.79 x 10(-4)F and reduces the charge transfer resistance (R(ct)) from 6.58 x 10(4) to 6.64 x 10(3)Omega cm(2). In spite of the active dissolution, the Ti-15Mo alloy exhibit passivity at anodic potentials at all concentrations of the fluoride ions studied. In dental implants since the exposure of the alloy will be limited only to its 'neck', the amount of Mo ions released from Ti-15Mo alloy is not likely to have an adverse and hence, in terms of biocompatibility this alloy seems to be acceptable for dental implant applications. The results of the study suggest that Ti-15Mo alloy can be a suitable alternative for dental implant applications.     

Adherence of investment to Au–Pd–Ag alloy using a vacuum–argon pressure casting machine

OBJECTIVE: The removal of adhered investment material from marginal metal surfaces represents a possible risk of poor marginal adaptation.The aim of this work was to evaluate the effects of argon on investment adherence to the casting surface and on the alloy surface microstructure. METHODS: A die of stainless steel was used. 10 wax copings were cast by vacuum-argon pressure, while 10 copings by vacuum-air pressure using a Combilabor CLG-77 A in a graphite crucible; supply was direct with curved sprues of slashed circle 3.5 mm. The alloy used was Herabond. After coarse investment, removal of all specimens were investigated with scanning electron microscopy and semi-quantitative digital densitometry. RESULTS: The specimens cast under vacuum-argon pressure showed less amount of investment adhered (unpaired t test of grouped specimens, difference 2.896x10(5)pixel; p=0.002) while the grain size on the casting surface increased significantly p=0.000 (difference 5.968(microm). SIGNIFICANCE: Vacuum-argon pressure supply during casting reduces the investment adherence to the metal surface, and increases the packing density and size of the grains, especially on the casting surface. These minimize the risk of marginal distortions due to casting cleaning procedures and facilitate the finishing and polishing procedures.