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Sample records for dental gold alloy

  1. Dissolution ad uptake of cadmium from dental gold solder alloy implants

    International Nuclear Information System (INIS)

    Bergman, B.; Bergman, M.; Soeremark, R.

    1977-01-01

    Pure metallic cadmium was irradiated by means of thermal neutrons. The irradiated cadmium ( 115 Cd) was placed in bags of gold foil and the bags were implanted subcutaneously in the neck region of mice. Two and 3 d respectively after implantation the mice were killed, the bags removed and the animals subjected to whole-body autoradiography. The autoradiograms revealed an uptake of 115 Cd in liver and kidney. In another experiment specimens of a cadmium-containing dental gold solder alloy, a cadmium-free dental casting gold alloy and soldered assemblies made of these two alloys were implanted subcutaneously in the neck region of mice. The animals were killed after 6 months; cadmium analysis showed significant increases in the cadmium concentration in liver and kidney of those mice which had been given implants of gold solder alloy. The study clearly shows that due to electrochemical corrosion cadmium can be released from implants and accumulated in the kidneys and the liver. (author)

  2. Biocompatibility of dental alloys

    Energy Technology Data Exchange (ETDEWEB)

    Braemer, W. [Heraeus Kulzer GmbH and Co. KG, Hanau (Germany)

    2001-10-01

    Modern dental alloys have been used for 50 years to produce prosthetic dental restorations. Generally, the crowns and frames of a prosthesis are prepared in dental alloys, and then veneered by feldspar ceramics or composites. In use, the alloys are exposed to the corrosive influence of saliva and bacteria. Metallic dental materials can be classified as precious and non-precious alloys. Precious alloys consist of gold, platinum, and small amounts of non-precious components such as copper, tin, or zinc. The non-precious alloys are based on either nickel or cobalt, alloyed with chrome, molybdenum, manganese, etc. Titanium is used as Grade 2 quality for dental purposes. As well as the dental casting alloys, high purity electroplated gold (99.8 wt.-%) is used in dental technology. This review discusses the corrosion behavior of metallic dental materials with saliva in ''in vitro'' tests and the influence of alloy components on bacteria (Lactobacillus casei and Streptococcus mutans). The test results show that alloys with high gold content, cobalt-based alloys, titanium, and electroplated gold are suitable for use as dental materials. (orig.)

  3. Photoelectron spectroscopic study on the electronic structures of the dental gold alloys and their interaction with L-cysteine

    International Nuclear Information System (INIS)

    Ogawa, Koji; Takahashi, Kazutoshi; Azuma, Junpei; Kamada, Masao; Tsujibayashi, Toru; Ichimiya, Masayoshi; Fujimoto, Hitoshi; Sumimoto, Michinori

    2011-01-01

    The valence electronic structures of the dental gold alloys, type 1, type 3, and K14, and their interaction with L-cysteine have been studied by ultraviolet photoelectron spectroscopy with synchrotron radiation. It was found that the electronic structures of the type-1 and type-3 dental alloys are similar to that of polycrystalline Au, while that of the K14 dental alloy is much affected by Cu. The peak shift and the change in shape due to alloying are observed in all the dental alloys. It is suggested that the new peak observed around 2 eV for the L-cysteine thin films on all the dental alloys may be due to the bonding of S 3sp orbitals with the dental alloy surfaces, and the Cu-S bond, as well as the Au-S and Au-O bonds, may cause the change in the electronic structure of the L-cysteine on the alloys.

  4. Dissolution and uptake of cadmium from dental gold solder alloy implants

    Energy Technology Data Exchange (ETDEWEB)

    Bergman, B; Bergman, M; Soeremark, R [Umeaa Univ. (Sweden); Karolinska Institutet, Stockholm (Sweden))

    1977-01-01

    Pure metallic cadmium was irradiated by means of thermal neutrons. The irradiated cadmium (/sup 115/Cd) was placed in bags of gold foil and the bags were implanted subcutaneously in the neck region of mice. Two and 3 d respectively after implantation the mice were killed, the bags removed and the animals subjected to whole-body autoradiography. The autoradiograms revealed an uptake of /sup 115/Cd in liver and kidney. In another experiment specimens of a cadmium-containing dental gold solder alloy, a cadmium-free dental casting gold alloy and soldered assemblies made of these two alloys were implanted subcutaneously in the neck region of mice. The animals were killed after 6 months; cadmium analysis showed significant increases in the cadmium concentration in liver and kidney of those mice which had been given implants of gold solder alloy. The study clearly shows that due to electrochemical corrosion cadmium can be released from implants and accumulated in the kidneys and the liver.

  5. Dental implant suprastructures using cobalt-chromium alloy compared with gold alloy framework veneered with ceramic or acrylic resin: a retrospective cohort study up to 18 years.

    Science.gov (United States)

    Teigen, Kyrre; Jokstad, Asbjørn

    2012-07-01

    An association between the long-term success and survival of implant-supported prostheses as a function of biomaterial combinations has not been established. The use of cast cobalt-chromium for the suprastructure framework may be an alternative to the conventional approach of using type 3 gold alloys. A retrospective chart audit of all patients who had received implant-supported fixed dental prostheses (FDP) before 1996 was identified in a private practice clinic. Data were recorded for FDPs made from four combinations of alloy frameworks and veneering material, i.e. type 3 gold and cobalt-chromium with ceramic or prefabricated acrylic teeth. The extracted data from the charts were subjected to explorative statistical tests including Kaplan-Meier survival analyses. Patients (n=198) with 270 short and extensive FDPs supported entirely by 1117 implants were identified. The average follow-up observation periods varied between 4 and 220 months, with an average of 120 months. The success and survival, as well as event rates and types of biological and technical complications, were similar for implant-supported FDPs using cobalt-chromium and type 3 gold alloy frameworks veneered with ceramics or prefabricated acrylic teeth. An influence of the suprastructure biomaterial combination on the clinical performance of the individual supporting implants could not be established. Implant-supported FDPs made from type 3 gold or cobalt-chromium frameworks and veneered with ceramic or prefabricated acrylic teeth demonstrate comparable clinical performance. The biomaterial combinations do not appear to influence the success or survival of the individual implants. © 2011 John Wiley & Sons A/S.

  6. Grindability of dental magnetic alloys.

    Science.gov (United States)

    Hayashi, Eisei; Kikuchi, Masafumi; Okuno, Osamu; Kimura, Kohei

    2005-06-01

    In this study, the grindability of cast magnetic alloys (Fe-Pt-Nb magnetic alloy and magnetic stainless steel) was evaluated and compared with that of conventional dental casting alloys (Ag-Pd-Au alloy, Type 4 gold alloy, and cobalt-chromium alloy). Grindability was evaluated in terms of grinding rate (i.e., volume of metal removed per minute) and grinding ratio (i.e., volume ratio of metal removed compared to wheel material lost). Solution treated Fe-Pt-Nb magnetic alloy had a significantly higher grinding rate than the aged one at a grinding speed of 750-1500 m x min(-1). At 500 m x min(-1), there were no significant differences in grinding rate between solution treated and aged Fe-Pt-Nb magnetic alloys. At a lower speed of 500 m x min(-1) or 750 m x min(-1), it was found that the grinding rates of aged Fe-Pt-Nb magnetic alloy and stainless steel were higher than those of conventional casting alloys.

  7. Optical characteristics of jewellery gold alloys

    International Nuclear Information System (INIS)

    Wan Mahmood bin Mat Yunus; Zainal Abidin bin Talib; Maarof bin Moksin; Abdul Fatah bin Awang Mat

    1994-01-01

    Measurements of the reflection of various sample of gold alloys were made over the wavelength range 400-800 nm. Samples were measured using a single beam spectrophotometer at 45 deg. angle of incidence. In this measurement no attempt was made to obtain the optical constants of the samples. The results showed that there were significant differences between bulk and thick samples, with sufficient spectra difference between different composition of the alloys

  8. Electronic structures of the L-cysteine film on dental alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, K., E-mail: e7141@cc.saga-u.ac.jp [Synchrotron Light Application Center, Saga University, Saga 840-8502 (Japan); Tsujibayashi, T. [Department of Physics, Osaka Dental University, Osaka 573-1121 (Japan); Takahashi, K.; Azuma, J. [Synchrotron Light Application Center, Saga University, Saga 840-8502 (Japan); Kakimoto, K. [Department of Geriatric Dentistry, Osaka Dental University, Osaka 573-1121 (Japan); Kamada, M. [Synchrotron Light Application Center, Saga University, Saga 840-8502 (Japan)

    2011-04-15

    Research highlights: {yields} The electronic structures of dental alloys and L-cysteine film were studied by PES. {yields} The density of states in the dental alloy originates from Au and Cu as constituents. {yields} The Cu-3d states contribute dominantly to the occupied states near the Fermi level. {yields} The electronic structure of L-cysteine thin film is different from the thick film. {yields} The bonding between Cu-3d and S-3sp states are formed at the interface. - Abstract: Metal-organic interfaces have been attracting continuous attention in many fields including basic biosciences. The surface of dental alloys could be one of such interfaces since they are used in a circumstance full of organic compounds such as proteins and bacteria. In this work, electronic structures of Au-dominant dental alloys, which have Ag and Cu besides Au, and those of L-cysteine on the dental alloys have been studied by photoelectron spectroscopy with synchrotron radiation. It was found that the density of states in the dental alloy originate from gold and copper as constituents, and the Cu-3d states contribute dominantly to the occupied states near the Fermi level. It was also found that the electronic structure of the L-cysteine thin film on the dental alloy is different from that of the L-cysteine thick film. The result indicates the formation of the orbital bonding between Cu-3d and S-3sp states in the thin film on the dental alloy.

  9. Electronic structures of the L-cysteine film on dental alloys

    International Nuclear Information System (INIS)

    Ogawa, K.; Tsujibayashi, T.; Takahashi, K.; Azuma, J.; Kakimoto, K.; Kamada, M.

    2011-01-01

    Research highlights: → The electronic structures of dental alloys and L-cysteine film were studied by PES. → The density of states in the dental alloy originates from Au and Cu as constituents. → The Cu-3d states contribute dominantly to the occupied states near the Fermi level. → The electronic structure of L-cysteine thin film is different from the thick film. → The bonding between Cu-3d and S-3sp states are formed at the interface. - Abstract: Metal-organic interfaces have been attracting continuous attention in many fields including basic biosciences. The surface of dental alloys could be one of such interfaces since they are used in a circumstance full of organic compounds such as proteins and bacteria. In this work, electronic structures of Au-dominant dental alloys, which have Ag and Cu besides Au, and those of L-cysteine on the dental alloys have been studied by photoelectron spectroscopy with synchrotron radiation. It was found that the density of states in the dental alloy originate from gold and copper as constituents, and the Cu-3d states contribute dominantly to the occupied states near the Fermi level. It was also found that the electronic structure of the L-cysteine thin film on the dental alloy is different from that of the L-cysteine thick film. The result indicates the formation of the orbital bonding between Cu-3d and S-3sp states in the thin film on the dental alloy.

  10. [Microanalytical determinations of gold alloys for fixed dentures].

    Science.gov (United States)

    Lotito, M; Negri, P; Fraschini, M

    1993-01-01

    In this work the authors analyse gold alloys for fixed prosthesis by X-ray spectrometry in energy dispersion (EDS). The results of this analysis, given in graphic and table form, show remarkable differences in alloy composition. For this reason recommended dentists are to be attentive and severe in the control of gold alloys for fixed prosthesis.

  11. In vivo effects of dental casting alloys

    Czech Academy of Sciences Publication Activity Database

    Venclíková, Z.; Benada, Oldřich; Bártová, J.; Joska, L.; Mrklas, L.; Procházková, J.; Stejskal, V.D.M.; Podzimek, Š.

    2006-01-01

    Roč. 27, č. 1 (2006), s. 25-32 ISSN 0172-780X R&D Projects: GA MZd NK7437 Institutional research plan: CEZ:AV0Z50200510 Keywords : dental alloys * metals * gingiva Subject RIV: EE - Microbiology, Virology Impact factor: 0.924, year: 2006

  12. Experimental observation of silver and gold penetration into dental ceramic by means of a radiotracer technique

    International Nuclear Information System (INIS)

    Moya, F.; Payan, J.; Bernardini, J.; Moya, E.G.

    1987-01-01

    A radiotracer technique was used to study silver and gold diffusion into dental porcelain under experimental conditions close to the real conditions in prosthetic laboratories for porcelain bakes. It was clearly shown that these non-oxidizable elements were able to diffuse into the ceramic as well as oxidizable ones. The penetration depth varied widely according to the element. The ratio DAg/DAu was about 10(3) around 850 degrees C. In contrast to gold, the silver diffusion rate was high enough to allow silver, from the metallic alloy, to be present at the external ceramic surface after diffusion into the ceramic. Hence, the greening of dental porcelains baked on silver-rich alloys could be explained mainly by a solid-state diffusion mechanism

  13. Effects of chemical composition on the corrosion of dental alloys.

    Science.gov (United States)

    Galo, Rodrigo; Ribeiro, Ricardo Faria; Rodrigues, Renata Cristina Silveira; Rocha, Luís Augusto; de Mattos, Maria da Glória Chiarello

    2012-01-01

    The aim of this study was to determine the effect of the oral environment on the corrosion of dental alloys with different compositions, using electrochemical methods. The corrosion rates were obtained from the current-potential curves and electrochemical impedance spectroscopy (EIS). The effect of artificial saliva on the corrosion of dental alloys was dependent on alloy composition. Dissolution of the ions occurred in all tested dental alloys and the results were strongly dependent on the general alloy composition. Regarding the alloys containing nickel, the Ni-Cr and Ni-Cr-Ti alloys released 0.62 mg/L of Ni on average, while the Co-Cr dental alloy released ions between 0.01 and 0.03 mg/L of Co and Cr, respectively.The open-circuit potential stabilized at a higher level with lower deviation (standard deviation: Ni-Cr-6Ti = 32 mV/SCE and Co-Cr = 54 mV/SCE). The potenciodynamic curves of the dental alloys showed that the Ni-based dental alloy with >70 wt% of Ni had a similar curve and the Co-Cr dental alloy showed a low current density and hence a high resistance to corrosion compared with the Ni-based dental alloys. Some changes in microstructure were observed and this fact influenced the corrosion behavior for the alloys. The lower corrosion resistance also led to greater release of nickel ions to the medium. The quantity of Co ions released from the Co-Cr-Mo alloy was relatively small in the solutions. In addition, the quantity of Cr ions released into the artificial saliva from the Co-Cr alloy was lower than Cr release from the Ni-based dental alloys.

  14. Corrosion of gold alloys and titanium in artificial saliva

    International Nuclear Information System (INIS)

    Brune, D.; Evje, D.

    1982-01-01

    Two types of gold alloys and one type of pure titanium have been submitted to corrosion in artificial saliva for periods of up to about 2 months. The release of copper, gold and silver from the gold alloys as well as titanium from the titanium matrix was measured with nuclear tracer technique. The physical/chemical state of the corrosion products of gold alloys referring to the ionic state or presence in particulate form has been examined retaining the particulate matter on a glass filter. Copper was observed to be mainly present in the ionic state. Considerable amounts of gold were observed to be retained on the glass filter explained by the presence of gold in particulate form or as a compentent of a dispersed collloidal phase. The estimation of the release of titanium was registered by the tracer nuclide 46 Sc assuming particulate matter to be deteriorated from the titanium surface. (author)

  15. Low gravity containerless processing of immiscible gold rhodium alloys

    Science.gov (United States)

    Andrews, J. Barry

    1986-01-01

    Under normal one-g conditions immiscible alloys segregate extensively during solidification due to sedementation of the more dense of the immiscible liquid phases. However, under low-g conditions it should be possible to form a dispersion of the two immiscible liquids and maintain this dispersed structure during solidification. Immiscible (hypermonotectic) gold-rhodium alloys were processed in the Marshall Space Flight Center 105 meter drop tube in order to investigate the influence of low gravity, containerless solidification on their microstructure. Hypermonotectic alloys composed of 65 atomic % rhodium exhibited a tendency for the gold rich liquid to wet the outer surface of the containerless processed samples. This tendency led to extensive segregation in several cases. However, well dispersed microstructures consisting of 2 to 3 micron diameter rhodium-rich spheres in a gold-rich matrix were produced in 23.4 atomic % rhodium alloys. This is one of the best dispersions obtained in research on immiscible alloy-systems to data.

  16. The effect of hydrogen peroxide concentration on metal ion release from dental casting alloys.

    Science.gov (United States)

    Al-Salehi, S K; Hatton, P V; Johnson, A; Cox, A G; McLeod, C

    2008-04-01

    There are concerns that tooth bleaching agents may adversely affect dental materials. The aim of this study was to test the hypothesis that increasing concentrations of hydrogen peroxide (HP) are more effective than water at increasing metal ion release from two typical dental casting alloys during bleaching. Discs (n = 28 for each alloy) were prepared by casting and heat treated to simulate a typical porcelain-firing cycle. Discs (n = 7) of each alloy were immersed in either 0%, 3%, 10% or 30% (w/v) HP solutions for 24 h at 37 degrees C. Samples were taken for metal ion release determination using inductively coupled plasma-mass spectrometry and the data analysed using a two-way anova followed by a one-way anova. The surface roughness of each disc was measured using a Talysurf contact profilometer before and after bleaching and the data analysed using a paired t-test. With the exception of gold, the differences in metal ion concentration after treatment with 0% (control) and each of 3%, 10% and 30% HP (w/v) were statistically significant (P alloys increased with increasing HP concentrations (over 3000% increase in Ni and 1400% increase in Pd ions were recorded when HP concentration increased from 0% to 30%). Surface roughness values of the samples before and after bleaching were not significantly different (P > 0.05) Exposure of the two dental casting alloys to HP solutions increased metal ion release of all the elements except gold.

  17. Determination of Commercial Karats on Gold Alloys for Jewellery

    International Nuclear Information System (INIS)

    Morales, S.E.A.

    1986-12-01

    An XRF method for the gold content determination in gold alloys was proposed and tested. Gold coins and ingot samples were analyzed. Monoelemental standards and two pint regression curves calculated with the NBSGSC program, Cd-109 annular source, Si-Li detector, 4096 channels analyzer and AXIL deconvolution software were employed. Good precision better than 1.5% and accuracy better than 2% were obtained. (author)

  18. Corrosion of Dental Au-Ag-Cu-Pd Alloys in 0.9 % Sodium Chloride Solution

    International Nuclear Information System (INIS)

    Chiba, Atsushi; Kusayanagi, Yukiharu

    2005-01-01

    Two Au-Ag-Cu-Pd dental casting alloys (Au:12% and 20%) used. The test solutions used 0.9 % NaCl solution (isotonic sodium chloride solution), 0.9 % NaCl solution containing 1 % lactic acid, and 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol dm -3 Na 2 S. The surface of two samples in three sample solutions was not natural discoloration during one year. The alloy containing 12 % gold was easily alloyed and the composition was uniform comparing with the alloy containing 20 % gold. The rest potentials have not a little effect after three months. The kinds of metals could not definitely from the oxidation and reduction waves of metal on the cyclic voltammograms. The dissolutions of gold and palladium were 12 % Au sample in the 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol dm -3 Na 2 S. The pH of solution had an affect on dissolution of copper, and sulfur ion had an affect on dissolution of silver. The copper dissolved amount from 20 % gold sample was about 26 times comparing with that of 12 % gold sample in the 0.9 % solution containing 1 % lactic acid. Corrosion products were silver chloride and copper chloride in NaCl solution, and silver sulfide and copper sulfide in NaCl solution containing Na 2 S

  19. The influence of a hyperbaric environment and increased oxygen partial pressure on the corrosion of dental alloys.

    Science.gov (United States)

    Mehl, Christian; Heblich, Frank; Lenz, Rudolf; Ludwig, Klaus; Kern, Matthias

    2011-09-01

    The purpose of this in-vitro study was to determine whether there is a correlation between a hyperbaric environment or increased oxygen partial pressure and the corrosion of dental alloys used for dental restorations in divers. Samples of three commercially available dental alloys (palladium-based, reduced-gold-content and high-gold-content) were tested in the DIN EN ISO 1562 static immersion test and the amount of dissolved ions measured by atomic absorption spectrometry. The specimens were exposed to one of the following three conditions: normobaric and normoxic conditions (PO2 21 kPa); 608 kPa (6 bar, PO2 127 kPa) pressurised air in a pressure chamber or 506 kPa (5 bar, PO2 304 kPa) pressurised nitrox in a pressure chamber. None of the exposures suggested a correlation between increased ion solubility as a measure of corrosion and increased ambient pressure of the three alloys. The reduced-gold-content alloy released zinc ions at twice the weekly recommended dose. When the palladium-based alloy was exposed to a hyperbaric or hyperbaric/hyperoxic environment, ion solubility increased only slightly for gallium and silver. Within the limited sample size of the current study it can be concluded that hyperbaric and/or hyperoxic conditions do not seem to be a risk for increased corrosion for any of the three tested alloys.

  20. Corrosion behavior of dental alloys used for retention elements in prosthodontics.

    Science.gov (United States)

    Nierlich, Judith; Papageorgiou, Spyridon N; Bourauel, Christoph; Hültenschmidt, Robert; Bayer, Stefan; Stark, Helmut; Keilig, Ludger

    2016-06-01

    The purpose of this study was to investigate the corrosion behavior of 10 different high noble gold-based dental alloys, used for prosthodontic retention elements, according to ISO 10271. Samples of 10 high-noble and noble gold-based dental alloys were subjected to: (i) static immersion tests with subsequent analysis of ion release for eight different elements using mass spectrometry; (ii) electrochemical tests, including open-circuit potential and potentiodynamic scans; and (iii) scanning electron microscopy, followed by energy-dispersive X-ray microscopy. The results were analyzed using one-way ANOVA and Sidak multiple-comparisons post-hoc test at a level of significance of α = 0.05. Significant differences were found among the 10 alloys studied for all ions (P alloys. Scanning electron microscopy analysis confirmed the existence of typically small-diameter corrosion defects, whilst the energy-dispersive X-ray analysis found no significant alteration in the elemental composition of the alloys. The results of this study reveal the variability in the corrosive resistance among the materials used for retention elements in prosthodontics. © 2016 Eur J Oral Sci.

  1. Cytotoxicity of dental alloys, metals, and ceramics assessed by millipore filter, agar overlay, and MTT tests.

    Science.gov (United States)

    Sjögren, G; Sletten, G; Dahl, J E

    2000-08-01

    Biocompatibility of dental materials is dependent on the release of elements from the materials. In addition, the composition, pretreatment, and handling of the materials influence the element release. This study evaluated the cytotoxicity of dental alloys, metals, and ceramics, with specific emphasis on the effects of altering the composition and the pretreatment. By using cells from a mouse fibroblast cell line and the agar overlay test, Millipore filter test, and MTT test, cytotoxicity of various metals, metal alloys, and ceramics for dental restoration were studied. Effects of altering the composition of a high noble gold alloy and of pretreatment of a ceramic-bonding alloy were also studied. In addition, the release of elements into the cell culture medium by the materials studied was measured using an inductively coupled plasma optical emission spectrophotometer. The results of the MTT test were analyzed statistically using ANOVA and Scheffé test at a significance level of P filter tests. For the MTT test, no significant differences were observed between these materials and controls, with the exception of JS C-gold and unalloyed titanium. The modified materials were ranked from "mildly cytotoxic" to "moderately cytotoxic" in the agar overlay and Millipore filter tests and from "noncytotoxic" to "moderately cytotoxic" in the MTT test. Thus, cytotoxicity was related to the alloy composition and treatment. The release of Cu and Zn seemed to be important for the cytotoxic effect. Alterations in the composition and the pretreatment can greatly influence the cytotoxicity, and the results stress the importance of carefully following the manufacturers' instructions when handling dental materials.

  2. Determination of phosphorus in gold or silver brazing alloys

    International Nuclear Information System (INIS)

    Antepenko, R.J.

    1976-01-01

    A spectrophotometric method has been devised for measuring microgram levels of phosphorus in brazing alloys of gold or silver alloys is normally measured by solid mass spectrometry, but the high nickel concentration produces a double ionized nickel spectral interference. The described procedures is based upon the formation of molybdovandophosphoric acid when a molybdate solution is added to an acidic solution containing orthophosphate and vanadate ions. The optimum acidity for forming the yellow colored product is 0.5 N hydrochloric acid. The working concentration range is from 0.1 to 1 ppm phosphorus using 100-mm cells and measuring the absorbance at 460 nm. The sample preparation procedure employs aqua regia to dissolve the alloy oxidize the phosphorus to orthophosphate. Cation-exchange chromatography is used to remove nickel ions and anion-exchange and chromatography to remove gold ions as the chloride complex. Excellent recoveries are obtained for standard phosphorus solutions run through the sample procedure. The procedure is applicable to a variety of gold or silver braze alloys requiring phosphorus analysis

  3. Evaluation of interface characterization and adhesion of glass ceramics to commercially pure titanium and gold alloy after thermal- and mechanical-loading

    NARCIS (Netherlands)

    Ccahuana Vasqueza, Vanessa Zulema; Ozcan, Mutlu; Kimpara, Estevao Tomomitsu

    Objectives. This study evaluated the effect of thermal- and mechanical-cycling on the shear bond strength of three low-fusing glassy matrix dental ceramics to commercial pure titanium (cpTi) when compared to conventional feldspathic ceramic fused to gold alloy. Methods. Metallic frameworks

  4. Assessment of exposures and potential risks to the US adult population from wear (attrition and abrasion) of gold and ceramic dental restorations.

    Science.gov (United States)

    Richardson, G Mark; Clemow, Scott R; Peters, Rachel E; James, Kyle J; Siciliano, Steven D

    2016-01-01

    Little has been published on the chemical exposures and risks of dental restorative materials other than from dental amalgam and composite resins. Here we provide the first exposure and risk assessment for gold (Au) alloy and ceramic restorative materials. Based on the 2001-2004 US National Health and Nutrition Examination Survey (NHANES), we assessed the exposure of US adults to the components of Au alloy and ceramic dental restorations owing to dental material wear. Silver (Ag) is the most problematic component of Au alloy restorations, owing to a combination of toxicity and proportional composition. It was estimated that adults could possess an average of four tooth surfaces restored with Au alloy before exceeding, on average, the reference exposure level (REL) for Ag. Lithium (Li) is the most problematic component of dental ceramics. It was estimated that adults could possess an average of 15 tooth surfaces restored with ceramics before exceeding the REL for Li. Relative risks of chemical exposures from dental materials decrease in the following order: Amalgam>Au alloys>ceramics>composite resins.

  5. Silver, gold, and alloyed silver-gold nanoparticles: characterization and comparative cell-biologic action

    Energy Technology Data Exchange (ETDEWEB)

    Mahl, Dirk; Diendorf, Joerg; Ristig, Simon [University of Duisburg-Essen, Department of Inorganic Chemistry, Center for Nanointegration Duisburg-Essen (CeNIDE) (Germany); Greulich, Christina [Ruhr-University of Bochum, Bergmannsheil University Hospital/Surgical Research (Germany); Li Zian; Farle, Michael [University of Duisburg-Essen, Faculty of Physics, Center for Nanointegration Duisburg-Essen (CeNIDE) (Germany); Koeller, Manfred [Ruhr-University of Bochum, Bergmannsheil University Hospital/Surgical Research (Germany); Epple, Matthias, E-mail: matthias.epple@uni-due.de [University of Duisburg-Essen, Department of Inorganic Chemistry, Center for Nanointegration Duisburg-Essen (CeNIDE) (Germany)

    2012-10-15

    Silver, gold, and silver-gold-alloy nanoparticles were prepared by citrate reduction modified by the addition of tannin during the synthesis, leading to a reduction in particle size by a factor of three. Nanoparticles can be prepared by this easy water-based synthesis and subsequently functionalized by the addition of either tris(3-sulfonatophenyl)phosphine or poly(N-vinylpyrrolidone). The resulting nanoparticles of silver (diameter 15-25 nm), gold (5-6 nm), and silver-gold (50:50; 10-12 nm) were easily dispersable in water and also in cell culture media (RPMI + 10 % fetal calf serum), as shown by nanoparticle tracking analysis and differential centrifugal sedimentation. High-resolution transmission electron microscopy showed a polycrystalline nature of all nanoparticles. EDX on single silver-gold nanoparticles indicated that the concentration of gold is higher inside a nanoparticle. The biologic action of the nanoparticles toward human mesenchymal stem cells (hMSC) was different: Silver nanoparticles showed a significant concentration-dependent influence on the viability of hMSC. Gold nanoparticles showed only a small effect on the viability of hMSC after 7 days. Surprisingly, silver-gold nanoparticles had no significant influence on the viability of hMSC despite the silver content. Silver nanoparticles and silver-gold nanoparticles in the concentration range of 5-20 {mu}g mL{sup -1} induced the activation of hMSC as indicated by the release of IL-8. In contrast, gold nanoparticles led to a reduction of the release of IL-6 and IL-8.

  6. Silver, gold, and alloyed silver-gold nanoparticles: characterization and comparative cell-biologic action

    Science.gov (United States)

    Mahl, Dirk; Diendorf, Jörg; Ristig, Simon; Greulich, Christina; Li, Zi-An; Farle, Michael; Köller, Manfred; Epple, Matthias

    2012-10-01

    Silver, gold, and silver-gold-alloy nanoparticles were prepared by citrate reduction modified by the addition of tannin during the synthesis, leading to a reduction in particle size by a factor of three. Nanoparticles can be prepared by this easy water-based synthesis and subsequently functionalized by the addition of either tris(3-sulfonatophenyl)phosphine or poly( N-vinylpyrrolidone). The resulting nanoparticles of silver (diameter 15-25 nm), gold (5-6 nm), and silver-gold (50:50; 10-12 nm) were easily dispersable in water and also in cell culture media (RPMI + 10 % fetal calf serum), as shown by nanoparticle tracking analysis and differential centrifugal sedimentation. High-resolution transmission electron microscopy showed a polycrystalline nature of all nanoparticles. EDX on single silver-gold nanoparticles indicated that the concentration of gold is higher inside a nanoparticle. The biologic action of the nanoparticles toward human mesenchymal stem cells (hMSC) was different: Silver nanoparticles showed a significant concentration-dependent influence on the viability of hMSC. Gold nanoparticles showed only a small effect on the viability of hMSC after 7 days. Surprisingly, silver-gold nanoparticles had no significant influence on the viability of hMSC despite the silver content. Silver nanoparticles and silver-gold nanoparticles in the concentration range of 5-20 μg mL-1 induced the activation of hMSC as indicated by the release of IL-8. In contrast, gold nanoparticles led to a reduction of the release of IL-6 and IL-8.

  7. Silver, gold, and alloyed silver–gold nanoparticles: characterization and comparative cell-biologic action

    International Nuclear Information System (INIS)

    Mahl, Dirk; Diendorf, Jörg; Ristig, Simon; Greulich, Christina; Li Zian; Farle, Michael; Köller, Manfred; Epple, Matthias

    2012-01-01

    Silver, gold, and silver–gold-alloy nanoparticles were prepared by citrate reduction modified by the addition of tannin during the synthesis, leading to a reduction in particle size by a factor of three. Nanoparticles can be prepared by this easy water-based synthesis and subsequently functionalized by the addition of either tris(3-sulfonatophenyl)phosphine or poly(N-vinylpyrrolidone). The resulting nanoparticles of silver (diameter 15–25 nm), gold (5–6 nm), and silver–gold (50:50; 10–12 nm) were easily dispersable in water and also in cell culture media (RPMI + 10 % fetal calf serum), as shown by nanoparticle tracking analysis and differential centrifugal sedimentation. High-resolution transmission electron microscopy showed a polycrystalline nature of all nanoparticles. EDX on single silver–gold nanoparticles indicated that the concentration of gold is higher inside a nanoparticle. The biologic action of the nanoparticles toward human mesenchymal stem cells (hMSC) was different: Silver nanoparticles showed a significant concentration-dependent influence on the viability of hMSC. Gold nanoparticles showed only a small effect on the viability of hMSC after 7 days. Surprisingly, silver–gold nanoparticles had no significant influence on the viability of hMSC despite the silver content. Silver nanoparticles and silver–gold nanoparticles in the concentration range of 5–20 μg mL −1 induced the activation of hMSC as indicated by the release of IL-8. In contrast, gold nanoparticles led to a reduction of the release of IL-6 and IL-8.

  8. Application of the Fundamental Parameter Method for X-ray fluorescence analysis of gold jewellery alloys

    International Nuclear Information System (INIS)

    Le Hong Khiem

    2004-01-01

    The Fundamental Parameter Method has been used for the correction of the matrix effects for determination of the fineness of gold in the ternary Au-Ag-Cu yellow jewellery alloys. A computer code GOLDANA based on this algorithm has been developed for both data taking and on-line determining the fineness of gold jewellery. Only one ternary Au-Ag-Cu standard sample is required. The analysis performance has been tested by measurements conducted on certified gold reference materials, with the use of the fundamental method, could be used for quickly determining the gold concentration in gold jewellery alloys with an acceptable accuracy for the gold jewellery producers. (author)

  9. 21 CFR 872.3070 - Dental amalgam, mercury, and amalgam alloy.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Dental amalgam, mercury, and amalgam alloy. 872... SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3070 Dental amalgam, mercury... elemental mercury, supplied as a liquid in bulk, sachet, or predosed capsule form, and amalgam alloy...

  10. Enhancement of antibiotic effect via gold:silver-alloy nanoparticles

    International Nuclear Information System (INIS)

    Moreira dos Santos, Margarida; Queiroz, Margarida João; Baptista, Pedro V.

    2012-01-01

    A strategy for the development of novel antimicrobials is to combine the stability and pleiotropic effects of inorganic compounds with the specificity and efficiency of organic compounds, such as antibiotics. Here we report on the use of gold:silver-alloy (Au:Ag-alloy) nanoparticles, obtained via a single-step citrate co-reduction method, combined to conventional antibiotics to enhance their antimicrobial effect on bacteria. Addition of the alloy nanoparticles considerably decreased the dose of antibiotic necessary to show antimicrobial effect, both for bacterial cells growing in rich medium in suspension and for bacterial cells resting in a physiological buffer on a humid cellulose surface. The observed effect was more pronounced than the sum of the individual effects of the nanoparticles and antibiotic. We demonstrate the enhancement effect of Au:Ag-alloy nanoparticles with a size distribution of 32.5 ± 7.5 nm mean diameter on the antimicrobial effect of (i) kanamycin on Escherichia coli (Gram-negative bacterium), and (ii) a β-lactam antibiotic on both a sensitive and resistant strain of Staphylococcus aureus (Gram-positive bacterium). Together, these results may pave the way for the combined use of nanoparticle–antibiotic conjugates towards decreasing antibiotic resistance currently observed for certain bacteria and conventional antibiotics.

  11. Enhancement of antibiotic effect via gold:silver-alloy nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Moreira dos Santos, Margarida, E-mail: margarida.santos@fct.unl.pt; Queiroz, Margarida Joao; Baptista, Pedro V. [Universidade Nova de Lisboa, CIGMH, Departamento Ciencias da Vida, Faculdade de Ciencias e Tecnologia (Portugal)

    2012-05-15

    A strategy for the development of novel antimicrobials is to combine the stability and pleiotropic effects of inorganic compounds with the specificity and efficiency of organic compounds, such as antibiotics. Here we report on the use of gold:silver-alloy (Au:Ag-alloy) nanoparticles, obtained via a single-step citrate co-reduction method, combined to conventional antibiotics to enhance their antimicrobial effect on bacteria. Addition of the alloy nanoparticles considerably decreased the dose of antibiotic necessary to show antimicrobial effect, both for bacterial cells growing in rich medium in suspension and for bacterial cells resting in a physiological buffer on a humid cellulose surface. The observed effect was more pronounced than the sum of the individual effects of the nanoparticles and antibiotic. We demonstrate the enhancement effect of Au:Ag-alloy nanoparticles with a size distribution of 32.5 {+-} 7.5 nm mean diameter on the antimicrobial effect of (i) kanamycin on Escherichia coli (Gram-negative bacterium), and (ii) a {beta}-lactam antibiotic on both a sensitive and resistant strain of Staphylococcus aureus (Gram-positive bacterium). Together, these results may pave the way for the combined use of nanoparticle-antibiotic conjugates towards decreasing antibiotic resistance currently observed for certain bacteria and conventional antibiotics.

  12. Structure and grindability of dental Ti-Cr alloys

    International Nuclear Information System (INIS)

    Hsu, H.-C.; Wu, S.-C.; Chiang, T.-Y.; Ho, W.-F.

    2009-01-01

    The purpose of this study was to investigate the structure and microhardness of a series of binary Ti-Cr alloys with Cr contents up to 30 wt%. In addition, the grindability was also evaluated using an electric dental handpiece with SiC wheels, with the goal of developing a titanium alloy with better mechanical properties and machinability than commercially pure titanium (c.p. Ti), a metal generally considered to be difficult to machine. This study evaluated the phase and structure of Ti-Cr alloys, using an X-ray diffraction (XRD) for phase analysis and optical microscope for microstructure of the etched alloys. Grindability was evaluated by measuring the amount of metal volume removed after grinding for 1 min. Results indicated that the structure of Ti-Cr alloys is sensitive to the Cr content. The cast c.p. Ti has a hexagonal α phase. With 5 wt% Cr, metastable β phase starts to be retained. With Cr contents higher than 10 wt%, the equi-axed β phase is almost entirely retained. In addition, athermal ω phase was found in the Ti-5Cr and Ti-10Cr alloys. The largest quantity of ω phase and highest microhardness were found in Ti-10Cr alloy. The grinding rate of the Ti-Cr alloys showed a similar tendency to the microhardness. The Ti-10Cr alloy exhibited the best grindability, especially at 1000 m/min, which presumably due to the brittle nature of the alloy containing the ω phase in the β matrix.

  13. [Studies on high temperature oxidation of noble metal alloys for dental use. (III) On high temperature oxidation resistance of noble metal alloys by adding small amounts of alloying elements. (author's transl)].

    Science.gov (United States)

    Ohno, H

    1976-11-01

    The previous report pointed out the undesirable effects of high temperature oxidation on the casting. The influence of small separate additions of Zn, Mg, Si, Be and Al on the high temperature oxidation of the noble metal alloys was examined. These alloying elements were chosen because their oxide have a high electrical resistivity and they have much higher affinity for oxygen than Cu. The casting were oxidized at 700 degrees C for 1 hour in air. The results obtained were as follows: 1. The Cu oxides are not observed on the as-cast surface of noble metal alloys containing small amounts of Zn, Mg, Si, Be, and Al. The castings have gold- or silver-colored surface. 2. After heating of the unpolished and polished castings, the additions of Si, Be and Al are effective in preventing oxidation of Cu in the 18 carats gold alloys. Especially the golden surface is obtained by adding Be and Al. But there is no oxidation-resistance on the polished castings in the alloys containing Zn and Mg. 3. The zinc oxide film formed on the as-cast specimen is effective in preventing of oxidation Cu in 18 carats gold alloys. 4. It seems that the addition of Al is most available in dental application.

  14. Measurement of in-vivo dosage increase due to dental alloys during therapeutic irradiation of the mouth cavity

    International Nuclear Information System (INIS)

    Thilmann, C.; Mose, S.; Saran, F.; Schopohl, B.; Boettcher, H.D.

    1995-01-01

    The degree of dosage increase in the immediate surrounding of metallic dental materials was measured in an in-vivo study during therapeutic irradiation with 60 Co gamma rays in the area of mouth cavity of 11 patients. Measurements were carried out by thermoluminescent dosimetry at permamently fixed golden teeth and alloy specimens containing gold and palladium and amalgam. The following relative dodage values according to a simultanelusly measured reference value were measured at the surface of the different dental materials: 161% near fixed golden caps, 168% near the specimen containing gold in a high percentage, 133% near the specimen of palladium and 161% near the specimen of amalgam. The in vivo measured dosage increases due to metallic dental prosthesis are less than values obtained using back scatter arramgements for irradiating phantoms. Despite this, they could be of clinical relevance. Thus the usage of a mucous membrane protection during irradiation with 60 Co, as a means of preventing local lesions of the oral mucosa, due to dental alloys within the treatment volume remains inevitable. (orig.) [de

  15. Influence of S. mutans on base-metal dental casting alloy toxicity.

    Science.gov (United States)

    McGinley, E L; Dowling, A H; Moran, G P; Fleming, G J P

    2013-01-01

    We have highlighted that exposure of base-metal dental casting alloys to the acidogenic bacterium Streptococcus mutans significantly increases cellular toxicity following exposure to immortalized human TR146 oral keratinocytes. With Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), S. mutans-treated nickel-based (Ni-based) and cobalt-chromium-based (Co-Cr-based) dental casting alloys were shown to leach elevated levels of metal ions compared with untreated dental casting alloys. We targeted several biological parameters: cell morphology, viable cell counts, cell metabolic activity, cell toxicity, and inflammatory cytokine expression. S. mutans-treated dental casting alloys disrupted cell morphology, elicited significantly decreased viable cell counts (p casting alloys induced elevated levels of cellular toxicity compared with S. mutans-treated Co-Cr-based dental casting alloys. While our findings indicated that the exacerbated release of metal ions from S. mutans-treated base-metal dental casting alloys was the likely result of the pH reduction during S. mutans growth, the exact nature of mechanisms leading to accelerated dissolution of alloy-discs is not yet fully understood. Given the predominance of S. mutans oral carriage and the exacerbated cytotoxicity observed in TR146 cells following exposure to S. mutans-treated base-metal dental casting alloys, the implications for the long-term stability of base-metal dental restorations in the oral cavity are a cause for concern.

  16. Magnesium–Gold Alloy Formation by Underpotential Deposition of Magnesium onto Gold from Nitrate Melts

    Directory of Open Access Journals (Sweden)

    Vesna S. Cvetković

    2017-03-01

    Full Text Available Magnesium underpotential deposition on gold electrodes from magnesium nitrate –ammonium nitrate melts has been investigated. Linear sweep voltammetry and potential step were used as electrochemical techniques. Scanning electron microscopy (SEM, energy dispersive spectrometry (EDS and X-ray diffraction (XRD were used for characterization of obtained electrode surfaces. It was observed that reduction processes of nitrate, nitrite and traces of water (when present, in the Mg underpotential range studied, proceeded simultaneously with magnesium underpotential deposition. There was no clear evidence of Mg/Au alloy formation induced by Mg UPD from the melt made from eutectic mixture [Mg(NO32·6H2O + NH4NO3·XH2O]. However, EDS and XRD analysis showed magnesium present in the gold substrate and four different Mg/Au alloys being formed as a result of magnesium underpotential deposition and interdiffusion between Mg deposit and Au substrate from the melt made of a nonaqueous [Mg(NO32 + NH4NO3] eutectic mixture at 460 K.

  17. Stress corrosion cracking and dealloying of copper-gold alloy in iodine vapor

    International Nuclear Information System (INIS)

    Galvez, M.F.; Bianchi, G.L.; Galvele, J.R.

    1993-01-01

    The susceptibility to stress corrosion cracking of copper-gold alloy in iodine vapor was studied and the results were analyzed under the scope of the surface mobility stress corrosion cracking mechanism. The copper-gold alloy undergoes stress corrosion cracking in iodine. Copper iodide was responsible of that behavior. The copper-gold alloy shows two processes in parallel: stress corrosion cracking and dealloying. As was predicted by the surface mobility stress corrosion cracking mechanism, the increase in strain rate induces an increase in the crack propagation rate. (Author)

  18. Alloying behavior of iron, gold and silver in AlCoCrCuNi-based equimolar high-entropy alloys

    International Nuclear Information System (INIS)

    Hsu, U.S.; Hung, U.D.; Yeh, J.W.; Chen, S.K.; Huang, Y.S.; Yang, C.C.

    2007-01-01

    High-entropy alloys are newly developed alloys that are composed, by definition, of at least five principal elements with concentrations in the range of 5-35 at.%. Therefore, the alloying behavior of any given principal element is significantly affected by all the other principal elements present. In order to elucidate this further, the influence of iron, silver and gold addition on the microstructure and hardness of AlCoCrCuNi-based equimolar alloys has been examined. The as-cast AlCoCrCuNi base alloy is found to have a dendritic structure, of which only solid solution FCC and BCC phases can be observed. The BCC dendrite has a chemical composition close to that of the nominal alloy, with a deficiency in copper however, which is found to segregate and form a FCC Cu-rich interdendrite. The microstructure of the iron containing alloys is similar to that of the base alloy. It is found that both of these aforementioned alloys have hardnesses of about 420 HV, which is equated to their similar microstructures. The as-cast ingot forms two layers of distinct composition with the addition of silver. These layers, which are gold and silver in color, are determined to have a hypoeutectic Ag-Cu composition and a multielement mixture of the other principal elements, respectively. This indicates the chemical incompatibility of silver with the other principal elements. The hardnesses of the gold (104 HV) and silver layers (451 HV) are the lowest and highest of the alloy systems studied. This is attributed to the hypoeutectic Ag-Cu composition of the former and the reduced copper content of the latter. Only multielement mixtures, i.e. without copper segregation, form in the gold containing alloy. Thus, it may be said that gold acts as a 'mixing agent' between copper and the other elements. Although several of the atom pairs in the gold containing alloy have positive enthalpies, thermodynamic considerations show that the high entropy contribution is sufficient to counterbalance

  19. Measurement of the isotope effect of the diffusion of silver and gold in gold and of silver in silver-gold alloys

    International Nuclear Information System (INIS)

    Wolter, D.

    1974-01-01

    The silver isotopes Ag 105 and Agsup(110m) and the gold isotopes Au 195 and Au 199 were used for isotope effect measurements. The isotope effect of the gold self-diffusion was measured on four monocrystals samples at about 850 0 C, that of silver in gold monocrystals at five different temperatures between 731 0 C and 1050 0 C. Furthermore, the isotope effect for silver at 904 0 C was measured on seven silver-gold alloys of varying silver concentration. The correlation factor was determined from the measurements. (HPOE/LH) [de

  20. Electronic structure of the L-cysteine films on dental alloys studied by ultraviolet photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Ogawa, K; Takahashi, K; Azuma, J; Kamada, M; Tsujibayashi, T; Ichimiya, M

    2013-01-01

    The valence electronic structures of the dental alloys, type 1, type 3, K14, and MC12 and their interaction with L-cysteine have been studied by ultraviolet photoelectron spectroscopy with synchrotron radiation. It was found that the electronic structures of the type-1 and type-3 dental alloys are similar to that of polycrystalline Au, while that of the K14 dental alloy is much affected by Cu. The electronic states of the MC12 dental alloy originate dominantly from Cu 3d states and Pd 4d states around the top of the valence bands, while the 4∼7-eV electronic structure of MC12 originates from the Ag 4d states. The peak shift and the change in shape due to alloying are observed in all the dental alloys. For the L-cysteine thin films, new peak or structure observed around 2 eV on all the dental alloys is suggested to be due to the bonding of S 3sp orbitals with the dental alloy surfaces. The Cu-S bond as well as the Au-S and Au-O bonds may cause the change in the electronic structure of the L-cysteine on type 1, type 3 and K14. For MC12, the interaction with L-cysteine may be dominantly due to the Pd-S, Cu-S, and Ag-O bonds, while the contribution of the Ag-S bond is small.

  1. In situ gold nanoparticles formation: contrast agent for dental optical coherence tomography

    Science.gov (United States)

    Braz, Ana K. S.; Araujo, Renato E. de; Ohulchanskyy, Tymish Y.; Shukla, Shoba; Bergey, Earl J.; Gomes, Anderson S. L.; Prasad, Paras N.

    2012-06-01

    In this work we demonstrate the potential use of gold nanoparticles as contrast agents for the optical coherence tomography (OCT) imaging technique in dentistry. Here, a new in situ photothermal reduction procedure was developed, producing spherical gold nanoparticles inside dentinal layers and tubules. Gold ions were dispersed in the primer of commercially available dental bonding systems. After the application and permeation in dentin by the modified adhesive systems, the dental bonding materials were photopolymerized concurrently with the formation of gold nanoparticles. The gold nanoparticles were visualized by scanning electron microscopy (SEM). The SEM images show the presence of gold nanospheres in the hybrid layer and dentinal tubules. The diameter of the gold nanoparticles was determined to be in the range of 40 to 120 nm. Optical coherence tomography images were obtained in two- and three-dimensions. The distribution of nanoparticles was analyzed and the extended depth of nanosphere production was determined. The results show that the OCT technique, using in situ formed gold nanoparticles as contrast enhancers, can be used to visualize dentin structures in a non-invasive and non-destructive way.

  2. Technical aspects of casting and their effect on the quality of Remanium CSe dental alloys

    Directory of Open Access Journals (Sweden)

    Dorota Klimecka-Tatar

    2016-03-01

    Full Text Available The study concerns on investigation of Remanium CSE alloy, one of the dental alloys used in metal-ceramic connection preparation. The alloys based on Ni-Cr-Mo are widely used in dental engineering because of their high mechanical, tribological properties as well as high corrosion resistance. The tested alloy has been processed in three ways – it has been remelted and then casted using three technologiescommonly used in dental laboratories, i.e. with: oxy-acetylene burner (1, induction furnace (2 and Volts arc (3. The aim of the study was to evaluate the effect of the melting and casting techniques on the mechanical strength and stereometric surface properties. The results revealed that the quality of Remanium CSe dental alloys significantly depend on the method of the material processing.

  3. Biocorrosion of dental alloys due to Desulfotomaculum nigrificans bacteria.

    Science.gov (United States)

    Mystkowska, Joanna

    2016-01-01

    Degradation processes of metallic biomaterials in the oral cavity limit the stability and reliability of dental materials. The influence of environment bacteria Desulfotomaculum nigrificans sulfate reducing bacteria on the corrosion processes of Co-Cr-Mo and Ti-6Al-4V alloys was assessed. After 28 and 56 days of contact of the materials with the bacterial environment, the surfaces of the biomaterials tested were observed by means of confocal scanning laser microscopy (CSLM), and their chemical composition was studied using X-Ray Photoelectron Spectrometry (XPS). Corrosive changes and the presence of sulfur (with medium atomic concentration of 0.5% for Co-Cr-Mo and 0.3% for Ti-6AL-4V) were observed on the surface of the biomaterials. Image analysis conducted using Aphelion software indicated that corrosion pits took up approx. 2.3% and 1.8% (after 28 days) and 4.2% and 3.1% (after 56 days) of the total test surfaces of cobalt and titanium alloys respectively. The greatest number of corrosion pits had a surface area within the range of 1-50 m2. They constituted from 37% up to 83% of all changes, depending on the type of material. An evident influence of the SRB on the surfaces of cobalt and titanium alloys was observed. Significant corrosive losses caused by the activity of microorganisms were observed on the metallic surfaces under study. The results of this study have much cognitive and utilitarian significance.

  4. Investigation of the mechanism of mercury removal from a silver dental amalgam alloy

    Directory of Open Access Journals (Sweden)

    M. DJURDJEVIC

    2004-12-01

    Full Text Available An investigation of silver dental amalgam decomposition and the mercury removal mechanism was performed. The decomposition process was analysed during thermal treatment in the temperature interval from 400 °C to 850 °C and for times from 0.5 to 7.5 h. The chemical compositions of the silver dental amalgam alloy and the treated alloy were tested and microstructure analysis using optical and scanning electron microscopy was carried out. The phases were identified using energy disperse electron probe microanalysis. A mechanism for the mercury removal process from silver dental amalgam alloy is suggested.

  5. Development of a discriminatory biocompatibility testing model for non-precious dental casting alloys.

    LENUS (Irish Health Repository)

    McGinley, Emma Louise

    2011-12-01

    To develop an enhanced, reproducible and discriminatory biocompatibility testing model for non-precious dental casting alloys, prepared to a clinically relevant surface finishing condition, using TR146 oral keratinocyte cells.

  6. Effect of heat treatments on machinability of gold alloy with age-hardenability at intraoral temperature.

    Science.gov (United States)

    Watanabe, I; Baba, N; Watanabe, E; Atsuta, M; Okabe, T

    2004-01-01

    This study investigated the effect of heat treatment on the machinability of heat-treated cast gold alloy with age-hardenability at intraoral temperature using a handpiece engine with SiC wheels and an air-turbine handpiece with carbide burs and diamond points. Cast gold alloy specimens underwent various heat treatments [As-cast (AC); Solution treatment (ST); High-temperature aging (HA), Intraoral aging (IA)] before machinability testing. The machinability test was conducted at a constant machining force of 0.784N. The three circumferential speeds used for the handpiece engine were 500, 1,000 and 1,500 m/min. The machinability index (M-index) was determined as the amount of metal removed by machining (volume loss, mm(3)). The results were analyzed by ANOVA and Scheffé's test. When an air-turbine handpiece was used, there was no difference in the M-index of the gold alloy among the heat treatments. The air-turbine carbide burs showed significantly (pmachinability of the gold alloy using the air-turbine handpiece. The heat treatments had a small effect on the M-index of the gold alloy machined with a SiC wheel for a handpiece engine.

  7. Reciprocal interaction between dental alloy biocorrosion and Streptococcus mutans virulent gene expression.

    Science.gov (United States)

    Zhang, Songmei; Qiu, Jing; Ren, Yanfang; Yu, Weiqiang; Zhang, Fuqiang; Liu, Xiuxin

    2016-04-01

    Corrosion of dental alloys is a major concern in dental restorations. Streptococcus mutans reduces the pH in oral cavity and induces demineralization of the enamel as well as corrosion of restorative dental materials. The rough surfaces of dental alloys induced by corrosion enhance the subsequent accumulation of plaque. In this study, the corrosion process of nickel-chromium (Ni-Cr) and cobalt-chromium (Co-Cr) alloys in a nutrient-rich medium containing S. mutans was studied using inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray photoelectron spectroscopy (XPS) and electrochemical corrosion test. Our results showed that the release of Ni and Co ions increased, particularly after incubation for 3 days. The electrochemical corrosion results showed a significant decrease in the corrosion resistance (Rp) value after the alloys were immersed in the media containing S. mutans for 3 days. Correspondingly, XPS revealed a reduction in the relative dominance of Ni, Co, and Cr in the surface oxides after the alloys were immersed in the S. mutans culture. After removal of the biofilm, the pre-corroded alloys were re-incubated in S. mutans medium, and the expressions of genes associated with the adhesion and acidogenesis of S. mutans, including gtfBCD, gbpB, fif and ldh, were evaluated by detecting the mRNA levels using real-time reverse transcription polymerase chain reaction (RT-PCR). We found that the gtfBCD, gbpB, ftf and Idh expression of S. mutans were noticeably increased after incubation with pre-corroded alloys for 24 h. This study demonstrated that S. mutans enhanced the corrosion behavior of the dental alloys, on the other hand, the presence of corroded alloy surfaces up-regulated the virulent gene expression in S. mutans. Compared with smooth surfaces, the rough corroded surfaces of dental alloys accelerated the bacteria-adhesion and corrosion process by changing the virulence gene expression of S. mutans.

  8. X-ray diffraction analysis of cold rolled strip from jewelry 585 gold alloy

    Directory of Open Access Journals (Sweden)

    Karastojković Zoran

    2017-01-01

    Full Text Available Here is investigated an golden alloy 585 as one of widely used gold alloy in jewelry production. Insufficient data, even in nowadays, exist about the production schedule of gold alloys, including melting, rolling and heat treatment regimes. The structures of complex alloys, such as used golden alloy, are less known and/or investigated. Principally, the constitutional diagram of Au-Ag-Cu system is known, as a (metastable equilibrium diagram. But, after relatively fast cooling from liquid state during casting will be obtained polycrystalline grains, different from equilibrium conditions. Such polycrystalline material frequently undergoes to rolling for obtaining a desired shape of (semiproduct. Those processes, casting and rolling, will show the influence on the final structure to be obtained, also on properties of such treated alloy. The structural changes and obtained phases in metal working processes of 585 gold alloy still are not well examined, so here is provided an XRD examination after heavy reduction at cold rolling of a strip. The castings were in the flat form in dimension of 4,5x50x50mm, than cold rolled to 1,5mm, intermediate annealed and finally cold rolled to thickness of 0,5mm with height reduction of 66,7%.

  9. Surface Plasmons and Surface Enhanced Raman Spectra of Aggregated and Alloyed Gold-Silver Nanoparticles

    Directory of Open Access Journals (Sweden)

    Y. Fleger

    2009-01-01

    Full Text Available Effects of size, morphology, and composition of gold and silver nanoparticles on surface plasmon resonance (SPR and surface enhanced Raman spectroscopy (SERS are studied with the purpose of optimizing SERS substrates. Various gold and silver films made by evaporation and subsequent annealing give different morphologies and compositions of nanoparticles and thus different position of the SPR peak. SERS measurements of 4-mercaptobenzoic acid obtained from these films reveal that the proximity of the SPR peak to the exciting laser wavelength is not the only factor leading to the highest Raman enhancement. Silver nanoparticles evaporated on top of larger gold nanoparticles show higher SERS than gold-silver alloyed nanoparticles, in spite of the fact that the SPR peak of alloyed nanoparticles is narrower and closer to the excitation wavelength. The highest Raman enhancement was obtained for substrates with a two-peak particle size distribution for excitation wavelengths close to the SPR.

  10. Hydrogen and deuterium permeation in copper alloys, copper--gold brazing alloys, gold, and the in situ growth of stable oxide permeation barriers

    International Nuclear Information System (INIS)

    Begeal, D.R.

    1978-01-01

    The deuterium permeation through several copper alloys has been measured over a temperature range of 550 to 830 K using the membrane technique. In some cases, the hydrogen permeability was also measured. The results were divided into three categories: common alloys, gold alloys, and stable oxide forming alloys. Common alloys which showed typical bulk metallic diffusion with litle change in the permeation activation energy as compared to copper (77 kJ/mol for D 2 ) were: (additions are in weight percent) 5% Sn, 2.3% U, 0.15% Zr, 4% Sn+4% Pb+4% Zn, 3% Si, and 7% Al+2% Fe. Compared to copper, the D 2 permeability at 573 K was reduced by factors of 2.0, 2.7, 4.5, 5.3, 5.9, and 7.0, respectively. A series of gold--copper alloys including pure gold, 80% Au, 50% Au, 49% Au, and 35% Au also showed typical bulk metallic diffusion with a trend of decreasing permeability (increasing activation energies for permeation) with increasing gold content. There were also pronounced inflections or shifts in the permeability at approx.370 0 C, or about the order--disorder transition for Cu 3 Au and CuAu, for the 80% and 50% alloys. Two alloys did not exhibit bulk metallic permeation behavior and the permeabiltiy was in fact controlled by surface oxide layers. It was found that a layer of beryllium oxide could be formed on Cu+2% Be and a layer of aluminum oxide could be formed on Cu+7% Al+2% Si. As compared to 0.25 mm-thick copper, the deuterium permeability at 500 0 C was reduced by a factor of approx.250 for Cu--Be and approx.1000 for Cu--Al--Si. The activation energies for deuterium permeation were 98 kJ/mol and 132 kJ/mol, respectively. The mechanism for the oxide growth is the high-temperature hydrogen reduction of nearby less stable oxides, simultaneous with oxidation of the active metal, Be or Al, by trace amounts of water in the hydrogen. Ion microprobe mass analysis identified the oxide layers as containing beryllium or aluminum but not containing copper

  11. Effect of different oxidation treatments on the bonding strength of new dental alloys

    International Nuclear Information System (INIS)

    Lee, Sang-Bae; Lee, Ju-hye; Kim, Woong-Chul; Oh, Sae-Yoon; Kim, Kyoung-Nam; Kim, Ji-Hwan

    2009-01-01

    The influences of heat treatment and addition of a small amount of base metal (In, Sn, and Ir) for oxidation in Au-Pt-based alloy were investigated by electron spectroscopy and scanning electron microscopy. Au-Pt-based alloys were prepared by argon-arc melting furnace and then they are heat treated. Oxidation on alloy was significantly affected by addition of base metal (In and Sn) and heat treatment. The bond strength of the alloys was not dependent on the changing heat treatment. These results indicated that the Sn and In could be effective as oxidation elements for porcelain bonding to gold alloys.

  12. Variations of color with alloying elements in Pd-free Au-Pt-based high noble dental alloys

    International Nuclear Information System (INIS)

    Shiraishi, Takanobu; Takuma, Yasuko; Miura, Eri; Fujita, Takeshi; Hisatsune, Kunihiro

    2007-01-01

    The effects of alloying addition of a small amount of base metals (In, Sn, Fe, Zn) on color variations in Pd-free Au-Pt-based high noble dental alloys were investigated in terms of rectilinear and polar color coordinates. The ternary Au-Pt-X (X = In, Sn, Fe, Zn) and quaternary Au-Pt-In-Y (Y = Sn, Fe, Zn) alloys were prepared from high purity component metals. The amount of alloying base metals, X and Y, were restricted up to 2 at.%. The alloying addition of a small amount of Fe, In, Sn, to a binary Au-10 at.% Pt alloy (referred to as AP10) effectively increased chroma, C *. On the other hand, the addition of Zn to the parent alloy AP10 did not change color coordinates greatly. The increase in chroma in the present Au-Pt-based high noble alloys was attributed to the increase in the slope of spectral reflectance curve at its absorption edge near 515 nm. It was found that the addition of a small amount of Fe to the parent alloy AP10 markedly increased lightness, L *, and the addition of Sn gave a very light tint of red to the parent alloy. Although red-green chromaticity index a * contributed to chroma to some extent, contribution of yellow-blue chromaticity index b * was much greater in determining chroma in this Pd-free Au-Pt-based multi-component alloys. The present results are expected to be valuable in case color is to be taken into account in designing Pd-free Au-Pt-based high noble dental alloys

  13. Variations of color with alloying elements in Pd-free Au-Pt-based high noble dental alloys

    Energy Technology Data Exchange (ETDEWEB)

    Shiraishi, Takanobu [Department of Dental and Biomedical Materials Science, Unit of Basic Medical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki 852-8588 (Japan)]. E-mail: siraisi@nagasaki-u.ac.jp; Takuma, Yasuko [Department of Dental and Biomedical Materials Science, Unit of Basic Medical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki 852-8588 (Japan); Miura, Eri [Department of Dental and Biomedical Materials Science, Unit of Basic Medical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki 852-8588 (Japan); Fujita, Takeshi [Department of Dental and Biomedical Materials Science, Unit of Basic Medical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki 852-8588 (Japan); Hisatsune, Kunihiro [Department of Dental and Biomedical Materials Science, Unit of Basic Medical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki 852-8588 (Japan)

    2007-06-15

    The effects of alloying addition of a small amount of base metals (In, Sn, Fe, Zn) on color variations in Pd-free Au-Pt-based high noble dental alloys were investigated in terms of rectilinear and polar color coordinates. The ternary Au-Pt-X (X = In, Sn, Fe, Zn) and quaternary Au-Pt-In-Y (Y = Sn, Fe, Zn) alloys were prepared from high purity component metals. The amount of alloying base metals, X and Y, were restricted up to 2 at.%. The alloying addition of a small amount of Fe, In, Sn, to a binary Au-10 at.% Pt alloy (referred to as AP10) effectively increased chroma, C *. On the other hand, the addition of Zn to the parent alloy AP10 did not change color coordinates greatly. The increase in chroma in the present Au-Pt-based high noble alloys was attributed to the increase in the slope of spectral reflectance curve at its absorption edge near 515 nm. It was found that the addition of a small amount of Fe to the parent alloy AP10 markedly increased lightness, L *, and the addition of Sn gave a very light tint of red to the parent alloy. Although red-green chromaticity index a * contributed to chroma to some extent, contribution of yellow-blue chromaticity index b * was much greater in determining chroma in this Pd-free Au-Pt-based multi-component alloys. The present results are expected to be valuable in case color is to be taken into account in designing Pd-free Au-Pt-based high noble dental alloys.

  14. The release of elements from dental casting alloy into cell-culture medium and artificial saliva.

    Science.gov (United States)

    Can, Gülşen; Akpınar, Gül; Aydın, Ahmet

    2007-04-01

    The biocompatibility of dental casting alloys is a critical issue because these alloys are in long-term intimate contact with oral tissues. Since the biocompatibility of alloys is not completely known; the release of elements from the alloys has been studied. The aim of this study was to compare the elemental release from dental casting alloy during exposure to artificial saliva and cell-culture medium. Twenty specimens made from Ni-Cr alloy were provided in the form of 5 mm diameter discs, 2 mm in thickness with a 7 mm stem attached to one face to facilitate handling. Ten of twenty samples were polished separately using a conventional technique. The remaining ten samples were left sandblasted with 50 mum Al(2)0(3). Ten samples (5 polished, 5 sandblasted) were separately placed into cell-culture wells with Dulbecco's Modified Eagle's Medium. The other ten samples were placed separately into cell-culture wells with artificial saliva. The samples were subjected in contact with these medium for 30 days. These medium were collected every 7 days. The cell-culture medium and artificial saliva without alloy samples were subjected to elemental analyses as a control. At the end of the exposure time, Atomic Absorption Spectrometry (AAS) was used to determine the release of elements from the alloys into all collected medium. Statistical analyses were assessed with two-way ANOVA. In general, the elemental release occurred with in all medium. The elemental releases of sandblasted alloys were higher than polished alloys. Artificial saliva was found to cause more release from the samples. In both media, Ni released from polished and sandblasted alloys were higher than Cr and Mo. The results suggest that the release of elements from the alloys might have correlated with the environments and the surface of dental alloy.

  15. Mechanical properties and grindability of dental cast Ti-Nb alloys.

    Science.gov (United States)

    Kikuchi, Masafumi; Takahashi, Masatoshi; Okuno, Osamu

    2003-09-01

    Aiming at developing a dental titanium alloy with better mechanical properties and machinability than unalloyed titanium, a series of Ti-Nb alloys with Nb concentrations up to 30% was made. They were cast into magnesia-based molds using a dental casting machine and the mechanical properties and grindability of the castings were examined. The hardness of the alloys with Nb concentrations of 5% and above was significantly higher than that of titanium. The yield strength and tensile strength of the alloys with Nb concentrations of 10% and above were significantly higher than those of titanium, while the elongation was significantly lower. A small addition of niobium to titanium did not contribute to improving the grindability of titanium. The Ti-30% Nb alloy exhibited significantly better grindability at low grinding speed with higher hardness, strength, and Young's modulus than titanium, presumably due to precipitation of the omega phase in the beta matrix.

  16. Electroplating Gold-Silver Alloys for Spherical Capsules for NIF Double-Shell Targets

    Energy Technology Data Exchange (ETDEWEB)

    Bhandarkar, N. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Horwood, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Bunn, T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Stadermann, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-08-17

    For Inertial Confinement Fusion (ICF) implosions, a design based on gradients of high and mid Z materials could potentially be more robust than single element capsule systems. To that end, gold and silver alloys were electroplated on 2.0 mm diameter surrogate brass spheres using a new flow–based pulsed plating method specifically designed to minimize surface roughness without reducing plating rates. The coatings were analyzed by scanning electron microscope (SEM) and white light interferometry for surface topography, and by energy dispersive x-ray spectroscopy (EDX) to determine near-surface gold and silver compositions. The alloy range attainable was 15 to 85 weight percent gold using 1:1 and 1:3 silver to gold ratio plating baths at applied potentials of -0.7 volts to -1.8 volts. This range was bounded by the open circuit potential of the system and hydrogen evolution, and in theory could be extended by using ionic liquids or aprotic solutions. Preliminary gradient trials proved constant composition alloy data could be translated to smooth gradient plating, albeit at higher gold compositions.

  17. Grindability of dental cast Ti-Ag and Ti-Cu alloys.

    Science.gov (United States)

    Kikuchi, Masafumi; Takahashi, Masatoshi; Okabe, Toru; Okuno, Osamu

    2003-06-01

    Experimental Ti-Ag alloys (5, 10, and 20 mass% Ag) and Ti-Cu alloys (2, 5, and 10 mass% Cu) were cast into magnesia molds using a dental casting machine, and their grindability was investigated. At the lowest grinding speed (500 m min(-1)), there were no statistical differences among the grindability values of the titanium and titanium alloys. The grindability of the alloys increased as the grinding speed increased. At the highest grinding speed (1500 m x min(-1)), the grindability of the 20% Ag, 5% Cu, and 10% Cu alloys was significantly higher than that of titanium. It was found that alloying with silver or copper improved the grindability of titanium, particularly at a high speed. It appeared that the decrease in elongation caused by the precipitation of small amounts of intermetallic compounds primarily contributed to the favorable grindability of the experimental alloys.

  18. Wear resistance of a pressable low-fusing ceramic opposed by dental alloys.

    Science.gov (United States)

    Faria, Adriana Cláudia Lapria; de Oliveira, André Almeida; Alves Gomes, Érica; Silveira Rodrigues, Renata Cristina; Faria Ribeiro, Ricardo

    2014-04-01

    Dental alloys have increasingly replaced by dental ceramics in dentistry because of aesthetics. As both dental alloys and ceramics can be present in the oral cavity, the evaluation of the wear resistance of ceramics opposed by dental alloys is important. The aim of the present study was to evaluate wear resistance of a pressable low-fusing ceramic opposed by dental alloys as well as the microhardness of the alloys and the possible correlation of wear and antagonist microhardness. Fifteen stylus tips samples of pressable low-fusing ceramic were obtained, polished and glazed. Samples were divided into three groups according to the disk of alloy/metal to be used as antagonist: Nickel-Chromium (Ni-Cr), Cobalt-Chromium (Co-Cr) and commercially pure titanium (cp Ti). Vickers microhardness of antagonist disks was evaluated before wear tests. Then, antagonist disks were sandblasted until surface roughness was adjusted to 0.75μm. Wear tests were performed at a speed of 60 cycles/min and distance of 10mm, in a total of 300,000 cycles. Before and after wear tests, samples were weighted and had their profile designed in an optical comparator to evaluate weight and height loss, respectively. Ni-Cr and cp Ti caused greater wear than Co-Cr, presenting greater weight (p=.009) and height (p=.002) loss. Cp Ti microhardness was lower than Ni-Cr and Co-Cr (pceramic presents different wear according to the dental alloy used as antagonist and the wear is not affected by antagonist microhardness. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Structure, mechanical properties and grindability of dental Ti-10Zr-X alloys

    International Nuclear Information System (INIS)

    Ho, W.-F.; Cheng, C.-H.; Pan, C.-H.; Wu, S.-C.; Hsu, H.-C.

    2009-01-01

    This study aimed to investigate the structure, mechanical properties and grindability of a binary Ti-Zr alloy added to a series of alloying elements (Nb, Mo, Cr and Fe). The phase and structure of Ti-10Zr-X alloys were evaluated using an X-ray diffraction (XRD) for phase analysis and optical microscope for microstructure of the etched alloys. Three-point bending tests were performed using a desk-top mechanical tester. Grindability was evaluated by measuring the amount of metal volume removed after grinding for 1 min at each of the four rotational speeds of the wheel (500, 750, 1000 or 1200 m/min). Results were compared with c.p. Ti, which was chosen as a control. Results indicated that the phase/crystal structure, microstructure, mechanical properties and grindability of the Ti-10Zr alloy can be significantly changed by adding small amounts of alloying elements. The alloying elements Nb, Mo, Cr and Fe contributed significantly to increasing the grinding ratio under all grinding conditions, although the grinding rate of all the metals was found to be largely dependent on grinding speed. The Ti-10Zr-1Mo alloy showed increases in microhardness (63%), bending strength (40%), bending modulus (30%) and elastic recovery angle (180%) over those of c.p. Ti, and was also found to have better grindability. The Ti-10Zr-1Mo alloy could therefore be used for prosthetic dental applications if other conditions necessary for dental casting are met

  20. Evaluation of the new TAMZ titanium alloy for dental cast application.

    Science.gov (United States)

    Zhang, Y M; Guo, T W; Li, Z C

    2000-12-01

    To reveal the potential of the new titanium alloy as dental prosthodontic materials. Dental castings of TAMZ alloy were investigated in the casting machine specially designed for titanium. A mesh pattern was used to count the castability value. The mechanical properties were measured by means of a universal testing machine. Optical micrography was done on the exposed cross-section of TAMZ alloy casting. From the surface to the inner part the Knoop hardness in reacted layer of TAMZ alloy casting was measured. The structure and elemental analyses of the reacted layer were made by SEM and element line scanning observation. The castability value (Cv = 98%) and the tensile test (sigma b = 850 Mpa, sigma 0.2 = 575 Mpa, delta = 7.33%) data were collected. The castings microstructure showed main alpha phase and small beta phase. Knoop hardness in the surface reacted layer was greater than that in the inner part. From the SEM and element line scanning observation, there are three different layers in the surface reacted layer of the TAMZ alloy castings, and higher level of element of O, Al, Si and Zr were found in the reacted layer while the Si permeated deeper than others. TAMZ alloy can be accepted as a material for dental alloy in prosthodontics.

  1. Growth of a Copper-Gold Alloy Phase by Bulk Copper Electrodeposition on Gold Investigated by In Situ STM

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov; Møller, Per

    1995-01-01

    the potential in the double-layer charging region from 500 to -100 mV and back to 500 mV at a sweep rate of 1 mV/s in an acidified copper sulfate electrolyte (0.01M H2SO4, 0.01M CuSO4, and Millipore water). After completion of the first cycle the gold surface had recrystallized and nuclei of an alloy phase were...... in peak potential for the anodic current transient from E = 20 mV to E = -2 mV was observed after completion of four subsequent cycles of copper electrodeposition/dissolution. The shift is suggested to be equal to the change in potential of the working electrode owing to the formation of the alloy phase....

  2. Gold-Copper alloy “nano-dumplings” with tunable compositions and plasmonic properties

    International Nuclear Information System (INIS)

    Verma, Manoj; Kedia, Abhitosh; Kumar, P. Senthil

    2016-01-01

    The unique yet tunable optical properties of plasmonic metal nanoparticles have made them attractive targets for a wide range of applications including nanophotonics, molecular sensing, catalysis etc. Such diverse applications that require precisely stable / reproducible plasmonic properties depend sensitively on the particle morphology ie. the shape, size and constituents. Herein, we systematically study the size / shape controlled synthesis of gold-copper “dumpling” shaped alloy nanoparticles by simultaneous reduction of gold and copper salts in the PVP-methanol solute-solvent system, by effectively utilizing the efficient but mild reduction as well as capping abilities of Poly (N-vinylpyrrolidone). Introduction of copper salts not only yielded the alloy nanoparticles, but also slowed down the growth process to maintain high mono-dispersity of the new shapes evolved. Copper and gold has different lattice constants (0.361 and 0.408 nm respectively) and hence doping/addition/replacement of copper atoms to gold FCC unit cell introduces strain into the lattice which is key parameter to the shape evolution in anisotropic nanoparticles. Synthesized alloy nanoparticles were characterized by UV-visible absorption spectroscopy, XRD and TEM imaging.

  3. The effect of urea on the corrosion behavior of different dental alloys.

    Science.gov (United States)

    Geckili, Onur; Bilhan, Hakan; Bilgin, Tayfun; Anthony von Fraunhofer, J

    2012-01-01

    Intraoral corrosion of dental alloys has biological, functional, and esthetic consequences. Since it is well known that the salivary urea concentrations undergo changes with various diseases, the present study was undertaken to determine the effect of salivary urea concentrations on the corrosion behavior of commonly used dental casting alloys. Three casting alloys were subjected to polarization scans in synthetic saliva with three different urea concentrations. Cyclic polarization clearly showed that urea levels above 20 mg/100 ml decreased corrosion current densities, increased the corrosion potentials and, at much higher urea levels, the breakdown potentials. The data indicate that elevated urea levels reduced the corrosion susceptibility of all alloys, possibly through adsorption of organics onto the metal surface. This study indicates that corrosion testing performed in sterile saline or synthetic saliva without organic components could be misleading.

  4. Properties of experimental copper-aluminium-nickel alloys for dental post-and-core applications.

    Science.gov (United States)

    Rittapai, Apiwat; Urapepon, Somchai; Kajornchaiyakul, Julathep; Harniratisai, Choltacha

    2014-06-01

    This study aimed to develop a copper-aluminium-nickel alloy which has properties comparable to that of dental alloys used for dental post and core applications with the reasonable cost. Sixteen groups of experimental copper alloys with variants of 3, 6, 9, 12 wt% Al and 0, 2, 4, 6 wt% Ni were prepared and casted. Their properties were tested and evaluated. The data of thermal, physical, and mechanical properties were analyzed using the two-way ANOVA and Tukey's test (α=0.05). The alloy toxicity was evaluated according to the ISO standard. The solidus and liquidus points of experimental alloys ranged from 1023℃ to 1113℃ and increased as the nickel content increased. The highest ultimate tensile strength (595.9 ± 14.2 MPa) was shown in the Cu-12Al-4Ni alloy. The tensile strength was increased as the both elements increased. Alloys with 3-6 wt% Al exhibited a small amount of 0.2% proof strength. Accordingly, the Cu-9Al-2Ni and Cu-9Al-4Ni alloys not only demonstrated an appropriate modulus of elasticity (113.9 ± 8.0 and 122.8 ± 11.3 GPa, respectively), but also had a value of 0.2% proof strength (190.8 ± 4.8 and 198.2 ± 3.4 MPa, respectively), which complied with the ISO standard requirement (>180 MPa). Alloys with the highest contents of nickel (6 wt% Ni) revealed a widespread decolourisation zone (5.0-5.9 mm), which correspondingly produced the largest cell response, equating positive control. The copper alloys fused with 9 wt% Al and 2-4 wt% Ni can be considered for a potential use as dental post and core applications.

  5. Gold-silver-alloy nanoprobes for one-pot multiplex DNA detection

    International Nuclear Information System (INIS)

    Doria, G; Larguinho, M; Dias, J T; Baptista, P V; Pereira, E; Franco, R

    2010-01-01

    A specific colorimetric DNA detection method based on oligonucleotide functionalized gold-silver-alloy nanoparticles (AuAg-alloy-nanoprobes) is presented. The AuAg-alloy-nanoprobes were then used for the specific detection of a DNA sequence from TP53-a gene involved in cancer development. The AuAg-alloy-nanoprobes were then used in combination with Au-nanoprobes for a one-pot dual-colour detection strategy that allowed for the simultaneous differential detection of two distinct target sequences. This system poses an unprecedented opportunity to explore the combined use of metal nanoparticles with different composition towards the development of a multiplex one-pot colorimetric assay for DNA detection.

  6. Gold-silver-alloy nanoprobes for one-pot multiplex DNA detection

    Energy Technology Data Exchange (ETDEWEB)

    Doria, G; Larguinho, M; Dias, J T; Baptista, P V [Centro de Investigacao em Genetica Molecular Humana (CIGMH), Departamento de Ciencias da Vida, Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Pereira, E [Rede de Quimica e Tecnologia (REQUIMTE), Departamento de Quimica, Faculdade de Ciencias, Universidade do Porto, 4169-007 Porto (Portugal); Franco, R, E-mail: pmvb@fct.unl.pt [Rede de Quimica e Tecnologia (REQUIMTE), Departamento de Quimica, Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal)

    2010-06-25

    A specific colorimetric DNA detection method based on oligonucleotide functionalized gold-silver-alloy nanoparticles (AuAg-alloy-nanoprobes) is presented. The AuAg-alloy-nanoprobes were then used for the specific detection of a DNA sequence from TP53-a gene involved in cancer development. The AuAg-alloy-nanoprobes were then used in combination with Au-nanoprobes for a one-pot dual-colour detection strategy that allowed for the simultaneous differential detection of two distinct target sequences. This system poses an unprecedented opportunity to explore the combined use of metal nanoparticles with different composition towards the development of a multiplex one-pot colorimetric assay for DNA detection.

  7. Influence of the casting processing route on the corrosion behavior of dental alloys.

    Science.gov (United States)

    Galo, Rodrigo; Rocha, Luis Augusto; Faria, Adriana Claudia; Silveira, Renata Rodrigues; Ribeiro, Ricardo Faria; de Mattos, Maria da Gloria Chiarello

    2014-12-01

    Casting in the presence of oxygen may result in an improvement of the corrosion performance of most alloys. However, the effect of corrosion on the casting without oxygen for dental materials remains unknown. The aim of this study was to investigate the influence of the casting technique and atmosphere (argon or oxygen) on the corrosion behavior response of six different dental casting alloys. The corrosion behavior was evaluated by electrochemical measurements performed in artificial saliva for the different alloys cast in two different conditions: arc melting in argon and oxygen-gas flame centrifugal casting. A slight decrease in open-circuit potential for most alloys was observed during immersion, meaning that the corrosion tendency of the materials increases due to the contact with the solution. Exceptions were the Co-based alloys prepared by plasma, and the Co-Cr-Mo and Ni-Cr-4Ti alloys processed by oxidized flame, in which an increase in potential was observed. The amount of metallic ions released into the artificial saliva solution during immersion was similar for all specimens. Considering the pitting potential, a parameter of high importance when considering the fluctuating conditions of the oral environment, Co-based alloys show the best performance in comparison with the Ni-based alloys, independent of the processing route. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Study of dilute aluminum--gold alloys for superconducting stabilizer applications

    International Nuclear Information System (INIS)

    Hartwig, K.T. Jr.

    1977-01-01

    Control over a wide variation in mechanical and physical characteristics was achieved by subjecting Al--Au alloys to precipitation hardening treatments. Annealing phenomena were monitored by resistivity measurements at 273, 77, and 4.2 K and by yield strength measurements at 296, 77, and 4.2 K. Transmission electron microscopy was employed to confirm the presence of an intermetallic precipitate dispersion in aged Al--Au. Artificial aging of Al--Au results in a remarkable strength increase and a large decrease in resistivity at 4.2 K as numerous Al 2 Au precipitates form. The precipitation mechanism is independent of composition up to at least 0.2 wt % Au. Regardless of the heat treatment used to induce aging the alloy resistivity is directly proportional to gold concentration. At long aging times the residual resistivity ratio (RRR identical with rho/sub 273 K//rho sub 4.2 K/) of Al--0.2 wt % Au approaches 1000. The yield strength of Al--Au alloys at 4.2 K is shown to be directly proportional to gold concentration for aged alloy and is six to seven times greater than that of pure aluminum. The optimum strength-resistivity relationship was defined for Al--0.2 wt % Au. Thus, Al--Au seems to be comparable to other materials now used as stabilizers. Consideration was also given to the potential stabilizer use of dilute Al--Sb alloys, the prospect for use was not promising

  9. [Corrosion property and oxide film of dental casting alloys before and after porcelain firing].

    Science.gov (United States)

    Ma, Qian; Wu, Feng-ming

    2011-03-01

    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. 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. 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 [Ni-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 Cr(2)O(3) and Mo-Ni oxide on the surface of all the alloys after PFM firing. 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

  10. Microstructural evidence of presence of beryllium in Ni-Cr alloys for dental prostheses

    International Nuclear Information System (INIS)

    Alkmin, L.B.; Nunes, C.A.; Santos, C.

    2010-01-01

    This study aimed to characterize the microstructure of commercial Ni-Cr alloys for dental prosthesis, with special focus on those containing Be. For this, the materials were characterized in terms of chemical composition, phases and melting point temperature. The following techniques were used: X-ray fluorescence, ICP-OES, scanning electron microscopy, electron probe microanalysis, X-ray diffraction and differential thermal analysis. The results clearly showed the presence of a typical eutectic, formed by the Ni ss and NiBe phases in those alloys containing Be, which can be considered a 'fingerprint' of the presence of this element in these alloys. (author)

  11. Effects of surface finishing conditions on the biocompatibility of a nickel-chromium dental casting alloy.

    LENUS (Irish Health Repository)

    McGinley, Emma Louise

    2011-07-01

    To assess the effects of surface finishing condition (polished or alumina particle air abraded) on the biocompatibility of direct and indirect exposure to a nickel-chromium (Ni-Cr) d.Sign®10 dental casting alloy on oral keratinocytes. Biocompatibility was performed by assessing cellular viability and morphology, metabolic activity, cellular toxicity and presence of inflammatory cytokine markers.

  12. Sensitization to palladium and nickel in Europe and the relationship with oral disease and dental alloys

    NARCIS (Netherlands)

    Muris, J.; Goossens, A.; Gonçalo, M.; Bircher, A.J.; Giménez-Arnau, A.; Foti, C.; Rustemeyer, T.; Feilzer, A.J.; Kleverlaan, C.J.

    2015-01-01

    Background The role of palladium and nickel sensitization in oral disease and dermatitis is not fully understood. Objectives To investigate whether sensitization to these metals was associated with exposure to dental alloys and oral and skin complaints/symptoms in a European multicentre study.

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

    NARCIS (Netherlands)

    Milheiro, A.; Muris, J.; Kleverlaan, C.J.; Feilzer, A.J.

    2015-01-01

    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

  14. Influence of ceramic surface texture on the wear of gold alloy and heat-pressed ceramics.

    Science.gov (United States)

    Saiki, Osamu; Koizumi, Hiroyasu; Nogawa, Hiroshi; Hiraba, Haruto; Akazawa, Nobutaka; Matsumura, Hideo

    2014-01-01

    The purpose of this study was to evaluate the influence of ceramic surface texture on the wear of rounded rod specimens. Plate specimens were fabricated from zirconia (ZrO2), feldspathic porcelain, and lithium disilicate glass ceramics (LDG ceramics). Plate surfaces were either ground or polished. Rounded rod specimens with a 2.0-mm-diameter were fabricated from type 4 gold alloy and heat-pressed ceramics (HP ceramics). Wear testing was performed by means of a wear testing apparatus under 5,000 reciprocal strokes of the rod specimen with 5.9 N vertical loading. The results were statistically analyzed with a non-parametric procedure. The gold alloy showed the maximal height loss (90.0 µm) when the rod specimen was abraded with ground porcelain, whereas the HP ceramics exhibited maximal height loss (49.8 µm) when the rod specimen was abraded with ground zirconia. There was a strong correlation between height loss of the rod and surface roughness of the underlying plates, for both the gold alloy and HP ceramics.

  15. Structural and morphological approach of Co-Cr dental alloys processed by alternative manufacturing technologies

    Science.gov (United States)

    Porojan, Sorin; Bîrdeanu, Mihaela; Savencu, Cristina; Porojan, Liliana

    2017-08-01

    The integration of digitalized processing technologies in traditional dental restorations manufacturing is an emerging application. The objective of this study was to identify the different structural and morphological characteristics of Co-Cr dental alloys processed by alternative manufacturing techniques in order to understand the influence of microstructure on restorations properties and their clinical behavior. Metallic specimens made of Co-Cr dental alloys were prepared using traditional casting (CST), and computerized milling (MIL), selective laser sintering (SLS) and selective laser melting (SLM). The structural information of the samples was obtained by X-ray diffraction, the morphology and the topography of the samples were investigated by Scanning Electron Microscopy and Atomic Force Microscope. Given that the microstructure was significantly different, further differences in the clinical behavior of prosthetic restorations manufactured using additive techniques are anticipated.

  16. A thermodynamic investigation of liquid gold-antimony alloys

    International Nuclear Information System (INIS)

    Hayer, E.; Castanet, R.

    1995-01-01

    The enthalpies of mixing of liquid Au-Sb alloys were determined between 906 and 1028 K giving Δ mix H o m = x Sb x Au (-11.234-1.1078x Sb + 5.713x Sb 2 ) kJ mol -1 . The minimum was found at x Sb = 0.45 with Δ mix H o m = -2.62 ± 0.2 kJ mol -1 contrary to published measurements on liquid Au-Sb alloys. The limiting partial molar enthalpy of Au in Sb at 935 K was measured to Δ mix h o m (Au, liq, in ∞Sb, liq) = -6.05 ± 0.4 kJ mol -1 . The enthalpy of formation of the solid compound AuSb 2 determined at 298 K by solution calorimetry in liquid Sb, Δ f H o m (AuSb 2 ) = -5.40 ± 0.6 kJ mol -1 , is found in fair agreement with literature data. DTA measurements were performed on the Au-rich part of the liquidus and a new liquidus curve is suggested between Au and the eutectic concentration. The eutectic point was found at 630.37 ± 0.25 K and x Sb 0.350. (orig.)

  17. Fabricating High-Quality 3D-Printed Alloys for Dental Applications

    Directory of Open Access Journals (Sweden)

    Min-Ho Hong

    2017-07-01

    Full Text Available Metal additive manufacturing (AM, especially selective laser melting (SLM, has been receiving particular attention because metallic functional structures with complicated configurations can be effectively fabricated using the technique. However, there still exist some future challenges for the fabrication of high-quality SLM products for dental applications. First, the surface quality of SLM products should be further improved by standardizing the laser process parameters or by appropriately post-treating the surface. Second, it should be guaranteed that dental SLM restorations have good dimensional accuracy and, in particular, a good marginal fit. Third, a definitive standard regarding building and scanning strategies, which affect the anisotropy, should be established to optimize the mechanical properties and fatigue resistance of SLM dental structures. Fourth, the SLM substructure’s bonding and support to veneering ceramic should be further studied to facilitate the use of esthetic dental restorations. Finally, the biocompatibility of SLM dental alloys should be carefully examined and improved to minimize the potential release of toxic metal ions from the alloys. Future research of SLM should focus on solving the above challenges, as well as on fabricating dental structures with “controlled” porosity.

  18. Structure, mechanical properties, and grindability of dental Ti-Zr alloys.

    Science.gov (United States)

    Ho, Wen-Fu; Chen, Wei-Kai; Wu, Shih-Ching; Hsu, Hsueh-Chuan

    2008-10-01

    Structure, mechanical properties and grindability of a series of binary Ti-Zr alloys with zirconium contents ranging from 10 to 40 wt% have been investigated. Commercially pure titanium (c.p. Ti) was used as a control. Experimental results indicated that the diffraction peaks of all the Ti-Zr alloys matched those for alpha Ti. No beta-phase peaks were found. The hardness of the Ti-Zr alloys increased as the Zr contents increased, and ranged from 266 HV (Ti-10Zr) to 350 HV (Ti-40Zr). As the concentration of zirconium in the alloys increased, the strength, elastic recovery angles and hardness increased. Moreover, the elastically recoverable angle of Ti-40Zr was higher than of c.p. Ti by as much as 550%. The grindability of each metal was found to be largely dependent on the grinding conditions. The Ti-40Zr alloy had a higher grinding rate and grinding ratio than c.p. Ti at low speed. The grinding rate of the Ti-40Zr alloy at 500 m/min was about 1.8 times larger than that of c.p. Ti, and the grinding ratio was about 1.6 times larger than that of c.p. Ti. Our research suggested that the Ti-40Zr alloy has better mechanical properties, excellent elastic recovery capability and improved grindability at low grinding speed. The Ti-40Zr alloy has a great potential for use as a dental machining alloy.

  19. Further studies on gold alloys used in fabrication of porcelain-fused-to-metal restorations.

    Science.gov (United States)

    Civjan, S; Huget, E F; Dvivedi, N; Cosner, H J

    1975-03-01

    Composition, microstructure, castability, mechanical properties, and heat treatment characteristics of two gold-palladium-silver-based alloys were studied. The materials exhibited compositional as well as microstructural differences. Clinically acceptable castings could not be obtained when manufacturers' recommended casting temperatures were used. Ultimate tensile strength, yield strength, modulus of elasticity, and Brinell hardness values for the alloys were comparable. The elastic limit of Cameo, however, was significantly higher than that of vivo-star. Maximum rehardening of annealed castings occurred on reheat treatment at temperatures between 1,200 and 1,300 F. As-cast specimens, however, were not heat hardenable. The sequence of heat treatments used in the application of porcelain reduced slightly the hardness of both alloys. Hardness of the metal substructures was not increased by return of porcelain-coated specimens to a 1,250 F oven for final heat treatment.

  20. Evaluation of cast Ti-Fe-O-N alloys for dental applications

    International Nuclear Information System (INIS)

    Koike, Marie; Ohkubo, Chikahiro; Sato, Hideki; Fujii, Hideki; Okabe, Toru

    2005-01-01

    Good mechanical properties, biocompatibility and corrosion resistance make titanium an excellent material for biomedical applications. However, when better mechanical properties than those offered by commercially pure titanium (CPTi) are needed, Ti-6Al-4V is sometimes a good alternative. Some new titanium alloys, developed as industrial structural materials, aim at an intermediate range of strength between that of CP Ti and Ti-6Al-4V. Two of these alloys are Super-TIX800TM (Ti-1% Fe-0.35% O-0.01% N) and Super-TIX800NTM (Ti-1% Fe-0.3% O-0.04% N) (both produced by Nippon Steel Corp., Japan). Besides being stronger than CP Ti, the cost of manufacturing these alloys is reportedly lower than for Ti-6Al-4V since they do not contain any expensive elements. In addition, they are not composed of elements such as aluminum or vanadium, which have caused biocompatibility concerns in medical and dental appliances. To evaluate these alloys as candidates for dental use, it is helpful to compare them to CP Ti (ASTM Grade 2) and Ti-6Al-4V (ASTM Grade 5), which have already been employed in dentistry. We evaluated the tensile properties, mold filling capacity, corrosion characteristics and grindability of these industrial alloys prepared by investment casting. Compared to the strengths of cast CPTi, the yield strength and tensile strength of these cast alloys were more than 20% and approximately 30% higher, respectively. On the other hand, both of these properties were 30% lower than for Ti-6Al-4V. Better grindability and wear resistance were additional benefits of these new alloys for dental applications

  1. Ni-Cr based dental alloys; Ni release, corrosion and biological evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Reclaru, L., E-mail: lucien.reclaru@pxgroup.com [PX Holding S.A., Dep R and D Corrosion and Biocompatibility Group, Bd. des Eplatures 42, CH-2304 La Chaux-de-Fonds (Switzerland); Unger, R.E.; Kirkpatrick, C.J. [Institute for Pathology, REPAIR Lab, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr.1, D-55101 Mainz (Germany); Susz, C.; Eschler, P.-Y.; Zuercher, M.-H. [PX Holding S.A., Dep R and D Corrosion and Biocompatibility Group, Bd. des Eplatures 42, CH-2304 La Chaux-de-Fonds (Switzerland); Antoniac, I. [Materials Science and Engineering Faculty, Politehnica of Bucharest, 060042 Bucharest (Romania); Luethy, H. [Institute of Dental Materials Science and Technology, University of Basel, Hebelstrasse 3, CH-4056 Basel (Switzerland)

    2012-08-01

    In the last years the dental alloy market has undergone dramatic changes for reasons of economy and biocompatibility. Nickel based alloys have become widely used substitute for the much more expensive precious metal alloys. In Europe the prevalence of nickel allergy is 10-15% for female adults and 1-3% for male adults. Despite the restrictions imposed by the EU for the protection of the general population in contact dermatitis, the use of Ni-Cr dental alloys is on the increase. Some questions have to be faced regarding the safety risk of nickel contained in dental alloys. We have collected based on many EU markets, 8 Ni-Cr dental alloys. Microstructure characterization, corrosion resistance (generalized, crevice and pitting) in saliva and the quantities of cations released in particular nickel and CrVI have been evaluated. We have applied non parametric classification tests (Kendall rank correlation) for all chemical results. Also cytotoxicity tests and an evaluation specific to TNF-alpha have been conducted. According to the obtained results, it was found that their behavior to corrosion was weak but that nickel release was high. The quantities of nickel released are higher than the limits imposed in the EU concerning contact with the skin or piercing. Surprisingly the biological tests did not show any cytotoxic effect on Hela and L929 cells or any change in TNF-alpha expression in monocytic cells. The alloys did not show any proinflammatory response in endothelial cells as demonstrated by the absence of ICAM-1 induction. We note therefore that there is really no direct relationship between the in vitro biological evaluation tests and the physico-chemical characterization of these dental alloys. Clinical and epidemiological studies are required to clarify these aspects. - Highlights: Black-Right-Pointing-Pointer Nickel released was higher than the limits imposed in EU in contact with the skin. Black-Right-Pointing-Pointer No direct relationship between the

  2. An Investigation on Metallic Ion Release from Four Dental Casting Alloys

    Directory of Open Access Journals (Sweden)

    F. Nejatidanesh

    2005-12-01

    Full Text Available Statement of Problem: Element release from dental casting alloys into the oral environment is of clinical concern and is considered to be a potential health problem to all patients.Purpose: The aim of this study was to investigate the metallic ion release of four base metal alloys.Materials and Methods: Two Ni-Cr (Minalux and Supercast and two Co-Cr alloys (Minalia and Wironit were examined. Nine specimens of each type were prepared in 13×11×1.4 mm dimensions and each of the four alloys (3 specimens per group were conditioned in artificial saliva at 37 c for one, three and seven days.The conditioning media were analyzed for element-release using Inductive CoupledPlasma Atomic Emission Spectrophotometer (ICPAES. Collected data were statistically analyzed using ANOVA and Duncan multiple range test (P< 0.05.Results: The greatest amount of element release was seen after seven days (134.9 ppb Supercast, 159.2 ppb Minalux, 197.2 ppb Minalia, and 230.2 ppb Wironit. There was a significant difference between the released elements from the alloys after the three conditioning times (p<0.001.Conclusion: Element release from the studied alloys is proportional to the conditioning time. The Ni-Cr alloys tested in this investigation were more resistant to corrosion as compared to the Co-Cr alloys in artificial saliva. Supercast had the highest corrosion resistance.

  3. Microstructure and mechanical properties of Ti-15Zr alloy used as dental implant material.

    Science.gov (United States)

    Medvedev, Alexander E; Molotnikov, Andrey; Lapovok, Rimma; Zeller, Rolf; Berner, Simon; Habersetzer, Philippe; Dalla Torre, Florian

    2016-09-01

    Ti-Zr alloys have recently started to receive a considerable amount of attention as promising materials for dental applications. This work compares mechanical properties of a new Ti-15Zr alloy to those of commercially pure titanium Grade4 in two surface conditions - machined and modified by sand-blasting and etching (SLA). As a result of significantly smaller grain size in the initial condition (1-2µm), the strength of Ti-15Zr alloy was found to be 10-15% higher than that of Grade4 titanium without reduction in the tensile elongation or compromising the fracture toughness. The fatigue endurance limit of the alloy was increased by around 30% (560MPa vs. 435MPa and 500MPa vs. 380MPa for machined and SLA-treated surfaces, respectively). Additional implant fatigue tests showed enhanced fatigue performance of Ti-15Zr over Ti-Grade4. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Laser-induced damage thresholds of gold, silver and their alloys in air and water

    Energy Technology Data Exchange (ETDEWEB)

    Starinskiy, Sergey V.; Shukhov, Yuri G.; Bulgakov, Alexander V., E-mail: bulgakov@itp.nsc.ru

    2017-02-28

    Highlights: • Laser damage thresholds of Ag, Au and Ag-Au alloys in air and water are measured. • Alloy thresholds are lower than those of Ag and Au due to low thermal conductivity. • Laser damage thresholds in water are ∼1.5 times higher than those in air. • Light scattering mechanisms responsible for high thresholds in water are suggested. • Light scattering mechanisms are supported by optical reflectance measurements. - Abstract: The nanosecond-laser-induced damage thresholds of gold, silver and gold-silver alloys of various compositions in air and water have been measured for single-shot irradiation conditions. The experimental results are analyzed theoretically by solving the heat flow equation for the samples irradiated in air and in water taking into account vapor nucleation at the solid-water interface. The damage thresholds of Au-Ag alloys are systematically lower than those for pure metals, both in air and water that is explained by lower thermal conductivities of the alloys. The thresholds measured in air agree well with the calculated melting thresholds for all samples. The damage thresholds in water are found to be considerably higher, by a factor of ∼1.5, than the corresponding thresholds in air. This cannot be explained, in the framework of the used model, neither by the conductive heat transfer to water nor by the vapor pressure effect. Possible reasons for the high damage thresholds in water such as scattering of the incident laser light by the vapor-liquid interface and the critical opalescence in the superheated water are suggested. Optical pump-probe measurements have been performed to study the reflectance dynamics of the surface irradiated in air and water. Comparison of the transient reflectance signal with the calculated nucleation dynamics provides evidence that the both suggested scattering mechanisms are likely to occur during metal ablation in water.

  5. Laser-induced damage thresholds of gold, silver and their alloys in air and water

    Science.gov (United States)

    Starinskiy, Sergey V.; Shukhov, Yuri G.; Bulgakov, Alexander V.

    2017-02-01

    The nanosecond-laser-induced damage thresholds of gold, silver and gold-silver alloys of various compositions in air and water have been measured for single-shot irradiation conditions. The experimental results are analyzed theoretically by solving the heat flow equation for the samples irradiated in air and in water taking into account vapor nucleation at the solid-water interface. The damage thresholds of Au-Ag alloys are systematically lower than those for pure metals, both in air and water that is explained by lower thermal conductivities of the alloys. The thresholds measured in air agree well with the calculated melting thresholds for all samples. The damage thresholds in water are found to be considerably higher, by a factor of ∼1.5, than the corresponding thresholds in air. This cannot be explained, in the framework of the used model, neither by the conductive heat transfer to water nor by the vapor pressure effect. Possible reasons for the high damage thresholds in water such as scattering of the incident laser light by the vapor-liquid interface and the critical opalescence in the superheated water are suggested. Optical pump-probe measurements have been performed to study the reflectance dynamics of the surface irradiated in air and water. Comparison of the transient reflectance signal with the calculated nucleation dynamics provides evidence that the both suggested scattering mechanisms are likely to occur during metal ablation in water.

  6. Surface and elemental alterations of dental alloys induced by electro discharge machining (EDM).

    Science.gov (United States)

    Zinelis, Spiros

    2007-05-01

    To evaluate the surface and elemental alterations induced by electro discharge machining (EDM) on the surface of dental cast alloys used for the fabrication of implant retained meso- and super-structures. A completed cast model of an arch that received dental implants was used for the preparation of six wax patterns which were divided into three groups (Au, Co and Ti). The wax patterns of the Au and Co groups were invested with conventional phosphate-bonded silica-based investment material and the Ti group with magnesia-based investment material. The investment rings of the Au and Co groups were cast with an Au-Ag alloy (Stabilor G) and a Co-Cr base alloy (Okta C), respectively, while the investment rings of group Ti were cast with cp Ti (Biotan). One casting of each group was subjected to electro discharge machining (EDM); the other was conventionally ground and polished. The surface morphology and the elemental compositions of conventionally and EDM-finished surfaces were studied by SEM/X-ray EDS analysis. Six spectra were collected from each surface employing the area scan mode and the mean value of each element between conventionally and EDM-finished surfaces was statistically analyzed by t-test (a=0.05). Then the specimens of each group were cut perpendicular to their longitudinal axis and after metallographic grinding and polishing the cross-sections studied under the SEM. The EDM surfaces showed a significant increase in C due to the decomposition of the dielectric fluid during spark erosion. Moreover, a significant Cu uptake was noted on these surfaces from the decomposition of the Cu electrodes used for EDM. Cross-sectional analysis showed that all alloys developed a superficial zone (recast layer) varying from 2 microm for Au-Ag to 10 microm for Co-Cr alloy. The elemental composition of dental alloy surfaces is significantly altered after EDM treatment.

  7. In vitro biocompatibility of CoCrMo dental alloys fabricated by selective laser melting.

    Science.gov (United States)

    Hedberg, Yolanda S; Qian, Bin; Shen, Zhijian; Virtanen, Sannakaisa; Wallinder, Inger Odnevall

    2014-05-01

    Selective laser melting (SLM) is increasingly used for the fabrication of customized dental components made of metal alloys such as CoCrMo. The main aim of the present study is to elucidate the influence of the non-equilibrium microstructure obtained by SLM on corrosion susceptibility and extent of metal release (measure of biocompatibility). A multi-analytical approach has been employed by combining microscopic and bulk compositional tools with electrochemical techniques and chemical analyses of metals in biologically relevant fluids for three differently SLM fabricated CoCrMo alloys and one cast CoCrMo alloy used for comparison. Rapid cooling and strong temperature gradients during laser melting resulted in the formation of a fine cellular structure with cell boundaries enriched in Mo (Co depleted), and suppression of carbide precipitation and formation of a martensitic ɛ (hcp) phase at the surface. These features were shown to decrease the corrosion and metal release susceptibility of the SLM alloys compared with the cast alloy. Unique textures formed in the pattern of the melting pools of the three different laser melted CoCrMo alloys predominantly explain observed small, though significant, differences. The susceptibility for corrosion and metal release increased with an increased number (area) of laser melt pool boundaries. This study shows that integrative and interdisciplinary studies of microstructural characteristics, corrosion, and metal release are essential to assess and consider during the design and fabrication of CoCrMo dental components of optimal biocompatibility. The reason is that the extent of metal release from CoCrMo is dependent on fabrication procedures. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  8. [The effect of hydrogen peroxide on the electrochemical corrosion properties and metal ions release of nickel-chromium dental alloys].

    Science.gov (United States)

    Wang, Jue; Qiao, Guang-yan

    2013-04-01

    To investigate the effect of hydrogen peroxide on the electrochemical corrosion and metal ions release of nickel-chromium dental alloys. The corrosion resistance of nickel-chromium dental alloys was compared by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curve (PD) methods in artificial saliva after immersed in different concentrations of hydrogen peroxide for 112 h. The metal ions released from nickel-chromium dental alloys to the artificial saliva were detected after electrochemical measurements using inductively coupled plasma mass spectrometry (ICP-MS). The data was statistically analyzed by analysis of variance (ANOVA) using SPSS 13.0 software package. The electrochemical experiment showed that the sequence of polarization resistance in equivalent circuit (Rct), corrosion potential (Ecorr), pitting breakdown potential (Eb), and the difference between Ecorr and Eb representing the "pseudo-passivation" (δE) of nickel-chromium alloys in artificial saliva was 30% alloys to the artificial saliva, and the order of the concentrations of metal ions was 0% corrosion resistance of nickel-chromium dental alloys decrease after immersed in different concentrations of hydrogen peroxide for 112 h. Nickel-chromium dental alloys are more prone to corrosion in the artificial saliva with the concentration of hydrogen peroxide increased, and more metal ions are released in the artificial saliva.

  9. Mechanical Characterisation and Biomechanical and Biological Behaviours of Ti-Zr Binary-Alloy Dental Implants

    Directory of Open Access Journals (Sweden)

    Aritza Brizuela-Velasco

    2017-01-01

    Full Text Available The objective of the study is to characterise the mechanical properties of Ti-15Zr binary alloy dental implants and to describe their biomechanical behaviour as well as their osseointegration capacity compared with the conventional Ti-6Al-4V (TAV alloy implants. The mechanical properties of Ti-15Zr binary alloy were characterised using Roxolid© implants (Straumann, Basel, Switzerland via ultrasound. Their biomechanical behaviour was described via finite element analysis. Their osseointegration capacity was compared via an in vivo study performed on 12 adult rabbits. Young’s modulus of the Roxolid© implant was around 103 GPa, and the Poisson coefficient was around 0.33. There were no significant differences in terms of Von Mises stress values at the implant and bone level between both alloys. Regarding deformation, the highest value was observed for Ti-15Zr implant, and the lowest value was observed for the cortical bone surrounding TAV implant, with no deformation differences at the bone level between both alloys. Histological analysis of the implants inserted in rabbits demonstrated higher BIC percentage for Ti-15Zr implants at 3 and 6 weeks. Ti-15Zr alloy showed elastic properties and biomechanical behaviours similar to TAV alloy, although Ti-15Zr implant had a greater BIC percentage after 3 and 6 weeks of osseointegration.

  10. Hermetic diamond capsules for biomedical implants enabled by gold active braze alloys.

    Science.gov (United States)

    Lichter, Samantha G; Escudié, Mathilde C; Stacey, Alastair D; Ganesan, Kumaravelu; Fox, Kate; Ahnood, Arman; Apollo, Nicholas V; Kua, Dunstan C; Lee, Aaron Z; McGowan, Ceara; Saunders, Alexia L; Burns, Owen; Nayagam, David A X; Williams, Richard A; Garrett, David J; Meffin, Hamish; Prawer, Steven

    2015-01-01

    As the field of biomedical implants matures the functionality of implants is rapidly increasing. In the field of neural prostheses this is particularly apparent as researchers strive to build devices that interact with highly complex neural systems such as vision, hearing, touch and movement. A retinal implant, for example, is a highly complex device and the surgery, training and rehabilitation requirements involved in deploying such devices are extensive. Ideally, such devices will be implanted only once and will continue to function effectively for the lifetime of the patient. The first and most pivotal factor that determines device longevity is the encapsulation that separates the sensitive electronics of the device from the biological environment. This paper describes the realisation of a free standing device encapsulation made from diamond, the most impervious, long lasting and biochemically inert material known. A process of laser micro-machining and brazing is described detailing the fabrication of hermetic electrical feedthroughs and laser weldable seams using a 96.4% gold active braze alloy, another material renowned for biochemical longevity. Accelerated ageing of the braze alloy, feedthroughs and hermetic capsules yielded no evidence of corrosion and no loss of hermeticity. Samples of the gold braze implanted for 15 weeks, in vivo, caused minimal histopathological reaction and results were comparable to those obtained from medical grade silicone controls. The work described represents a first account of a free standing, fully functional hermetic diamond encapsulation for biomedical implants, enabled by gold active alloy brazing and laser micro-machining. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. The effects of thermal-neutron irradiation on platinum and dilute platinum-gold alloys

    International Nuclear Information System (INIS)

    Piani, C.S.B.

    1978-12-01

    The effect of varying defect concentrations on the recovery spectrum of thermal-neutron-irradiated pure platinum after isochronal anneals was investigated. The dose-independence of substages I(A), I(B) and I(C), and the dose dependence of substage I(D) and I(E), were observed to be in agreement with electron-irradiated studies. The 120 K substage in pure platinum was shown not to be due to interstitial-interstitial reactions, but could possibly be accounted for in terms of detrapping of interstitials from impurities or intrinsic immobile defects. The 360 K stage was shown to shift and was suppressed with increasing defect concentration. The possible conversion of the crowdion to a dumbbell near 160 K in Stage ll in platinum, as predicted by the two-interstitial model, was investigated by consideration of the initial slopes of the production curves between 80 K and 300 K. A minimum in these slopes was observed near 160 K and could be interpreted as due to the conversion of the highly mobile crowdion to an immobile dumbbell at this temperature. The influence of varying gold concentrations on the recovery spectrum of platinum was investigated in dilute platinum-gold alloys. The characteristics of several additional substages in Stage ll, due to the gold alloying were comparable to the results of electron-irradiation experiments. The observations made with regard to the impurity (gold) dependence of these substages could be interpreted in terms of the concentrations of the interstitials, vacancies and impurities present in the material. The interpretation of these substages was found to be consistent, if the recovery spectrum was investigated as a function of defect concentration [af

  12. Interaction of InGa liquid alloy coolant with gold coated optical materials

    International Nuclear Information System (INIS)

    Hulbert, S.L.

    1991-01-01

    A significant reaction is reported between gold surfaces and an indium-gallium eutectic liquid alloy often used to transfer heat away from optical elements in high power synchrotron radiation beamlines. This reaction proceeds at the slightly elevated temperatures (70 degrees C) typical of conservative bakeouts used to achieve ultrahigh vacuum in the chambers which house these optical elements (mirrors, gratings, and crystals) without damaging their highly precise figure and finish. The nature and extent of this reaction is discussed, based mostly on the experience gained recently during the vacuum commissioning of two mirror chambers for a VUV wiggler-based synchrotron radiation beamline. 2 refs., 5 figs

  13. Polarographic determination of selenium and tellurium in silver-gold alloys

    International Nuclear Information System (INIS)

    Gornostaeva, T.D.; Shmargun, S.V.

    1986-01-01

    The determination of selenium and tellurium is of importance in monitoring the composition of silver-gold alloys (SGA) since these elements are harmful impurities in the pure metals. Tellurium is determined in silver alloys by atomic absorption and atomic emmission methods; selenium determination is made by atomic absorption methods. This paper examines the polarographic determination of silver and tellurium in SGA containing platinum metals and copper. Copper and the bulk of the platinum and palladium were removed by precipitating selenium and tellurium with potassium hypophosphite in the elementary state from 6 M HC1. The results of an analysis of samples of SGA according to the proposed method were compared with the results obtained by the atomic absorption method. the relative deviation in the determination of 0.02-1.0% by weight selenium and tellurium does not exceed 0.12 (n = 5)

  14. Evaluation of bonding strength of porcelain to some commercial nickel-base dental alloys and comparing their interface

    Directory of Open Access Journals (Sweden)

    Rahim Asghari Salavat

    2017-12-01

    Conclusion: To replace the replacing of deleterious elements from the chemical composition of dental alloys. The added new elements should control through the oxide layer and the formation of Cr2O3 in porcelain-alloy interfaces for adequate bond strength.

  15. Analysis of four dental alloys following torch/centrifugal and induction/ vacuum-pressure casting procedures.

    Science.gov (United States)

    Thompson, Geoffrey A; Luo, Qing; Hefti, Arthur

    2013-12-01

    Previous studies have shown casting methodology to influence the as-cast properties of dental casting alloys. It is important to consider clinically important mechanical properties so that the influence of casting can be clarified. The purpose of this study was to evaluate how torch/centrifugal and inductively cast and vacuum-pressure casting machines may affect the castability, microhardness, chemical composition, and microstructure of 2 high noble, 1 noble, and 1 base metal dental casting alloys. Two commonly used methods for casting were selected for comparison: torch/centrifugal casting and inductively heated/ vacuum-pressure casting. One hundred and twenty castability patterns were fabricated and divided into 8 groups. Four groups were torch/centrifugally cast in Olympia (O), Jelenko O (JO), Genesis II (G), and Liberty (L) alloys. Similarly, 4 groups were cast in O, JO, G, and L by an inductively induction/vacuum-pressure casting machine. Each specimen was evaluated for casting completeness to determine a castability value, while porosity was determined by standard x-ray techniques. Each group was metallographically prepared for further evaluation that included chemical composition, Vickers microhardness, and grain analysis of microstructure. Two-way ANOVA was used to determine significant differences among the main effects. Statistically significant effects were examined further with the Tukey HSD procedure for multiple comparisons. Data obtained from the castability experiments were non-normal and the variances were unequal. They were analyzed statistically with the Kruskal-Wallis rank sum test. Significant results were further investigated statistically with the Steel-Dwass method for multiple comparisons (α=.05). The alloy type had a significant effect on surface microhardness (Pcasting did not affect the microhardness of the test specimen (P=.465). Similarly, the interaction between the alloy and casting technique was not significant (P=.119). A high

  16. Comparative study of cytotoxicity of direct metal laser sintered and cast Co-Cr-Mo dental alloy

    Directory of Open Access Journals (Sweden)

    T. Puskar

    2015-07-01

    Full Text Available The presented work investigated the cytotoxicity of direct metal laser sintered (DMLS and cast Co-Cr-Mo (CCM dental alloy. In vitro tests were done on human fibroblast cell line MRC-5. There was no statistically significant difference in the cytotoxic effects of DMLS and CCM alloy specimens. The results of this investigation show good potential of DMLS Co-Cr-Mo alloy for application in dentistry.

  17. Macrophage proinflammatory response to the titanium alloy equipment in dental implantation.

    Science.gov (United States)

    Chen, X; Li, H S; Yin, Y; Feng, Y; Tan, X W

    2015-08-07

    Titanium alloy and stainless steel (SS) had been widely used as dental implant materials because of their affinity with epithelial tissue and connective tissue, and good physical, chemical, biological, mechanical properties and processability. We compared the effects of titanium alloy and SS on macrophage cytokine expression as well as their biocompatibility. Mouse macrophage RAW264.7 cells were cultured on titanium alloy and SS surfaces. Cells were counted by scanning electron microscopy. A nitride oxide kit was used to detect released nitric oxide by macrophages on the different materials. An enzyme linked immunosorbent assay was used to detect monocyte chemoattractant protein-1 levels. Scanning electron microscopy revealed fewer macrophages on the surface of titanium alloy (48.2 ± 6.4 x 10(3) cells/cm(2)) than on SS (135 ± 7.3 x 10(3) cells/cm(2)). The nitric oxide content stimulated by titanium alloy was 22.5 mM, which was lower than that stimulated by SS (26.8 mM), but the difference was not statistically significant (P = 0.07). The level of monocyte chemoattractant protein-1 released was significantly higher in the SS group (OD value = 0.128) than in the titanium alloy group (OD value = 0.081) (P = 0.024). The transforming growth factor-b1 mRNA expression levels in macrophages after stimulation by titanium alloy for 12 and 36 h were significantly higher than that after stimulation by SS (P = 0.31 and 0.25, respectively). Macrophages participate in the inflammatory response by regulating cytokines such as nitric oxide, monocyte chemoattractant protein-1, and transforming growth factor-b1. There were fewer macrophages and lower inflammation on the titanium alloy surface than on the SS surface. Titanium alloy materials exhibited better biological compatibility than did SS.

  18. Corrosion of dental alloys in artificial saliva with Streptococcus mutans.

    Science.gov (United States)

    Lu, Chunhui; Zheng, Yuanli; Zhong, Qun

    2017-01-01

    A comparative study of the corrosion resistance of CoCr and NiCr alloys in artificial saliva (AS) containing tryptic soy broth (Solution 1) and Streptococcus mutans (S. mutans) species (Solution 2) was performed by electrochemical methods, including open circuit potential measurements, impedance spectroscopy, and potentiodynamic polarization. The adherence of S. mutans to the NiCr and CoCr alloy surfaces immersed in Solution 2 for 24 h was verified by scanning electron microscopy, while the results of electrochemical impedance spectroscopy confirmed the importance of biofilm formation for the corrosion process. The R(QR) equivalent circuit was successfully used to fit the data obtained for the AS mixture without S. mutans, while the R(Q(R(QR))) circuit was found to be more suitable for describing the biofilm properties after treatment with the AS containing S. mutans species. In addition, a negative shift of the open circuit potential with immersion time was observed for all samples regardless of the solution type. Both alloys exhibited higher charge transfer resistance after treatment with Solution 2, and lower corrosion current densities were detected for all samples in the presence of S. mutans. The obtained results suggest that the biofilm formation observed after 24 h of exposure to S. mutans bacteria might enhance the corrosion resistance of the studied samples by creating physical barriers that prevented oxygen interactions with the metal surfaces.

  19. The effect of Electro Discharge Machining (EDM) on the corrosion resistance of dental alloys.

    Science.gov (United States)

    Ntasi, Argyro; Mueller, Wolf Dieter; Eliades, George; Zinelis, Spiros

    2010-12-01

    The aim of the present study was to evaluate the effect of Electro Discharge Machining (EDM) on the corrosion resistance of two types of dental alloys used for fabrication of implant retained superstructures. Two groups of specimens were prepared from a Co-Cr (Okta-C) and a grade II cpTi (Biotan) alloys respectively. Half of the specimens were subjected to EDM with Cu electrodes and the rest were conventionally finished (CF). The corrosion resistance of the alloys was evaluated by anodic polarization in Ringer's solution. Morphological and elemental alterations before and after corrosion testing were studied by SEM/EDX. Six regions were analyzed on each surface before and after corrosion testing and the results were statistically analyzed by paired t-test (a=0.05). EDM demonstrated inferior corrosion resistance compared to CF surfaces, the latter being passive in a wider range of potential demonstrating higher polarization resistance and lower I(corr) values. Morphological alterations were found before and after corrosion testing for both materials tested after SEM analysis. EDX showed a significant decrease in Mo, Cr, Co, Cu (Co-Cr) and Ti, Cu (cpTi) after electrochemical testing plus an increase in C. According to the results of this study the EDM procedure decreases the corrosion resistance of both the alloys tested, increasing thus the risk of possible adverse biological reactions. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  20. Corrosion behavior of novel imitation-gold copper alloy with rare earth in 3.5% NaCl solution

    International Nuclear Information System (INIS)

    Chen, J.L.; Li, Z.; Zhu, A.Y.; Luo, L.Y.; Liang, J.

    2012-01-01

    Highlights: → The design alloy has better anti-tarnish property than that of H7211 alloy during salt-spray test. → The corrosion rate of design alloy is much lower than that of H7211 alloy as immersed in NaCl solution. → In the low frequency region, the capacitive behavior normally faded and diffusion process had a key role. → In the medium frequency region, the Bode pattern showed a capacitive behavior. -- Abstract: A novel imitation-gold copper alloy with rare earth was designed and prepared. The corrosion behavior of the alloy immersed in 3.5% NaCl solution and its anti-tarnish property in the salt spray for different days has been studied. The designed alloy (CuZnAlNiMeRe) has more excellent anti-tarnish property and lower corrosion rate than those of currency coinage materials of H7211 alloy (used in China). A uniform and compact of corrosion film has been formed after the designed alloy immersed in 3.5% NaCl solution. The corrosion current densities I corr of the alloy decreased while the polarization resistance R p increased with time. The capacitance of the corrosion product film C film of the alloy decreased while the charge transfer resistance R ct . The Warburg diffusion impedance W R and the resistance of the equivalent circuit R increased with time.

  1. Electrochemical and corrosion behavior of two chromium dental alloys in artificial bioenvironments

    Directory of Open Access Journals (Sweden)

    Banu Alexandra

    2017-01-01

    Full Text Available The purpose of this study is to compare the corrosion and tarnish behavior of NiCrMo and CoCrMo cast dental alloys in artificial bio environments. The cobalt chromium alloys are known and used in dentistry for many years, but its difficult machinability because of the strength and hardness, is an argument for scientists to study alternative materials with comparable biocompatibility. On the other hand, for dentistry devices beside corrosion behavior is important the aesthetic so, the used alloys have to preserve their shining and do not stain. The corrosion resistance has been evaluated using the Atomic mass spectroscopy method for ion release determination, the anodic polarization curves and the open circuit potential – time monitoring for corrosion behavior evaluation and optical microscopy for the structure analysis. The tarnish tendency of alloys was estimated using the method of cyclic immersion with frequency of 10 seconds for each minute during 72 hours in Na2S containing solution. The most important conclusion is that the alloys are comparable from corrosion and tarnish point of view, but we recommend to use the nickel base alloy only for orthodontic devices implanted for short periods of time, because of higher quantity of released ions.

  2. Assessment of exposures and potential risks to the US adult population from the leaching of elements from gold and ceramic dental restorations.

    Science.gov (United States)

    Richardson, G Mark; James, Kyle Jordan; Peters, Rachel Elizabeth; Clemow, Scott Richard; Siciliano, Steven Douglas

    2016-01-01

    Using data from the 2001 to 2004 US National Health and Nutrition Examination Survey (NHANES) on the number and placement of tooth restorations in adults, we quantified daily doses due to leaching of elements from gold (Au) alloy and ceramic restorative materials. The elements with the greatest leaching rates from these materials are often the elements of lowest proportional composition. As a result, exposure due to wear will predominate for those elements of relatively high proportional composition, while exposure due leaching may predominate for elements of relatively low proportional composition. The exposure due to leaching of silver (Ag) and palladium (Pd) from Au alloys exceeded published reference exposure levels (RELs) for these elements when multiple full surface crowns were present. Six or more molar crowns would result in exceeding the REL for Ag, whereas three or more crowns would be necessary to exceed the REL for Pd. For platinum (Pt), the majority of tooth surfaces, beyond just molar crowns, would be necessary to exceed the REL for Pd. Exposures due to leaching of elements from ceramic dental materials were less than published RELs for all components examined here, including having all restorations composed of ceramic.

  3. Evaluation of the mechanical properties and porcelain bond strength of cobalt-chromium dental alloy fabricated by selective laser melting.

    Science.gov (United States)

    Wu, Lin; Zhu, Haiting; Gai, Xiuying; Wang, Yanyan

    2014-01-01

    Limited information is available regarding the microstructure and mechanical properties of dental alloy fabricated by selective laser melting (SLM). The purpose of this study was to evaluate the mechanical properties of a cobalt-chromium (Co-Cr) dental alloy fabricated by SLM and to determine the correlation between its microstructure and mechanical properties and its porcelain bond strength. Five metal specimens and 10 metal ceramic specimens were fabricated to evaluate the mechanical properties of SLM Co-Cr dental alloy (SLM alloy) with a tensile test and its porcelain bond strength with a 3-point bending test. The relevant properties of the SLM alloy were compared with those of the currently used Co-Cr dental alloy fabricated with conventional cast technology (cast alloy). The Student t test was used to compare the results of the SLM alloy and the cast alloy (α=.05). The microstructure of the SLM alloy was analyzed with a metallographic microscope; the metal ceramic interface of the SLM porcelain bonded alloy was studied with scanning electron microscopy, energy dispersive x-ray spectroscopy, and an electron probe microanalyzer. Both the mean (standard deviation) yield strength (884.37 ± 8.96 MPa) and tensile strength (1307.50 ±10.65 MPa) of the SLM alloy were notably higher than yield strength (568.10 ± 30.94 MPa) and tensile strength (758.73 ± 25.85 MPa) of the currently used cast alloy, and the differences were significant (P.05). Microstructure analysis suggested that the SLM alloy had a dense and obviously orientated microstructure, which led to excellent mechanical properties. Analysis from scanning electron microscopy, energy dispersive x-ray spectroscopy, and the electron probe microanalyzer indicated that the SLM alloy had an intermediate layer with elemental interpenetration between the alloy and the porcelain, which resulted in an improved bonding interface. Compared with the currently used cast alloy, SLM alloy possessed improved mechanical

  4. Development of casting investment preventing blackening of noble metal alloys Part 2. Application of developed investment for type 4 gold alloy.

    Science.gov (United States)

    Nakai, Akira; Kakuta, Kiyoshi; Goto, Shin-ichi; Kato, Katuma; Yara, Atushi; Ogura, Hideo

    2003-09-01

    The objective of this study was to evaluate the efficacy of the developed investment for the prevention of blackening of a cast Type 4 gold and to analyze the oxides on its surface in relation to the blackening of the alloy. The experimental investments were prepared using a gypsum-bonded investment in which boron (B) or aluminum (Al) was added as a reducing agent. A Type 4 gold alloy was cast into the mold made of the prepared investment. The effect of the additives was evaluated from the color difference (deltaE*) between the as-cast surface and the polished surface of the cast specimen. B and Al were effective to prevent the blackening of a Type 4 gold alloy and the color of the as-cast surface approached that of the polished surface with increasing B and Al content. The prevention of the blackening of the gold alloy can be achieved by restraining the formation of CuO.

  5. Effect of preconditioning cobalt and nickel based dental alloys with Bacillus sp. extract on their surface physicochemical properties and theoretical prediction of Candida albicans adhesion

    Energy Technology Data Exchange (ETDEWEB)

    Balouiri, Mounyr, E-mail: b.mounyr@gmail.com [Faculté des Sciences et Techniques, Université Sidi Mohamed Ben Abdellah, BP 2202, 30007 Fez (Morocco); Bouhdid, Samira [Faculté des Sciences de Tétouan, Université Abdelmalek Essaadi, Avenue de Sebta, Mhannech II, 93002 Tétouan (Morocco); Sadiki, Moulay; Ouedrhiri, Wessal; Barkai, Hassan; El Farricha, Omar [Faculté des Sciences et Techniques, Université Sidi Mohamed Ben Abdellah, BP 2202, 30007 Fez (Morocco); Ibnsouda, Saad Koraichi [Faculté des Sciences et Techniques, Université Sidi Mohamed Ben Abdellah, BP 2202, 30007 Fez (Morocco); Cité de l' innovation, Université Sidi Mohamed Ben Abdellah, BP 2626, 30007 Fez (Morocco); Harki, El Houssaine [Faculté des Sciences et Techniques, Université Sidi Mohamed Ben Abdellah, BP 2202, 30007 Fez (Morocco)

    2017-02-01

    Biofilm formation on dental biomaterials is implicated in various oral health problems. Thus the challenge is to prevent the formation of this consortium of microorganisms using a safe approach such as antimicrobial and anti-adhesive natural products. Indeed, in the present study, the effects of an antifungal extract of Bacillus sp., isolated from plant rhizosphere, on the surface physicochemical properties of cobalt and nickel based dental alloys were studied using the contact angle measurements. Furthermore, in order to predict the adhesion of Candida albicans to the treated and untreated dental alloys, the total free energy of adhesion was calculated based on the extended Derjaguin-Landau-Verwey-Overbeek approach. Results showed hydrophobic and weak electron-donor and electron-acceptor characteristics of both untreated dental alloys. After treatment with the antifungal extract, the surface free energy of both dental alloys was influenced significantly, mostly for cobalt based alloy. In fact, treated cobalt based alloy became hydrophilic and predominantly electron donating. Those effects were time-dependent. Consequently, the total free energy of adhesion of C. albicans to this alloy became unfavorable after treatment with the investigated microbial extract. A linear relationship between the electron-donor property and the total free energy of adhesion has been found for both dental alloys. Also, a linear relationship has been found between this latter and the hydrophobicity for the cobalt based alloy. However, the exposure of nickel based alloy to the antifungal extract failed to produce the same effect. - Highlights: • Assessment of dental alloys physicochemical properties using contact angle method • Evaluation for the first time of microbial coating impact on dental alloys surface • Decrease of hydrophobicity of treated cobalt-chromium alloy with antifungal extract • Increase of Lewis base property of treated cobalt-chromium with treatment

  6. Effect of preconditioning cobalt and nickel based dental alloys with Bacillus sp. extract on their surface physicochemical properties and theoretical prediction of Candida albicans adhesion

    International Nuclear Information System (INIS)

    Balouiri, Mounyr; Bouhdid, Samira; Sadiki, Moulay; Ouedrhiri, Wessal; Barkai, Hassan; El Farricha, Omar; Ibnsouda, Saad Koraichi; Harki, El Houssaine

    2017-01-01

    Biofilm formation on dental biomaterials is implicated in various oral health problems. Thus the challenge is to prevent the formation of this consortium of microorganisms using a safe approach such as antimicrobial and anti-adhesive natural products. Indeed, in the present study, the effects of an antifungal extract of Bacillus sp., isolated from plant rhizosphere, on the surface physicochemical properties of cobalt and nickel based dental alloys were studied using the contact angle measurements. Furthermore, in order to predict the adhesion of Candida albicans to the treated and untreated dental alloys, the total free energy of adhesion was calculated based on the extended Derjaguin-Landau-Verwey-Overbeek approach. Results showed hydrophobic and weak electron-donor and electron-acceptor characteristics of both untreated dental alloys. After treatment with the antifungal extract, the surface free energy of both dental alloys was influenced significantly, mostly for cobalt based alloy. In fact, treated cobalt based alloy became hydrophilic and predominantly electron donating. Those effects were time-dependent. Consequently, the total free energy of adhesion of C. albicans to this alloy became unfavorable after treatment with the investigated microbial extract. A linear relationship between the electron-donor property and the total free energy of adhesion has been found for both dental alloys. Also, a linear relationship has been found between this latter and the hydrophobicity for the cobalt based alloy. However, the exposure of nickel based alloy to the antifungal extract failed to produce the same effect. - Highlights: • Assessment of dental alloys physicochemical properties using contact angle method • Evaluation for the first time of microbial coating impact on dental alloys surface • Decrease of hydrophobicity of treated cobalt-chromium alloy with antifungal extract • Increase of Lewis base property of treated cobalt-chromium with treatment

  7. Dental amalgam: effects of alloy/mercury mixing ratio, uses and waste management

    International Nuclear Information System (INIS)

    Kefi, I.; Maria, A.; Sana, J.; Afreen, J.; Adel, S.; Iftikhar, A.; Yawer, A.; Kaleem, M.

    2011-01-01

    Background: Silver dental amalgam is one of the oldest filling materials used in dentistry. The American Dental Association (ADA) has estimated that billions of amalgam restorations have been placed in patients in the last 150 years. Due to the presence of mercury and mishandling during the filling make it more controversial. The objective of this study was to conduct a survey of the use of different brands and to assess any deviations in practice from the hand mixing manual method of elemental mercury and alloy in a pestle/mortar and encapsulated form. Methods: A questionnaire was sent to 250 of randomly selected dental practitioner in various localities of Karachi. Data was analysed to record the specified brands used along with their powder/liquid (P/L) ratio and the different methods for disposing off mercury in this study. Results: The most commonly used form of dispensing method was hand mixing (57%) and only 30% of the dentists followed the manufacturer instruction for hand mixing ratio. Eighty-seven percent of dental amalgam restoration was performed and 13% removed by the dentist per month and the method of disposing the amalgam wastage that 55%, 25%, and 20% dentists were used the sink, bin and other methods respectively in their dental clinics. Conclusion: Amalgam restoration is still popular filling material in the posterior region of the mouth but we need to create awareness among the dentists who do not follow the ADA specifications. (author)

  8. A dual energy gamma-ray transmission technique for gold alloy identification

    International Nuclear Information System (INIS)

    Sumi, Tetsuo; Shingu, Hiroyasu; Iwase, Hirotoshi

    1991-01-01

    An application of the dual energy gamma-ray transmission techniques to gold alloy identification is presented. The measurement by dual energy gamma-ray transmission is independent of thickness and density of a sample. Due to this advantage, golden accessories such as necklaces, earrings and rings can be assayed in spite of their various thicknesses and irregular sectional shapes. Choice of a gamma-ray energy pair suitable for the object is important. The authors chose 511 keV and 1275 keV gamma-rays from 22 Na. With this energy pair, R value (a ratio of mass attenuation coefficients for low and high energy gamma-rays) is predominantly related to the weight fraction of gold of the sample. Using a 370 kBq 22 Na small source and a 50 mm dia.x 50 mm thick NaI(Tl) scintillator for 1200 seconds, a resolution of 2% for the R value was obtained. This corresponds to approximately 5% of the weight fraction of gold. A better resolution can be obtained by increasing the source activity or measurement time. (author)

  9. Corrosive and cytotoxic properties of compact specimens and microparticles of Ni-Cr dental alloy.

    Science.gov (United States)

    Ristic, Ljubisa; Vucevic, Dragana; Radovic, Ljubica; Djordjevic, Snezana; Nikacevic, Milutin; Colic, Miodrag

    2014-04-01

    Nickel-chromium (Ni-Cr) dental alloys have been widely used in prosthodontic practice, but there is a permanent concern about their biocompatibility due to the release of metal ions. This is especially important when Ni-Cr metal microparticles are incorporated into gingival tissue during prosthodontic procedures. Therefore, the aim of this study was to examine and compare the corrosion and cytotoxic properties of compact specimens and microparticles of Ni-Cr dental alloy. Ni-Cr alloy, Remanium CSe bars (4 mm diameter), were made by the standard casting method and then cut into 0.5-mm-thick disks. Metal particles were obtained by scraping the bars using a diamond instrument for crown preparation. The microstructure was observed by an optical microscope. Quantitative determination and morphological and dimensional characterization of metal particles were carried out by a scanning electron microscope and Leica Application Suite software for image analysis. Corrosion was studied by conditioning the alloy specimens in the RPMI 1640 medium, containing 10% fetal calf serum in an incubator with 5% CO2 for 72 hours at 37°C. Inductively coupled plasma-optical emission spectrometry was used to assess metal ion release. The cytotoxity of conditioning medium (CM) was investigated on L929 cells using an MTT test. One-way ANOVA was used for statistical analysis. After casting, the microstructure of the Remanium CSe compact specimen composed of Ni, Cr, Mo, Si, Fe, Al, and Co had a typical dendritic structure. Alloy microparticles had an irregular shape with a wide size range: from less than 1 μm to more than 100 μm. The release of metal ions, especially Ni and Mo from microparticles, was significantly higher, compared to the compact alloy specimen. The CM prepared from compact alloy was not cytotoxic at any tested dilutions, whereas CM from alloy microparticles showed dose-dependent cytotoxicity (90% CM and 45% CM versus control; p alloy. This could affect health on long

  10. Oxygen reduction of several gold alloys in 1-molar potassium hydroxide

    Science.gov (United States)

    Miller, R. O.

    1975-01-01

    With rotated disk-and-ring equipment, polarograms and other electrochemical measurements were made of oxygen reduction in 1-molar potassium hydroxide on an equiatomic gold-copper (Au-Cu) alloy and a Au-Cu alloy doped with either indium (In) or cobalt (Co) and on Au doped with either nickel (Ni) or platinum (Pt). The results were compared with those for pure Au and pure Pt. The two-electron reaction dominated on all Au alloys as it did on Au. The polarographic results at lower polarization potentials were compared, assuming exclusively a two-step reduction. A qualified ranking of cathodic electrocatalytic activity on the freshly polished reduced disks was indicated: anodized Au Au-Cu-In Au-Cu Au-Cu-Co is equivalent or equal to Au-Pt Au-Ni. Aging in distilled water improved the electrocatalytic efficiency of Au-Cu-Co, Au-Cu, and (to a lesser extent) Au-Cu-In.

  11. Effects of soldering methods on tensile strength of a gold-palladium metal ceramic alloy.

    Science.gov (United States)

    Ghadhanfari, Husain A; Khajah, Hasan M; Monaco, Edward A; Kim, Hyeongil

    2014-10-01

    The tensile strength obtained by conventional postceramic application soldering and laser postceramic welding may require more energy than microwave postceramic soldering, which could provide similar tensile strength values. The purpose of the study was to compare the tensile strength obtained by microwave postceramic soldering, conventional postceramic soldering, and laser postceramic welding. A gold-palladium metal ceramic alloy and gold-based solder were used in this study. Twenty-seven wax specimens were cast in gold-palladium noble metal and divided into 4 groups: laser welding with a specific postfiller noble metal, microwave soldering with a postceramic solder, conventional soldering with the same postceramic solder used in the microwave soldering group, and a nonsectioned control group. All the specimens were heat treated to simulate a normal porcelain sintering sequence. An Instron Universal Testing Machine was used to measure the tensile strength for the 4 groups. The means were analyzed statistically with 1-way ANOVA. The surface and fracture sites of the specimens were subjectively evaluated for fracture type and porosities by using a scanning electron microscope. The mean (standard deviation) ultimate tensile strength values were as follows: nonsectioned control 818 ±30 MPa, microwave 516 ±34 MPa, conventional 454 ±37 MPa, and laser weld 191 ±39 MPa. A 1-way ANOVA showed a significant difference in ultimate tensile strength among the groups (F3,23=334.5; Ptensile strength for gold and palladium noble metals than either conventional soldering or laser welding. Conventional soldering resulted in a higher tensile strength than laser welding. Under the experimental conditions described, either microwave or conventional postceramic soldering would appear to satisfy clinical requirements related to tensile strength. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  12. Gold nanoparticles in injectable calcium phosphate cement enhance osteogenic differentiation of human dental pulp stem cells.

    Science.gov (United States)

    Xia, Yang; Chen, Huimin; Zhang, Feimin; Bao, Chongyun; Weir, Michael D; Reynolds, Mark A; Ma, Junqing; Gu, Ning; Xu, Hockin H K

    2018-01-01

    In this study, a novel calcium phosphate cement containing gold nanoparticles (GNP-CPC) was developed. Its osteogenic induction ability on human dental pulp stem cells (hDPSCs) was investigated for the first time. The incorporation of GNPs improved hDPSCs behavior on CPC, including better cell adhesion (about 2-fold increase in cell spreading) and proliferation, and enhanced osteogenic differentiation (about 2-3-fold increase at 14 days). GNPs endow CPC with micro-nano-structure, thus improving surface properties for cell adhesion and subsequent behaviors. In addition, GNPs released from GNP-CPC were internalized by hDPSCs, as verified by transmission electron microscopy (TEM), thus enhancing cell functions. The culture media containing GNPs enhanced the cellular activities of hDPSCs. This result was consistent with and supported the osteogenic induction results of GNP-CPC. In conclusion, GNP-CPC significantly enhanced the osteogenic functions of hDPSCs. GNPs are promising to modify CPC with nanotopography and work as bioactive additives thus enhance bone regeneration. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Comparative study on the corrosion behavior of Ti-Nb and TMA alloys for dental application in various artificial solutions

    International Nuclear Information System (INIS)

    Bai, Y.J.; Wang, Y.B.; Cheng, Y.; Deng, F.; Zheng, Y.F.; Wei, S.C.

    2011-01-01

    The corrosion behavior of Ti-Nb dental alloy in artificial saliva with and without the addition of lactic acid and sodium fluoride was investigated by electrochemical techniques, with the commercial Titanium-molybdenum alloy (TMA) as a comparison. The chemical composition, microstructure and constitutional phase were characterized via energy dispersive spectrometry, optical microscope and X-ray diffraction, meanwhile the open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization measurements were carried out to study the corrosion resistance of experimental alloys, with the corroded surface being further characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that the corrosion behavior of Ti-Nb alloy was similar to those TMA alloy samples in both artificial and acidified saliva solutions, whereas statistical analysis of the electrochemical impedance spectroscopy and polarization parameters showed Ti-Nb alloy exhibited better corrosion resistance in fluoridated saliva and fluoridated acidified saliva. SEM observation indicated that TMA alloy corroded heavily than Ti-Nb alloy in fluoride containing saliva. XPS surface analysis suggested that Nb 2 O 5 played an important role in anti-corrosion from the attack of fluoride ion. Based on the above finding, Ti-Nb alloy is believed to be suitable for the usage in certain fluoride treated dental works with excellent corrosion resistance in fluoride-containing oral media.

  14. Artifacts in MRI of the temporomandibular joint caused by dental alloys: a phantom study at 1.5 T

    International Nuclear Information System (INIS)

    Fellner, C.; Erlangen-Nuernberg Univ., Erlangen; Behr, M.; Fellner, F.; Held, P.; Handel, G.; Feuerbach, S.

    1997-01-01

    Purpose: The influence of dental alloys on MRI of the temporomandibular joint was studied using a phantom model for this joint. Methods: At 1,5 T, 15 dental alloys and 14 of their most important components were investigated acquiring sagittal (FOV: 150 mm) and transverse (FOV: 250 mm) T 1 -weighted SE additionally. The artifacts were assessed qualitatively as well as quantitatively, and the samples were subdivided into four artifact categories. Results: Ag, Cu, Ga, In, Ti, Sn, Zn, amalgan, the precious alloys, the Au-Pd and Ag-Pd alloys showed no artifacts (category I). Minimal artifacts below 10 mm on transverse images (category II) were found for Cr, Pd, Pt and for the Ni-Cr alloy. Mn and the remaining non-precious alloys induced artifacts up to 30 mm (category III). Significant artifacts - more than 30 mm - (category IV) were to be more susceptible for artifacts than T 1 -weighted SE and FLASH techniques. Conclusions: In contrast to dental alloys for fixed prosthodontics, Ni-Cr- or 18/8 wires used for orthodontic bands can influence not only the image quality, but also the diagnostic reliability of MRI of the temporomandibular joint. (orig.) [de

  15. Defects-tolerant Co-Cr-Mo dental alloys prepared by selective laser melting.

    Science.gov (United States)

    Qian, B; Saeidi, K; Kvetková, L; Lofaj, F; Xiao, C; Shen, Z

    2015-12-01

    CrCoMo alloy specimens were successfully fabricated using selective laser melting (SLM). The aim of this study was to carefully investigate microstructure of the SLM specimens in order to understand the influence of their structural features inter-grown on different length scales ranging from nano- to macro-levels on their mechanical properties. Two different sets of processing parameters developed for building the inner part (core) and the surface (skin) of dental prostheses were tested. Microstructures were characterized by SEM, EBSD and XRD analysis. The elemental distribution was assessed by EDS line profile analysis under TEM. The mechanical properties of the specimens were measured. The microstructures of both specimens were characterized showing formation of grains comprised of columnar sub-grains with Mo-enrichment at the sub-grain boundaries. Clusters of columnar sub-grains grew coherently along one common crystallographic direction forming much larger single crystal grains which are intercrossing in different directions forming an overall dendrite-like microstructure. Three types of microstructural defects were occasionally observed; small voids (10 μm). Despite the presence of these defects, the yield and the ultimate tensile strength (UTS) were 870 and 430MPa and 1300MPa and 1160MPa, respectively, for the skin and core specimens which are higher than casted dental alloy. Although the formation of microstructural defects is hard to be avoided during the SLM process, the SLM CoCrMo alloys can achieve improved mechanical properties than their casted counterparts, implying they are "defect-tolerant". Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  16. A new dental powder from nanocrystalline melt-spun Ag-Sn-Cu alloy ribbons

    International Nuclear Information System (INIS)

    Do-Minh, N.; Le-Thi, C.; Nguyen-Anh, S.

    2003-01-01

    A new non-gamma-two dental powder has been developed from nanocrystalline melt-spun Ag-Sn-Cu alloy ribbons. The amalgam made from this powder exhibits excellent properties for dental filling. The nanocrystalline microstructure was found for the first time in as-spun and heat treated Ag(27-28)Sn(9-32) Cu alloy ribbons, using X-ray diffraction, scanning electron microscopy and energy-dispersive spectroscopy. As-spun ribbons exhibited a multi-phase microstructure with preferred existence of β (Ag 4 Sn) phase formed during rapid solidification (RS) due to supersaturating of copper (Cu) atoms and homogenous nanostructure with subgrain size of about (40-50) nm, which seems to be developed during RS process and can be caused by eutectic reaction of the Ag 3 Sn/Ag 4 Sn-Cu 3 Sn system. In heat treated ribbons the clustering of Cu atoms was always favored and stable in an ageing temperature and time interval determined by Cu content. The heat treatment led to essential changes of subgrain morphology, resulted in the appearance of large-angle boundaries with fine Cu 3 Sn precipitates and forming typical recrystallization twins. Such a microstructure variation in melt-spun ribbons could eventually yield enhanced technological, clinical and physical properties of the dental products, controlled by the ADA Specification N deg 1 and reported before. Thus, using the rapid solidification technique a new non-gamma-two dental material of high quality, nanocrystalline ribbon powder, can be produced. Copyright (2003) AD-TECH - International Foundation for the Advancement of Technology Ltd

  17. Morphological Analysis (SEM) of the Surface of a Non-Noble Dental Alloy Subjected to Electrocorrosion

    Science.gov (United States)

    Baciu, E. R.; Grădinaru, I.; Baciu, M.; Vasluianu, R. I.; Cimpoesu, R.; Baciu, C.; Bejinariu, C.

    2017-06-01

    Corrosion consists in the degradation of a material under the chemical or electrochemical action of the environment where it is placed. The investigations carried out aimed to show the structural modifications produced in Co-Cr-Mo alloy, Robur 400 (Eisenbacher Dental - Waren ED GmbH, Germany) subjected to electrocorrosion in Fusayama-Mayer artificial saliva. The specimens prepared by mechanical polishing were analysed structurally by using a scanning electron microscope. During the tests run we could notice a general corrosion of the surfaces of the specimens made from Robur alloy. Through 2D and 3D microscopy and qualitative determinations of the luminous variation we could notice the effects of electrocorrosion tests on the surface of the metal material.

  18. Phase composition of rapidly solidified Ag-Sn-Cu dental alloys

    International Nuclear Information System (INIS)

    Lecong Dzuong; Do Minh Nghiep; Nguyen van Dzan; Cao the Ha

    1996-01-01

    The phase composition of some rapidly solidified Ag-Sn-Cu dental alloys with different copper contents (6.22 wtpct) has been studied by XRD, EMPA and optical microscopy. The samples were prepared from melt-spun ribbons. The microstructure of the as-quenched ribbons was microcrystalline and consisted of the Ag sub 3 Sn, Ag sub 4 Sn, Cu sub 3 Sn and Cu sub 3 Sn sub 8 phases. Mixing with mercury (amalgamation) led to formation of the Ag sub 2 Hg sub 3, Sn sub 7 Hg and Cu sub 6 Sn sub 5 phases. The amount of copper atoms in the alloys played an important role in phase formation in the amalgams

  19. A theoretical study of CH4 dissociation on pure and gold-alloyed Ni(111) surfaces

    DEFF Research Database (Denmark)

    Kratzer, P.; Hammer, Bjørk; Nørskov, Jens Kehlet

    1996-01-01

    We present a density functional theory study of the first step of CH4 adsorption on the Ni(111) surface, dissociation into adsorbed CH3 and H. The rupture of the C-H bond occurs preferentially on top of a Ni atom, with a dissociation barrier of about 100 kJ/mol (including zero point corrections......). The transition state involves considerable internal excitation of the molecule. The active C-H bond is both stretched to 1.6 Angstrom and tilted relative to the methyl group. A normal mode analysis shows that the reaction coordinate is mainly a C-H stretch, while the orientation of the C-H bond relative...... to the surface is responsible for the highest real mode. Alloying the surface with gold also affects the reactivity of the Ni atoms on adjacent surface sites. The dissociation barrier is increased by 16 and 38 kJ/mol for a Ni atom with one or two gold neighbors, respectively. We attribute these changes...

  20. Effects of Ni and Mo on the microstructure and some other properties of Co-Cr dental alloys

    International Nuclear Information System (INIS)

    Matkovic, Tanja; Matkovic, Prosper; Malina, Jadranka

    2004-01-01

    Influences of adding Ni and Mo on the microstructure and properties of as-cast Co-Cr base alloys have been investigated in order to determine the region of their optimal characteristics for biomedical application. The alloys were produced by arc-melting technique under argon atmosphere. Using optical metallography and scanning electron micro analyser it has been established that among 10 samples of Co-Cr-Ni alloys only samples 5 and 9 with the composition Co 55 Cr 40 Ni 5 and Co 60 Cr 30 Ni 10 have appropriate dendritic solidification microstructure. This microstructure, typical for commercial dental alloys, appears and beside greater number of as-cast Co-Cr-Mo alloys. The results of hardness and corrosion resistance measurements revealed the strong influence of different alloy chemistry and of as-cast microstructure. Hardness of alloys decreases with nickel content, but increases with chromium content. Therefore all Co-Cr-Ni alloys have significantly lower hardness than Co-Cr-Mo alloys. Corrosion resistance of alloys in artificial saliva was evaluated on the base of pitting potential. Superior corrosion characteristics have the samples with typical dendritic microstructure and higher chromium content, until nickel content have not significant effect. According to this, in ternary Co-Cr-Ni phase diagram was located the small concentration region (about samples 5 and 9) in them alloy properties can satisfied the high requirements for biomedical applications. This region is considerably larger in Co-Cr-Mo phase diagram

  1. Galvanic coupling of steel and gold alloy lingual brackets with orthodontic wires.

    Science.gov (United States)

    Polychronis, Georgios; Al Jabbari, Youssef S; Eliades, Theodore; Zinelis, Spiros

    2018-03-06

    The aim of this research was to assess galvanic behavior of lingual orthodontic brackets coupled with representative types of orthodontic wires. Three types of lingual brackets: Incognito (INC), In-Ovation L (IOV), and STb (STB) were combined with a stainless steel (SS) and a nickel-titanium (NiTi) orthodontic archwire. All materials were initially investigated by scanning electron microscopy / x-ray energy dispersive spectroscopy (SEM/EDX) while wires were also tested by x-ray diffraction spectroscopy (XRD). All bracket-wire combinations were immersed in acidic 0.1M NaCl 0.1M lactic acid and neutral NaF 0.3% (wt) electrolyte, and the potential differences were continuously recorded for 48 hours. The SEM/EDX analysis revealed that INC is a single-unit bracket made of a high gold (Au) alloy while IOV and STB are two-piece appliances in which the base and wing are made of SS alloys. The SS wire demonstrated austenite and martensite iron phase, while NiTi wire illustrated an intense austenite crystallographic structure with limited martensite. All bracket wire combinations showed potential differences below the threshold of galvanic corrosion (200 mV) except for INC and STB coupled with NiTi wire in NaF media. The electrochemical results indicate that all brackets tested demonstrated galvanic compatibility with SS wire, but fluoride treatment should be used cautiously with NiTi wires coupled with Au and SS brackets.

  2. Base-metal dental casting alloy biocompatibility assessment using a human-derived 3D oral mucosal model

    OpenAIRE

    MORAN, GARY; MC GINLEY, EMMA LOUISE; FLEMING, GARRY

    2012-01-01

    PUBLISHED Nickel-chromium (Ni-Cr) alloys used in fixed prosthodontics have been associated with type IV nickel-induced hypersensitivity. We hypothesized the full-thickness human-derived oral mucosa model employed for biocompatibility testing of base-metal dental alloys would provide insights into mechanisms of nickel-induced toxicity. Primary oral keratinocytes and gingival fibroblasts were seeded onto Alloderm? and maintained until full-thickness was achieved prior to Ni-Cr and cobalt-chr...

  3. Microstructure, mechanical properties, castability and in vitro biocompatibility of Ti-Bi alloys developed for dental applications.

    Science.gov (United States)

    Qiu, K J; Liu, Y; Zhou, F Y; Wang, B L; Li, L; Zheng, Y F; Liu, Y H

    2015-03-01

    In this study, the microstructure, mechanical properties, castability, electrochemical behaviors, cytotoxicity and hemocompatibility of Ti-Bi alloys with pure Ti as control were systematically investigated to assess their potential applications in the dental field. The experimental results showed that, except for the Ti-20Bi alloy, the microstructure of all other Ti-Bi alloys exhibit single α-Ti phase, while Ti-20Bi alloy is consisted of mainly α-Ti phase and a small amount of BiTi2 and BiTi3 phases. The tensile strength, hardness and wear resistance of Ti-Bi alloys were demonstrated to be improved monotonically with the increase of Bi content. The castability test showed that Ti-2Bi alloy increased the castability of pure Ti by 11.7%. The studied Ti-Bi alloys showed better corrosion resistance than pure Ti in both AS (artificial saliva) and ASFL (AS containing 0.2% NaF and 0.3% lactic acid) solutions. The concentrations of both Ti ion and Bi ion released from Ti-Bi alloys are extremely low in AS, ASF (AS containing 0.2% NaF) and ASL (AS containing 0.3% lactic acid) solutions. However, in ASFL solution, a large number of Ti and Bi ions are released. In addition, Ti-Bi alloys produced no significant deleterious effect to L929 cells and MG63 cells, similar to pure Ti, indicating a good in vitro biocompatibility. Besides, both L929 and MG63 cells perform excellent cell adhesion ability on Ti-Bi alloys. The hemolysis test exhibited that Ti-Bi alloys have an ultra-low hemolysis percentage below 1% and are considered nonhemolytic. To sum up, the Ti-2Bi alloy exhibits the optimal comprehensive performance and has great potential for dental applications. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  4. Comparison of Dental Prostheses Cast and Sintered by SLM from Co-Cr-Mo-W Alloy

    Directory of Open Access Journals (Sweden)

    Myszka D.

    2016-12-01

    Full Text Available The article presents the results of a comparative analysis of the metal substructure for dental prosthesis made from a Co-Cr-Mo-W alloy by two techniques, i.e. precision investment casting and selective laser melting (SLM. It was found that the roughness of the raw surface of the SLM sinter is higher than the roughness of the cast surface, which is compensated by the process of blast cleaning during metal preparation for the application of a layer of porcelain. Castings have a dendritic structure, while SLM sinters are characterized by a compact, fine-grain microstructure of the hardness higher by about 100 HV units. High performance and high costs of implementation the SLM technology are the cause to use it for the purpose of many dental manufacturers under outsourcing rules. The result is a reduction in manufacturing costs of the product associated with dental work time necessary to scan, designing and treatment of sinter compared with the time needed to develop a substructure in wax, absorption in the refractory mass, casting, sand blasting and finishing. As a result of market competition and low cost of materials, sinter costs decrease which brings the total costs related to the construction unit making using the traditional method of casting, at far less commitment of time and greater predictability and consistent sinter quality.

  5. Base-metal dental casting alloy biocompatibility assessment using a human-derived three-dimensional oral mucosal model.

    LENUS (Irish Health Repository)

    McGinley, E L

    2012-01-01

    Nickel-chromium (Ni-Cr) alloys used in fixed prosthodontics have been associated with type IV Ni-induced hypersensitivity. We hypothesised that the full-thickness human-derived oral mucosa model employed for biocompatibility testing of base-metal dental alloys would provide insights into the mechanisms of Ni-induced toxicity. Primary oral keratinocytes and gingival fibroblasts were seeded onto Alloderm™ and maintained until full thickness was achieved prior to Ni-Cr and cobalt-chromium (Co-Cr) alloy disc exposure (2-72 h). Biocompatibility assessment involved histological analyses with cell viability measurements, oxidative stress responses, inflammatory cytokine expression and cellular toxicity analyses. Inductively coupled plasma mass spectrometry analysis determined elemental ion release levels. We detected adverse morphology with significant reductions in cell viability, significant increases in oxidative stress, inflammatory cytokine expression and cellular toxicity for the Ni-Cr alloy-treated oral mucosal models compared with untreated oral mucosal models, and adverse effects were increased for the Ni-Cr alloy that leached the most Ni. Co-Cr demonstrated significantly enhanced biocompatibility compared with Ni-Cr alloy-treated oral mucosal models. The human-derived full-thickness oral mucosal model discriminated between dental alloys and provided insights into the mechanisms of Ni-induced toxicity, highlighting potential clinical relevance.

  6. [The effect of epigallocatechin gallate (EGCG) on the surface properties of nickel-chromium dental casting alloys after electrochemical corrosion].

    Science.gov (United States)

    Qiao, Guang-yan; Zhang, Li-xia; Wang, Jue; Shen, Qing-ping; Su, Jian-sheng

    2014-08-01

    To investigate the effect of epigallocatechin gallate (EGCG) on the surface properties of nickel-chromium dental alloys after electrochemical corrosion. The surface morphology and surface structure of nickel-chromium dental alloys were examined by stereomicroscope and scanning electron microscopy before and after electrochemical tests in 0 g/L and 1.0 g/L EGCG artificial saliva. The surface element component and chemical states of nickel-chromium dental alloys were analyzed by X-ray photoelectron spectrograph after electrochemical tests in 0 g/L and 1.0 g/L EGCG artificial saliva. More serious corrosion happened on the surface of nickel-chromium alloy in 1.0 g/L EGCG artificial saliva than in 0 g/L EGCG. The diameters of corrosion pits were smaller, and the dendrite structure of the alloy surface was not affected in 0 g/L EGCG. While the diameters of corrosion pits were larger, the dendritic interval of the alloy surface began to merge, and the dendrite structure was fuzzy in 1.0 g/L EGCG. In addition, the O, Ni, Cr, Be, C and Mo elements were detected on the surface of nickel-chromium alloys after sputtered for 120 s in 0 g/L EGCG and 1.0 g/L EGCG artificial saliva after electrochemical corrosion, and the surface oxides were mainly NiO and Cr(2)O(3). Compared with 0 g/L EGCG artificial saliva, the content of O, NiO and Cr(2)O(3) were lower in 1.0 g/L EGCG. The results of surface morphology and the corrosion products both show that the corrosion resistance of nickel-chromium alloys become worse and the oxide content of corrosion products on the surface reduce in 1.0 g/L EGCG artificial saliva.

  7. Are new TiNbZr alloys potential substitutes of the Ti6Al4V alloy for dental applications? An electrochemical corrosion study

    International Nuclear Information System (INIS)

    Ribeiro, Ana Lúcia Roselino; Hammer, Peter; Vaz, Luís Geraldo; Rocha, Luís Augusto

    2013-01-01

    The main aim of this work was to assess the electrochemical behavior of new Ti35Nb5Zr and Ti35Nb10Zr alloys in artificial saliva at 37 °C to verify if they are indicated to be used as biomaterials in dentistry as alternatives to Ti6Al4V alloys in terms of corrosion protection efficiency of the material. Electrochemical impedance spectroscopy (EIS) experiments were carried out for different periods of time (0.5–216 h) in a three-electrode cell, where the working electrode (Ti alloys) was exposed to artificial saliva at 37 °C. The near-surface region of the alloys was investigated using x-ray photoelectron spectroscopy (XPS). All alloys exhibited an increase in corrosion potential with the immersion time, indicating the growth and stabilization of the passive film. Ti35Nb5Zr and Ti6Al4V alloys had their EIS results interpreted by a double-layer circuit, while the Ti35Nb10Zr alloy was modeled by a one-layer circuit. In general, the new TiNbZr alloys showed similar behavior to that observed for the Ti6Al4V. XPS results suggest, in the case of the TiNbZr alloys, the presence of a thicker passive layer containing a lower fraction of TiO 2  phase than that of Ti6Al4V. After long-term immersion, all alloys develop a calcium phosphate phase on the surface. The new TiNbZr alloys appear as potential candidates to be used as a substitute to Ti6Al4V in the manufacturing of dental implant-abutment sets. (paper)

  8. Are new TiNbZr alloys potential substitutes of the Ti6Al4V alloy for dental applications? An electrochemical corrosion study.

    Science.gov (United States)

    Ribeiro, Ana Lúcia Roselino; Hammer, Peter; Vaz, Luís Geraldo; Rocha, Luís Augusto

    2013-12-01

    The main aim of this work was to assess the electrochemical behavior of new Ti35Nb5Zr and Ti35Nb10Zr alloys in artificial saliva at 37 °C to verify if they are indicated to be used as biomaterials in dentistry as alternatives to Ti6Al4V alloys in terms of corrosion protection efficiency of the material. Electrochemical impedance spectroscopy (EIS) experiments were carried out for different periods of time (0.5-216 h) in a three-electrode cell, where the working electrode (Ti alloys) was exposed to artificial saliva at 37 °C. The near-surface region of the alloys was investigated using x-ray photoelectron spectroscopy (XPS). All alloys exhibited an increase in corrosion potential with the immersion time, indicating the growth and stabilization of the passive film. Ti35Nb5Zr and Ti6Al4V alloys had their EIS results interpreted by a double-layer circuit, while the Ti35Nb10Zr alloy was modeled by a one-layer circuit. In general, the new TiNbZr alloys showed similar behavior to that observed for the Ti6Al4V. XPS results suggest, in the case of the TiNbZr alloys, the presence of a thicker passive layer containing a lower fraction of TiO2 phase than that of Ti6Al4V. After long-term immersion, all alloys develop a calcium phosphate phase on the surface. The new TiNbZr alloys appear as potential candidates to be used as a substitute to Ti6Al4V in the manufacturing of dental implant-abutment sets.

  9. A novel luminol chemiluminescent method catalyzed by silver/gold alloy nanoparticles for determination of anticancer drug flutamide.

    Science.gov (United States)

    Chaichi, Mohammad Javad; Azizi, Seyed Naser; Heidarpour, Maryam

    2013-12-01

    It was found that silver/gold alloy nanoparticles enhance the chemiluminescence (CL) of the luminol-H2O2 system in alkaline solution. The studies of UV-Vis spectra, CL spectra, effects of concentrations luminol, hydrogen peroxide and silver/gold alloy nanoparticles solutions were carried out to explore the CL enhancement mechanism. Flutamide was found to quench the CL signals of the luminol-H2O2 reaction catalyzed by silver/gold alloy nanoparticles, which made it applicable for the determination of flutamide. Under the optimum conditions, the CL intensity is proportional to the concentration of the flutamide in solution over the range 5.0 × 10(-7) to 1.0 × 10(-4)mol L(-1). Detection limit was obtained 1.2 × 10(-8)mol L(-1)and the relative standard deviation (RSD) γ5%. This work is introduced as a new method for the determination of flutamide in commercial tablets. Box-Behnken experimental design is applied to investigate and validate the CL measurement parameters. Copyright © 2013 Elsevier B.V. All rights reserved.

  10. Influence of metal dental materials on MR imaging

    Energy Technology Data Exchange (ETDEWEB)

    Tsuchihashi, Toshio; Chiba, Michiko; Yoshizawa, Satoshi; Sasaki, Sadayuki; Maki, Toshio; Kitagawa, Matsuo; Suzuki, Takeshi [Nippon Medical School, Tokyo (Japan). Main Hospital; Nakata, Minoru; Fujita, Isao

    1998-11-01

    Differences in magnetic susceptibility produce artifacts and signal loss in magnetic resonance imaging (MRI). This study was undertaken to compare the degree of artifacts on MRI caused by metallic dental materials. The influence on MRI of six types of dental alloys, a dental implant, orthodontic appliance, and magnetic attachment was investigated. Among the dental metals, nickel-chromium alloy and cobalt-chromium alloy, which have ferromagnetism, caused significant metal artifacts. Gold-platinum alloy, gold-silver-palladium alloy, silver alloy, and amalgam alloy produced slight metal artifacts. The orthodontic appliance mainly consisted of iron, and the keeper for its magnetic attachment was made of stainless steel. For these reasons, marked metal artifacts and signal loss could be seen in both of them owing to their ferromagnetism. These results suggest that orthodontic appliances and magnetic attachments impair evaluation of the GRE and EPI techniques. It is therefore preferable to use predominantly diamagnetic or paramagnetic dental materials for MRI of the head and neck. Removable keepers should be used more widely to prevent metal artifacts and enhance safety on MRI. (author)

  11. Influence of metal dental materials on MR imaging

    International Nuclear Information System (INIS)

    Tsuchihashi, Toshio; Chiba, Michiko; Yoshizawa, Satoshi; Sasaki, Sadayuki; Maki, Toshio; Kitagawa, Matsuo; Suzuki, Takeshi; Nakata, Minoru; Fujita, Isao

    1998-01-01

    Differences in magnetic susceptibility produce artifacts and signal loss in magnetic resonance imaging (MRI). This study was undertaken to compare the degree of artifacts on MRI caused by metallic dental materials. The influence on MRI of six types of dental alloys, a dental implant, orthodontic appliance, and magnetic attachment was investigated. Among the dental metals, nickel-chromium alloy and cobalt-chromium alloy, which have ferromagnetism, caused significant metal artifacts. Gold-platinum alloy, gold-silver-palladium alloy, silver alloy, and amalgam alloy produced slight metal artifacts. The orthodontic appliance mainly consisted of iron, and the keeper for its magnetic attachment was made of stainless steel. For these reasons, marked metal artifacts and signal loss could be seen in both of them owing to their ferromagnetism. These results suggest that orthodontic appliances and magnetic attachments impair evaluation of the GRE and EPI techniques. It is therefore preferable to use predominantly diamagnetic or paramagnetic dental materials for MRI of the head and neck. Removable keepers should be used more widely to prevent metal artifacts and enhance safety on MRI. (author)

  12. The estimation of corrosion behaviour of ZrTi binary alloys for dental applications using electrochemical techniques

    International Nuclear Information System (INIS)

    Mareci, Daniel; Bolat, Georgiana; Chelariu, Romeu; Sutiman, Daniel; Munteanu, Corneliu

    2013-01-01

    Titanium and zirconium are in the same group in the periodic table of elements and are known to have similar physical and chemical properties. Both Ti and Zr usually have their surfaces covered by a thin oxide film spontaneously formed in air. However, the cytotoxicity of ZrO 2 is lower than that of TiO 2 rutile. Treatments with fluoride are known as the main methods to prevent plaque formation and dental caries. The corrosion behaviour of ZrTi alloys with Ti contents of 5, 25 and 45 wt.% and cp-Ti was investigated for dental applications. All samples were tested by linear potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) performed in artificial saliva with different pH levels (5.6 and 3.4) and different fluoride (1000 ppm F − ) and albumin protein (0.6%) contents. In addition, scanning electron microscopy (SEM) was employed to observe the surface morphology of the test materials after linear potentiodynamic polarisation. The corrosion current densities for the ZrTi alloys increased with the titanium content. The Zr5Ti and Zr25Ti alloys were susceptible to localised corrosion. The role that Ti plays as an alloying element is that of increasing the resistance of ZrTi alloy to localised corrosion. The presence of 0.6% albumin protein in fluoridated acidified artificial saliva with 1000 ppm F − could protect the cp-Ti and ZrTi alloys from attack by fluoride ions. - Highlights: • Electrochemical and corrosion behaviour of the new ZrTi alloys were investigated. • The passive behaviour for all the ZrTi alloys is observed. • Addition of Ti to Zr improves the corrosion resistance in some fluoridated saliva. • The presence of albumin could prevent the ZrTi alloys from attack by fluoride ions

  13. The estimation of corrosion behaviour of ZrTi binary alloys for dental applications using electrochemical techniques

    Energy Technology Data Exchange (ETDEWEB)

    Mareci, Daniel [“Gheorghe Asachi” Technical University of Iasi, Faculty of Chemical Engineering and Environmental Protection, Iasi (Romania); Bolat, Georgiana, E-mail: georgiana20022@yahoo.com [“Gheorghe Asachi” Technical University of Iasi, Faculty of Chemical Engineering and Environmental Protection, Iasi (Romania); Chelariu, Romeu [“Gheorghe Asachi” Technical University of Iasi, Faculty of Materials Science and Engineering, Iasi (Romania); Sutiman, Daniel [“Gheorghe Asachi” Technical University of Iasi, Faculty of Chemical Engineering and Environmental Protection, Iasi (Romania); Munteanu, Corneliu [“Gheorghe Asachi” Technical University of Iasi, Faculty of Mechanical, Iasi (Romania)

    2013-08-15

    Titanium and zirconium are in the same group in the periodic table of elements and are known to have similar physical and chemical properties. Both Ti and Zr usually have their surfaces covered by a thin oxide film spontaneously formed in air. However, the cytotoxicity of ZrO{sub 2} is lower than that of TiO{sub 2} rutile. Treatments with fluoride are known as the main methods to prevent plaque formation and dental caries. The corrosion behaviour of ZrTi alloys with Ti contents of 5, 25 and 45 wt.% and cp-Ti was investigated for dental applications. All samples were tested by linear potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) performed in artificial saliva with different pH levels (5.6 and 3.4) and different fluoride (1000 ppm F{sup −}) and albumin protein (0.6%) contents. In addition, scanning electron microscopy (SEM) was employed to observe the surface morphology of the test materials after linear potentiodynamic polarisation. The corrosion current densities for the ZrTi alloys increased with the titanium content. The Zr5Ti and Zr25Ti alloys were susceptible to localised corrosion. The role that Ti plays as an alloying element is that of increasing the resistance of ZrTi alloy to localised corrosion. The presence of 0.6% albumin protein in fluoridated acidified artificial saliva with 1000 ppm F{sup −} could protect the cp-Ti and ZrTi alloys from attack by fluoride ions. - Highlights: • Electrochemical and corrosion behaviour of the new ZrTi alloys were investigated. • The passive behaviour for all the ZrTi alloys is observed. • Addition of Ti to Zr improves the corrosion resistance in some fluoridated saliva. • The presence of albumin could prevent the ZrTi alloys from attack by fluoride ions.

  14. Precipitation hardening of a Cu-free Au-Ag-Pd-In dental alloy

    Energy Technology Data Exchange (ETDEWEB)

    Seol, Hyo-Joung [Department of Dental Materials, College of Dentistry and Research Institute for Oral Biotechnology, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of); Son, Kuk-Hyeon [Department of Dental Materials, College of Dentistry and Research Institute for Oral Biotechnology, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of); Yu, Chin-Ho [Department of Dental Materials, College of Dentistry and Research Institute for Oral Biotechnology, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of); Kwon, Yong Hoon [Department of Dental Materials, College of Dentistry and Research Institute for Oral Biotechnology, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of); Kim, Hyung-Il [Department of Dental Materials, College of Dentistry and Research Institute for Oral Biotechnology, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of)]. E-mail: hilkim@pusan.ac.kr

    2005-10-27

    The hardening mechanism and related microstructural changes of the Cu-free dental casting alloy composed of Au-Ag-Pd-In was examined by means of hardness test, X-ray diffraction (XRD), scanning electron microscopic (SEM) observations and electron probe microanalysis (EPMA). The Au-Ag-Pd-In alloy showed apparent age-hardenability. In the SEM photograph, three phases were observed in the solution-treated specimen, that is, the Au-Ag based phase with small amounts of In and Pd as matrix, the InPd phase as particle-like structures, and the Pd-rich phase as lamellar precipitates. By aging the specimen, the very fine Pd-rich inter-granular precipitates grew toward the grain interior as lamellar structure, and finally the coarsened Pd-rich precipitates covered a large part of the Au-Ag based matrix. The hardness increase in the early stage of the age-hardening process was assumed to be caused by the diffusion and aggregation of Pd atoms from the Au-Ag based matrix. The hardness decrease in the later stage of age-hardening process was caused by coarsening of the lamellar precipitates composed of the Pd-rich phase.

  15. Precipitation hardening of a Cu-free Au-Ag-Pd-In dental alloy

    International Nuclear Information System (INIS)

    Seol, Hyo-Joung; Son, Kuk-Hyeon; Yu, Chin-Ho; Kwon, Yong Hoon; Kim, Hyung-Il

    2005-01-01

    The hardening mechanism and related microstructural changes of the Cu-free dental casting alloy composed of Au-Ag-Pd-In was examined by means of hardness test, X-ray diffraction (XRD), scanning electron microscopic (SEM) observations and electron probe microanalysis (EPMA). The Au-Ag-Pd-In alloy showed apparent age-hardenability. In the SEM photograph, three phases were observed in the solution-treated specimen, that is, the Au-Ag based phase with small amounts of In and Pd as matrix, the InPd phase as particle-like structures, and the Pd-rich phase as lamellar precipitates. By aging the specimen, the very fine Pd-rich inter-granular precipitates grew toward the grain interior as lamellar structure, and finally the coarsened Pd-rich precipitates covered a large part of the Au-Ag based matrix. The hardness increase in the early stage of the age-hardening process was assumed to be caused by the diffusion and aggregation of Pd atoms from the Au-Ag based matrix. The hardness decrease in the later stage of age-hardening process was caused by coarsening of the lamellar precipitates composed of the Pd-rich phase

  16. Electrochemical assessment of some titanium and stainless steel implant dental alloys

    Directory of Open Access Journals (Sweden)

    Echevarría, A.

    2003-12-01

    Full Text Available Commercially pure titanium alloy, Ti-6Al-4V alloy and stainless steel screw implants were evaluated in both Ringer and synthetic saliva physiological solutions at body temperature by EIS (Electrochemical Impedance Spectroscopy with immersion times of 30 d. Results were simulated as a "sandwich system" composed by four capacitors-resistances connected in series with the solution resistance. A model explaining the results in terms of the porosity and thickness of four different layers, was proposed.

    Se utilizó la técnica de la Espectroscopia de Impedancia Electroquímica para evaluar en soluciones fisiológicas artificiales (Ringer y saliva sintética muestras extraídas de tornillos de implantes dentales certificados de titanio comercialmente puro, aleación Ti-6Al-W y acero inoxidable a temperatura corporal, con tiempos de inmersión hasta de 30 d. Los resultados se simularon mediante un modelo del tipo sandwich de cuatro elementos RC, conectados en serie con una resistencia de la solución. A partir de de esta simulación, se propone un modelo que explica los resultados obtenidos en términos de la evolución de la porosidad y el espesor de cuatro diferentes capas que se desarrollan en la superficie de los materiales evaluados.

  17. A benign route to fabricate nanoporous gold through electrochemical dealloying of Al-Au alloys in a neutral solution

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Qian; Wang Xiaoguang; Qi Zhen [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), School of Materials Science and Engineering, Shandong University, Jingshi Road 73, Jinan 250061 (China); Wang Yan [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), School of Materials Science and Engineering, Shandong University, Jingshi Road 73, Jinan 250061 (China); School of Materials Science and Engineering, University of Jinan, Jiwei Road 106, Jinan 250022 (China); Zhang Zhonghua [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), School of Materials Science and Engineering, Shandong University, Jingshi Road 73, Jinan 250061 (China)], E-mail: zh_zhang@sdu.edu.cn

    2009-11-01

    Nanoporous gold (NPG) ribbons have been fabricated through electrochemical dealloying of melt-spun Al-Au alloys with 20-50 at.% Au in a 10 wt.% NaCl aqueous solution under potential control at room temperature. The microstructures of NPG were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray (EDX) analysis. The microstructures of the NPG ribbons strongly depend upon the phase constitutions of the starting Al-Au alloys. The single-phase Al{sub 2}Au or AlAu intermetallic compound can be fully dealloyed, resulting in the formation of NPG with a homogeneous porous structure. The separate dealloying of Al{sub 2}Au and AlAu in the two-phase Al-45 Au alloy leads to the formation of NPG composites (NPGCs). In addition, the dealloying of the Al-20 Au alloy comprising {alpha}-Al and Al{sub 2}Au leads to the formation of NPG with bimodal channel size distributions. According to the ligament size, the surface diffusivity of Au adatoms along the alloy/electrolyte interface has been evaluated and increases with increasing applied potential. The dealloying mechanism in the neutral NaCl solution has been explained based upon pourbaix diagram and chloride ion effect.

  18. Evaluation of mechanical properties of recasted dental base metal alloys for considering their reusability in dentistry and engineering field

    Directory of Open Access Journals (Sweden)

    Nandish Bantarahalli Thopegowda

    2014-01-01

    Full Text Available Background: Base metal casting alloys are extensively used in dentistry to fabricate many oral appliances and a huge amount is wasted in the form of sprues and buttons during the casting procedure. Recycling and reusing these alloys by clean technologies may save our natural resources from being depleted and as well reduce the cost of the treatment of the patients. Objectives: To study the mechanical properties of recasted dental base metal alloys, and explore possible ways to recycle and reuse in dentistry and other fields of science and technology. Materials and Methods: Two beryllium-free Cobalt-Chromium (Co-Cr dental casting alloys, Wironit and Wirobond-C, were used for this study. Six groups of specimen (melted once, twice, five, ten, fifteen and twenty times per each alloy were casted. The tensile strength and hardness of these samples were measured by using universal testing machine and Vickers hardness number (VHN tester. Results: Tensile strength decreased from 850 MPa to 777 MPa after 5 th recasting and to 674 MPa at the end of 20 th recasting procedure for the Wironit samples. For Wirobond-C samples, tensile strength decreased from 720 MPa to 678 MPa after 5 th recasting and further reduced to 534 MPa at the end of 20 th recasting procedure. Hardness decreased from 380VHN to 335VHN at the end of 20 th recasting for Wironit samples and 328VHN to 247VHN for Wirobond-C samples after 20 th recasting procedure. The slight decrease in their mechanical properties will not have any impact on the clinical performance for dental applications. Conclusion: There is no major degradation in the mechanical properties after recycling, and hence, the left over alloys after casting procedures can be reused in dentistry with a condition to satisfy cytotoxicity tests.

  19. Artefacts in multimodal imaging of titanium, zirconium and binary titanium-zirconium alloy dental implants: an in vitro study.

    Science.gov (United States)

    Smeets, Ralf; Schöllchen, Maximilian; Gauer, Tobias; Aarabi, Ghazal; Assaf, Alexandre T; Rendenbach, Carsten; Beck-Broichsitter, Benedicta; Semmusch, Jan; Sedlacik, Jan; Heiland, Max; Fiehler, Jens; Siemonsen, Susanne

    2017-02-01

    To analyze and evaluate imaging artefacts induced by zirconium, titanium and titanium-zirconium alloy dental implants. Zirconium, titanium and titanium-zirconium alloy implants were embedded in gelatin and MRI, CT and CBCT were performed. Standard protocols were used for each modality. For MRI, line-distance profiles were plotted to quantify the accuracy of size determination. For CT and CBCT, six shells surrounding the implant were defined every 0.5 cm from the implant surface and histogram parameters were determined for each shell. While titanium and titanium-zirconium alloy induced extensive signal voids in MRI owing to strong susceptibility, zirconium implants were clearly definable with only minor distortion artefacts. For titanium and titanium-zirconium alloy, the MR signal was attenuated up to 14.1 mm from the implant. In CT, titanium and titanium-zirconium alloy resulted in less streak artefacts in comparison with zirconium. In CBCT, titanium-zirconium alloy induced more severe artefacts than zirconium and titanium. MRI allows for an excellent image contrast and limited artefacts in patients with zirconium implants. CT and CBCT examinations are less affected by artefacts from titanium and titanium-zirconium alloy implants compared with MRI. The knowledge about differences of artefacts through different implant materials and image modalities might help support clinical decisions for the choice of implant material or imaging device in the clinical setting.

  20. Artefacts in multimodal imaging of titanium, zirconium and binary titanium–zirconium alloy dental implants: an in vitro study

    Science.gov (United States)

    Schöllchen, Maximilian; Aarabi, Ghazal; Assaf, Alexandre T; Rendenbach, Carsten; Beck-Broichsitter, Benedicta; Semmusch, Jan; Sedlacik, Jan; Heiland, Max; Fiehler, Jens; Siemonsen, Susanne

    2017-01-01

    Objectives: To analyze and evaluate imaging artefacts induced by zirconium, titanium and titanium–zirconium alloy dental implants. Methods: Zirconium, titanium and titanium–zirconium alloy implants were embedded in gelatin and MRI, CT and CBCT were performed. Standard protocols were used for each modality. For MRI, line–distance profiles were plotted to quantify the accuracy of size determination. For CT and CBCT, six shells surrounding the implant were defined every 0.5 cm from the implant surface and histogram parameters were determined for each shell. Results: While titanium and titanium–zirconium alloy induced extensive signal voids in MRI owing to strong susceptibility, zirconium implants were clearly definable with only minor distortion artefacts. For titanium and titanium–zirconium alloy, the MR signal was attenuated up to 14.1 mm from the implant. In CT, titanium and titanium–zirconium alloy resulted in less streak artefacts in comparison with zirconium. In CBCT, titanium–zirconium alloy induced more severe artefacts than zirconium and titanium. Conclusions: MRI allows for an excellent image contrast and limited artefacts in patients with zirconium implants. CT and CBCT examinations are less affected by artefacts from titanium and titanium–zirconium alloy implants compared with MRI. The knowledge about differences of artefacts through different implant materials and image modalities might help support clinical decisions for the choice of implant material or imaging device in the clinical setting. PMID:27910719

  1. Corrosion of dental nickel-aluminum bronze with a minor gold content-mechanism and biological impact.

    Science.gov (United States)

    Ardlin, Berit I; Lindholm-Sethson, Britta; Dahl, Jon E

    2009-02-01

    To study corrosion and to evaluate biological effects in vitro of corrosion products of a copper-aluminum-nickel alloy with 2% gold. The alloy NPGtrade mark+2 with the nominal composition Cu:77.3; Al:7.8; Ni:4.3; Fe:3.0; Zn:2.7; Au:2.0; and Mn:1.7 was characterized. Static immersion in acidic saline, pH 2.2-2.4, was used to determine release of metallic elements in a milieu simulating the condition of plaque build-up in interproximal areas of the tooth. Corrosion and surface reactions in saline and artificial saliva were studied by electrochemical techniques including registration of open-circuit-potentials, polarization curves and impedance spectra. Extracts were made in cell culture media and acidic saline and used for MTT test for cytotoxicity and HET-CAM method for irritation. The mean amount of elements released in the acidic saline were in microg cm(-2) : Cu:632; Al:210; Ni:144; Fe:122; Zn:48; Mn:52. No protective film was formed on the surface of the alloy, as extensive corrosion was observed in both saline and artificial saliva. The corrosion rate was higher in saline than in artificial saliva. Acidic extracts of the alloy diluted up to 64 times reduced cell viability with 80% or more. The extract induced coagulation of the blood vessels of the CAM and was rated as moderate irritant solution. The nickel-aluminum bronze showed high corrosion rate caused by an inability to create a protective surface layer. High levels of toxic elements were found after static immersion testing, and the corrosion products had a distinct adverse effect on the biological activity. Copyright 2008 Wiley Periodicals, Inc.

  2. Brazing open cell reticulated copper foam to stainless steel tubing with vacuum furnace brazed gold/indium alloy plating

    Science.gov (United States)

    Howard, Stanley R [Windsor, SC; Korinko, Paul S [Aiken, SC

    2008-05-27

    A method of fabricating a heat exchanger includes brush electroplating plated layers for a brazing alloy onto a stainless steel tube in thin layers, over a nickel strike having a 1.3 .mu.m thickness. The resultant Au-18 In composition may be applied as a first layer of indium, 1.47 .mu.m thick, and a second layer of gold, 2.54 .mu.m thick. The order of plating helps control brazing erosion. Excessive amounts of brazing material are avoided by controlling the electroplating process. The reticulated copper foam rings are interference fit to the stainless steel tube, and in contact with the plated layers. The copper foam rings, the plated layers for brazing alloy, and the stainless steel tube are heated and cooled in a vacuum furnace at controlled rates, forming a bond of the copper foam rings to the stainless steel tube that improves heat transfer between the tube and the copper foam.

  3. Oxide layer characteristics and interfacial analysis of porcelain fused to high-gold alloy using multitechnique analysis methods

    Directory of Open Access Journals (Sweden)

    Hao-Sheng Chang

    2017-12-01

    Full Text Available Background/purpose: In a previous fractural study, high-gold crowns possessed the second highest fracture force. The objective of this study is to analyze the interface of porcelain fused to high-gold alloy using different observation devices. Materials and methods: High-gold crowns specimens with the morphology of a maxillary second premolar were compressed vertically in the center of the occlusal surface until fracture using a universal testing machine. The fractured surfaces were examined using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM/EDX to determine the failure mode. The ceramic–metal interface of the crown was examined with electron probe microanalysis (EPMA. In addition, sheet specimens with dimensions of 10×9×4 mm3 were prepared to examine the surface morphology and composition of high-gold alloy after oxidation using X-ray photoelectron spectrometer (XPS. Results: The average fracture force was 1368±312 N. Photograph of fractured crown and SEM/EDX analyses reveal that the crown initially suffered from cohesive failure in the upper and middle regions, with the fracture occurring mostly within the ceramic. XPS results and both EPMA color photomicrographs of crown and sheet specimens show that indium was observed along the porcelain–metal interface with a 1- to 2-μm disrupted zone of oxide layer. Conclusion: In2O3 and Au were found along the interface from the multitechnique analysis methods; the presence of this oxide at the boundary promotes ceramic–metal adhesion. In2O3 is suggested to be beneficial for the second highest fracture resistance in a previous fractural study of implant-supported crowns. Keywords: electron probe microanalysis, gold–platinum alloy, scanning electron microscopy combined with energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy

  4. Chemical passivation as a method of improving the electrochemical corrosion resistance of Co-Cr-based dental alloy.

    Science.gov (United States)

    Rylska, Dorota; Sokołowski, Grzegorz; Sokołowski, Jerzy; Łukomska-Szymańska, Monika

    2017-01-01

    The purpose of the study was to evaluate corrosion resistance of Wirobond C® alloy after chemical passivation treatment. The alloy surface undergone chemical passivation treatment in four different media. Corrosion studies were carried out by means of electrochemical methods in saline solution. Corrosion effects were determined using SEM. The greatest increase in the alloy polarization resistance was observed for passive layer produced in Na2SO4 solution with graphite. The same layer caused the highest increase in corrosion current. Generally speaking, the alloy passivation in Na2SO4 solution with graphite caused a substantial improvement of the corrosion resistance. The sample after passivation in Na2SO4 solution without graphite, contrary to others, lost its protective properties along with successive anodic polarization cycles. The alloy passivation in Na3PO4 solution with graphite was the only one that caused a decrease in the alloy corrosion properties. The SEM studies of all samples after chemical passivation revealed no pit corrosion - in contrast to the sample without any modification. Every successive polarization cycle in anodic direction of pure Wirobond C® alloy enhances corrosion resistance shifting corrosion potential in the positive direction and decreasing corrosion current value. The chemical passivation in solutions with low pH values decreases susceptibility to electrochemical corrosion of Co-Cr dental alloy. The best protection against corrosion was obtained after chemical passivation of Wirobond C® in Na2SO4 solution with graphite. Passivation with Na2SO4 in solution of high pH does not cause an increase in corrosion resistance of WIROBOND C. Passivation process increases alloy resistance to pit corrosion.

  5. Microstructures and mechanical properties of Co-29Cr-6Mo alloy fabricated by selective laser melting process for dental applications.

    Science.gov (United States)

    Takaichi, Atsushi; Suyalatu; Nakamoto, Takayuki; Joko, Natsuka; Nomura, Naoyuki; Tsutsumi, Yusuke; Migita, Satoshi; Doi, Hisashi; Kurosu, Shingo; Chiba, Akihiko; Wakabayashi, Noriyuki; Igarashi, Yoshimasa; Hanawa, Takao

    2013-05-01

    The selective laser melting (SLM) process was applied to a Co-29Cr-6Mo alloy, and its microstructure, mechanical properties, and metal elution were investigated to determine whether the fabrication process is suitable for dental applications. The microstructure was evaluated using scanning electron microscopy with energy-dispersed X-ray spectroscopy (SEM-EDS), X-ray diffractometry (XRD), and electron back-scattered diffraction pattern analysis. The mechanical properties were evaluated using a tensile test. Dense builds were obtained when the input energy of the laser scan was higher than 400 J mm⁻³, whereas porous builds were formed when the input energy was lower than 150 J mm⁻³. The microstructure obtained was unique with fine cellular dendrites in the elongated grains parallel to the building direction. The γ phase was dominant in the build and its preferential orientation was confirmed along the building direction, which was clearly observed for the builds fabricated at lower input energy. Although the mechanical anisotropy was confirmed in the SLM builds due to the unique microstructure, the yield strength, UTS, and elongation were higher than those of the as-cast alloy and satisfied the type 5 criteria in ISO22764. Metal elution from the SLM build was smaller than that of the as-cast alloy, and thus, the SLM process for the Co-29Cr-6Mo alloy is a promising candidate for fabricating dental devices. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. Corrosion behaviours of the dental magnetic keeper complexes made by different alloys and methods.

    Science.gov (United States)

    Wu, Min-Ke; Song, Ning; Liu, Fei; Kou, Liang; Lu, Xiao-Wen; Wang, Min; Wang, Hang; Shen, Jie-Fei

    2016-09-29

    The keeper and cast dowel-coping, as a primary component for a magnetic attachment, is easily subjected to corrosion in a wet environment, such as the oral cavity, which contains electrolyte-rich saliva, complex microflora and chewing behaviour and so on. The objective of this in vitro study was to examine the corrosion resistance of a dowel and coping-keeper complex fabricated by finish keeper and three alloys (cobalt-chromium, CoCr; silver-palladium-gold, PdAu; gold-platinum, AuPt) using a laser-welding process and a casting technique. The surface morphology characteristics and microstructures of the samples were examined by means of metallographic microscope and scanning electron microscope (SEM). Energy-dispersive spectroscopy (EDS) with SEM provided elements analysis information for the test samples after 10% oxalic acid solution etching test. Tafel polarization curve recordings demonstrated parameter values indicating corrosion of the samples when subjected to electrochemical testing. This study has suggested that massive oxides are attached to the surface of the CoCr-keeper complex but not to the AuPt-keeper complex. Only the keeper area of cast CoCr-keeper complex displayed obvious intergranular corrosion and changes in the Fe and Co elements. Both cast and laser-welded AuPt-keeper complexes had the highest free corrosion potential, followed by the PdAu-keeper complex. We concluded that although the corrosion resistance of the CoCr-keeper complex was worst, the keeper surface passive film was actually preserved to its maximum extent. The laser-welded CoCr- and PdAu-keeper complexes possessed superior corrosion resistance as compared with their cast specimens, but no significant difference was found between the cast and laser-welded AuPt-keeper complexes. The Fe-poor and Cr-rich band, appearing on the edge of the keeper when casting, has been proven to be a corrosion-prone area.

  7. Annealing of Co-Cr dental alloy: effects on nanostructure and Rockwell hardness.

    Science.gov (United States)

    Ayyıldız, Simel; Soylu, Elif Hilal; Ide, Semra; Kılıç, Selim; Sipahi, Cumhur; Pişkin, Bulent; Gökçe, Hasan Suat

    2013-11-01

    The aim of the study was to evaluate the effect of annealing on the nanostructure and hardness of Co-Cr metal ceramic samples that were fabricated with a direct metal laser sintering (DMLS) technique. Five groups of Co-Cr dental alloy samples were manufactured in a rectangular form measuring 4 × 2 × 2 mm. Samples fabricated by a conventional casting technique (Group I) and prefabricated milling blanks (Group II) were examined as conventional technique groups. The DMLS samples were randomly divided into three groups as not annealed (Group III), annealed in argon atmosphere (Group IV), or annealed in oxygen atmosphere (Group V). The nanostructure was examined with the small-angle X-ray scattering method. The Rockwell hardness test was used to measure the hardness changes in each group, and the means and standard deviations were statistically analyzed by one-way ANOVA for comparison of continuous variables and Tukey's HSD test was used for post hoc analysis. P values of directly affected both the nanostructure and hardness of the Co-Cr alloy. Group III exhibited a non-homogeneous structure and increased hardness (48.16 ± 3.02 HRC) because the annealing process was incomplete and the inner stress was not relieved. Annealing in argon atmosphere of Group IV not only relieved the inner stresses but also decreased the hardness (27.40 ± 3.98 HRC). The results of fitting function presented that Group IV was the most homogeneous product as the minimum bilayer thickness was measured (7.11 Å). After the manufacturing with DMLS technique, annealing in argon atmosphere is an essential process for Co-Cr metal ceramic substructures. The dentists should be familiar with the materials that are used in clinic for prosthodontics treatments.

  8. In vitro comparative analysis of the fit of gold alloy or commercially pure titanium implant-supported prostheses before and after electroerosion.

    Science.gov (United States)

    Sartori, Ivete Aparecida de Mattias; Ribeiro, Ricardo Faria; Francischone, Carlos Eduardo; de Mattos, Maria da Gloria Chiarello

    2004-08-01

    For implant-supported prostheses, passive fit is critical for the success of rehabilitation, especially when alternative materials are used. The purpose of this study was to compare interfacial fit of implant-supported prostheses cast in titanium to those cast in gold alloy. Five 3-unit fixed partial dentures were fabricated in gold alloy (Degudent U) as 1-piece castings, and 5 others were similarly cast in commercially pure titanium (Grade 1). The interfacial gaps between the prostheses and the abutments were evaluated with an optical microscope, before and after electroerosion. Readings were made with both screws tightened (10 N.cm torque), and with only 1 side tightened, so as to also evaluate the passive fit of the prostheses. Data were compared statistically by 2-way analysis of variance and the post hoc Tukey multiple range test (alpha=.05). Before electroerosion, the interfacial gaps for the 1-piece prostheses were significantly smaller (Pelectroerosion procedure significantly (Pelectroerosion did not present significant differences when the side opposite the tightened side was analyzed, but the gold alloy group showed better fit when the tightened side was analyzed (12.8 +/- 1.4 microm for gold alloy; 29.6 +/- 4.4 microm for titanium) and when both screws were tightened (5.4 +/- 2.3 microm for gold alloy; 16.1 +/- 5.5 microm for titanium). Cast titanium prostheses, despite showing larger interfacial gaps between the prosthesis and abutment than those obtained with gold alloy, had improved fit after being subjected to electroerosion.

  9. Evaluation of metal-ceramic bond characteristics of three dental Co-Cr alloys prepared with different fabrication techniques.

    Science.gov (United States)

    Wang, Hongmei; Feng, Qing; Li, Ning; Xu, Sheng

    2016-12-01

    Limited information is available regarding the metal-ceramic bond strength of dental Co-Cr alloys fabricated by casting (CAST), computer numerical control (CNC) milling, and selective laser melting (SLM). The purpose of this in vitro study was to evaluate the metal-ceramic bond characteristics of 3 dental Co-Cr alloys fabricated by casting, computer numerical control milling, and selective laser melting techniques using the 3-point bend test (International Organization for Standardization [ISO] standard 9693). Forty-five specimens (25×3×0.5 mm) made of dental Co-Cr alloys were prepared by CAST, CNC milling, and SLM techniques. The morphology of the oxidation surface of metal specimens was evaluated by scanning electron microscopy (SEM). After porcelain application, the interfacial characterization was evaluated by SEM equipped with energy-dispersive spectrometry (EDS) analysis, and the metal-ceramic bond strength was assessed with the 3-point bend test. Failure type and elemental composition on the debonding interface were assessed by SEM/EDS. The bond strength was statistically analyzed by 1-way ANOVA and Tukey honest significant difference test (α=.05). The oxidation surfaces of the CAST, CNC, and SLM groups were different. They were porous in the CAST group but compact and irregular in the CNC and SLM groups. The metal-ceramic interfaces of the SLM and CNC groups showed excellent combination compared with those of the CAST group. The bond strength was 37.7 ±6.5 MPa for CAST, 43.3 ±9.2 MPa for CNC, and 46.8 ±5.1 MPa for the SLM group. Statistically significant differences were found among the 3 groups tested (P=.028). The debonding surfaces of all specimens exhibited cohesive failure mode. The oxidation surface morphologies and thicknesses of dental Co-Cr alloys are dependent on the different fabrication techniques used. The bond strength of all 3 groups exceed the minimum acceptable value of 25 MPa recommended by ISO 9693; hence, dental Co-Cr alloy

  10. Hardening mechanism of an Ag-Pd-Cu-Au dental casting alloy

    International Nuclear Information System (INIS)

    Seol, Hyo-Joung; Kim, Gi-Chul; Son, Kuk-Hyeon; Kwon, Yong Hoon; Kim, Hyung-Il

    2005-01-01

    Age-hardening behaviour and the related microstructural changes were studied to elucidate the hardening mechanism of an Ag-Pd-Cu-Au dental casting alloy by means of hardness test, X-ray diffraction (XRD), scanning electron microscopic (SEM) observations and electron probe microanalysis (EPMA). By considering hardness test and XRD results together, it was revealed that the hardness increased during the early stage of phase transformation of α into α 1 . In the SEM photographs, two phases of matrix and particle-like structures were observed, and the precipitation of element from the matrix progressed during isothermal aging. By SEM observations and EPMA analysis, it could be supposed that the increase in hardness was caused by the diffusion and aggregation of Cu atoms from the Ag-rich α matrix containing Au and Cu in the early stage of age-hardening process, and that the decrease in hardness was caused by the progress of coarsening of Cu-rich lamellar precipitates in the later stage of the age-hardening process. The changes in the Ag-rich matrix caused both the increase and decrease in hardness, and the CuPd phase containing small amounts of Zn and Sn did not contribute to the hardness changes

  11. Microstructures, mechanical properties and corrosion resistance of the Zr−xTi (Ag) alloys for dental implant application

    Energy Technology Data Exchange (ETDEWEB)

    Cui, W.F., E-mail: cuiwf@atm.neu.edu.cn; Liu, N.; Qin, G.W.

    2016-06-15

    The Zr−xTi (Ag) alloys were designed for the application of dental implants. The microstructures of Zr−20Ti and Zr−40Ti alloy were observed using optical microscope and transmission electronic microscope. The hardness and compressive tests were performed to evaluate the mechanical properties of the Zr−xTi alloys. The electrochemical behavior of the Zr−xTi alloys with and without 6% Ag was investigated in the acidified artificial saliva containing 0.1% NaF (pH = 4). For comparison, the electrochemical behavior of cp Ti was examined in the same condition. The results show that the quenched Zr−20Ti and Zr−40Ti alloy exhibit acicular martensite microstructures containing twin substructure. They display good mechanical properties with the hardness of ∼330HV, the yield strength of ∼1000 MPa and the strain to fracture of ∼25% at room temperature. Adding 6% Ag to Zr−20Ti alloy enhances the passivity breakdown potential and the self-corrosion potential, but hardly affects the corrosion current density and the impedance modulus. 6% Ag in Zr−40Ti alloy distinctly increases pitting corrosion resistance, which is attributed the formation of thick, dense and stable passive film under the joint action of titanium and silver. In comparison with cp Ti, Zr−40Ti−6Ag alloy possesses the same good corrosion resistance in the rigorous oral environment as well as the superior mechanical properties. - Highlights: • The quenched Zr20Ti and Zr40Ti obtain acicular martensite microstructure. • Zr20Ti and Zr40Ti possess high hardness, strength and strain to fracture. • Increasing Ti content decreases corrosion current density. • Adding Ag enhances passivation breakdown potentials of Zr20Ti and Zr40Ti. • Zr40Ti6Ag has optimum mechanical properties and pitting corrosion resistance.

  12. Metallurgical and interfacial characterization of PFM Co-Cr dental alloys fabricated via casting, milling or selective laser melting.

    Science.gov (United States)

    Al Jabbari, Y S; Koutsoukis, T; Barmpagadaki, X; Zinelis, S

    2014-04-01

    Bulk and interfacial characterization of porcelain fused to metal (PFM) Co-Cr dental alloys fabricated via conventional casting, milling and selective laser melting. Three groups of metallic specimens made of PFM Co-Cr dental alloys were prepared using casting (CST), milling (MIL) and selective laser sintering (SLM). The porosity of the groups was evaluated using X-ray scans. The microstructures of the specimens were evaluated via SEM examination, EDX and XRD analysis. Vickers hardness testing was utilized to measure the hardness of the specimens. Interfacial characterization was conducted on the porcelain-covered specimens from each group to test the elemental distribution with and without the application of INmetalbond. The elemental distribution of the probed elements was assessed using EDX line profile analysis. Hardness results were statistically analyzed using one-way ANOVA and Holm-Sidak's method (α=0.05). X-ray radiography revealed the presence of porosity only in the CST group. Different microstructures were identified among the groups. Together with the γ phase matrix, a second phase, believed to be the Co3Mo phase, was also observed by SEM and subsequent XRD analysis. Cr7C3 and Cr23C6 carbides were also identified via XRD analysis in the CST and MIL groups. The hardness values were 320±12 HV, 297±5 HV and 371±10 HV, and statistically significant differences were evident among the groups. The microstructure and hardness of PFM Co-Cr dental alloys are dependent on the manufacturing technique employed. Given the differences in microstructural and hardness properties among the tested groups, further differences in their clinical behavior are anticipated. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  13. Effect of chemical composition of Ni-Cr dental casting alloys on the bonding characterization between porcelain and metal.

    Science.gov (United States)

    Huang, H-H; Lin, M-C; Lee, T-H; Yang, H-W; Chen, F-L; Wu, S-C; Hsu, C-C

    2005-03-01

    The purpose of this study was to investigate the influence of chemical composition of Ni-Cr dental casting alloys on the bonding behaviour between porcelain and metal. A three-point bending test was used to measure the fracture load of alloy after porcelain firing. A scanning electron microscope, accompanied by an energy dispersion spectrometer, was used to analyse the morphology and chemical composition of the fracture surface. An X-ray photoelectron spectrometer and glow discharge spectrometer were used to identify the structure and cross-sectional chemical composition, respectively, of oxide layers on Ni-Cr alloys after heat treatment at 990 degrees C for 5 min. Results showed that the oxide layers formed on all Ni-Cr alloys contained mainly Cr2O3, NiO, and trace MoO3. The Ni-Cr alloy with a higher Cr content had a thicker oxide layer, as well as a weaker bonding behaviour of porcelain/metal interface. The presence of Al (as Al2O3) and Be (as BeO) on the oxide layer suppressed the growth of the oxide layer, leading to a better porcelain/metal bonding behaviour. However, the presence of a small amount of Ti (as TiO2) on the oxide layer did not have any influence on the bonding behaviour. The fracture propagated along the interface between the opaque porcelain and metal, and exhibited an adhesive type of fracture morphology.

  14. Assessment of corrosion resistance of cast cobalt- and nickel-chromium dental alloys in acidic environments.

    Science.gov (United States)

    Mercieca, Sven; Caligari Conti, Malcolm; Buhagiar, Joseph; Camilleri, Josette

    2018-01-01

    The aim of this study was to compare the degradation resistance of nickel-chromium (Ni-Cr) and cobalt-chromium (Co-Cr) alloys used as a base material for partial dentures in contact with saliva. Wiron® 99 and Wironit Extra-Hard® were selected as representative casting alloys for Ni-Cr and Co-Cr alloys, respectively. The alloys were tested in contact with deionized water, artificial saliva and acidified artificial saliva. Material characterization was performed by X-ray diffractometry (XRD) and microhardness and nanohardness testing. The corrosion properties of the materials were then analyzed using open circuit potential analysis and potentiodynamic analysis. Alloy leaching in solution was assessed by inductively coupled plasma mass spectrometry techniques. Co-Cr alloy was more stable than the Ni-Cr alloy in all solutions tested. Leaching of nickel and corrosion attack was higher in Ni-Cr alloy in artificial saliva compared with the acidified saliva. The corrosion resistance of the Co-Cr alloy was seen to be superior to that of the Ni-Cr alloy, with the former exhibiting a lower corrosion current in all test solutions. Microstructural topographical changes were observed for Ni-Cr alloy in contact with artificial saliva. The Ni-Cr alloy exhibited microstructural changes and lower corrosion resistance in artificial saliva. The acidic changes did not enhance the alloy degradation. Ni-Cr alloys are unstable in solution and leach nickel. Co-Cr alloys should be preferred for clinical use.

  15. Noble metal alloys for metal-ceramic restorations.

    Science.gov (United States)

    Anusavice, K J

    1985-10-01

    A review of the comparative characteristics and properties of noble metal alloys used for metal-ceramic restorations has been presented. Selection of an alloy for one's practice should be based on long-term clinical data, physical properties, esthetic potential, and laboratory data on metal-ceramic bond strength and thermal compatibility with commercial dental porcelains. Although gold-based alloys, such as the Au-Pt-Pd, Au-Pd-Ag, and Au-Pd classes, may appear to be costly compared with the palladium-based alloys, they have clearly established their clinical integrity and acceptability over an extended period of time. Other than the relatively low sag resistance of the high gold-low silver content alloys and the potential thermal incompatibility with some commercial porcelain products, few clinical failures have been observed. The palladium-based alloys are less costly than the gold-based alloys. Palladium-silver alloys require extra precautions to minimize porcelain discoloration. Palladium-copper and palladium-cobalt alloys may also cause porcelain discoloration, as copper and cobalt are used as colorants in glasses. The palladium-cobalt alloys are least susceptible to high-temperature creep compared with all classes of noble metals. Nevertheless, insufficient clinical data exist to advocate the general use of the palladium-copper and palladium-cobalt alloys at the present time. One should base the selection and use of these alloys in part on their ability to meet the requirements of the ADA Acceptance Program. A list of acceptable or provisionally acceptable alloys is available from the American Dental Association and is published annually in the Journal of the American Dental Association. Dentists have the legal and ethical responsibility for selection of alloys used for cast restorations. This responsibility should not be delegated to the dental laboratory technician. It is advisable to discuss the criteria for selection of an alloy with the technician and the

  16. Osseointegration of titanium, titanium alloy and zirconia dental implants: current knowledge and open questions.

    Science.gov (United States)

    Bosshardt, Dieter D; Chappuis, Vivianne; Buser, Daniel

    2017-02-01

    Bone healing around dental implants follows the pattern and sequence of intramembraneous osteogenesis with formation of woven bone first of all followed later by formation of parallel-fibered and lamellar bone. Bone apposition onto the implant surface starts earlier in trabecular bone than in compact bone. While the first new bone may be found on the implant surface around 1 week after installation, bone remodeling starts at between 6 and 12 weeks and continues throughout life. Bone remodeling also involves the bone-implant interface, thus transiently exposing portions of the implant surface. Surface modifications creating micro-rough implant surfaces accelerate the osseointegration process of titanium implants, as demonstrated in numerous animal experiments. Sandblasting followed by acid-etching may currently be regarded as the gold standard technique to create micro-rough surfaces. Chemical surface modifications, resulting in higher hydrophilicity, further increase the speed of osseointegration of titanium and titanium-zirconium implants in both animals and humans. Surface modifications of zirconia and alumina-toughened zirconia implants also have an influence on the speed of osseointegration, and some implant types reach high bone-to-implant contact values in animals. Although often discussed independently of each other, surface characteristics, such as topography and chemistry, are virtually inseparable. Contemporary, well-documented implant systems with micro-rough implant surfaces, placed by properly trained and experienced clinicians, demonstrate high long-term survival rates. Nevertheless, implant failures do occur. A low percentage of implants are diagnosed with peri-implantitis after 10 years in function. In addition, a low number of implants seem to be lost for primarily reasons other than biofilm-induced infection. Patient factors, such as medications interfering with the immune system and bone cells, may be an element contributing to continuous bone

  17. A Comparative Analysis of the Corrosive Effect of Artificial Saliva of Variable pH on DMLS and Cast Co-Cr-Mo Dental Alloy.

    Science.gov (United States)

    Puskar, Tatjana; Jevremovic, Danimir; Williams, Robert J; Eggbeer, Dominic; Vukelic, Djordje; Budak, Igor

    2014-09-11

    Dental alloys for direct metal laser sintering (DMLS) are available on the market today, but there is little scientific evidence reported on their characteristics. One of them is the release of ions, as an indicator of the corrosion characteristics of a dental alloy. Within this research, the difference in the elution of metals from DMLS and cast (CM) samples of Co-Cr-Mo dental alloy in saliva-like medium of three different pH was examined by inductively-coupled plasma mass spectrometry (ICP-MS). The obtained results show that the metal elution in artificial saliva from the DMLS alloy was lower than the elution from the CM alloy. The release of all investigated metal ions was influenced by the acidity, both from the DMLS and CM alloy, throughout the investigated period of 30 days. The change in acidity from a pH of 6.8 to a pH of 2.3 for the cast alloy led to a higher increase of the elution of Co, Cr and Mo from CM than from the DMLS alloy. The greatest release out of Co, Cr and Mo was for Co for both tested alloys. Further, the greatest release of all ions was measured at pH 2.3. In saliva of pH 2.3 and pH 4.5, the longer the investigated period, the higher the difference between the total metal ion release from the CM and DMLS alloys. Both alloys showed a safe level of elution according to the ISO definition in all investigated acidic environments.

  18. A Comparative Analysis of the Corrosive Effect of Artificial Saliva of Variable pH on DMLS and Cast Co-Cr-Mo Dental Alloy

    Directory of Open Access Journals (Sweden)

    Tatjana Puskar

    2014-09-01

    Full Text Available Dental alloys for direct metal laser sintering (DMLS are available on the market today, but there is little scientific evidence reported on their characteristics. One of them is the release of ions, as an indicator of the corrosion characteristics of a dental alloy. Within this research, the difference in the elution of metals from DMLS and cast (CM samples of Co-Cr-Mo dental alloy in saliva-like medium of three different pH was examined by inductively-coupled plasma mass spectrometry (ICP-MS. The obtained results show that the metal elution in artificial saliva from the DMLS alloy was lower than the elution from the CM alloy. The release of all investigated metal ions was influenced by the acidity, both from the DMLS and CM alloy, throughout the investigated period of 30 days. The change in acidity from a pH of 6.8 to a pH of 2.3 for the cast alloy led to a higher increase of the elution of Co, Cr and Mo from CM than from the DMLS alloy. The greatest release out of Co, Cr and Mo was for Co for both tested alloys. Further, the greatest release of all ions was measured at pH 2.3. In saliva of pH 2.3 and pH 4.5, the longer the investigated period, the higher the difference between the total metal ion release from the CM and DMLS alloys. Both alloys showed a safe level of elution according to the ISO definition in all investigated acidic environments.

  19. In vitro corrosion of dental Au-based casting alloys in polyvinylpyrrolidone-iodine solution.

    Science.gov (United States)

    Takasusuki, Norio; Ida, Yusuke; Hirose, Yukito; Ochi, Morio; Endo, Kazuhiko

    2013-01-01

    The corrosion and tarnish behaviors of two Au-based casting alloys (ISO type 1 and type 4 Au alloys) and their constituent pure metals, Au, Ag, Cu, Pt, and Pd in a polyvinylpyrrolidone-iodine solution were examined. The two Au alloys actively corroded, and the main anodic reaction for both was dissolution of Au as AuI₂(-). The amount of Au released from the ISO type 1 Au alloy was significantly larger than that from the ISO type 4 Au alloy (Palloy exhibited higher susceptibility to tarnishing than the type 4 alloy. The corrosion forms of the two Au alloys were found to be completely different, i.e., the type 1 alloy exhibited the corrosion attack over the entire exposed surface with a little irregularity whereas the type 4 alloy exhibited typical intergranular corrosion, which was caused by local cells produced by segregation of Pd and Pt.

  20. Mn-coatings on the micro-pore formed Ti-29Nb-xHf alloys by RF-magnetron sputtering for dental applications

    Science.gov (United States)

    Park, Seon-Yeong; Choe, Han-Cheol

    2018-02-01

    In this study, Mn-coatings on the micro-pore formed Ti-29Nb-xHf alloys by RF-magnetrons sputtering for dental applications were studied using different experimental techniques. Mn coating films were formed on Ti-29Nb-xHf alloys by a radio frequency magnetron sputtering technique for 0, 1, 3, and 5 min at 45 W. The microstructure, composition, and phase structure of the coated alloys were examined by optical microscopy, field emission scanning electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The microstructure of Ti-29Nb alloy showed α" phase in the needle-like structure and Ti-29Nb-15Hf alloy showed β phase in the equiaxed structure. As the sputtering time increased, the circular particles of Mn coatings on the Ti-29Nb alloy increased at inside and outside surfaces. As the sputtering time increased, [Mn + Ca/P] ratio of the plasma electrolytic oxidized films in Ti- 29Nb-xHf alloys increased. The corrosion potential (Ecorr) of Mn coatings on the Ti-29Nb alloy showed higher than that of Mn coatings on the Ti-29Nb-15Hf alloy. The passive current density (Ipass) of the Mn coating on the Ti-29Nb alloy and Mn coatings on the Ti-29Nb-15Hf alloy was less noble than the non-Mn coated Ti-29Nb and Ti-29Nb-15Hf alloys surface.

  1. SU-C-BRC-05: Monte Carlo Calculations to Establish a Simple Relation of Backscatter Dose Enhancement Around High-Z Dental Alloy to Its Atomic Number

    Energy Technology Data Exchange (ETDEWEB)

    Utsunomiya, S; Kushima, N; Katsura, K; Tanabe, S; Hayakawa, T; Sakai, H; Yamada, T; Takahashi, H; Abe, E; Wada, S; Aoyama, H [Niigata University, Niigata (Japan)

    2016-06-15

    Purpose: To establish a simple relation of backscatter dose enhancement around a high-Z dental alloy in head and neck radiation therapy to its average atomic number based on Monte Carlo calculations. Methods: The PHITS Monte Carlo code was used to calculate dose enhancement, which is quantified by the backscatter dose factor (BSDF). The accuracy of the beam modeling with PHITS was verified by comparing with basic measured data namely PDDs and dose profiles. In the simulation, a high-Z alloy of 1 cm cube was embedded into a tough water phantom irradiated by a 6-MV (nominal) X-ray beam of 10 cm × 10 cm field size of Novalis TX (Brainlab). The ten different materials of high-Z alloys (Al, Ti, Cu, Ag, Au-Pd-Ag, I, Ba, W, Au, Pb) were considered. The accuracy of calculated BSDF was verified by comparing with measured data by Gafchromic EBT3 films placed at from 0 to 10 mm away from a high-Z alloy (Au-Pd-Ag). We derived an approximate equation to determine the relation of BSDF and range of backscatter to average atomic number of high-Z alloy. Results: The calculated BSDF showed excellent agreement with measured one by Gafchromic EBT3 films at from 0 to 10 mm away from the high-Z alloy. We found the simple linear relation of BSDF and range of backscatter to average atomic number of dental alloys. The latter relation was proven by the fact that energy spectrum of backscatter electrons strongly depend on average atomic number. Conclusion: We found a simple relation of backscatter dose enhancement around high-Z alloys to its average atomic number based on Monte Carlo calculations. This work provides a simple and useful method to estimate backscatter dose enhancement from dental alloys and corresponding optimal thickness of dental spacer to prevent mucositis effectively.

  2. Mg-containing hydroxyapatite coatings on Ti-6Al-4V alloy for dental materials

    Science.gov (United States)

    Yu, Ji-Min; Choe, Han-Cheol

    2018-02-01

    In this study, Mg-containing hydroxyapatite coatings on Ti-6A1-4 V alloy for dental materials were researched using various experimental instruments. Plasma electrolytic oxidation (PEO) was performed in electrolytes containing Mg (symbols of specimens: CaP, 5M%, 10M%, and 20M%) at 280 V for 3 min. The electrolyte used for PEO was produced by mixing Ca(CH3COO)2·H2O, C3H7NaCaO6P, and MgCl2·6H2O. The phases and composition of the oxide films were evaluated by X-ray diffraction and field-emission scanning electron microscopy with energy dispersive X-ray spectrometry. The irregularity of the surface, pore size, and number of pores decreased as the Mg concentration increased. The ratio of the areas occupied and not occupied by pores decreased as the Mg concentration increased, with the numbers of both large and small pores decreasing with increasing Mg concentration. The number of particles on the internal surfaces of pores was increased as the Mg content increased. Mg content of all samples containing Mg ions showed higher in the pore outside than that of pore inside, whereas the Ca content was higher inside the pores. The P content of samples with the addition of Mg ions showed higher values inside the pores than outside. The Ca/P and [Mg + Ca]/P molar ratios in the PEO films decreased with Mg content. The crystallite size of anatase was increased with increasing Mg concentration in the solution.

  3. Templated synthesis of gold-iron alloy nanoparticles using pulsed laser deposition

    International Nuclear Information System (INIS)

    Chang, Won-Suk; Park, Jin-Won; Rawat, Vijay; Sands, Timothy; Lee, Gil U

    2006-01-01

    A means for synthesizing paramagnetic nanoparticles composed of an Au-Fe alloy is described using pulsed laser deposition (PLD) of the alloy into a mesoporous alumina membrane template. Nanoparticles 46 ± 13 nm in diameter and composed of a 17% Fe alloy have been created by depositing a 35% Fe alloy into a template with 65 nm diameter pores. These paramagnetic nanoparticles had a saturation magnetization of 11.5 emu g -1 at 2000 G, and their UV-visible extinction spectrum was dominated by strong absorption similar to that of Fe 3 O 4 nanoparticles. The surfaces of these nanoparticles were readily functionalized with a dense monolayer of DNA oligonucleotides that had a 5' thiol group. The Au-Fe nanoparticles appear to be well suited for biotechnological applications and single molecule measurements as they can be synthesized in a specific size range, are strongly paramagnetic, and may be easily functionalized with biological macromolecules

  4. [Effect of heat treatment on the structure of a Cu-Zn-Al-Ni system dental alloy].

    Science.gov (United States)

    Guastaldi, A C; Adorno, A T; Beatrice, C R; Mondelli, J; Ishikiriama, A; Lacefield, W

    1990-01-01

    This article characterizes the structural phases present in the copper-based metallic alloy system "Cu-Zn-Al-Ni" developed for dental use, and relates those phases to other properties. The characterization was obtained after casting (using the lost wax process), and after heat treatment. In order to obtain better corrosion resistance by changing the microstructure, the castings were submitted to 30, 45 and 60 minutes of heat treatment at the following temperatures: 750 degrees C, 800 degrees C, and 850 degrees C. The various phases were analyzed using X-ray diffraction and scanning electron microscopy (SEM). The results after heat treatment showed a phase (probably Cu3Al), that could be responsible for the improvement in the alloy's resistance to corrosion as compared to the as-cast structure.

  5. Biocompatibility effects of indirect exposure of base-metal dental casting alloys to a human-derived three-dimensional oral mucosal model.

    Science.gov (United States)

    McGinley, Emma Louise; Moran, Gary P; Fleming, Garry J P

    2013-11-01

    The study employed a three-dimensional (3D) human-derived oral mucosal model to assess the biocompatibility of base-metal dental casting alloys ubiquitous in fixed prosthodontic and orthodontic dentistry. Oral mucosal models were generated using primary human oral keratinocyte and gingival fibroblast cells seeded onto human de-epidermidised dermal scaffolds. Nickel-chromium (Ni-Cr) and cobalt-chromium (Co-Cr) base-metal alloy immersion solutions were exposed to oral mucosal models for increasing time periods (2-72h). Analysis methodologies (histology, viable cell counts, oxidative stress, cytokine expression and toxicity) were performed following exposure. Ni-based alloy immersion solutions elicited significantly decreased cell viability (P0.4755) or cellular toxicity (Pcasting alloys through discriminatory experimental parameters. Increasing incidences of Ni hypersensitivity in the general population warrants serious consideration from dental practitioners and patients alike where fixed prosthodontic/orthodontic dental treatments are the treatment modality involved. The novel and analytical oral mucosal model has the potential to significantly contribute to the advancement of reproducible dental medical device and dental material appraisals. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. A nanoflower shaped gold-palladium alloy on graphene oxide nanosheets with exceptional activity for electrochemical oxidation of ethanol

    International Nuclear Information System (INIS)

    Wang, Qiyu; Cui, Xiaoqiang; Zhang, Xiaoming; Liu, Chang; Xue, Tianyu; Wang, Haitao; Zheng, Weitao; Guan, Weiming

    2014-01-01

    We report on a new and facile method for the preparation of well-dispersed gold-palladium (AuPd) flower-shaped nanostructures on sheets of graphene oxide (GO). Transmission electron microscopy and high angle annular dark field STEM were used to characterize the morphology and composition of the new nanohybrids. The AuPd/GO composites display high electrocatalytic activity for the oxidation of ethanol in strongly alkaline medium as examined by cyclic voltammetry and chronoamperometry. Both the current density (13.16 mA · cm −2 at a working potential of −0.12 V) and the long-time stability are superior to a commercial Pd-on-carbon catalyst which is attributed to the cooperative action of the catalytic activities of Au and Pd, and the good dispersion of the alloy on the nanosheets. (author)

  7. Electrochemical deposition of gold-platinum alloy nanoparticles on an indium tin oxide electrode and their electrocatalytic applications

    Energy Technology Data Exchange (ETDEWEB)

    Song Yan; Ma Yuting; Wang Yuan [Department of Chemistry, Soochow University, Suzhou, Jiangsu 215123 (China); Di Junwei, E-mail: djw@suda.edu.c [Department of Chemistry, Soochow University, Suzhou, Jiangsu 215123 (China); Tu Yifeng [Department of Chemistry, Soochow University, Suzhou, Jiangsu 215123 (China)

    2010-07-01

    Gold-platinum (Au-Pt) hybrid nanoparticles (Au-PtNPs) were successfully deposited on an indium tin oxide (ITO) surface using a direct electrochemical method. The resulting nanoparticles were characterized by scanning electron microscopy (SEM), UV-vis spectroscopy, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and electrochemical methods. It was found that the size of the Au-PtNPs depends on the number of electrodeposition cycles. Au-PtNPs obtained by 20 electrodeposition cycles had a cauliflower-shaped structure with an average diameter of about 60 nm. These Au-PtNPs exhibited alloy properties. Electrochemical measurements showed that the charge transfer resistivity was significantly decreased for the Au-PtNPs/ITO electrode. Additionally, the Au-PtNPs displayed an electrocatalytic activity for nitrite oxidation and oxygen reduction. The Au-PtNPs/ITO electrodes reported herein could possibly be used as electrocatalysts and sensors.

  8. Study by electrical resistivity measurements of the radiation induced defects in gold-copper alloys

    International Nuclear Information System (INIS)

    Alamo, A.

    1983-09-01

    Point defect production rate in Cu 3 Au and CuAu ordered and disordered alloys was studied by electrical resistivity measurements, as function of electron energy ranging from 0.4 to 2.5 MeV. The irradiations were performed at 20 K. The production curves are analysed using a displacement model for diatomic materials and the following values are found for the average displacement threshold energies: Esub(d)sup(Cu) approximately 22 eV and Esub(d)sup(Au) approximately 18 eV, for both alloys. Elementary defect migration was examined during isochronal annealing performed after irradiations. A simple type of self-interstitial seems to migrate in the ordered alloys: probably a split-interstitial of Cu-Cu type. Interstitial migration seems to be very difficult and complex in the disordered alloys. Vacancy mobility was detected after recovery at temperature above 300 K and was responsible of an increase of long range order. Fast neutron irradiations at 20 K produce disordering in the initially ordered alloys. Ratios of 38 and 18 antistructure defects per atomic displacement are estimated for Cu 3 Au and CuAu respectively [fr

  9. Alloy hardening of a smectic A liquid crystal doped with gold nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Oswald, P.; Milette, J.; Relaix, S.; Reven, L.; Dequidt, A.; Lejček, Lubor

    2013-01-01

    Roč. 103, AUG (2013), "46004-p1"-"46004-p6" ISSN 0295-5075 Institutional support: RVO:68378271 Keywords : smectic A liquid crystals * gold nanoparticles * edge dislocation * precipitation hardening Subject RIV: BK - Fluid Dynamics Impact factor: 2.269, year: 2013

  10. Potentiodynamic polarization study of the corrosion behavior of palladium-silver dental alloys.

    Science.gov (United States)

    Sun, Desheng; Brantley, William A; Frankel, Gerald S; Heshmati, Reza H; Johnston, William M

    2018-04-01

    Although palladium-silver alloys have been marketed for over 3 decades for metal-ceramic restorations, understanding of the corrosion behavior of current alloys is incomplete; this understanding is critical for evaluating biocompatibility and clinical performance. The purpose of this in vitro study was to characterize the corrosion behavior of 3 representative Pd-Ag alloys in simulated body fluid and oral environments and to compare them with a high-noble Au-Pd alloy. The study obtained values of important electrochemical corrosion parameters, with clinical relevance, for the rational selection of casting alloys. The room temperature in vitro corrosion characteristics of the 3 Pd-Ag alloys and the high-noble Au-Pd alloy were evaluated in 0.9% NaCl, 0.09% NaCl, and Fusayama solutions. After simulated porcelain firing heat treatment, 5 specimens of each alloy were immersed in the electrolytes for 24 hours. For each specimen, the open-circuit potential (OCP) was first recorded, and linear polarization was then performed from -20 mV to +20 mV (versus OCP) at a rate of 0.125 mV/s. Cyclic polarization was subsequently performed on 3 specimens of each alloy from -300 mV to +1000 mV and back to -300 mV (versus OCP) at a scanning rate of 1 mV/s. The differences in OCP and corrosion resistance parameters (zero-current potential and polarization resistance) among alloys and electrolyte combinations were compared with the 2-factor ANOVA (maximum-likelihood method) with post hoc Tukey adjustments (α=.05). The 24-hour OCPs and polarization resistance values of the 3 Pd-Ag alloys and the Au-Pd alloy were not significantly different (P=.233 and P=.211, respectively) for the same electrolyte, but significant differences were found for corrosion test results in different electrolytes (Palloy and electrolyte (P=.249 and P=.713, respectively). The 3 Pd-Ag silver alloys appeared to be resistant to chloride ion corrosion, and passivation and de-alloying were identified for these

  11. Comparison of the microstructure and phase stability of as-cast, CAD/CAM and powder metallurgy manufactured Co-Cr dental alloys.

    Science.gov (United States)

    Li, Kai Chun; Prior, David J; Waddell, J Neil; Swain, Michael V

    2015-12-01

    The objective of this study was to identify the different microstructures produced by CC, PM and as-cast techniques for Co-Cr alloys and their phase stability following porcelain firings. Three bi-layer porcelain veneered Co-Cr specimens and one monolithic Co-Cr specimen of each alloy group [cast, powder metallurgy (PM), CAD/CAM (CC)] were manufactured and analyzed using electron backscatter diffraction (EBSD), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). Specimens were treated to incremental numbers of porcelain firings (control 0, 5, 15) with crystallographic data, grain size and chemical composition subsequently obtained and analyzed. EBSD datasets of the cast alloy indicated large grains >200 μm whereas PM and CC alloy consisted of mean arithmetic grain sizes of 29.6 μm and 19.2 μm respectively. XRD and EBSD results both indicated the highest increase in hcp content (>13vol%) for cast Co-Cr alloy after treatment with porcelain firing while PM and CC indicated .05) was observed in CC. EDS line scans indicated an increase in Cr content at the alloy surface after porcelain firing treatment for all three alloys. PM and CC produced alloy had superior fcc phase stability after porcelain firings compared to a traditional cast alloy. It is recommended that PM and CC alloys be used for porcelain-fused-to-metal restorations. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  12. Effect of nitrogen on the microstructure and mechanical properties of Co-33Cr-9W alloys prepared by dental casting.

    Science.gov (United States)

    Yamanaka, Kenta; Mori, Manami; Torita, Yasuhiro; Chiba, Akihiko

    2018-01-01

    The effect of nitrogen concentration on the mechanical properties of Co-33Cr-9W alloy dental castings fabricated using the "high-Cr and high-N" concept was investigated. Microstructural analysis was performed on the alloys, and findings were discussed in relation to the mechanical properties. Owing to their high nitrogen concentrations (0.25-0.35wt%), all alloys prepared exhibited face-centered cubic (fcc) γ-phase matrices with a-few-millimeter grains consisting of dendritic substructures. Strain-induced martensitic transformations to produce hexagonal close-packed (hcp) ε-phases were not identified under tensile deformation. The precipitation of the intermetallic σ-phase was identified at the interdendritic regions where solidification segregation of Cr and W occurred. The size and chemical composition of this σ-phase did not vary with the bulk nitrogen concentration. Adding nitrogen to the alloys did not alter their tensile yield stress or Vickers hardness values significantly, suggesting that the nitrogen strengthening effect is affected by the manufacturing route as well as local chemistry that is involved in the microstructural evolution during solidification. The tensile ductility, on the other hand, increased with an increase in nitrogen concentration; the alloy with 0.35wt% nitrogen exhibited 21% elongation with a high 0.2% proof stress (589MPa). This significant improvement in ductility was likely caused by the reduction in the amount of σ-phase precipitates at the interdendritic regions following the addition of nitrogen. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Long-period structures in gold-copper alloys; Structures a longues periodes dans les alliages or-cuivre

    Energy Technology Data Exchange (ETDEWEB)

    Jehanno, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-07-01

    We first proceed to reevaluation of the gold-copper equilibrium diagram for alloys between Au{sub 20}Cu{sub 80} and Au{sub 65}Cu{sub 35}. The identification of the various phases was performed by X-rays diffraction on quenched polycrystalline samples. We next study the structure of the phase AuCuII. X-ray data collected from bulk single crystals show that this long-period structure must be described with the help of two correlated periodic functions: an 'order function' and a 'displacement function'. The 'order function' conciliates the non-integer value of the period with its rigorous definition. The 'displacement function' accounts for the dis-symmetries of the observed intensities for the antiphase homologous reflections as the appearance of satellites around the fundamental reflections. These two functions are remarkably well defined at long distance in carefully annealed samples and, in some conditions, can be obtained independently. We observe that the improvement of the degree of order increases the 'modulation of position'. In the case of non stoichiometric alloys, the excess of gold atoms (gold rich alloys) is distributed at random whereas the excess of copper (copper rich alloys) is distributed in a preferential manner close to the antiphase boundaries. (author) [French] Nous procedons, tout d'abord, a une reevaluation du diagramme d'equilibre des alliages or-cuivre compris entre Au{sub 20}Cu{sub 80} et Au{sub 65}Cu{sub 35}. L'identification des differentes phases s'est faite par diffraction de rayons X sur des echantillons polycristallins trempes. Nous etudions ensuite, aux rayons X, la structure de la phase AuCuII. Les donnees rassemblees sur monocristaux massifs indiquent que cette structure a longue periode doit etre decrite a l'aide de deux fonctions periodiques correlees: une fonction d'ordre et une fonction de deplacement des atomes. La fonction d'ordre concilie le caractere non entier de la periode avec sa rigoureuse definition. La fonction de

  14. Microstructural evidence of presence of beryllium in Ni-Cr alloys for dental prostheses; Evidencia microestrutural da presenca de berilio em ligas Ni-Cr para proteses dentarias

    Energy Technology Data Exchange (ETDEWEB)

    Alkmin, L.B.; Nunes, C.A., E-mail: lba@ppgem.eel.usp.b [Universidade de Sao Paulo (EEL/USP), Lorena, SP (Brazil). Escola de Engenharia; Coelho, G.C. [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil); Santos, C. [Protmat Materiais Avancados, Guaratingueta, SP (Brazil)

    2010-07-01

    This study aimed to characterize the microstructure of commercial Ni-Cr alloys for dental prosthesis, with special focus on those containing Be. For this, the materials were characterized in terms of chemical composition, phases and melting point temperature. The following techniques were used: X-ray fluorescence, ICP-OES, scanning electron microscopy, electron probe microanalysis, X-ray diffraction and differential thermal analysis. The results clearly showed the presence of a typical eutectic, formed by the Ni{sub ss} and NiBe phases in those alloys containing Be, which can be considered a 'fingerprint' of the presence of this element in these alloys. (author)

  15. Electrochemical behavior of 45S5 bioactive ceramic coating on Ti6Al4V alloy for dental applications

    Science.gov (United States)

    Machado López, M. M.; Espitia Cabrera, M. I.; Faure, J.; Contreras García, M. E.

    2016-04-01

    Titanium and its alloys are widely used as implant materials because of their mechanical properties and non-toxic behavior. Unfortunately, they are not bioinert, which means that they can release ions and can only fix the bone by mechanical anchorage, this can lead to the encapsulation of dense fibrous tissue in the body. The bone fixation is required in clinical conditions treated by orthopedic and dental medicine. The proposal is to coat metallic implants with bioactive materials to establish good interfacial bonds between the metal substrate and bone by increasing bioactivity. Bioactive glasses, ceramics specifically 45 S5 Bioglass, have drawn attention as a serious functional biomaterial because osseointegration capacity. The EPD method of bioglass gel precursor was proposed in the present work as a new method to obtain 45S5/Ti6A14V for dental applications. The coatings, were thermally treated at 700 and 800°C and presented the 45 S5 bioglass characteristic phases showing morphology and uniformity with no defects, quantification percentages by EDS of Si, Ca, Na, P and O elements in the coating scratched powders, showed a good proportional relationship demonstrating the obtention of the 45S5 bioglass. The corrosion tests were carried out in Hank's solution. By Tafel extrapolation, Ti6Al4V alloy showed good corrosion resistance in Hank's solution media, by the formation of a passivation layer on the metal surface, however, in the system 45S5/Ti6Al4V there was an increase in the corrosion resistance; icon-, Ecorr and corrosion rate decreased, the mass loss and the rate of release of ions, were lower in this system than in the titanium alloy without coating.

  16. Immunological parameters of dental alloy corrosion; A study of gingival inflammation after placement of stainless steel crown

    Directory of Open Access Journals (Sweden)

    Ratna Indriyanti

    2008-11-01

    Full Text Available The dental alloy is widely used in many fields of dentistry as a restoration material, orthodontic, prosthodontic, oral surgery and endodontic treatments. Naturally, most of the metallic materials without exception to stainless steel alloy will experience a process of corrosion in a form of electrochemical reaction to achieve thermodynamic equilibrium. The corrosion process in the oral cavity is due to the reaction of metal with saliva as an oral cavity electrolyte fluid. SSC has preformed restoration material conform with dental anatomy, manufactured from stainless steel alloy which is formable and adaptable to the teeth. Stainless Steel Crown generally made of austenitic stainless steel 18/8 of AISI 304 group contain chrome 18% and Nickel 8%, can be used as a restoration for teeth with excessive caries, crown fracture, email hypoplasia, or restoration after endodontic treatment. The toxic effect of Ni+2 released due to corrosion process may cause an inflammation of the gingiva and periodontal tissue. Laboratorically this condition indicated by the expression of pro-inflammation cytokines as immunological parameters such as IL-6, IL-8, TNF and IL-1β whose main role is to initiate and enhance any inflammation responses. The presence of pro-inflammation cytokines can be detected as soon as 1 hour after placement of SSC by examination of gingival crevicular fluid (GCF by ELISA technique. The magnitude of the toxic effect depends on corrosion rate and ions release which is influenced by metal chemical composition, environment temperature and pH, metal wear due to abrasion and friction, soldering if any, and elongation of the metal. Conclusion: The release of Ni+2 during corrosion process after placement of SSC cause gingival inflammation which is indicated by the change of the immunological parameters.

  17. An overview of NiTi shape memory alloy: Corrosion resistance and antibacterial inhibition for dental application

    Energy Technology Data Exchange (ETDEWEB)

    Fadlallah, Sahar A., E-mail: sahar.fadlallah@yahoo.com [Materials and Corrosion Lab. (MCL), Faculty of Science, Taif University, Taif (Saudi Arabia); Chemistry Department, Faculty of Science, Cairo University, Cairo (Egypt); El-Bagoury, Nader [Materials and Corrosion Lab. (MCL), Faculty of Science, Taif University, Taif (Saudi Arabia); Casting Technology Lab., Manufacturing Technology Dept., CMRDI, P.O. Box 87, Helwan, Cairo (Egypt); Gad El-Rab, Sanaa M.F. [Biotechnology Department, Faculty of Science, Taif University, Taif (Saudi Arabia); Botany Department, Faculty of Science, Asuit University, Asuit (Egypt); Ahmed, Rasha A. [Materials and Corrosion Lab. (MCL), Faculty of Science, Taif University, Taif (Saudi Arabia); Forensic Chemistry Laboratories, Medico Legal Department, Ministry of Justice, Cairo (Egypt); El-Ousamii, Ghaida [Materials and Corrosion Lab. (MCL), Faculty of Science, Taif University, Taif (Saudi Arabia)

    2014-01-15

    Highlights: • Evaluate the corrosion resistance of NiTi alloy by using electrochemical techniques. • Estimate the Antibacterial inhibition rate of NiTi alloy. • Assessment the mechanical properties of NiTi from the hardness measurements. • Comparsion the microstructures of cast NiTi with Ti, this indicate the role of Ni to change the behavior of alloy in oral environment. • Advise drinking green tea in small quantities in small quantities in the event of present NiTi alloy in the oral cavity. • Recommendation to use NiTi for dental application. -- Abstract: Nowadays, Nickel–titanium nearly equiatomic is considered as one of the best biomaterials. The aim of the present work deals with the evolution of the electrochemical behavior of NiTi in simulated oral environment. The hardness, microstructures corrosion resistance and antibacterial performance of NiTi alloy were compared with pure titanium. The hardness of NiTi is twice the hardness of pure titanium. Electrochemical techniques were used to detect the corrosion resistance of both biomaterials in Hank’s solution containing (−)-epigallocatechin gallate (EGCG) which used to simulate the oral environment. In the physiological solution selected for the present study, the impedance spectroscopy (EIS) results showed that EGCG sharply increase the corrosion resistance of NiTi from 129 kΩ cm{sup 2} to 1.10 T Ω cm{sup 2} while slowly increase the corrosion resistance of pure titanium from 9.4 kΩ cm{sup 2} to 11.3 kΩ cm{sup 2} during the duration time of immersion at 37 °C. The plate-counting method was used to evaluate the antibacterial performance against Staphylococcus aureus (ATCC 6538). Among the two specimens of biomaterials studied, the antibacterial performance results revealed that the NiTi alloy is better than the pure titanium. The morphology and chemical structure of NiTi and Ti samples were systematically investigated by scanning electron microscope (SEM) and energy dispersive X

  18. An overview of NiTi shape memory alloy: Corrosion resistance and antibacterial inhibition for dental application

    International Nuclear Information System (INIS)

    Fadlallah, Sahar A.; El-Bagoury, Nader; Gad El-Rab, Sanaa M.F.; Ahmed, Rasha A.; El-Ousamii, Ghaida

    2014-01-01

    Highlights: • Evaluate the corrosion resistance of NiTi alloy by using electrochemical techniques. • Estimate the Antibacterial inhibition rate of NiTi alloy. • Assessment the mechanical properties of NiTi from the hardness measurements. • Comparsion the microstructures of cast NiTi with Ti, this indicate the role of Ni to change the behavior of alloy in oral environment. • Advise drinking green tea in small quantities in small quantities in the event of present NiTi alloy in the oral cavity. • Recommendation to use NiTi for dental application. -- Abstract: Nowadays, Nickel–titanium nearly equiatomic is considered as one of the best biomaterials. The aim of the present work deals with the evolution of the electrochemical behavior of NiTi in simulated oral environment. The hardness, microstructures corrosion resistance and antibacterial performance of NiTi alloy were compared with pure titanium. The hardness of NiTi is twice the hardness of pure titanium. Electrochemical techniques were used to detect the corrosion resistance of both biomaterials in Hank’s solution containing (−)-epigallocatechin gallate (EGCG) which used to simulate the oral environment. In the physiological solution selected for the present study, the impedance spectroscopy (EIS) results showed that EGCG sharply increase the corrosion resistance of NiTi from 129 kΩ cm 2 to 1.10 T Ω cm 2 while slowly increase the corrosion resistance of pure titanium from 9.4 kΩ cm 2 to 11.3 kΩ cm 2 during the duration time of immersion at 37 °C. The plate-counting method was used to evaluate the antibacterial performance against Staphylococcus aureus (ATCC 6538). Among the two specimens of biomaterials studied, the antibacterial performance results revealed that the NiTi alloy is better than the pure titanium. The morphology and chemical structure of NiTi and Ti samples were systematically investigated by scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX). The

  19. Effects of shot-peening and atmospheric-pressure plasma on aesthetic improvement of Ti-Nb-Ta-Zr alloy for dental applications

    Science.gov (United States)

    Miura-Fujiwara, Eri; Suzuki, Yuu; Ito, Michiko; Yamada, Motoko; Matsutake, Sinpei; Takashima, Seigo; Sato, Hisashi; Watanabe, Yoshimi

    2018-01-01

    Ti and Ti alloys are widely used for biomedical applications such as artificial joints and dental devices because of their good mechanical properties and biochemical compatibility. However, dental devices made of Ti and Ti alloys do not have the same color as teeth, so they are inferior to ceramics and polymers in terms of aesthetic properties. In a previous study, Ti-29Nb-13Ta-4.6Zr was coated with a white Ti oxide layer by heat treatment to improve its aesthetic properties. Shot-peening is a severe plastic deformation process and can introduce a large shear strain on the peened surface. In this study, the effects of shot-peening and atmospheric-pressure plasma on Ti-29Nb-13Ta-4.6Zr were investigated to form a white layer on the surface for dental applications.

  20. Optical properties of supported core-shell and alloy silver/gold nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hubenthal, Frank; Traeger, Frank [Universitaet Kassel (Germany)

    2008-07-01

    For many applications like surface enhanced Raman scattering in which the optical field enhancement associated with surface plasmon excitation is exploited, tunability of this collective resonance over a wide range is required. For this purpose we have prepared core-shell and alloy nanoparticles consisting of Ag and Au. The core-shell nanoparticles were made by subsequent deposition of Ag and Au atoms and vice versa on dielectric substrates followed by diffusion and nucleation. One of the most interesting among the numerous results is that the plasmon frequency can be tuned from 2.8 eV (442 nm) to 2.1 eV (590 nm) depending on the Au shell thickness. Subsequent annealing of the core-shell nanoparticles causes a shift of the resonance frequency to 2.6 eV. Theoretical modelling allows us to attribute this observation to the formation of alloy nanoparticles. Finally, we have measured the dephasing time T{sub 2} of the alloy nanoparticles by means of spectral hole burning. T{sub 2} amounts to 8.1{+-}1.6 fs, in good agreement with the dephasing time T{sub 2}=8.9 fs that is included in the dielectric function of the bulk.

  1. Selective Laser Melting Technique of Co-Cr Dental Alloys: A Review of Structure and Properties and Comparative Analysis with Other Available Techniques.

    Science.gov (United States)

    Koutsoukis, Theodoros; Zinelis, Spiros; Eliades, George; Al-Wazzan, Khalid; Rifaiy, Mohammed Al; Al Jabbari, Youssef S

    2015-06-01

    The aim of this study was to review the effect of selective laser melting (SLM) procedure on the properties of dental structures made of Co-Cr alloys and to evaluate its quality and compare it to those produced by conventional casting and milling fabrication techniques. A computerized database search using PubMed and Scopus was conducted for peer-reviewed scientific research studies regarding the use of SLM in Co-Cr dental alloys with no restrictions for publication years. The search engines provided hundreds of results, and only 48 scientific research papers, case studies, or literature reviews were considered relevant for this review. The innovative manufacturing concept of SLM offers many advantages compared with casting and milling fabrication techniques. SLM provides different microstructure from casting and milling with minimal internal porosity and internal fitting, marginal adaptation, and comparable bond strength to porcelain. Mechanical and electrochemical properties of SLM structures are enhanced compared to cast, while clinical longevity of single-metal ceramic crowns is comparable to Au-Pt dental alloy. The SLM technique provides dental prosthetic restorations more quickly and less expensively without compromising their quality compared with restorations prepared by casting and milling techniques. The current SLM devices provide metallic restorations made of Co-Cr alloys for removable and fixed partial dentures without compromising the alloy or restoration properties at a fraction of the time and cost, showing great potential to replace the aforementioned fabrication techniques in the long term; however, further clinical studies are essential to increase the acceptance of this technology by the worldwide dental community. © 2015 by the American College of Prosthodontists.

  2. Nanotube formation and morphology change of Ti alloys containing Hf for dental materials use

    International Nuclear Information System (INIS)

    Jeong, Yong-Hoon; Lee, Kang; Choe, Han-Cheol; Ko, Yeong-Mu; Brantley, William A.

    2009-01-01

    In this paper, Ti-Hf (10, 20, 30 and 40 wt.%) alloys were prepared by arc melting, and subjected to heat treatment for 24 h at 1000 o C in an argon atmosphere. Formation of surface nanotubes was achieved by anodizing a Ti-Hf alloy in 1.0 M H 3 PO 4 electrolytes with small amounts of NaF at room temperature. Microstructures of the alloys and nanotube morphology were examined by field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The homogenized Ti-Hf alloys had a needle-like microstructure of α phase, and nanotubes formed on Ti-xHf alloys had the anatase phase after treatment that promoted crystallization. Uniform nanotubes formed for Hf contents up to 20 wt.%. Irregular nanotubes formed on the Ti-30Hf and Ti-40Hf alloys. The structure of the irregular layers on the Ti-30Hf and Ti-40Hf alloys had nanotubes of two sizes. Increasing the Hf content in Ti led to the formation of nanotubes with more narrow size. The pores in the nanotubes typically had a diameter ranging from 80-120 nm and a length of approximately 1.7 μm. It is concluded that nanotube morphology on Ti-Hf alloys can controlled by varying the amount of Hf.

  3. Electrodeposition of gold-platinum alloy nanoparticles on carbon nanotubes as electrochemical sensing interface for sensitive detection of tumor marker

    Energy Technology Data Exchange (ETDEWEB)

    Li Ya [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Yuan Ruo, E-mail: yuanruo@swu.edu.cn [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Chai Yaqin; Song Zhongju [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China)

    2011-07-30

    Graphical abstract: Electrodeposition of gold-platinum alloy (Au-PtNPs) on carbon nanotubes as electrochemical sensing interface and HRP as blocking agent for the fabrication of high sensitive immunosensor. Display Omitted Highlights: > In this work, we proposed a novel electrochemical sensing surface. > The sensing surface possessed larger electro-active areas and higher conductivity due to the introduction of MWCNTs. > The signal could be amplified effectively by synergetic catalysis effect of Au-PtNPs and HRP towards the reduction of H{sub 2}O{sub 2}. > Biomolecules could be immobilized on the surface of Au-PtNPs tightly with the bioactivity kept well. > The simple fabrication method provided a new potential for the future development of practical devices for clinical diagnosis application. - Abstract: A novel electrochemical sensing interface, electrodeposition of gold-platinum alloy nanoparticles (Au-PtNPs) on carbon nanotubes, was proposed and used to fabricate a label-free amperometric immunosensor. On the one hand, the multiwalled carbon nanotubes (MWCNTs) could increase active area of the electrode and enhance the electron transfer ability between the electrode and redox probe; on the other hand, the Au-PtNPs not only could be used to assemble biomolecules with bioactivity kept well, but also could further facilitate the shuttle of electrons. In the meanwhile, horseradish peroxidase (HRP) instead of bovine serum albumin (BSA) was employed to block the possible remaining active sites and avoid the nonspecific adsorption. With the synergetic catalysis effect of Au-PtNPs and HRP towards the reduction of hydrogen peroxide (H{sub 2}O{sub 2}), the signal could be amplified and the sensitivity could be enhanced. Using alpha-fetoprotein (AFP) as model analyte, the fabricated immunosensor exhibited two wide linear ranges in the concentration ranges of 0.5-20 ng mL{sup -1} and 20-200 ng mL{sup -1} with a detection limit of 0.17 ng mL{sup -1} at a signal-to-noise of

  4. Análisis del comportamiento mecánico de una aleación Ni-Cr-Mo para pilares dentales/Analysis of Mechanical Behavior of Ni-Cr-Mo alloy for Dental Abutments

    Directory of Open Access Journals (Sweden)

    Luis Alberto Laguado Villamizar

    2012-12-01

    Full Text Available El presente estudio caracteriza una aleación aplicable al diseño de pilares para implantes dentales. Se propone un material biocompatible y de alta resistencia mecánica como alternativa a las aleaciones de Titanio, disminuyendo los costos de materia prima y procesamiento. Se realizan pruebas mecánicas de tracción y de compresión a la aleación de Ni-Cr-Mo, posteriormente se realiza modelado 3D y simulación de sus propiedades mecánicas por medio de análisis de elementos finitos. Como resultado se obtiene que el material disminuye su resistencia mecánica después del proceso de fundición empleado. El modelo de simulación es válido para análisis de resistencia en pilares dentales.This study presents the characterization of a dental implant alloy for abutments. It proposes a biocompatible material and high mechanical resistance as an alternative to Titanium alloys, lowering costs of raw materials and processing. Mechanical testing of the Ni-Cr-Mo alloy and subsequently perform simulations of its mechanical properties by means of finite element analysis. As a result is obtained that the material reduces its mechanical strength after the casting for electric induction molding process. The simulation model is valid to make analysis of resistance to this type of dental devices.

  5. The recovery between 30K and 400K of copper and copper alloyed with gold after thermal-neutron irradiation

    International Nuclear Information System (INIS)

    Aspeling, J.C.

    1977-08-01

    The point defect reactions responsible for the recovery in resistivity between substages I(D) and I(E) in Stage I after thermal-neutron irradiation were investigated, using a new method termed the ideal isochronal method. Another substage was observed between I(D) and I(E). Whereas the peak temperatures of substages I(D) and I(E) are dependent on applied holding times in a well-known way, the main and very unusual characteristic of the new substage is that its peak temperature does not shift with a change in holding time. Using the ideal isochronal method, it was confirmed that substages I(D) and I(E) have a uniquely thermally activated energy. The new substage was attributed to a process whereby the interstitial has to overcome an energy barrier before recombining with a vacancy. In pure copper several recovery stages are observed between substage I(E) (about 52K) and Stage III (about 300K), whereas with the alloying of gold as a substitutional impurity, additional recovery stages are observed. In the alloyed copper a dose dependence contrary to that normally expected for interstitial-impurity reactions was observed. This phenomenon can, however, be explained consistently when the concentrations of interstitials, vacancies, impurities and impurity agglomerates are considered. No other free migrating point defect stage was observed between substage I(E) and Stage III. High-resolution measurements of the recovery stage at 225K, previously believed to shift in temperature with dose, showed that this stage actually consists of two stages and that the latter do not shift with dose. The two stages were explained in terms of close-pair recovery, in contrast to the previous explanation [af

  6. Unexpected Au Alloying in Tailoring In-Doped SnTe Nanostructures with Gold Nanoparticles

    Directory of Open Access Journals (Sweden)

    Samuel Atherton

    2017-03-01

    Full Text Available Materials with strong spin-orbit interaction and superconductivity are candidates for topological superconductors that may host Majorana fermions (MFs at the edges/surfaces/vortex cores. Bulk-superconducting carrier-doped topological crystalline insulator, indium-doped tin telluride (In-SnTe is one of the promising materials. Robust superconductivity of In-SnTe nanostructures has been demonstrated recently. Intriguingly, not only 3-dimensional (3D nanostructures but also ultra-thin quasi-2D and quasi-1D systems can be grown by the vapor transport method. In particular, nanostructures with a controlled dimension will give us a chance to understand the dimensionality and the quantum confinement effects on the superconductivity of the In-SnTe and may help us work on braiding MFs in various dimensional systems for future topological quantum computation technology. With this in mind, we employed gold nanoparticles (GNPs with well-identified sizes to tailor In-SnTe nanostructures grown by vapor transport. However, we could not see clear evidence that the presence of the GNPs is necessary or sufficient to control the size of the nanostructures. Nevertheless, it should be noted that a weak correlation between the diameter of GNPs and the dimensions of the smallest nanostructures has been found so far. To our surprise, the ones grown under the vapor–liquid–solid mechanism, with the use of the GNPs, contained gold that is widely and inhomogeneously distributed over the whole body.

  7. Fractal study of Ni-Cr-Mo alloy for dental applications: effect of beryllium

    Energy Technology Data Exchange (ETDEWEB)

    Eftekhari, Ali

    2003-12-30

    Different Ni-based alloys with various compositions were prepared by varying the amounts of beryllium. Effect of the amount of beryllium added to the alloy on its corrosion in an electrolyte solution of artificial saliva was investigated. Fractal dimension was used as a quantitative factor for surface analysis of the alloys before and after storage in the artificial salvia. The fractal dimensions of the electrode surfaces were determined by means of the most reliable method in this context viz. time dependency of the diffusion-limited current for a system involving 'diffusion towards electrode surface'. The results showed that increase of the beryllium amount in the alloy composition significantly increases the alloy corrosion. It is accompanied by increase of the fractal dimension and roughness of the electrode surface, whereas a smooth and shiny surface is required for dentures. From the methodology point of view, the approach utilized for fractal analysis of the alloy surfaces (Au-masking of metallic surfaces) is a novel and efficient method for study of denture surfaces. Generally, this approach is of interest for corrosion studies of different metals and alloys, particularly where changes in surface structure have a significant importance.

  8. Microstructure and mechanical properties of sintered Ti Binary alloys for dental applications

    Energy Technology Data Exchange (ETDEWEB)

    Yilmaz Atay, H.; Haro Rodriguez, M.; Amigo Mata, A.; Vicente Escuder, V.; Amigo Borras, V.

    2016-07-01

    Biomaterials have shown rapid growth in the field of elderly population demands with the prolongation of human life. One of those biomaterials, titanium, has excellent properties and biocompatibility though it may cause weakening in the structures due to its higher stiffness. In this study, powder metallurgy process was used to produce Ti-Cr, Ti-Mo and Ti-Cu metal alloys to overcome this problem. Metal powders were mixed by mechanical alloying. After pressing and sintering, alloys structures were investigated. Characterizations were carried out by size analyzer, SEM-EDX, optical microscope and three points bending test. (Author)

  9. Electrochemical assessment of some titanium and stainless steel impact dental alloys

    International Nuclear Information System (INIS)

    Echavarria, A.; Arroyave, C.

    2003-01-01

    Commercially pure titanium alloy, Ti-6Al-4V alloy and stainless steel screw implants were evaluated in both Ringer and synthetic saliva physiological solutions at body temperature by EIS (Electrochemical Impedance Spectroscopy) with immersion times of 30 d. Results were simulated as a sandwich system composed by four capacitors-resistances connected in series with the solution resistance. A model explaining the results in terms of the porosity and thickness of four different layers, was proposed. (Author) 22 refs

  10. Effects of carbon concentration on microstructure and mechanical properties of as-cast nickel-free Co–28Cr–9W-based dental alloys

    International Nuclear Information System (INIS)

    Yamanaka, Kenta; Mori, Manami; Chiba, Akihiko

    2014-01-01

    We determined the effects of carbon concentration on the microstructures and tensile properties of the Ni-free Co–29Cr–9W–1Si–C (mass%) cast alloys used in dental applications. Alloy specimens prepared with carbon concentrations in the range 0.01–0.27 mass% were conventionally cast. Scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) revealed that precipitates had formed in all the alloy specimens. The σ phase, a chromium-rich intermetallic compound, had formed in the region between the dendrite arms of the low-carbon-content (e.g., 0.01C) alloys. Adding carbon to the alloys increased the amount of interdendritic precipitates that formed and changed the precipitation behavior; the precipitated phase changed from the σ phase to the M 23 C 6 carbide with increasing carbon concentration. Adding a small amount of carbon (i.e., 0.04 mass%) to the alloys dramatically enhanced the 0.2% proof stress, which subsequently gradually increased with increasing content of carbon in the alloys. Elongation-to-failure, on the other hand, increased with increasing carbon content and showed a maximum at carbon concentrations of ∼ 0.1 mass%. The M 23 C 6 carbide formed at the interdendritic region may govern the tensile properties of the as-cast Co–Cr–W alloys similar to how it governed those of the hot-rolled alloys prepared in our previous study. - Highlights: • Microstructure and tensile properties of C-doped Co–Cr–W cast alloys was studied. • Adding carbon stabilized the γ matrix and changed the precipitation behavior. • Formation of carbide precipitates strengthened C-doped Co–Cr–Mo alloys. • A maximum tensile elongation was obtained at carbon concentrations of ∼0.1 mass%

  11. Development and properties of Ti–In binary alloys as dental biomaterials

    International Nuclear Information System (INIS)

    Wang, Q.Y.; Wang, Y.B.; Lin, J.P.; Zheng, Y.F.

    2013-01-01

    The objective of this study is to investigate the effect of alloying element indium on the microstructure, mechanical properties, corrosion behavior and in vitro cytotoxicity of Ti–In binary alloys, with the addition of 1, 5, 10 and 15 at.% indium. The phase constitution was studied by optical microscopic observation and X-ray diffraction measurements. The mechanical properties were characterized by tension and microhardness tests. Potentiodynamic polarization measurements were employed to investigate the corrosion behavior in artificial saliva solutions with and without fluoride. In vitro cytotoxicity was conducted by using L929 and NIH 3T3 mouse fibroblast cell lines, with commercially pure Ti (CP–Ti, ASTM grade 2) as negative control. All of the binary Ti–In alloys investigated in this work were found to have higher strength and microhardness than CP–Ti. Electrochemical results showed that Ti–In alloys exhibited the same order of magnitude of passivation current densities with CP–Ti in artificial saliva solutions. With the presence of NaF, Ti–10In and Ti–15In showed transpassive behavior and lower current densities at high potentials. All experimental Ti–In alloys showed good cytocompatibility, at the same level as CP–Ti. The addition of indium to titanium was effective on increasing the strength and microhardness, without impairing its good corrosion resistance and cytocompatibility. - Highlights: ► The addition of In into Ti can increase the mechanical property. ► Ti-In alloys exhibited similar passivation behavior with CP-Ti. ► Ti-In alloys had good cytocompatibility comparable with CP-Ti. ► Ti-10In and Ti-15In showed transpassive baheviour with the addition of NaF

  12. Corrosion in artificial saliva of a Ni-Cr-based dental alloy joined by TIG welding and conventional brazing.

    Science.gov (United States)

    Matos, Irma C; Bastos, Ivan N; Diniz, Marília G; de Miranda, Mauro S

    2015-08-01

    Fixed prosthesis and partial dental prosthesis frameworks are usually made from welded Ni-Cr-based alloys. These structures can corrode in saliva and have to be investigated to establish their safety. The purpose of this study was to evaluate the corrosion behavior of joints joined by tungsten inert gas (TIG) welding and conventional brazing in specimens made of commercial Ni-Cr alloy in Fusayama artificial saliva at 37°C (pH 2.5 and 5.5). Eighteen Ni-Cr base metal specimens were cast and welded by brazing or tungsten inert gas methods. The specimens were divided into 3 groups (base metal, 2 welded specimens), and the composition and microstructure were qualitatively evaluated. The results of potential corrosion and corrosion current density were analyzed with a 1-way analysis of variance and the Tukey test for pairwise comparisons (α=.05). Base metal and tungsten inert gas welded material showed equivalent results in electrochemical corrosion tests, while the air-torched specimens exhibited low corrosion resistance. The performance was worst at pH 2.5. These results suggest that tungsten inert gas is a suitable welding process for use in dentistry, because the final microstructure does not reduce the corrosion resistance in artificial saliva at 37°C, even in a corrosion-testing medium that facilitates galvanic corrosion processes. Moreover, the corrosion current density of brazed Ni-Cr alloy joints was significantly higher (P<.001) than the base metal and tungsten inert gas welded joints. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  13. [Differential study of the bonding characterization of dental porcelain to Ni-Cr alloys].

    Science.gov (United States)

    Wei, Fang; Zhan, De-song; Wang, Yan-yan

    2008-10-01

    To study the bonding capability when Ni-Cr porcelain alloy was added with Ti, compound rare earth metals and removed the element of Be. Ni-Cr-Ti porcelain alloys manufactured by Institute of Metal Research of Chinese Academy of Sciences were tested. The test alloys were divided into three groups according to whether containing Be and compound rare earth metals or not. And HI BOND Ni-Cr base-metal alloy was chosen as control. The metal-ceramic specimens were prepared for shear test, scanning electron microscope (SEM) and energy spectrum analysis. The shear bond strength of the four groups were analyzed. No significant difference were observed among them (P > 0.05). No crackle was found and they were contacted tightly between the porcelain and metal. The composition and contents of the four groups' interfaces were closed. The shear bond strength of the self-made Ni-Cr-Ti porcelain alloys all can satisfy the clinical requirements. Experimental groups containing Ti, compound rare earth metals and removing the element of Be can be used as better recommendation for clinical practice.

  14. Castability of Ti-6Al-7Nb alloy for dental casting

    OpenAIRE

    Wang, Tie Jun; 小林, 郁夫; 土居, 壽; 米山, 隆之

    1999-01-01

    Castability of Ti-6Al-7Nb alloy, CP Ti, and Co-Cr alloy was examined for mesh type and plate type specimens. The casting was carried out with a pressure type casting machine and commercial molding material. The castability of the mesh type specimen was evaluated in terms of the number of cast segments (castability index), and that of the plate type was evaluated by the area of the speci­men (casting rate). X-ray images processed by a digital imaging technique were used to identify the casting...

  15. [A surface reacted layer study of titanium-zirconium alloy after dental casting].

    Science.gov (United States)

    Zhang, Y; Guo, T; Li, Z; Li, C

    2000-10-01

    To investigate the influence of the mold temperature on the surface reacted layer of Ti-Zr alloy castings. Ti-Zr alloy was casted into a mold which was made of a zircon (ZrO2.SiO2) for inner coating and a phosphate-bonded material for outer investing with a casting machine (China) designed as vacuum, pressure and centrifuge. At three mold temperatures (room temperature, 300 degrees C, 600 degrees C) the Ti-Zr alloy was casted separately. The surface roughness of the castings was calculated by instrument of smooth finish (China). From the surface to the inner part the Knoop hardness and thickness in reacted layer of Ti-Zr alloy casting was measured. The structure of the surface reacted layer was analysed by SEM. Elemental analyses of the interfacial zone of the casting was made by element line scanning observation. The surface roughness of the castings was increased significantly with the mold temperature increasing. At a higher mold temperature the Knoop hardness of the reactive layer was increased. At the three mold temperature the outmost surface was very hard, and microhardness data decreased rapidly where they reached constant values. The thickness was about 85 microns for castings at room temperature and 300 degrees C, 105 microns for castings at 600 degrees C. From the SEM micrograph of the Ti-Zr alloy casting, the surface reacted layer could be divided into three different layers. The first layer was called non-structure layer, which thickness was about 10 microns for room temperature group, 20 microns for 300 degrees C and 25 microns for 600 degrees C. The second layer was characterized by coarse-grained acicular crystal, which thickness was about 50 microns for three mold temperatures. The third layer was Ti-Zr alloy. The element line scanning showed non-structure layer with higher level of element of O, Al, Si and Zr, The higher the mold temperature during casting, the deeper the Si permeating and in the second layer the element Si could also be found

  16. In vitro biocompatibility and electrical stability of thick-film platinum/gold alloy electrodes printed on alumina

    Science.gov (United States)

    Carnicer-Lombarte, Alejandro; Lancashire, Henry T.; Vanhoestenberghe, Anne

    2017-06-01

    Objective. High-density electrode arrays are a powerful tool in both clinical neuroscience and basic research. However, current manufacturing techniques require the use of specialised techniques and equipment, which are available to few labs. We have developed a high-density electrode array with customisable design, manufactured using simple printing techniques and with commercially available materials. Approach. Electrode arrays were manufactured by thick-film printing a platinum-gold alloy (Pt/Au) and an insulating dielectric on 96% alumina ceramic plates. Arrays were conditioned in serum and serum-free conditions, with and without 1 kHz, 200 µA, charge balanced stimulation for up to 21 d. Array biocompatibility was assessed using an extract assay and a PC-12 cell contact assay. Electrode impedance, charge storage capacity and charge injection capacity were before and after array conditioning. Main results. The manufactured Pt/Au electrodes have a highly porous surface and exhibit electrical properties comparable to arrays manufactured using alternative techniques. Materials used in array manufacture were found to be non-toxic to L929 fibroblasts by extract assay, and neuronal-like PC-12 cells adhered and extended neurites on the array surfaces. Arrays remained functional after long-term delivery of electrical pulses while exposed to protein-rich environments. Charge storage capacities and charge injection capacities increased following stimulation accounted for by an increase in surface index (real surface area) observed by vertical scanning interferometry. Further, we observed accumulation of proteins at the electrode sites following conditioning in the presence of serum. Significance. This study demonstrates the in vitro biocompatibility of commercially available thick-film printing materials. The printing technique is both simple and versatile, with layouts readily modified to produce customized electrode arrays. Thick-film electrode arrays are an

  17. Effect of finishing process on the surface quality of Co-Cr-Mo dental alloys

    Directory of Open Access Journals (Sweden)

    Dorota Klimecka -Tatar

    2016-09-01

    Full Text Available Preparatory procedures for the material have a significant influence on the surface stereometry of the material. This study investigated the effect of the electropolishing process on the surface quality of metallic prosthetic constructions based on Co-Cr-Mo alloys. It has been found that the process of electropolishing prevents to excessive development of the surface of a material and consequently improves surface quality.

  18. Numerical assessment of bone remodeling around conventionally and early loaded titanium and titanium-zirconium alloy dental implants.

    Science.gov (United States)

    Akça, Kıvanç; Eser, Atılım; Çavuşoğlu, Yeliz; Sağırkaya, Elçin; Çehreli, Murat Cavit

    2015-05-01

    The aim of this study was to investigate conventionally and early loaded titanium and titanium-zirconium alloy implants by three-dimensional finite element stress analysis. Three-dimensional model of a dental implant was created and a thread area was established as a region of interest in trabecular bone to study a localized part of the global model with a refined mesh. The peri-implant tissues around conventionally loaded (model 1) and early loaded (model 2) implants were implemented and were used to explore principal stresses, displacement values, and equivalent strains in the peri-implant region of titanium and titanium-zirconium implants under static load of 300 N with or without 30° inclination applied on top of the abutment surface. Under axial loading, principal stresses in both models were comparable for both implants and models. Under oblique loading, principal stresses around titanium-zirconium implants were slightly higher in both models. Comparable stress magnitudes were observed in both models. The displacement values and equivalent strain amplitudes around both implants and models were similar. Peri-implant bone around titanium and titanium-zirconium implants experiences similar stress magnitudes coupled with intraosseous implant displacement values under conventional loading and early loading simulations. Titanium-zirconium implants have biomechanical outcome comparable to conventional titanium implants under conventional loading and early loading.

  19. Probing Interfacial Friction and Dissipation in Granular Gold­ Nickel Alloys with a Quartz Crystal Oscillator in an External Magnetic Field

    Science.gov (United States)

    Stevens, K. M.; Krim, J.

    2015-03-01

    We present here a quartz crystal microbalance study of two-phase gold nickel alloys whose internal granular properties are probed by exposure to a fluctuating external magnetic field. The work is motivated by prior studies demonstrating that granular two-phase materials exhibited lower friction and wear than solid solution alloys with identical compositions. In particular, we report a ``flexing'' effect which appears when an external magnetic field is applied, and is manifested as a decrease in the magnitude of oscillation amplitude that is synchronized with the applied field; the effect is not seen on the complimentary solid solution samples. The effect is consistent with internal interfacial friction between nickel and gold grains, indicating a degree of freedom which may decrease friction even in the absence of an external magnetic field. This is supported through analysis of energy dissipation in the system, using the Butterworth­-Van Dyke equivalent circuit model. Data and interpretation are also presented that rule out alternate explanations such as giant magnetoresistance and/or other resistive phenomenon within the film. Funding provided by NSF DMR0805204. Thanks to L. Pan for sample preparation.

  20. Enhancement of wear and corrosion resistance of low modulus β-type Zr-20Nb-xTi (x=0, 3) dental alloys through thermal oxidation treatment.

    Science.gov (United States)

    Zhang, Jianfeng; Gan, Xiaxia; Tang, Hongqun; Zhan, Yongzhong

    2017-07-01

    In order to obtain material with low elastic modulus, good abrasion resistance and high corrosion stability as screw for dental implant, the biomedical Zr-20Nb and Zr-20Nb-3Ti alloy with low elastic modulus were thermal oxidized respectively at 700°C for 1h and 600°C for 1.25h to obtain the compact oxidized layer to improve its wear resistance and corrosion resistance. The results show that smooth compact oxidized layer (composed of monoclinic ZrO 2 , tetragonal ZrO 2 and 6ZrO 2 -Nb 2 O 5 ) with 22.6μm-43.5μm thickness and 1252-1306HV hardness can be in-situ formed on the surface of the Zr-20Nb-xTi (x=0, 3). The adhesion of oxidized layers to the substrates is determined to be 58.35-66.25N. The oxidized Zr-20Nb-xTi alloys reveal great improvement of the pitting corrosion resistance in comparison with the un-oxidized alloys. In addition, the oxidized Zr-20Nb-3Ti exhibits sharply reduction of the corrosion rates and the oxidized Zr-20Nb shows higher corrosion rates than un-oxidized alloys, which is relevant with the content of the t-ZrO 2 . Wear test in artificial saliva demonstrates that the wear losses of the oxidized Zr-20Nb-xTi (x=0, 3) are superior to pure Ti. All of the un-oxidized Zr-20Nb-xTi (x=0, 3) alloys suffer from serious adhesive wear due to its high plasticity. Because of the protection from compact oxide layer with high adhesion and high hardness, the coefficients of friction and wear losses of the oxidized Zr-20Nb-xTi (x=0, 3) alloys decrease 50% and 95%, respectively. The defects on the oxidized Zr-20Nb have a negative effect on the friction and wear properties. In addition, after the thermal oxidation, compression test show that elastic modulus and strength of Zr-20Nb-xTi (x=0, 3) increase slightly with plastic deformation after 40% of transformation. Furthermore, stripping of the oxidized layer from the alloy matrix did not occur during the whole experiments. As the surface oxidized Zr-20Nb-3Ti alloy has a combination of excellent performance

  1. [The study of the colorimetric characteristics of the cobalt-chrome alloys abutments covered by four different all-ceramic crowns by using dental spectrophotometer].

    Science.gov (United States)

    Chen, Yifan; Liu, Hongchun; Meng, Yukun; Chao, Yonglie; Liu, Changhong

    2015-06-01

    This study aims to evaluate the optical data of the different sites of the cobalt-chrome (Co-Cr) alloy abutments covered by four different all-ceramic crowns and the color difference between the crowns and target tab using a digital dental spectrophotometer. Ten Co-Cr alloy abutments were made and tried in four different groups of all-ceramic crowns, namely, Procera aluminia, Procera zirconia, Lava zirconia (Lava-Zir), and IPS E.max glass-ceramic lithium disilicate-reinforced monolithic. The color data of the cervical, body, and incisal sites of the samples were recorded and analyzed by dental spectrophotometer. The CIE L*, a*, b* values were again measured after veneering. The color difference between the abutments covered by all-ceramic crowns and A2 dentine shade tab was evaluated. The L* and b* values of the abutments can be increased by all of the four groups of all-ceramic copings, but a* values were decreased in most groups. A statistical difference was observed among four groups. After being veneered, the L* values of all the copings declined slightly, and the values of a*, b* increased significantly. When compared with A2 dentine shade tab, the ΔE of the crowns was below 4. Four ceramic copings were demonstrated to promote the lightness and hue of the alloy abutments effecttively. Though the colorimetric baseline of these copings was uneven, veneer porcelain can efficiently decrease the color difference between the samples and thee target.

  2. New Ti-Alloys and Surface Modifications to Improve the Mechanical Properties and the Biological Response to Orthopedic and Dental Implants: A Review

    Science.gov (United States)

    Kirmanidou, Yvoni; Sidira, Margarita; Drosou, Maria-Eleni; Bennani, Vincent; Bakopoulou, Athina; Tsouknidas, Alexander; Michailidis, Nikolaos; Michalakis, Konstantinos

    2016-01-01

    Titanium implants are widely used in the orthopedic and dentistry fields for many decades, for joint arthroplasties, spinal and maxillofacial reconstructions, and dental prostheses. However, despite the quite satisfactory survival rates failures still exist. New Ti-alloys and surface treatments have been developed, in an attempt to overcome those failures. This review provides information about new Ti-alloys that provide better mechanical properties to the implants, such as superelasticity, mechanical strength, and corrosion resistance. Furthermore, in vitro and in vivo studies, which investigate the biocompatibility and cytotoxicity of these new biomaterials, are introduced. In addition, data regarding the bioactivity of new surface treatments and surface topographies on Ti-implants is provided. The aim of this paper is to discuss the current trends, advantages, and disadvantages of new titanium-based biomaterials, fabricated to enhance the quality of life of many patients around the world. PMID:26885506

  3. Fatigue Life of Titanium Alloys Fabricated by Additive Layer Manufacturing Techniques for Dental Implants

    Science.gov (United States)

    Chan, Kwai S.; Koike, Marie; Mason, Robert L.; Okabe, Toru

    2013-02-01

    Additive layer deposition techniques such as electron beam melting (EBM) and laser beam melting (LBM) have been utilized to fabricate rectangular plates of Ti-6Al-4V with extra low interstitial (ELI) contents. The layer-by-layer deposition techniques resulted in plates that have different surface finishes which can impact significantly on the fatigue life by providing potential sites for fatigue cracks to initiate. The fatigue life of Ti-6Al-4V ELI alloys fabricated by EBM and LBM deposition techniques was investigated by three-point testing of rectangular beams of as-fabricated and electro-discharge machined surfaces under stress-controlled conditions at 10 Hz until complete fracture. Fatigue life tests were also performed on rolled plates of Ti-6Al-4V ELI, regular Ti-6Al-4V, and CP Ti as controls. Fatigue surfaces were characterized by scanning electron microscopy to identify the crack initiation site in the various types of specimen surfaces. The fatigue life data were analyzed statistically using both analysis of variance techniques and the Kaplan-Meier survival analysis method with the Gehan-Breslow test. The results indicate that the LBM Ti-6Al-4V ELI material exhibits a longer fatigue life than the EBM counterpart and CP Ti, but a shorter fatigue life compared to rolled Ti-6Al-4V ELI. The difference in the fatigue life behavior may be largely attributed to the presence of rough surface features that act as fatigue crack initiation sites in the EBM material.

  4. Spectroscopic diagnostic of gold plasma

    International Nuclear Information System (INIS)

    Busquet, M.

    1986-01-01

    Results of a simulation of a gold-aluminium alloy target irradiated by laser are presented. FCI code has been used with a processing out of LTE of atomic physics of gold and of multigroup photonics. Emission and reabsorption of gold and aluminium lines are included [fr

  5. Spectroscopic diagnostic of gold plasma

    Energy Technology Data Exchange (ETDEWEB)

    Busquet, M.

    1986-06-01

    Results of a simulation of a gold-aluminium alloy target irradiated by laser are presented. FCI code has been used with a processing out of LTE of atomic physics of gold and of multigroup photonics. Emission and reabsorption of gold and aluminium lines are included.

  6. Current bonding systems for resin-bonded restorations and fixed partial dentures made of silver–palladium–copper–gold alloy

    Directory of Open Access Journals (Sweden)

    Hideo Matsumura

    2011-02-01

    Full Text Available This review article describes about the bonding systems for noble metal alloys, bonding techniques of restorations and fixed partial dentures (FPDs made of Ag–Pd–Cu–Au alloys, and their clinical performance. Thione monomers, 6-(4-vinylbenzyl-n-propyl amino-1,3,5-triazine-2,4-dithione (VTD, 6-methacryloyloxyhexyl-2-thiouracil-5-carboxylate (MTU-6, and 10-methacryloxydecyl 6,8-dithiooctanoate (MDDT, has been proved effective for bonding noble metal alloys. An acrylic adhesive consists of the tri-n-butylborane (TBB initiator, methyl methacrylate (MMA monomer liquid with 5% 4-methacryloyloxyethyl trimellitate anhydride (4-META, and poly(methyl methacrylate (PMMA, is being used for bonding metallic restorations to abutment surfaces. Clinical performance of restorations and FPDs made of Ag–Pd–Cu–Au alloys is overall excellent when they are seated with the currently available noble metal bonding systems.

  7. Measurement of absorbed doses near metal and dental material interfaces irradiated by x- and gamma-ray therapy beams

    International Nuclear Information System (INIS)

    Farahani, M.; Eichmiller, F.C.; McLaughlin, W.L.

    1990-01-01

    Soft-tissue damage adjacent to dental restorations is a deleterious side effect of radiation therapy associated with low-energy electron scatter from dental materials of high electron density. This study was designed to investigate the enhancement of dose to soft tissue (or water) close to high electron-density materials and to measure the detailed lateral and depth-dose profiles in soft-tissue-simulating polymer adjacent to planar interfaces of several higher atomic-number materials: 18-carat gold dental casting alloy; Ag-Hg dental amalgam alloy; Ni-Cr dental casting alloy; and natural human tooth structure. Results indicate that the dose-enhancement in 'tissue' is as great as a factor of 2 on the backscatter side adjacent to gold and a factor of 1.2 adjacent to tooth tissue, but is insignificant on the forward-scatter side because of the predominant effect of attenuation by the high-density, high atomic-number absorbing material. (author)

  8. Microstructure, hardness, corrosion resistance and porcelain shear bond strength comparison between cast and hot pressed CoCrMo alloy for metal-ceramic dental restorations.

    Science.gov (United States)

    Henriques, B; Soares, D; Silva, F S

    2012-08-01

    The purpose of this study was to compare the microstructure, hardness, corrosion resistance and metal-porcelain bond strength of a CoCrMo dental alloy obtained by two routes, cast and hot pressing. CoCrMo alloy substrates were obtained by casting and hot pressing. Substrates' microstructure was examined by the means of Optical Microscopy (OM) and by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). Hardness tests were performed in a microhardness indenter. The electrochemical behavior of substrates was investigated through potentiodynamic tests in a saline solution (8g NaCl/L). Substrates were bonded to dental porcelain and metal-porcelain bond strength was assessed by the means of a shear test performed in a universal test machine (crosshead speed: 0.5 mm/min) until fracture. Fractured surfaces as well as undestroyed interface specimens were examined with Stereomicroscopy and SEM-EDS. Data was analyzed with Shapiro-Wilk test to test the assumption of normality. The t-test (pmicrostructures whereas hot pressed specimens exhibited a typical globular microstructure with a second phase spread through the matrix. The hardness registered for hot pressed substrates was greater than that of cast specimens, 438±24HV/1 and 324±8HV/1, respectively. Hot pressed substrates showed better corrosion properties than cast ones, i.e. higher OCP; higher corrosion potential (E(corr)) and lower current densities (i(corr)). No significant difference was found (p<0.05) in metal-ceramic bond strength between cast (116.5±6.9 MPa) and hot pressed (114.2±11.9 MPa) substrates. The failure type analysis revealed an adhesive failure for all specimens. Hot pressed products arise as an alternative to cast products in dental prosthetics, as they impart enhanced mechanical and electrochemical properties to prostheses without compromising the metal-ceramic bond strength. Copyright © 2012 Elsevier Ltd. All rights reserved.

  9. Glossary of Dental Terms

    Science.gov (United States)

    ... more... Coffee and Doughnuts: A Disastrous Combo for Teeth? The sugars in doughnuts have been identified as ... More print this article enlarge text Glossary of Dental Terms Oral Health Defined Amalgam silver/mercury alloy ...

  10. Monodisperse gold-palladium alloy nanoparticles and their composition-controlled catalysis in formic acid dehydrogenation under mild conditions.

    Science.gov (United States)

    Metin, Önder; Sun, Xiaolian; Sun, Shouheng

    2013-02-07

    Monodisperse 4 nm AuPd alloy nanoparticles with controlled composition were synthesized by co-reduction of hydrogen tetrachloroaurate(III) hydrate and palladium(II) acetylacetonate with a borane-morpholine complex in oleylamine. These NPs showed high activity (TOF = 230 h(-1)) and stability in catalyzing formic acid dehydrogenation and hydrogen production in water at 50 °C without any additives.

  11. Effect of surface reaction layer on grindability of cast titanium alloys.

    Science.gov (United States)

    Ohkubo, Chikahiro; Hosoi, Toshio; Ford, J Phillip; Watanabe, Ikuya

    2006-03-01

    The purpose of this study was to investigate the effect of the cast surface reaction layer on the grindability of titanium alloys, including free-machining titanium alloy (DT2F), and to compare the results with the grindability of two dental casting alloys (gold and Co-Cr). All titanium specimens (pure Ti, Ti-6Al-4V and DT2F) were cast using a centrifugal casting machine in magnesia-based investment molds. Two specimen sizes were used to cast the titanium metals so that the larger castings would be the same size as the smaller gold and Co-Cr alloy specimens after removal of the surface reaction layer (alpha-case). Grindability was measured as volume loss ground from a specimen for 1 min using a handpiece engine with a SiC abrasive wheel at 0.1 kgf and four circumferential wheel speeds. For the titanium and gold alloys, grindability increased as the rotational speed increased. There was no statistical difference (p>0.05) in grindability for all titanium specimens either with or without the alpha-case. Of the titanium metals tested, Ti-6 Al-4V had the greatest grindability at higher speeds, followed by DT2F and CP Ti. The grindability of the gold alloy was similar to that of Ti-6 Al-4V, whereas the Co-Cr alloy had the lowest grindability. The results of this study indicated that the alpha-case did not significantly affect the grindability of the titanium alloys. The free-machining titanium alloy had improved grindability compared to CP Ti.

  12. Influence of thermo-mechanical cycling on porcelain bonding to cobalt-chromium and titanium dental alloys fabricated by casting, milling, and selective laser melting.

    Science.gov (United States)

    Antanasova, Maja; Kocjan, Andraž; Kovač, Janez; Žužek, Borut; Jevnikar, Peter

    2018-04-01

    The aim has been to determine the effect of thermo-mechanical cycling on shear-bond-strength (SBS) of dental porcelain to Co-Cr and Ti-based alloys fabricated by casting, computer-numerical-controlled milling, and selective-laser-melting (SLM). Seven groups (n=22/group) of metal cylinders were fabricated by casting (Co-Cr and commercially pure-cpTi), milling (Co-Cr, cpTi, Ti-6Al-4V) or by SLM (Co-Cr and Ti-6Al-4V) and abraded with airborne-particles. The average surface roughness (R a ) was determined for each group. Dental porcelain was applied and each metal-ceramic combination was divided into two subgroups - stored in deionized water (24-h, 37°C), or subjected to both thermal (6000-cycles, between 5 and 60°C) and mechanical cycling (10 5 -cycles, 60N-load). SBS test-values and failure modes were recorded. Metal-ceramic interfaces were analyzed with a focused-ion-beam/scanning-electron-microscope (FIB/SEM) and energy-dispersive-spectroscopy (EDS). The elastic properties of the respective metal and ceramic materials were evaluated by instrumented-indentation-testing. The oxide thickness on intact Ti-based substrates was measured with Auger-electron-spectroscopy (AES). Data were analyzed using ANOVA, Tukey's HSD and t-tests (α=0.05). The SBS-means differed according to the metal-ceramic combination (p<0.0005) and to the fatigue conditions (p<0.0005). The failure modes and interface analyses suggest better porcelain adherence to Co-Cr than to Ti-based alloys. Values of R a were dependent on the metal substrate (p<0.0005). Ti-based substrates were not covered with thick oxide layers following digital fabrication. Ti-based alloys are more susceptible than Co-Cr to reduction of porcelain bond strength following thermo-mechanical cycling. The porcelain bond strength to Ti-based alloys is affected by the applied metal processing technology. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  13. Selected Properties And Tribological Wear Alloys Co-Cr-Mo And Co-Cr-Mo-W Used In Dental Prosthetics

    Directory of Open Access Journals (Sweden)

    Augustyn-Pieniążek J.

    2015-09-01

    Full Text Available The presented work provides the results of the abrasive wear resistance tests performed on Co-Cr-Mo and Co-Cr-Mo-W alloys with the use of the Miller’s apparatus. The analyzed alloys underwent microstructure observations as well as hardness measurements, and the abraded surfaces of the examined materials were observed by means of electron scanning microscopy. The performed examinations made it possible to state that the Co-Cr alloys characterized in a high hardness, whereas the changes in the mass decrement were minimal, which proved a high abrasive wear resistance.

  14. Osseointegration of KrF laser hydroxylapatite films on Ti6A14V alloy by mini-pigs: loaded osseointegration of dental implants

    Science.gov (United States)

    Dostalova, Tatjana; Jelinek, Miroslav; Himmlova, Lucia; Grivas, Christos

    1999-05-01

    Aim of study was to evaluate osseointegration of the KrF laser hydroxyapatite coated titanium alloy Ti6Al4V dental implants. For deposition KrF excimer laser in stainless- steel deposition chamber was used. Thickness of HA films were round 1 μm . Mini-pigs were used in this investigation. Implants were placed vertically into the lower jaw. After 14 weeks unloaded osseointegration the metal ceramic crowns were inserted. the experimental animals were sacrificed (1 year post insertion). The vertical position of implants was controlled with a radiograph. Microscopical sections were cut and ground. Sections were viewed using microscope with CCD camera. 1 year osseointegration in lower jaw confirmed by all implants presence of newly formed bone around the all implants. Laser-deposited coating the layer of fibrous connective tissue was seen only seldom. In the control group (titamium implant without cover) the fibrous connective tissue was seen between implant and newly formed bone.

  15. Machinability of an experimental Ti-Ag alloy in terms of tool life in a dental CAD/CAM system.

    Science.gov (United States)

    Inagaki, Ryoichi; Kikuchi, Masafumi; Takahashi, Masatoshi; Takada, Yukyo; Sasaki, Keiichi

    2015-01-01

    Titanium is difficult to machine because of its intrinsic properties. In a previous study, the machinability of titanium was improved by alloying with silver. This study aimed to evaluate the durability of tungsten carbide burs after the fabrication of frameworks using a Ti-20%Ag alloy and titanium with a computer-aided design and computer-aided manufacturing system. There was a significant difference in attrition area ratio between the two metals. Compared with titanium, the ratio of the area of attrition of machining burs was significantly lower for the experimental Ti-20%Ag alloy. The difference in the area of attrition for titanium and Ti-20%Ag became remarkable with increasing number of machining operations. The results show that the same burs can be used for a longer time with Ti-20%Ag than with pure titanium. Therefore, in terms of tool life, the machinability of the Ti-20%Ag alloy is superior to that of titanium.

  16. Ceramic Defects in Metal-Ceramic Fixed Dental Prostheses Made from Co-Cr and Au-Pt Alloys: A Retrospective Study.

    Science.gov (United States)

    Mikeli, Aikaterini; Boening, Klaus W; Lißke, Benjamin

    2015-01-01

    Ceramic defects in porcelain-fused-to-metal (PFM) restorations may depend on framework alloy type. This study assessed ceramic defects on cobalt-chromium- (Co-Cr-) and gold-platinum- (Au-Pt-) based PFM restorations. In this study, 147 Co-Cr-based and 168 Au-Pt-based PFM restorations inserted between 1998 and 2010 (139 patients) were examined for ceramic defects. Detected defects were assigned to three groups according to clinical defect relevance. Ceramic defect rates (Co-Cr-based: 12.9%; Au-Pt-based: 7.2%) revealed no significant difference but a strong statistical trend (U test, P = .082). Most defects were of little clinical relevance. Co-Cr PFM restorations may be at higher risk for ceramic defects compared to Au-Pt-based restorations.

  17. Microstructures and Mechanical Properties of Co-Cr Dental Alloys Fabricated by Three CAD/CAM-Based Processing Techniques

    Directory of Open Access Journals (Sweden)

    Hae Ri Kim

    2016-07-01

    Full Text Available The microstructures and mechanical properties of cobalt-chromium (Co-Cr alloys produced by three CAD/CAM-based processing techniques were investigated in comparison with those produced by the traditional casting technique. Four groups of disc- (microstructures or dumbbell- (mechanical properties specimens made of Co-Cr alloys were prepared using casting (CS, milling (ML, selective laser melting (SLM, and milling/post-sintering (ML/PS. For each technique, the corresponding commercial alloy material was used. The microstructures of the specimens were evaluated via X-ray diffractometry, optical and scanning electron microscopy with energy-dispersive X-ray spectroscopy, and electron backscattered diffraction pattern analysis. The mechanical properties were evaluated using a tensile test according to ISO 22674 (n = 6. The microstructure of the alloys was strongly influenced by the manufacturing processes. Overall, the SLM group showed superior mechanical properties, the ML/PS group being nearly comparable. The mechanical properties of the ML group were inferior to those of the CS group. The microstructures and mechanical properties of Co-Cr alloys were greatly dependent on the manufacturing technique as well as the chemical composition. The SLM and ML/PS techniques may be considered promising alternatives to the Co-Cr alloy casting process.

  18. SU-F-T-426: Measurement of Dose Enhancement Due to Backscatter From Modern Dental Materials

    International Nuclear Information System (INIS)

    Hurwitz, M; Margalit, D; Williams, C; Tso, T; Lee, S; Rosen, E

    2016-01-01

    Purpose: High-density materials used in dental restoration can cause significant localized dose enhancement due to electron backscatter in head-and-neck radiotherapy, increasing the risk of mucositis. The materials used in prosthetic dentistry have evolved in the last decades from metal alloys to ceramics. We aim to determine the dose enhancement caused by backscatter from currently-used dental materials. Methods: Measurements were performed for three different dental materials: lithium disilicate (Li 2 Si 2 O 5 ), zirconium dioxide (ZrO 2 ), and gold alloy. Small thin squares (2×2×0.15 cm 3 ) of the material were fabricated, and placed into a phantom composed of tissue-equivalent material. The phantom was irradiated with a single 6 MV photon field. A thin-window parallel-plate ion chamber was used to measure the dose at varying distances from the proximal interface between the material and the plastic. Results: The dose enhancement at the interface between the high-density and tissue-equivalent materials, relative to a homogeneous phantom, was 54% for the gold alloy, 31% for ZrO 2 , and 9% for Li 2 Si 2 O 5 . This enhancement decreased rapidly with distance from the interface, falling to 11%, 5%, and 0.5%, respectively, 2 mm from the interface. Comparisons with the modeling of this effect in treatment planning systems are performed. Conclusion: While dose enhancement due to dental restoration is smaller with ceramic materials than with metal alloys, it can still be significant. A spacer of about 2–3 mm would be effective in reducing this enhancement, even for metal alloys.

  19. SU-F-T-426: Measurement of Dose Enhancement Due to Backscatter From Modern Dental Materials

    Energy Technology Data Exchange (ETDEWEB)

    Hurwitz, M; Margalit, D; Williams, C [Brigham and Women’s Hospital / Harvard Medical School, Boston, MA (United States); Tso, T; Lee, S; Rosen, E [Harvard School of Dental Medicine, Boston, MA (United States)

    2016-06-15

    Purpose: High-density materials used in dental restoration can cause significant localized dose enhancement due to electron backscatter in head-and-neck radiotherapy, increasing the risk of mucositis. The materials used in prosthetic dentistry have evolved in the last decades from metal alloys to ceramics. We aim to determine the dose enhancement caused by backscatter from currently-used dental materials. Methods: Measurements were performed for three different dental materials: lithium disilicate (Li{sub 2}Si{sub 2}O{sub 5}), zirconium dioxide (ZrO{sub 2}), and gold alloy. Small thin squares (2×2×0.15 cm{sup 3}) of the material were fabricated, and placed into a phantom composed of tissue-equivalent material. The phantom was irradiated with a single 6 MV photon field. A thin-window parallel-plate ion chamber was used to measure the dose at varying distances from the proximal interface between the material and the plastic. Results: The dose enhancement at the interface between the high-density and tissue-equivalent materials, relative to a homogeneous phantom, was 54% for the gold alloy, 31% for ZrO{sub 2}, and 9% for Li{sub 2}Si{sub 2}O{sub 5}. This enhancement decreased rapidly with distance from the interface, falling to 11%, 5%, and 0.5%, respectively, 2 mm from the interface. Comparisons with the modeling of this effect in treatment planning systems are performed. Conclusion: While dose enhancement due to dental restoration is smaller with ceramic materials than with metal alloys, it can still be significant. A spacer of about 2–3 mm would be effective in reducing this enhancement, even for metal alloys.

  20. The effect of moisture on the shear bond strength of gold alloy rods bonded to enamel with a self-adhesive and a hydrophobic resin cement.

    Science.gov (United States)

    Dursun, Elisabeth; Wiechmann, Dirk; Attal, Jean-Pierre

    2010-06-01

    The aim of this in vitro study was to investigate the influence of enamel moisture on the shear bond strength (SBS) of a hydrophobic resin cement, Maximum Cure (MC), and a self-adhesive resin cement, Multilink Sprint (MLS), after etching of the enamel. Forty cylindrical gold alloy rods were used to simulate the Incognito lingual bracket system. They were bonded to the enamel of 40 human teeth embedded in self-cured acrylic resin. Twenty were bonded with MC (10 on dry and 10 on wet enamel) and 20 with MLS (10 on dry and 10 on wet enamel). The SBS of MC and MLS was determined in a universal testing machine and the site of bond failure was defined by the adhesive remnant index (ARI). A Kruskal-Wallis test was performed followed by Games-Howell post hoc pairwise comparison tests on the SBS results (P enamel, no significant differences between MC (58 +/- 5 MPa) and MLS (64 +/- 13 MPa) were noted. On wet enamel, the adherence of MC (6 +/- 8 MPa) and MLS (37 +/- 13 MPa) significantly decreased but to a lesser extent for MLS. The ARI scores corroborated these results. In conclusion, MC did not tolerate moisture. MLS was also affected but maintained sufficient adherence.

  1. Electrodeposition of gold-platinum alloy nanoparticles on ionic liquid-chitosan composite film and its application in fabricating an amperometric cholesterol biosensor.

    Science.gov (United States)

    Safavi, Afsaneh; Farjami, Fatemeh

    2011-01-15

    An electrodeposition method was applied to form gold-platinum (AuPt) alloy nanoparticles on the glassy carbon electrode (GCE) modified with a mixture of an ionic liquid (IL) and chitosan (Ch) (AuPt-Ch-IL/GCE). AuPt nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical methods. AuPt-Ch-IL/GCE electrocatalyzed the reduction of H(2)O(2) and thus was suitable for the preparation of biosensors. Cholesterol oxidase (ChOx) was then, immobilized on the surface of the electrode by cross-linking ChOx and chitosan through addition of glutaraldehyde (ChOx/AuPt-Ch-IL/GCE). The fabricated biosensor exhibited two wide linear ranges of responses to cholesterol in the concentration ranges of 0.05-6.2 mM and 6.2-11.2 mM. The sensitivity of the biosensor was 90.7 μA mM(-1) cm(-2) and the limit of detection was 10 μM of cholesterol. The response time was less than 7 s. The Michaelis-Menten constant (K(m)) was found as 0.24 mM. The effect of the addition of 1 mM ascorbic acid and glucose was tested on the amperometric response of 0.5 mM cholesterol and no change in response current of cholesterol was observed. Copyright © 2010 Elsevier B.V. All rights reserved.

  2. Precipitation of β′ phase and hardening in dental-casting Ag–20Pd–12Au–14.5Cu alloys subjected to aging treatments

    International Nuclear Information System (INIS)

    Kim, Yonghwan; Niinomi, Mitsuo; Hieda, Junko; Nakai, Masaaki; Cho, Ken; Fukui, Hisao

    2014-01-01

    The age-hardening behavior of the dental-casting Ag–20Pd–12Au–14.5Cu alloy subjected to aging treatment at around 673 K is well known, and this hardening has been widely employed in various applications. To date, the age-hardening of this alloy has been explained to attribute to the precipitation of a β phase, which is a B2-type ordered CuPd phase or PdCu x Zn 1−x phase. In this study, results obtained from microstructural observations using a transmission electron microscopy and a scanning transmission electron microscopy revealed that a fine L1 0 -type ordered β′ phase precipitated in the matrix and a coarse-structure region (consisting of Ag- and Cu-rich regions) appeared after aging treatment at 673 K and contributed to increase in hardness. The microstructure of the coarse β phase, which existed before aging treatment, did not change by aging treatment. Thus, it is concluded that the fine β′ phase precipitated by aging treatment contributed more to increase in hardness than the coarse-structure region and coarse β phase. - Highlights: • Hardness of Ag–20Pd–12Au–14.5Cu alloy increased significantly by aging treatment. • A fine β′ phase and a coarse structure region appeared after aging treatment. • The microstructure of a coarse β phase did not change by aging treatment. • It is considered that the fine β′ phase contributed most to age-hardening

  3. Ulex europaeus agglutinin-I binding to dental primary afferent projections in the spinal trigeminal complex combined with double immunolabeling of substance P and GABA elements using peroxidase and colloidal gold.

    Science.gov (United States)

    Matthews, M A; Hoffmann, K D; Hernandez, T V

    1989-01-01

    Ulex europaeus agglutinin I (UEA-I) is a plant lectin with an affinity for L-fucosyl residues in the chains of lactoseries oligosaccharides associated with medium- and smaller-diameter dorsal root ganglion neurons and their axonal processes. These enter Lissauer's tract and terminate within the superficial laminae of the spinal cord overlapping projections known to have a nociceptive function. This implies that the surface coatings of neuronal membranes may have a relationship with functional modalities. The present investigation further examined this concept by studying a neuronal projection with a nociceptive function to determine whether fucosyl-lactoseries residues were incorporated in its primary afferent terminals. Transganglionic transport of horseradish peroxidase (HRP) following injection into tooth pulp chambers was employed to demonstrate dental pulp terminals in the trigeminal spinal complex, while peroxidase and fluorescent tags were used concomitantly to stain for UEA-I. Double immunolabeling for substance P (SP) and gamma-aminobutyric acid (GABA) using peroxidase and colloidal gold allowed a comparison of the distribution of a known excitatory nociceptive transmitter with that of UEA-I binding in specific subnuclei. Synaptic interrelationships between UEA-I positive dental pulp primary afferent inputs and specific inhibitory terminals were also examined. SP immunoreactivity occurred in laminae I and outer lamina II (IIo) of subnucleus caudalis (Vc) and in the ventrolateral and lateral marginal region of the caudal half of subnucleus interpolaris (Vi), including the periobex area in which Vi is slightly overlapped on its lateral aspect by cellular elements of Vc. The adjacent interstitial nucleus (IN) also showed an intense immunoreactivity for this peptide antibody. UEA-I binding displayed a similar distribution pattern in both Vc and Vi, but extended into lamina IIi and the superficial part of Lamina III in Vc. Dental pulp terminals were found to

  4. Wear properties of dental ceramics and porcelains compared with human enamel.

    Science.gov (United States)

    D'Arcangelo, Camillo; Vanini, Lorenzo; Rondoni, Giuseppe D; De Angelis, Francesco

    2016-03-01

    Contemporary pressable and computer-aided design/manufacturing (CAD/CAM) ceramics exhibit good mechanical and esthetic properties. Their wear resistance compared with human enamel and traditional gold based alloys needs to be better investigated. The purpose of this in vitro study was to compare the 2-body wear resistance of human enamel, gold alloy, and 5 different dental ceramics, including a recently introduced zirconia-reinforced lithium silicate ceramic (Celtra Duo). Cylindrical specimens were fabricated from a Type III gold alloy (Aurocast8), 2 hot pressed ceramics (Imagine PressX, IPS e.max Press), 2 CAD/CAM ceramics (IPS e.max CAD, Celtra Duo), and a CAD/CAM feldspathic porcelain (Vitablocs Mark II) (n=10). Celtra Duo was tested both soon after grinding and after a subsequent glaze firing cycle. Ten flat human enamel specimens were used as the control group. All specimens were subjected to a 2-body wear test in a dual axis mastication simulator for 120000 loading cycles against yttria stabilized tetragonal zirconia polycrystal cusps. The wear resistance was analyzed by measuring the vertical substance loss (mm) and the volume loss (mm(3)). Antagonist wear (mm) was also recorded. Data were statistically analyzed with 1-way ANOVA tests (α=.05). The wear depth (0.223 mm) of gold alloy was the closest to that of human enamel (0.217 mm), with no significant difference (P>.05). The greatest wear was recorded on the milled Celtra Duo (wear depth=0.320 mm), which appeared significantly less wear resistant than gold alloy or human enamel (Pceramics did not statistically differ in comparison with the human enamel. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  5. Effects of surface treatments on bond strength of dental Ti-20Cr and Ti-10Zr alloys to porcelain

    International Nuclear Information System (INIS)

    Lin, Hsi-Chen; Wu, Shih-Ching; Ho, Wen-Fu; Huang, Ling-Hsiu; Hsu, Hsueh-Chuan

    2010-01-01

    The purpose of this study was to investigate the effect of surface treatments, including sandblasting and grinding, on the bond strength between a low-fusing porcelain and c.p. Ti, Ti-20Cr and Ti-10Zr alloys. The surface treatments were divided into 2 groups. Grinding surface treatment was applied to the first group, which served as the control, and sandblasting was applied to the second group. After treatment, low-fusing porcelain (Titankeramik) was fired onto the surface of the specimens. A universal testing machine was used to perform a 3-point bending test. The metal-ceramic interfaces were subjected to scanning electron microscopic analysis. Of the sandblasted samples, the debonding test showed that Ti-20Cr alloy had the strongest (31.50 MPa) titanium-ceramic bond (p < 005), followed by c.p. Ti (29.4 MPa) and Ti-10Zr (24.3 MPa). Of the grinded samples, Ti-20Cr alloy showed 27.3 MPa titanium-ceramic bond (p < 005), followed by c.p. Ti (14.3 MPa) and Ti-10Zr (failure). The SEM micrographs of the metal surface after debonding showed residual porcelain retained on all samples. On the whole, sandblasting surface treatment appears to have had a more beneficial effect on the Ti-ceramic bond strength than grinding surface treatment. Furthermore, surface treatment of Ti-20Cr with either grinding or sandblasting resulted in adequate bond strength, which exceeded the lower limit value in the ISO 9693 standard (25 MPa).

  6. Osseointegration of loaded dental implant with KrF laser hydroxylapatite films on Ti6Al4V alloy by minipigs

    Science.gov (United States)

    Dostalova, Tatjana; Himmlova, Lucia; Jelinek, Miroslav; Grivas, Christos

    2001-04-01

    This study was performed with the objective of evaluating osseointegration of titanium alloy Ti6Al4V dental implants coated with hydroxylapatite (HA) deposited by a KrF laser. For this a KrF excimer laser and stainless-steel deposition chamber were used. The thickness of the HA films was approximately 1 micrometers . IN this investigation experimental animals minipigs were used; the implants were placed vertically into the lower jaw. After 14 weeks of unloaded osseointegration, metal-ceramic crowns were inserted and, at the same time, fluorescent solution was injected into the experimental animals. Six months after insertion of crowns the animals were sacrificed. The vertical position of the implants was checked by a radiograph. Microscopic sections were cut and ground, and the sections were examined under polarized and fluorescent light using a microscope with a charge coupled device camera. The six month long osseointegration in the lower jaw has confirmed the presence of newly formed bone around all the implants. In the experimental group, which had a laser-deposited coating, the layer of fibrous connective tissue was seen only randomly. In the control group (titanium implant without a cover) the fibrous connective tissue between the implant and the newly formed bone was observed more frequently, but this difference was not significant.

  7. Dental Amalgam

    Science.gov (United States)

    ... Products and Medical Procedures Dental Devices Dental Amalgam Dental Amalgam Share Tweet Linkedin Pin it More sharing options Linkedin Pin it Email Print Dental amalgam is a dental filling material which is ...

  8. 21 CFR 872.3640 - Endosseous dental implant.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Endosseous dental implant. 872.3640 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3640 Endosseous dental implant. (a) Identification. An endosseous dental implant is a device made of a material such as titanium or titanium alloy, that...

  9. The effect of surface treatments on the microroughness of laser-sintered and vacuum-cast base metal alloys for dental prosthetic frameworks.

    Science.gov (United States)

    Castillo-Oyagüe, Raquel; Osorio, Raquel; Osorio, Estrella; Sánchez-Aguilera, Fátima; Toledano, Manuel

    2012-09-01

    This study aimed to evaluate the effect of four chemomechanical surface treatments on the surface average microroughness and profile of laser-sintered and vacuum-cast dental prosthetic structures. Square-shaped blocks (10 mm × 10 mm × 1.5 mm) were prepared as follows: (1) laser-sintered CoCr (L) (ST2724G); (2) cast Co-Cr (C) (Gemium-cn); and (3) cast Ni-Cr-Ti (T) (Tilite). Specimens of each alloy group were randomly divided into five subgroups (n = 10 each), depending on the conditioning method used: (1) no treatment (control); (2) sandblasting (125 μm Al₂O₃-particles); (3) silica coating (50 μm silica-modified Al₂O₃-particles); (4) oxidation; and (5) oxidation plus opacification. Subgroups 2 and 3 represent "inner" pretreatments proposed for ceramometal restorations to improve the metal surface area available for luting cements. Subgroups 4 and 5 are the "outer" pretreatments required for bonding the aesthetic veneering ceramics to the underlying metal frameworks. Average surface roughness (Ra/μm) was determined using a surface profilometer. Data were analyzed by two-way ANOVA and Student-Newman-Keuls tests (α = 0.05). Metal surface topography was SEM-analyzed. Despite the inner pretreatment applied, L samples resulted in the highest microroughness (P < 0.001), whereas sandblasting produced a surface-smoothing effect in cast specimens. After oxidation, a significant increase in surface roughness occurred in all groups compared with controls, L specimens being the roughest (P < 0.001). Opacification caused a flattening effect of all oxidized structures; all opacified groups resulting in similar microroughness. Laser sintering of Co-Cr enhances the roughness of metal structures, which may improve the frameworks' microretention of the cements, and of the opaquer before the copings are veneered with the aesthetic ceramics. Copyright © 2012 Wiley Periodicals, Inc.

  10. Corrosion behaviour and surface analysis of a Co-Cr and two Ni-Cr dental alloys before and after simulated porcelain firing.

    Science.gov (United States)

    Qiu, Jing; Yu, Wei-Qiang; Zhang, Fu-Qiang; Smales, Roger J; Zhang, Yi-Lin; Lu, Chun-Hui

    2011-02-01

    This study evaluated the corrosion behaviour and surface properties of a commercial cobalt-chromium (Co-Cr) alloy and two nickel-chromium (Ni-Cr) alloys [beryllium (Be)-free and Be-containing] before and after a simulated porcelain-firing process. Before porcelain firing, the microstructure, surface composition and hardness, electrochemical corrosion properties, and metal-ion release of as-cast alloy specimens were examined. After firing, similar alloy specimens were examined for the same properties. In both as-cast and fired conditions, the Co-Cr alloy (Wirobond C) showed significantly more resistance to corrosion than the two Ni-Cr alloys. After firing, the corrosion rate of the Be-free Ni-Cr alloy (Stellite N9) increased significantly, which corresponded to a reduction in the levels of Cr, molybdenum (Mo), and Ni in the surface oxides and to a reduction in the thickness of the surface oxide film. The corrosion properties of the Co-Cr alloy and the Be-containing Ni-Cr alloy (ChangPing) were not significantly affected by the firing process. Porcelain firing also changed the microstructure and microhardness values of the alloys, and there were increases in the release of Co and Ni ions, especially for Ni from the Be-free Ni-Cr alloy. Thus, the corrosion rate of the Be-free Ni-Cr alloy increased significantly after porcelain firing, whereas the firing process had little effect on the corrosion susceptibility of the Co-Cr alloy and the Be-containing Ni-Cr alloy. © 2011 Eur J Oral Sci.

  11. Toxicological risk assessment of elemental gold following oral exposure to sheets and nanoparticles – A review

    DEFF Research Database (Denmark)

    Hadrup, Niels; Sharma, Anoop Kumar; Poulsen, Morten

    2015-01-01

    Elemental gold is used as a food coloring agent and in dental fillings. In addition, gold nanoparticles are gaining increasing attention due to their potential use as inert carriers for medical purposes. Although elemental gold is considered to be inert, there is evidence to suggest the release....... In addition, gold released from dental restorations has been reported to increase the risk of developing gold hypersensitivity. Regarding genotoxicity, in vitro studies indicate that gold nanoparticles induce DNA damage in mammalian cells. In vivo, gold nanoparticles induce genotoxic effects in Drosophila...

  12. Gold prices

    OpenAIRE

    Joseph G. Haubrich

    1998-01-01

    The price of gold commands attention because it serves as an indicator of general price stability or inflation. But gold is also a commodity, used in jewelry and by industry, so demand and supply affect its pricing and need to be considered when gold is a factor in monetary policy decisions.

  13. Stage II recovery behavior of a series of ion-irradiated platinum (gold) alloys as studied by field-ion microscopy. [0. 10, 0. 62, and 4. 0 at. percent Au and pure Pt

    Energy Technology Data Exchange (ETDEWEB)

    Wei, C.Y.; Seidman, D.N.

    1976-11-01

    Direct and visible evidence was obtained for long-range migration of self-interstitial atoms (SIAs) in Stage II of three different ion-irradiated platinum (gold) alloys. Field-ion microscope (FIM) specimens of Pt--0.10, 0.62 and 4.0 at. percent Au alloys were irradiated in-situ with 30-keV W/sup +/ or Pt/sup +/ ions at a tip temperature of 35 to 41 K at 2 x 10/sup -9/ torr. Direct observation of the surfaces of the FIM specimens during isochronal warming experiments to 100 K showed that a flux of SIAs crossed the surfaces of the specimens between 40 to 100 K. The spectrum for each alloy consisted of two recovery peaks (substages II/sub B/ and II/sub C/). The results are explained on the basis of an impurity-delayed diffusion mechanism employing a two-level trapping model. The application of this diffusion model to the isochronal recovery spectra yielded a dissociation enthalpy (DELTAh/sub li-Au//sup diss/) and an effective diffusion coefficient for each substage; for substage II/sub B/ DELTAh/sub li-Au//sup diss/ (II/sub B/) = 0.15 eV and for substage II/sub C/ DELTAh/sub li-Au//sup diss/ (II/sub C/) = 0.24 eV. A series of detailed control experiments was also performed to show that the imaging electric field had not caused the observed long-range migration of SIAs and that the observed effects were not the result of surface artifacts. 14 figures, 6 tables.

  14. The effect of the solute on the structure, selected mechanical properties, and biocompatibility of Ti–Zr system alloys for dental applications

    Energy Technology Data Exchange (ETDEWEB)

    Correa, D.R.N.; Vicente, F.B. [UNESP — Univ. Estadual Paulista, Laboratório de Anelasticidade e Biomateriais, 17.033-360, Bauru, SP (Brazil); Donato, T.A.G.; Arana-Chavez, V.E. [USP — Universidade de São Paulo, Faculdade de Odontologia, Departamento de Biologia Oral e Biomateriais, 05.508-900, São Paulo, SP (Brazil); Buzalaf, M.A.R. [USP — Universidade de São Paulo, Faculdade de Odontologia de Bauru, Departamento de Ciências Biológicas, 17.012-901, Bauru, SP (Brazil); Grandini, C.R., E-mail: betog@fc.unesp.br [UNESP — Univ. Estadual Paulista, Laboratório de Anelasticidade e Biomateriais, 17.033-360, Bauru, SP (Brazil)

    2014-01-01

    New titanium alloys have been developed with the aim of utilizing materials with better properties for application as biomaterials, and Ti–Zr system alloys are among the more promising of these. In this paper, the influence of zirconium concentrations on the structure, microstructure, and selected mechanical properties of Ti–Zr alloys is analyzed. After melting and swaging, the samples were characterized through chemical analysis, density measurements, X-ray diffraction, optical microscopy, Vickers microhardness, and elasticity modulus. In-vitro cytotoxicity tests were performed on cultured osteogenic cells. The results showed the formation essentially of the α′ phase (with hcp structure) and microhardness values greater than cp-Ti. The elasticity modulus of the alloys was sensitive to the zirconium concentrations while remaining within the range of values of conventional titanium alloys. The alloys presented no cytotoxic effects on osteoblastic cells in the studied conditions. - Highlights: • Ti–Zr alloys for biomedical applications were developed. • Only α′ phase was observed. • Influence of zirconium concentrations on the properties of Ti–Zr alloys was analyzed. • No cytotoxic effects were observed.

  15. The effect of the solute on the structure, selected mechanical properties, and biocompatibility of Ti–Zr system alloys for dental applications

    International Nuclear Information System (INIS)

    Correa, D.R.N.; Vicente, F.B.; Donato, T.A.G.; Arana-Chavez, V.E.; Buzalaf, M.A.R.; Grandini, C.R.

    2014-01-01

    New titanium alloys have been developed with the aim of utilizing materials with better properties for application as biomaterials, and Ti–Zr system alloys are among the more promising of these. In this paper, the influence of zirconium concentrations on the structure, microstructure, and selected mechanical properties of Ti–Zr alloys is analyzed. After melting and swaging, the samples were characterized through chemical analysis, density measurements, X-ray diffraction, optical microscopy, Vickers microhardness, and elasticity modulus. In-vitro cytotoxicity tests were performed on cultured osteogenic cells. The results showed the formation essentially of the α′ phase (with hcp structure) and microhardness values greater than cp-Ti. The elasticity modulus of the alloys was sensitive to the zirconium concentrations while remaining within the range of values of conventional titanium alloys. The alloys presented no cytotoxic effects on osteoblastic cells in the studied conditions. - Highlights: • Ti–Zr alloys for biomedical applications were developed. • Only α′ phase was observed. • Influence of zirconium concentrations on the properties of Ti–Zr alloys was analyzed. • No cytotoxic effects were observed

  16. A concise overview of dental implantology

    Directory of Open Access Journals (Sweden)

    Olanrewaju Abdurrazaq Taiwo

    2015-01-01

    Full Text Available Background: The emergence of osseointegrated dental implants has resulted in several applications in diverse clinical settings. Hence, has contributed to the suitable replacement of missing teeth and the realization of an optimal facial appearance. This paper describes the benefits, applications, contraindications, and complications of dental implants in contemporary dental practice. Materials and Methods: An electronic search was undertaken in PUBMED without time restriction for appropriate English papers on dental implants based on a series of keywords in different combinations. Results: Fifty-eight acceptable, relevant articles were selected for review. The review identified the various components of dental implants, classification, and brands. It also looked at osseointegration and factors promoting and inimical to it. It also explored primary and secondary stability; and patients' selection for a dental implant. Complications of dental implants were also highlighted. Conclusion: With over 95% success rate, dental implants remain the gold standard for achieving aesthetic and functional oral rehabilitation.

  17. Gold analysis by the gamma absorption technique

    International Nuclear Information System (INIS)

    Kurtoglu, Arzu; Tugrul, A.B.

    2003-01-01

    Gold (Au) analyses are generally performed using destructive techniques. In this study, the Gamma Absorption Technique has been employed for gold analysis. A series of different gold alloys of known gold content were analysed and a calibration curve was obtained. This curve was then used for the analysis of unknown samples. Gold analyses can be made non-destructively, easily and quickly by the gamma absorption technique. The mass attenuation coefficients of the alloys were measured around the K-shell absorption edge of Au. Theoretical mass attenuation coefficient values were obtained using the WinXCom program and comparison of the experimental results with the theoretical values showed generally good and acceptable agreement

  18. The effect of remelting various combinations of new and used cobalt-chromium alloy on the mechanical properties and microstructure of the alloy

    Directory of Open Access Journals (Sweden)

    Sharad Gupta

    2012-01-01

    Conclusion: Repeated remelting of base metal alloy for dental casting without addition of new alloy can affect the mechanical properties of the alloy. Microstructure analysis shows deterioration upon remelting. However, the addition of 25% and 50% (by weight of new alloy to the remelted alloy can bring about improvement both in mechanical properties and in microstructure.

  19. Hallmarking as an essential need of gold industry

    International Nuclear Information System (INIS)

    Mahmood, K.; Alam, S.; Ahmed, T.

    2006-01-01

    As gold is a soft metal, for Jewellery making it is alloyed with Silver or Copper so that its strength may increase. Other main alloying elements include; Zinc, Cadmium and Nickel. These alloying elements help to reduce cost, improve appearance and to improve chemical properties of gold. The percentage of alloying elements determines the caratages of gold. The gold Jewellery sold in local market is often under-carated. In order to improve the quality of product sold, complete quality assessment of gold should be done. A complete quality assessment includes both Assaying and Hallmarking. Assaying is the analysis of an individual sample of gold from a customer to find out it's composition and Hallmarking refers to physically marking: a piece of Jewellery according to specific laws to certify the purity of metal. In this paper we have assessed and compared the quality of locally manufactured gold ornaments and its alloying components with international market as well as standards of gold and its alloys. And as Hallmarking is one of the main strategic initiatives to improve the quality of product sold for domestic and export consumption, this paper discusses the necessary steps leading to Hallmarking. We have used micro-XRF spectrometer for assaying and Laser Engraving machine for the purpose of Hallmarking. (author)

  20. Shape memory effect and super elasticity. Its dental applications.

    Science.gov (United States)

    Kotian, R

    2001-01-01

    The shape memory alloys are quite fascinating materials characterized by a shape memory effect and super elasticity which ordinary metals do not have. This unique behaviour was first found in a Au-47.5 at % Cd alloy in 1951, and was published in 1963 by the discovery of Ti-Ni alloy. Shape memory alloys now being practically used as new functional alloys for various dental and medical applications.

  1. Atoms diffusion-induced phase engineering of platinum-gold alloy nanocrystals with high electrocatalytic performance for the formic acid oxidation reaction.

    Science.gov (United States)

    Li, Fu-Min; Kang, Yong-Qiang; Liu, Hui-Min; Zhai, Ya-Nan; Hu, Man-Cheng; Chen, Yu

    2018-03-15

    Bimetallic noble metal nanocrystals have been widely applied in many fields, which generally are synthesized by the wet-chemistry reduction method. This work presents a purposely designed atoms diffusion induced phase engineering of PtAu alloy nanocrystals on platy Au substrate (PtAu-on-Au nanostructures) through simple hydrothermal treatment. Benefitting from the synergistic effects of component and structure, PtAu-on-Au nanostructures remarkably enhance the dehydrogenation pathway of the formic acid oxidation reaction (FAOR), and thus exhibit much higher FAOR activity and durability compared with Pt nanocrystals on platy Au substrate (Pt-on-Au nanostructures) and commercial Pd black due to an excellent stability of platy Au substrate and a high oxidation resistance of PtAu alloy nanocrystals. The atoms diffusion-induced phase engineering demonstrated in this work builds a bridge between the traditional metallurgy and modern nanotechnologies, which also provides some useful insights in developing noble metals based alloyed nanostructures for the energy and environmental applications. Copyright © 2017 Elsevier Inc. All rights reserved.

  2. Gold alloys: study of the microstructural, mechanical characteristics and final optimization of production parameters for the realization of full and cable pipe chains

    OpenAIRE

    Cason, Claudio

    2017-01-01

    The gold market is one of the major world markets and the Italian companies place the country as one of the major players in this sector. However, the production in these companies is mostly based on the use of artisan skills, without investing in research and studies about the production processes of these materials. In fact, often the process depends on a "craft" way of working, in which the technical and scientific knowledge are dictated more by experience than by a systematic scientific a...

  3. [Cervical adaptation of complete cast crowns of various metal alloys, with and without die spacers].

    Science.gov (United States)

    Stephano, C B; Roselino, R F; Roselino, R B; Campos, G M

    1989-01-01

    A metallic replica from a dental preparation for crown was used to make 8 class-IV stone dies. The wax patterns for the casting of the crowns were obtained in two conditions: a) from the stone die with no spacer; and b) from the stone die with an acrylic spacer. Thus, 64 metallic crowns were casted, using 4 different alloys: DURACAST (Cu-Al), NICROCAST (Ni-Cr) and DURABOND (Ni-Cr), and gold. The casted crowns were fitted in the metallic replica and measured as to the cervical discrepance of fitting. The results showed that the use of die spacers decreases the clinical discrepancies of fitting of the casted crowns (in a statistically significant level), no matter the metallic alloy employed.

  4. Effects of TiN coating on the corrosion of nanostructured Ti-30Ta-xZr alloys for dental implants

    Science.gov (United States)

    Kim, Won-Gi; Choe, Han-Cheol

    2012-01-01

    Electrochemical characteristics of a titanium nitride (TiN)-coated/nanotube-formed Ti-Ta-Zr alloy for biomaterials have been researched by using the magnetic sputter and electrochemical methods. Ti-30Ta-xZr (x = 3, 7 and 15 wt%) alloys were prepared by arc melting and heat treated for 24 h at 1000 °C in an argon atmosphere and then water quenching. The formation of oxide nanotubes was achieved by anodizing a Ti-30Ta-xZr alloy in H3PO4 electrolytes containing small amounts of fluoride ions at room temperature. Anodization was carried out using a scanning potentiostat, and all experiments were conducted at room temperature. The microstructure and morphology of nanotube arrays were characterized by optical microscopy (OM), field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The TiN coatings were obtained by the radio-frequency (RF) magnetron sputtering technique. The depositions were performed from pure Ti targets on Ti-30Ta-xZr alloys substrates. The corrosion properties of the specimens were examined using potentiodynamic test in a 0.9% NaCl solution by using potentiostat. The microstructures of Ti-30Ta-xZr alloys were changed from an equiaxed to a needle-like structure with increasing Zr content. The interspace between the nanotubes was approximately 20, 80 and 200 nm for Zr contents of 3, 7 and 15 wt%, respectively. The corrosion resistance of the TiN-coated on the anodized Ti-30Ta-xZr alloys was higher than that of the untreated Ti alloys, indicating a better protective effect.

  5. Effects of Ar or O2 Gas Bubbling for Shape, Size, and Composition Changes in Silver-Gold Alloy Nanoparticles Prepared from Galvanic Replacement Reaction

    Directory of Open Access Journals (Sweden)

    Md. Jahangir Alam

    2013-01-01

    Full Text Available The galvanic replacement reaction between silver nanostructures and AuCl4- solution has recently been demonstrated as a versatile method for generating metal nanostructures with hollow interiors. Here we describe the results of a systematic study detailing the morphological, structural, compositional, and spectral changes involved in such a heterogeneous reaction on the nanoscale. Effects of Ar or O2 gas bubbling for the formation of Ag-Au alloy nanoparticles by the galvanic replacement between spherical Ag nanoparticles and AuCl4- especially were studied in ethylene glycol (EG at 150°C. The shape, size, and composition changes occur rapidly under O2 bubbling in comparison with those under Ar bubbling. The major product after 60 min heating under Ar gas bubbling was perforated Ag-Au alloy particles formed by the replacement reaction and the minor product was ribbon-type particles produced from splitting off some perforated particles. On the other hand, the major product after 60 min heating under O2 gas bubbling was ribbon-type particles. In addition, small spherical Ag particles are produced. They are formed through rereduction of Ag+ ions released from the replacement reaction and oxidative etching of Ag nanoparticles by O2/Cl− in EG.

  6. Gold Returns

    OpenAIRE

    Robert J. Barro; Sanjay P. Misra

    2013-01-01

    From 1836 to 2011, the average real rate of price change for gold in the United States is 1.1% per year and the standard deviation is 13.1%, implying a one-standard-deviation confidence band for the mean of (0.1%, 2.1%). The covariances of gold's real rate of price change with consumption and GDP growth rates are small and statistically insignificantly different from zero. These negligible covariances suggest that gold's expected real rate of return--which includes an unobserved dividend yiel...

  7. 21 CFR 872.3580 - Preformed gold denture tooth.

    Science.gov (United States)

    2010-04-01

    ... tooth in a fixed or removable partial denture. (b) Classification. Class I (general controls). The... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Preformed gold denture tooth. 872.3580 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3580 Preformed gold denture tooth. (a...

  8. Gold monetization and gold discipline

    OpenAIRE

    Robert P. Flood; Peter M. Garber

    1981-01-01

    The paper is a study of the price level and relative price effects of a policy to monetize gold and fix its price at a given future time and at the then prevailing nominal price. Price movements are analyzed both during the transition to the gold standard and during the post-monetization period. The paper also explores the adjustments to fiat money which are necessary to ensure that this type of gold monetization is non-inflationary. Finally, some conditions which produce a run on the governm...

  9. Osseointegration of loaded dental implant with KrF laser hydroxylapatite films on Ti6Al4V alloy by minipigs

    Czech Academy of Sciences Publication Activity Database

    Dostálová, T.; Jelínek, Miroslav; Grivas, C.

    2001-01-01

    Roč. 6, č. 2 (2001), s. 239-243 ISSN 1083-3668 Institutional research plan: CEZ:AV0Z1010914 Keywords : osseointegration * titanium alloy * KrF laser Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.292, year: 2001

  10. About Dental Amalgam Fillings

    Science.gov (United States)

    ... and Medical Procedures Dental Devices Dental Amalgam About Dental Amalgam Fillings Share Tweet Linkedin Pin it More ... should I have my fillings removed? What is dental amalgam? Dental amalgam is a dental filling material ...

  11. Dental cavities

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/001055.htm Dental cavities To use the sharing features on this page, please enable JavaScript. Dental cavities are holes (or structural damage) in the ...

  12. Dental sealants

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/patientinstructions/000779.htm Dental sealants To use the sharing features on this ... case a sealant needs to be replaced. How Dental Sealants are Applied Your dentist applies sealants on ...

  13. Influence of NiTi alloy on the root canal shaping capabilities of the ProTaper Universal and ProTaper Gold rotary instrument systems

    Directory of Open Access Journals (Sweden)

    Jussaro Alves DUQUE

    Full Text Available Abstract Objective This study aimed to evaluate the influence of the NiTi wire in Conventional NiTi (ProTaper Universal PTU and Controlled Memory NiTi (ProTaper Gold PTG instrument systems on the quality of root canal preparation. Material and Methods Twelve mandibular molars with separate mesial canals were scanned using a high-definition microcomputed tomography system. The PTU and PTG instruments were used to shape twelve mesial canals each. The canals were scanned after preparation with F2 and F3 instruments of the PTU and PTG systems. The analyzed parameters included the remaining dentin thickness at the apical and cervical levels, root canal volume and untouched canal walls. Data was analyzed for statistical significance by the Friedman and Dunn’s tests. For the comparison of data between groups, the Mann-Whitney test was used. Results In the pre-operative analysis, there were no statistically significant differences between the groups in terms of the area and volume of root canals (P>.05. There was also no statistically significant difference between the systems with respect to root canal volume after use of the F2 and F3 instruments. There was no statistical difference in the dentin thickness at the first apical level between, before and after instrumentation for both systems. At the 3 cervical levels, the PTG maintained centralization of the preparation on the transition between the F2 and F3 instruments, which did not occur with the PTU. Conclusion The Conventional NiTi (PTU and Controlled Memory NiTi (PTG instruments displayed comparable capabilities for shaping the straight mesial root canals of mandibular molars, although the PTG was better than the PTU at maintaining the centralization of the shape in the cervical portion.

  14. Influence of NiTi alloy on the root canal shaping capabilities of the ProTaper Universal and ProTaper Gold rotary instrument systems

    Science.gov (United States)

    DUQUE, Jussaro Alves; VIVAN, Rodrigo Ricci; CAVENAGO, Bruno Cavalini; AMOROSO-SILVA, Pablo Andrés; BERNARDES, Ricardo Affonso; de VASCONCELOS, Bruno Carvalho; DUARTE, Marco Antonio Hungaro

    2017-01-01

    Abstract Objective This study aimed to evaluate the influence of the NiTi wire in Conventional NiTi (ProTaper Universal PTU) and Controlled Memory NiTi (ProTaper Gold PTG) instrument systems on the quality of root canal preparation. Material and Methods Twelve mandibular molars with separate mesial canals were scanned using a high-definition microcomputed tomography system. The PTU and PTG instruments were used to shape twelve mesial canals each. The canals were scanned after preparation with F2 and F3 instruments of the PTU and PTG systems. The analyzed parameters included the remaining dentin thickness at the apical and cervical levels, root canal volume and untouched canal walls. Data was analyzed for statistical significance by the Friedman and Dunn’s tests. For the comparison of data between groups, the Mann-Whitney test was used. Results In the pre-operative analysis, there were no statistically significant differences between the groups in terms of the area and volume of root canals (P>.05). There was also no statistically significant difference between the systems with respect to root canal volume after use of the F2 and F3 instruments. There was no statistical difference in the dentin thickness at the first apical level between, before and after instrumentation for both systems. At the 3 cervical levels, the PTG maintained centralization of the preparation on the transition between the F2 and F3 instruments, which did not occur with the PTU. Conclusion The Conventional NiTi (PTU) and Controlled Memory NiTi (PTG) instruments displayed comparable capabilities for shaping the straight mesial root canals of mandibular molars, although the PTG was better than the PTU at maintaining the centralization of the shape in the cervical portion. PMID:28198973

  15. Dental negligence.

    Science.gov (United States)

    Tay, C S

    2000-02-01

    Medical and dental errors and negligence are again in the spotlight in recent news report. Dead because of doctor's bad handwriting Prescribing drug overdoses Germ-infested soap pumps--infections in hospitals This articles explains dental negligence including dental duty of care and the standard of care expected of dentists in relation to the Bolam principle.

  16. In vitro evaluation of cytotoxicity and corrosion behavior of commercially pure titanium and Ti-6Al-4V alloy for dental implants.

    Science.gov (United States)

    Chandar, Sanchitha; Kotian, Ravindra; Madhyastha, Prashanthi; Kabekkodu, Shama Prasada; Rao, Padmalatha

    2017-01-01

    The aim of this study was to investigate the cytotoxicity in human gingival fibroblast by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and corrosion behavior by potentiodynamic polarization technique of commercially pure titanium (Ti 12) and its alloy Ti-6Al-4V (Ti 31). In the present in vitro study, cytotoxicity of Ti 12 and Ti 31 in human gingival fibroblast by MTT assay and the corrosion behavior by potentiodynamic polarization technique in aqueous solutions of 0.1 N NaCl, 0.1 N KCl, and artificial saliva with and without NaF were studied. The independent t -test within materials and paired t-test with time interval showed higher cell viability for Ti 12 compared to Ti 31. Over a period, cell viability found to stabilize in both Ti 12 and Ti 31. The effects of ions of Ti and alloying elements aluminum and vanadium on the cell viability were found with incubation period of cells on samples to 72 h. The electrochemical behavior of Ti 12 and Ti 31 in different experimental solutions showed a general tendency for the immersion potential to shift steadily toward nobler values indicated formation of TiO 2 and additional metal oxides. The multiphase alloy Ti-6Al-4V showed more surface pitting. The commercially pure Ti showed better cell viability compared to Ti 31. Less cell viability in Ti 31 is because of the presence of aluminum and vanadium. A significant decrease in cytotoxicity due to the formation of TiO 2 over a period of time was observed both in Ti 12 and Ti 31. The electrochemical behavior of Ti 12 and Ti 31 in different experimental solutions showed a general tendency for the immersion potential to shift steadily toward nobler values indicated formation of TiO2 and additional metal oxides. Ti 31 alloy showed surface pitting because of its multiphase structure.

  17. Study of the microstructural and mechanical properties of titanium-niobium-zirconium based alloys processed with hydrogen and powder metallurgy for use in dental implants

    International Nuclear Information System (INIS)

    Duvaizem, Jose Helio

    2009-01-01

    Hydrogen has been used as pulverization agent in alloys based on rare earth and transition metals due to its extremely high diffusion rate even on low temperatures. Such materials are used on hydrogen storage dispositives, generation of electricity or magnetic fields, and are produced by a process which the first step is the transformation of the alloy in fine powder by miling. Besides those, hydrogenium is also being used to obtain alloys based on titanium - niobium - zirconium in the pulverization. Powder metallurgy is utilized on the production of these alloys, making it possible to obtain structures with porous surface as result, requirement for its application as biomaterials. Other advantages of powder metallurgy usage include better surface finish and better microstructural homogeneity. In this work samples were prepared in the Ti-13Nb-13Zr composition. The hydrogenation was performed at 700 degree C, 600 degree C, and 500 degree C for titanium, niobium and zirconium respectively. After hydrogenation, the milling stage was carried out on high energy planetary ball milling with 200rpm during 90 minutes, and also in conventional ball milling for 30 hours. Samples were pressed in uniaxial press, followed by isostatic cold press, and then sintered at 1150 degree C for 7-13 hours. Microstructural properties of the samples were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and x-ray diffraction. Mechanical and structural properties determined were density, microhardness and moduli of elasticity. The sample sintered at 1150 degree C for 7h, hydrogenated using 10.000 mbar and produced by milling on high energy planetary ball milling presented the best mechanical properties and microstructural homogeneity. (author)

  18. Red gold analysis by using gamma absorption tchnique

    International Nuclear Information System (INIS)

    Kurtoglu, A.; Tugrul, A.B.

    2001-01-01

    Gold is a valuable metal and also preferable materials for antique artefacts and some advanced technology products. It can be offered for the analysis of the gold as namely; neutron activation analysis, X-ray florescence technique, Auger spectroscopy, atomic absorption and wet chemistry. Some limitations exist in practice for these techniques, especially in the points of financial and applicability concepts. An advanced a practical technique is gamma absorption technique for the gold alloys. This technique is based on discontinuities in the absorption coefficient for gamma rays at corresponding to the electronic binding energies of the absorber. If irradiation is occurred at gamma absorption energy for gold, absorption rates of the red gold changes via the gold amounts in the alloy. Red gold is a basic and generally preferable alloy that has copper and silver additional of the gold in it. The gold amount defines as carat of the gold. Experimental studies were observed for four different carats of red gold; these are 8, 14, 18 and 22 carats. K-edge energy level of the gold is on 80 keV energy. So, Ba-133 radioisotope is preferred as the gamma source because of it has gamma energy peak in that energy. Experiments observed in the same geometry for all samples. NaI(Tl) detector and multichannel analyser were used for measurements. As a result of the experiments, the calibration curves could be drawn for red gold. For examine this curve, unknown samples are measured in experimental set and it can be determined the carat of it with the acceptability. So the red gold analysis can be observed non-destructively, easily and quickly by using the gamma absorption technique

  19. Gold Museum

    OpenAIRE

    Efraín Sánchez Cabra

    2003-01-01

    On 22 december 1939, the Banco de la República, the Central Bank of Colombia, purchased a 23.5 centimetres high pre-Columbian gold arte fact weighing 777·7 grams that was to become the Gold M useum's foundation stone. Described as a Quimbaya poporo, it is a masterpiece of pre-Hispanic goldwork, an object of beauty whose brightly burnished body and neck, crowned with four sphere-like or naments, rest on an exquisite cast metal tiligree base and which seems to ftoat in a space of its own. The b...

  20. New Leaf Gilding Alloys: Physico-Chemistry, Colour, Mechanical Behavior

    OpenAIRE

    Darque-Ceretti , Evelyne; Aucouturier , Marc; Felder , Eric; Burr , Alain; Robcis , Dominique; Thomas , Caroline

    2015-01-01

    International audience; In the frame of a systematic investigation on leaf gilding history and processes, in a research program intending to propose gold leaf alloys specially devoted to restoration, new gold alloys containing low concentration additions of In or Pd were designed and leaves were elaborated in collaboration with the goldbeater Dauvet. The influence of those elements on the colour change induced by alloying was obtained by colorimetry. The microstructural and metallurgical prop...

  1. CONCURRENT CONTACT SENSITIZATION TO METALS IN DENTAL EXPOSURES

    Directory of Open Access Journals (Sweden)

    Maya Lyapina

    2018-03-01

    Full Text Available Purpose: Sensitization to metals is a significant problem for both dental patients treated with dental materials and for dental professionals in occupational exposures. The purpose of the present study was to evaluate the incidence of concurrent contact sensitization to relevant for dental practice metals among students of dental medicine, students from dental technician school, dental professionals and patients. Material and Methods: A total of 128 participants were included in the study. All of them were patch-tested with nickel, cobalt, copper, potassium dichromate, palladium, aluminium, gold and tin. The results were subject to statistical analysis (p < 0.05. Results: For the whole studied population, potassium dichromate exhibited concomitant reactivity most often; copper and tin also often manifested co-reactivity. For the groups, exposed in dental practice, potassium dichromate and tin were outlined as the most often co-reacting metal allergens, but statistical significance concerning the co-sensitization to copper and the other metals was established only for aluminium. An increased incidence and OR for concomitant sensitization to cobalt and nickel was established in the group of dental students; to copper and nickel - in the control group; to palladium and nickel - in the group of dental professionals, the group of students of dental medicine and in the control group; to potassium dichromate and cobalt - in the group of dental students; to copper and palladium - in the control group of dental patients; to potassium dichromate and copper - in the group of dental professionals; to copper and aluminum - in the groups of students from dental technician school and of dental professionals; to copper and gold - in the groups of dental professionals and in the group of dental patients; to potassium dichromate and aluminum - in the group of dental professionals; to potassium dichromate and gold - in the group of dental professionals, and to

  2. 21 CFR 872.3080 - Mercury and alloy dispenser.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Mercury and alloy dispenser. 872.3080 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3080 Mercury and alloy dispenser. (a) Identification. A mercury and alloy dispenser is a device with a spring-activated valve intended to measure and...

  3. Green Gold

    International Nuclear Information System (INIS)

    Salamandra Martinez, Carlos

    2004-01-01

    The main purpose of this work is to offer a general panoramic of the processes or experiences pilot that are carried out in the Project Green Gold, as strategy of environmental sustainability and organizational invigoration in Choco, especially in the 12 communities of the municipalities of Tado and Condoto. It is also sought to offer a minimum of information on the techniques of handmade production and to show the possibilities to carry out in a rational way the use and use of the natural resources. The Project Green Gold is carried out by the Corporation Green Gold (COV) and co-financed with resources of international and national character, the intervention of the financial resources it achievement mainly for the use of clean processes in the extraction stages and metals benefit. The project is centered primarily in the absence of use of products or toxic substances as the mercury, fair trade, organizational invigoration, execution of 11 approaches and certification of the metals Gold and Platinum. The COV, it has come executing the proposal from the year 2001 with the premise of contributing to the balance between the rational exploitation of the natural resources and the conservation of the environment in the Choco. In the project they are used technical handmade characteristic of the region framed inside the mining activity and production activities are diversified in the productive family units. Those producing with the support of entities of juridical character, specify the necessary game rules for the extraction and products commercialization

  4. In vitro evaluation of cytotoxicity and corrosion behavior of commercially pure titanium and Ti-6Al-4V alloy for dental implants

    Directory of Open Access Journals (Sweden)

    Sanchitha Chandar

    2017-01-01

    Conclusion: The commercially pure Ti showed better cell viability compared to Ti 31. Less cell viability in Ti 31 is because of the presence of aluminum and vanadium. A significant decrease in cytotoxicity due to the formation of TiO2over a period of time was observed both in Ti 12 and Ti 31. The electrochemical behavior of Ti 12 and Ti 31 in different experimental solutions showed a general tendency for the immersion potential to shift steadily toward nobler values indicated formation of TiO2 and additional metal oxides. Ti 31 alloy showed surface pitting because of its multiphase structure.

  5. Fuel powder production from ductile uranium alloys

    International Nuclear Information System (INIS)

    Clark, C.R.; Meyer, M.K.

    1998-01-01

    Metallic uranium alloys are candidate materials for use as the fuel phase in very-high-density LEU dispersion fuels. These ductile alloys cannot be converted to powder form by the processes routinely used for oxides or intermetallics. Three methods of powder production from uranium alloys have been investigated within the US-RERTR program. These processes are grinding, cryogenic milling, and hydride-dehydride. In addition, a gas atomization process was investigated using gold as a surrogate for uranium. (author)

  6. Determination of gold in gold ores

    International Nuclear Information System (INIS)

    Keedy, C.R.; Parson, L.; Shen, J.

    1989-01-01

    The gold content of placer gold flakes and gold bearing ores was determined by instrumental and radiochemical neutron activation analysis, respectively. It was discovered that significant errors result in the instrumental method for gold flakes as small as 10 mg due to sample self-absorption of neutrons during irradiation. Reliable results were obtained for both ore samples and gold flakes by dissolving the samples in aqua regia prior to irradiation. (author) 7 refs.; 3 tabs

  7. High temperature creep of single crystals of gold, silver and solid solution gold silver 50-50

    International Nuclear Information System (INIS)

    Dorizzi, Paul

    1973-01-01

    We have studied in compression creep along a direction, single crystals of gold, silver and a 50-50 gold-silver solid solution. The experiments were made at temperatures above 0.7 Tf. We have shown that under these conditions and for these three metals a new slip system is operating: the deformation is due to the slip of dislocations having a 1/2 burgers vector on the {110} planes. For gold the activation energy for creep is equal to the self-diffusion energy. We found the same result for silver when the contribution of divacancies to the self-diffusion energy is taken into account. For the alloy the activation energy for creep is very close to the self-diffusion energy of gold in a 50-50 gold-silver alloy, gold being the slower diffusing species in the alloy. The curves giving the creep rate versus the stress can be fitted with the following laws: ε 0 = σ 5 for gold; ε 0 = σ 2,2 for silver and ε 0 = σ 2,5 for the alloy. The dislocation substructure was studied using the crystalline contrast given by the electron microprobe. This new method gives images which are very sensitive to the sub-grains misorientation. The substructure is made of parallelepipedic cells divided by tilt boundaries that are perpendicular to the {110} slip planes. (author) [fr

  8. Structural characterization and electrochemical behavior of 45S5 bioglass coating on Ti6Al4V alloy for dental applications

    Energy Technology Data Exchange (ETDEWEB)

    López, M.M. Machado, E-mail: machadolopez23@gmail.com [Instituto de Investigaciones Metalúrgicas, Universidad Michoacana de San Nicolás de Hidalgo, C.U. Edificio “U”, C.P. 58000, Morelia, Michoacán, México (Mexico); Fauré, J. [Laboratoire Ingénierie et Sciences des Matériaux (LISM EA 4695) - Université de Reims Champagne-Ardenne, 21 rue Clément Ader, Reims, BP 138 Cedex 02, 51685 France (France); Cabrera, M.I. Espitia [Facultad de ingeniería Química, Universidad Michoacana de San Nicolás de Hidalgo, C.U. Edificio “D”, C.P. 58000, Morelia, Michoacán, México (Mexico); García, M.E. Contreras, E-mail: eucontre@umich.mx [Instituto de Investigaciones Metalúrgicas, Universidad Michoacana de San Nicolás de Hidalgo, C.U. Edificio “U”, C.P. 58000, Morelia, Michoacán, México (Mexico)

    2016-04-15

    Graphical abstract: - Highlights: • Bioglass 45S5 nanostructured films were obtained by colloidal electrophoretic deposition (CEDP) method, proposed in this work, on Ti6Al4 V substrates. • Ti6Al4 V corrosion resistance in Hank's solution was increased with bioglass 45S5 coating. • Crystalline phases of 45S5 bioglass xerogels were obtained and characterized by XRD. • The model of chemical anchoring between Ti6Al4 V and bioglass 45S5 is proposed. - Abstract: In the present work, 45S5 bioglass coatings were deposited on the Ti6Al4 V alloy substrate through the cathodic colloidal electrophoretic deposition process (CEDP) proposed in this work. The coatings were thermally treated at temperatures of 500, 600, 700, and 800 °C for 2 h, and their structure was characterized by FESEM and DRX. Nanostructure and phase evolution of the coatings and xerogels was followed as a function of temperature. The corrosion resistance of the Ti6Al4 V alloy and the 45S5/Ti6Al4 V coating was studied by means of Tafel extrapolation in Hank's solution, at 37 °C, simulating the conditions inside the mouth. The 45S5 bioglass coatings displayed an amorphous nanostructure at lower temperatures, and partial crystallization at higher temperatures. An increase in the corrosion resistance was observed in the 45S5/Ti6l4 V coating treated at 700 °C because it reduced the i{sub corr}, and there was a change in the E{sub corr} towards more noble values. A model of the chemical anchorage of the 45S5 bioglass coating on Ti6Al4 V was proposed.

  9. Gold and not so real gold in Medieval treatises

    Directory of Open Access Journals (Sweden)

    Srebrenka Bogovic-Zeskoski

    2015-01-01

    Full Text Available The aim of this study is to evidence diverse materials and processes used by artisans (and alchemists required to synthesize a visually viable replacement for gold. The emphasis of the research is upon the production of mosaic gold or porporina, a pigment that has survived into modern times, which was used as ink and as paint. Base metals, mostly tin, but also alloys were used both into foils coated with glazes and varnishes and as pigment. The research focuses upon recipes documented in treatises dating from Antiquity to the late Medieval period (ca. 1500 and an attempt is made to answer two questions. In the first place, why was there a need for a surrogate? Secondly, why are there so few tangible examples detected on surviving artifacts? In conclusion, an argument is offered pointing out that, although much can be learned by scientific examination of artifacts, textual analysis is equally important and necessary to unravel mysteries of ancient technologies

  10. Byzantine gold coins and jewellery

    International Nuclear Information System (INIS)

    Oddy, A.; La Niece, S.

    1986-01-01

    The article deals with the dating of Byzantine gold coinage. The results of such a study are of fundamental importance for the study of the economic history of the later Byzantine Empire and they are also of importance for the historian of technology when studying the composition of the contemporary Byzantine jewellery. Although Carbon-14 dating cannot be used as a method af dating, historians can still benefit from the analysis of the alloy of which the antiquity is made, as this is sometimes characteristic of the period in which it was used. A number of pieces of Byzantine jewellery has been analysed by x-ray fluorescence analysis, after first gently abrading a small area of the surface of the gold with the carborundum paper in an inconspicious position on the back or side of the object. A table is given on the results of this analysis

  11. Potential hazards and artifacts of ferromagnetic and nonferromagnetic surgical and dental materials and devices in nuclear magnetic resonance imaging

    International Nuclear Information System (INIS)

    New, P.F.J.; Rosen, B.R.; Brady, T.J.

    1983-01-01

    The risks to patients with metal surgical implants who are undergoing nuclear magnetic resonance (NMR) imaging and the artifacts caused by such implants were studied. Twenty-one aneurysm and other hemostatic clips and a variety of other materials (e.g., dental amalgam, 14 karat gold) were used. Longitudinal forces and torques were found to be exerted upon 16 of the 21 clips. With five aneurysm clips, forces and torques sufficient to produce risk of hemorrhage from dislocation of the clip from the vessel or aneurysm, or cerebral injury by clip displacement without dislodgement were identified. The induced ferromagnetism was shown to be related to the composition of the alloys from which the clips were manufactured. Clips with 10-14% nickel are evidently without sufficient induced ferromagnetism to cause hazard. The extent of NMR imaging artifacts was greater for materials with measurable ferromagnetic properties, but metals without measurable ferromagnetism in our tests also resulted in significant artifacts. Dental amalgam and 14 karat gold produced no imaging artifacts, but stainless steels in dentures and orthodontic braces produced extensive artifacts in the facial region

  12. Direct determination of thermodynamic activities of gold in the systems gold-palladium and gold-silver-palladium

    International Nuclear Information System (INIS)

    Hoehn, R.; Herzig, C.

    1986-01-01

    The thermodynamic activity of the gold component was directly measured in Au-Pd alloys in the concentration range between X Au =0.048 and 0.850 and in the temperature range 1070 and 1300 K. The ratio of the vapour pressures of pure gold and of the gold component of the alloys was determined - after effusion from a Knudsen twin cell and condensation on a collecting plate - by analysing the decay rate of the radioisotopes 195 Au and 198 Au in an intrinsic germanium well-type detector. The partial mixing enthalpy and the partial mixing entropy of Au were directly obtained from these results. By Gibbs-Duhem integration the integral mixing functions were deduced. Similar measurements were performed in several ternary Au-Ag-Pd alloys of fixed mole fraction X Ag /X Pd =1/9. A comparison of the directly measured partial free excess enthalpy of Au in these ternary alloys with data obtained by the approximate models of Kohler, Toop and Bonnier using data of the corresponding three binary systems yields satisfactory agreement. (orig.) [de

  13. Investigation on adhering properties of dental materials by means of radioactively labelled bacteria

    International Nuclear Information System (INIS)

    Pfister, W.; Kleinert, P.; Sandig, H.C.; Wutzler, P.; Ruschitschka, A.; Schaefer, U.

    1987-01-01

    Bacteria of the species Streptococcus mutans were radioactively labelled with 113 In-oxinate. Different dental materials were incubated with the labelled bacteria. Counts per minute of the dental materials could be determined as proportion of the quantity of adhering microorganisms. Silver-palladium-alloy had a lower adherence than silver-tin-alloy. Finest polished alloys had lower adhering properties than unpolished surfaces of materials. (author)

  14. Dental OCT

    Science.gov (United States)

    Wilder-Smith, Petra; Otis, Linda; Zhang, Jun; Chen, Zhongping

    This chapter describes the applications of OCT for imaging in vivo dental and oral tissue. The oral cavity is a diverse environment that includes oral mucosa, gingival tissues, teeth and their supporting structures. Because OCT can image both hard and soft tissues of the oral cavity at high resolution, it offers the unique capacity to identity dental disease before destructive changes have progressed. OCT images depict clinically important anatomical features such as the location of soft tissue attachments, morphological changes in gingival tissue, tooth decay, enamel thickness and decay, as well as the structural integrity of dental restorations. OCT imaging allows for earlier intervention than is possible with current diagnostic modalities.

  15. Use of low fusing alloy in dentistry.

    Science.gov (United States)

    Wee, A G; Schneider, R L; Aquilino, S A

    1998-11-01

    Low fusing alloy has been used in dentistry for remount procedures in both fixed and removable prosthodontics, in implant prosthodontics for the fabrication of solid implant casts, in maxillofacial prosthetics as oral radiation shields, and in dental research for its unique properties. Previously, the use of low fusing alloy was thought to offer a high degree of dimensional accuracy. However, multiple in vitro studies have shown that its presumed dimensional accuracy may be questionable. This article reviews the physical properties, metallurgical considerations of low fusing alloy, its applications in dentistry, and a safe, simple method of using low fusing alloy.

  16. Adsorption and temperature-programmed desorption of hydrogen with dispersed platinum and platinum-gold catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, J.R.; Foger, K.; Breakspere, R.J.

    1979-05-01

    Adsorption and temperature-programmed desorption of hydrogen with dispersed platinum and platinum-gold catalysts was studied with 0.9-3Vertical Bar3< platinum on silica gel, aerosil, sodium and lanthanum Y zeolites, and ..gamma..-alumina, and on aerosil-supported gold-platinum alloys containing 2, 10, 24, 33, and 85Vertical Bar3< gold. Surface enrichment with gold in the alloy systems, as derived from hydrogen adsorption data and predicted from surface enrichment theory and electron microscopic measurements of particle size, were in good agreement, which indicated that equilibrium was achieved by the thermal treatment (oxygen at 573/sup 0/K, hydrogen at 620/sup 0/K, repeated cycles) used. Hydrogen spillover to gold was observed at the higher hydrogen pressures tested on the alloys with high gold content, and to the zeolite supports. The temperature-programed desorption profiles were independent of gold content, which indicated that gold acts only as diluent, and that isolated surface platinum atoms become populated with hydrogen atoms either by hydrogen atom spillover from platinum ensembles to gold and from the gold to the isolated platinum, and/or by adsorption of a molecule directly on the isolated platinum and chemisorption of one H atom at an adjacent gold atom. The distribution of surface platinum ensembles was evaluated by a computer simulation method.

  17. Infant dental care (image)

    Science.gov (United States)

    ... sugar water. As the child grows, establishing proper dental hygiene will promote healthy teeth and gums which are essential to overall good health. Poor dental development, dental disease, and dental trauma can result ...

  18. Alloy materials

    Energy Technology Data Exchange (ETDEWEB)

    Hans Thieme, Cornelis Leo (Westborough, MA); Thompson, Elliott D. (Coventry, RI); Fritzemeier, Leslie G. (Acton, MA); Cameron, Robert D. (Franklin, MA); Siegal, Edward J. (Malden, MA)

    2002-01-01

    An alloy that contains at least two metals and can be used as a substrate for a superconductor is disclosed. The alloy can contain an oxide former. The alloy can have a biaxial or cube texture. The substrate can be used in a multilayer superconductor, which can further include one or more buffer layers disposed between the substrate and the superconductor material. The alloys can be made a by process that involves first rolling the alloy then annealing the alloy. A relatively large volume percentage of the alloy can be formed of grains having a biaxial or cube texture.

  19. Dental Calculus Arrest of Dental Caries

    OpenAIRE

    Keyes, Paul H.; Rams, Thomas E.

    2016-01-01

    Background An inverse relationship between dental calculus mineralization and dental caries demineralization on teeth has been noted in some studies. Dental calculus may even form superficial layers over existing dental caries and arrest their progression, but this phenomenon has been only rarely documented and infrequently considered in the field of Cariology. To further assess the occurrence of dental calculus arrest of dental caries, this study evaluated a large number of extracted human t...

  20. Ordered arrays of nanoporous gold nanoparticles

    Directory of Open Access Journals (Sweden)

    Dong Wang

    2012-09-01

    Full Text Available A combination of a “top-down” approach (substrate-conformal imprint lithography and two “bottom-up” approaches (dewetting and dealloying enables fabrication of perfectly ordered 2-dimensional arrays of nanoporous gold nanoparticles. The dewetting of Au/Ag bilayers on the periodically prepatterned substrates leads to the interdiffusion of Au and Ag and the formation of an array of Au–Ag alloy nanoparticles. The array of alloy nanoparticles is transformed into an array of nanoporous gold nanoparticles by a following dealloying step. Large areas of this new type of material arrangement can be realized with this technique. In addition, this technique allows for the control of particle size, particle spacing, and ligament size (or pore size by varying the period of the structure, total metal layer thickness, and the thickness ratio of the as-deposited bilayers.

  1. Fifty years of Brazilian Dental Materials Group: scientific contributions of dental materials field evaluated by systematic review

    Science.gov (United States)

    ROSA, Wellington Luiz de Oliveira; SILVA, Tiago Machado; LIMA, Giana da Silveira; SILVA, Adriana Fernandes; PIVA, Evandro

    2016-01-01

    ABSTRACT Objective A systematic review was conducted to analyze Brazilian scientific and technological production related to the dental materials field over the past 50 years. Material and Methods This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (Prisma) statement. Searches were performed until December 2014 in six databases: MedLine (PubMed), Scopus, LILACS, IBECS, BBO, and the Cochrane Library. Additionally, the Brazilian patent database (INPI - Instituto Nacional de Propriedade Industrial) was screened in order to get an overview of Brazilian technological development in the dental materials field. Two reviewers independently analyzed the documents. Only studies and patents related to dental materials were included in this review. Data regarding the material category, dental specialty, number of documents and patents, filiation countries, and the number of citations were tabulated and analyzed in Microsoft Office Excel (Microsoft Corporation, Redmond, Washington, United States). Results A total of 115,806 studies and 53 patents were related to dental materials and were included in this review. Brazil had 8% affiliation in studies related to dental materials, and the majority of the papers published were related to dental implants (1,137 papers), synthetic resins (681 papers), dental cements (440 papers), dental alloys (392 papers) and dental adhesives (361 papers). The Brazilian technological development with patented dental materials was smaller than the scientific production. The most patented type of material was dental alloys (11 patents), followed by dental implants (8 patents) and composite resins (7 patents). Conclusions Dental materials science has had a substantial number of records, demonstrating an important presence in scientific and technological development of dentistry. In addition, it is important to approximate the relationship between academia and industry to expand the technological development in

  2. Fifty years of Brazilian Dental Materials Group: scientific contributions of dental materials field evaluated by systematic review.

    Science.gov (United States)

    Rosa, Wellington Luiz de Oliveira; Silva, Tiago Machado; Lima, Giana da Silveira; Silva, Adriana Fernandes; Piva, Evandro

    2016-01-01

    A systematic review was conducted to analyze Brazilian scientific and technological production related to the dental materials field over the past 50 years. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (Prisma) statement. Searches were performed until December 2014 in six databases: MedLine (PubMed), Scopus, LILACS, IBECS, BBO, and the Cochrane Library. Additionally, the Brazilian patent database (INPI - Instituto Nacional de Propriedade Industrial) was screened in order to get an overview of Brazilian technological development in the dental materials field. Two reviewers independently analyzed the documents. Only studies and patents related to dental materials were included in this review. Data regarding the material category, dental specialty, number of documents and patents, filiation countries, and the number of citations were tabulated and analyzed in Microsoft Office Excel (Microsoft Corporation, Redmond, Washington, United States). A total of 115,806 studies and 53 patents were related to dental materials and were included in this review. Brazil had 8% affiliation in studies related to dental materials, and the majority of the papers published were related to dental implants (1,137 papers), synthetic resins (681 papers), dental cements (440 papers), dental alloys (392 papers) and dental adhesives (361 papers). The Brazilian technological development with patented dental materials was smaller than the scientific production. The most patented type of material was dental alloys (11 patents), followed by dental implants (8 patents) and composite resins (7 patents). Dental materials science has had a substantial number of records, demonstrating an important presence in scientific and technological development of dentistry. In addition, it is important to approximate the relationship between academia and industry to expand the technological development in countries such as Brazil.

  3. Aluminium-gold reference material for the k0-standardisation of neutron activation analysis

    International Nuclear Information System (INIS)

    Ingelbrecht, C.; Peetermans, F.; Corte, F. de; Wispelaere, A. de; Vandecasteele, C.; Courtijn, E.; Hondt, P. d'

    1991-01-01

    Gold is an excellent comparator material for the k 0 -standardisation of neutron activation analysis because of its convenient and well defined nuclear properties. The most suitable form for a reference material is a dilute aluminium-gold alloy, for which the self-shielding effect for neutrons is small. Castings of composition Al-0.1 wt.% Au were prepared by crucible-less levitation melting, which gives close control of ingot composition with minimal contamination of the melt. The alloy composition was checked using induction-coupled plasma source emission spectrometry. The homogeneity of the alloy was measured by neutron activation analysis and a relative standard deviation of the gold content of 0.30% was found (10 mg samples). Metallography revealed a homogeneous distribution of AuAl 2 particles. The alloy was certified as Reference Materials CBNM-530, with certified gold mass fraction 0.100±0.002 wt.%. (orig.)

  4. Effect of gold subsurface layer on the surface activity and segregation in Pt/Au/Pt{sub 3}M (where M = 3d transition metals) alloy catalyst from first-principles

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chang-Eun [Fuel Cell Research Center, Korea Institute of Science and Technology (KIST), 39-1 Hawolgok, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Global E3 Institute and Department of Materials Science and Engineering, Yonsei University, 120-749 Seoul (Korea, Republic of); Lim, Dong-Hee [Fuel Cell Research Center, Korea Institute of Science and Technology (KIST), 39-1 Hawolgok, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Department of Environmental Engineering, Chungbuk National University, 1 Chungdae-ro, Seowon-Gu, Cheongju, Chungbuk 362-763 (Korea, Republic of); Jang, Jong Hyun; Kim, Hyoung Juhn; Yoon, Sung Pil; Han, Jonghee; Nam, Suk Woo [Fuel Cell Research Center, Korea Institute of Science and Technology (KIST), 39-1 Hawolgok, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Hong, Seong-Ahn [Fuel Cell Research Center, Korea Institute of Science and Technology (KIST), 39-1 Hawolgok, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Department of Advanced Materials Chemistry, Korea University, Sejong-city 339-700 (Korea, Republic of); Soon, Aloysius, E-mail: aloysius.soon@yonsei.ac.kr, E-mail: hchahm@kist.re.kr [Global E3 Institute and Department of Materials Science and Engineering, Yonsei University, 120-749 Seoul (Korea, Republic of); Ham, Hyung Chul, E-mail: aloysius.soon@yonsei.ac.kr, E-mail: hchahm@kist.re.kr [Fuel Cell Research Center, Korea Institute of Science and Technology (KIST), 39-1 Hawolgok, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Clean Energy and Chemical Engineering, University of Science and Technology (UST), 217 Gajungro, Yuseong-gu, Daejeon 305-333 (Korea, Republic of)

    2015-01-21

    The effect of a subsurface hetero layer (thin gold) on the activity and stability of Pt skin surface in Pt{sub 3}M system (M = 3d transition metals) is investigated using the spin-polarized density functional theory calculation. First, we find that the heterometallic interaction between the Pt skin surface and the gold subsurface in Pt/Au/Pt{sub 3}M system can significantly modify the electronic structure of the Pt skin surface. In particular, the local density of states projected onto the d states of Pt skin surface near the Fermi level is drastically decreased compared to the Pt/Pt/Pt{sub 3}M case, leading to the reduction of the oxygen binding strength of the Pt skin surface. This modification is related to the increase of surface charge polarization of outmost Pt skin atoms by the electron transfer from the gold subsurface atoms. Furthermore, a subsurface gold layer is found to cast the energetic barrier to the segregation loss of metal atoms from the bulk (inside) region, which can enhance the durability of Pt{sub 3}M based catalytic system in oxygen reduction condition at fuel cell devices. This study highlights that a gold subsurface hetero layer can provide an additional mean to tune the surface activity toward oxygen species and in turn the oxygen reduction reaction, where the utilization of geometric strain already reaches its practical limit.

  5. Effect of gold subsurface layer on the surface activity and segregation in Pt/Au/Pt3M (where M = 3d transition metals) alloy catalyst from first-principles.

    Science.gov (United States)

    Kim, Chang-Eun; Lim, Dong-Hee; Jang, Jong Hyun; Kim, Hyoung Juhn; Yoon, Sung Pil; Han, Jonghee; Nam, Suk Woo; Hong, Seong-Ahn; Soon, Aloysius; Ham, Hyung Chul

    2015-01-21

    The effect of a subsurface hetero layer (thin gold) on the activity and stability of Pt skin surface in Pt3M system (M = 3d transition metals) is investigated using the spin-polarized density functional theory calculation. First, we find that the heterometallic interaction between the Pt skin surface and the gold subsurface in Pt/Au/Pt3M system can significantly modify the electronic structure of the Pt skin surface. In particular, the local density of states projected onto the d states of Pt skin surface near the Fermi level is drastically decreased compared to the Pt/Pt/Pt3M case, leading to the reduction of the oxygen binding strength of the Pt skin surface. This modification is related to the increase of surface charge polarization of outmost Pt skin atoms by the electron transfer from the gold subsurface atoms. Furthermore, a subsurface gold layer is found to cast the energetic barrier to the segregation loss of metal atoms from the bulk (inside) region, which can enhance the durability of Pt3M based catalytic system in oxygen reduction condition at fuel cell devices. This study highlights that a gold subsurface hetero layer can provide an additional mean to tune the surface activity toward oxygen species and in turn the oxygen reduction reaction, where the utilization of geometric strain already reaches its practical limit.

  6. Dental caries

    DEFF Research Database (Denmark)

    Pitts, Nigel B; Zero, Domenick T; Marsh, Phil D

    2017-01-01

    Dental caries is a biofilm-mediated, sugar-driven, multifactorial, dynamic disease that results in the phasic demineralization and remineralization of dental hard tissues. Caries can occur throughout life, both in primary and permanent dentitions, and can damage the tooth crown and, in later life......, exposed root surfaces. The balance between pathological and protective factors influences the initiation and progression of caries. This interplay between factors underpins the classification of individuals and groups into caries risk categories, allowing an increasingly tailored approach to care. Dental...... caries is an unevenly distributed, preventable disease with considerable economic and quality-of-life burdens. The daily use of fluoride toothpaste is seen as the main reason for the overall decline of caries worldwide over recent decades. This Primer aims to provide a global overview of caries...

  7. Recent research and development in titanium alloys for biomedical applications and healthcare goods

    Directory of Open Access Journals (Sweden)

    Mitsuo Niinomi

    2003-01-01

    Full Text Available Nb, Ta and Zr are the favorable non-toxic alloying elements for titanium alloys for biomedical applications. Low rigidity titanium alloys composed of non-toxic elements are getting much attention. The advantage of low rigidity titanium alloy for the healing of bone fracture and the remodeling of bone is successfully proved by fracture model made in tibia of rabbit. Ni-free super elastic and shape memory titanium alloys for biomedical applications are energetically developed. Titanium alloys for not only implants, but also dental products like crowns, dentures, etc. are also getting much attention in dentistry. Development of investment materials suitable for titanium alloys with high melting point is desired in dental precision castings. Bioactive surface modifications of titanium alloys for biomedical applications are very important for achieving further developed biocompatibility. Low cost titanium alloys for healthcare goods, like general wheel chairs, etc. has been recently proposed.

  8. Fabrication and characterization of a flow-through nanoporous gold nanowire/AAO composite membrane

    Energy Technology Data Exchange (ETDEWEB)

    Liu, L; Lee, W; Huang, Z; Scholz, R; Goesele, U [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Germany)

    2008-08-20

    The fabrication of a composite membrane of nanoporous gold nanowires and anodic aluminum oxide (AAO) is demonstrated by the electrodeposition of Au-Ag alloy nanowires into an AAO membrane, followed by selective etching of silver from the alloy nanowires. This composite membrane is advantageous for flow-through type catalytic reactions. The morphology evolution of the nanoporous gold nanowires as a function of the diameter of the Au-Ag nanowire 'precursors' is also investigated.

  9. Fabrication and characterization of a flow-through nanoporous gold nanowire/AAO composite membrane

    International Nuclear Information System (INIS)

    Liu, L; Lee, W; Huang, Z; Scholz, R; Goesele, U

    2008-01-01

    The fabrication of a composite membrane of nanoporous gold nanowires and anodic aluminum oxide (AAO) is demonstrated by the electrodeposition of Au-Ag alloy nanowires into an AAO membrane, followed by selective etching of silver from the alloy nanowires. This composite membrane is advantageous for flow-through type catalytic reactions. The morphology evolution of the nanoporous gold nanowires as a function of the diameter of the Au-Ag nanowire 'precursors' is also investigated

  10. Fabrication and characterization of a flow-through nanoporous gold nanowire/AAO composite membrane.

    Science.gov (United States)

    Liu, L; Lee, W; Huang, Z; Scholz, R; Gösele, U

    2008-08-20

    The fabrication of a composite membrane of nanoporous gold nanowires and anodic aluminum oxide (AAO) is demonstrated by the electrodeposition of Au-Ag alloy nanowires into an AAO membrane, followed by selective etching of silver from the alloy nanowires. This composite membrane is advantageous for flow-through type catalytic reactions. The morphology evolution of the nanoporous gold nanowires as a function of the diameter of the Au-Ag nanowire 'precursors' is also investigated.

  11. One-step synthesis of gold bimetallic nanoparticles with various metal-compositions

    International Nuclear Information System (INIS)

    Bratescu, Maria Antoaneta; Takai, Osamu; Saito, Nagahiro

    2013-01-01

    Highlights: ► Synthesis of bimetallic nanoparticles in an aqueous solution discharge. ► Alloying gold with divalent sp metals, trivalent sp metals, 3d or 4d metals. ► Formation mechanism of bimetallic nanoparticles by metal reduction and gold erosion. ► Blue and red shift of surface plasmon resonance. -- Abstract: A rapid, one-step process for the synthesis of bimetallic nanoparticles by simultaneous metal reduction and gold erosion in an aqueous solution discharge was investigated. Gold bimetallic nanoparticles were obtained by alloying gold with various types of metals belonging to one of the following categories: divalent sp metals, trivalent sp metals, 3d or 4d metals. The composition of the various gold bimetallic nanoparticles obtained depends on electrochemical factors, charge transfer between gold and other metal, and initial concentration of metal in solution. Transmission electron microscopy and energy dispersive spectroscopy show that the gold bimetallic nanoparticles were of mixed pattern, with sizes of between 5 and 20 nm. A red-shift of the surface plasmon resonance band in the case of the bimetallic nanoparticles Au–Fe, Au–Ga, and Au–In, and a blue-shift of the plasmon band of the Au–Ag nanoparticles was observed. In addition, the interaction of gold bimetallic nanoparticles with unpaired electrons, provided by a stable free radical molecule, was highest for those NPs obtained by alloying gold with a 3d metal

  12. Dental Calculus Arrest of Dental Caries.

    Science.gov (United States)

    Keyes, Paul H; Rams, Thomas E

    An inverse relationship between dental calculus mineralization and dental caries demineralization on teeth has been noted in some studies. Dental calculus may even form superficial layers over existing dental caries and arrest their progression, but this phenomenon has been only rarely documented and infrequently considered in the field of Cariology. To further assess the occurrence of dental calculus arrest of dental caries, this study evaluated a large number of extracted human teeth for the presence and location of dental caries, dental calculus, and dental plaque biofilms. A total of 1,200 teeth were preserved in 10% buffered formal saline, and viewed while moist by a single experienced examiner using a research stereomicroscope at 15-25× magnification. Representative teeth were sectioned and photographed, and their dental plaque biofilms subjected to gram-stain examination with light microscopy at 100× magnification. Dental calculus was observed on 1,140 (95%) of the extracted human teeth, and no dental carious lesions were found underlying dental calculus-covered surfaces on 1,139 of these teeth. However, dental calculus arrest of dental caries was found on one (0.54%) of 187 evaluated teeth that presented with unrestored proximal enamel caries. On the distal surface of a maxillary premolar tooth, dental calculus mineralization filled the outer surface cavitation of an incipient dental caries lesion. The dental calculus-covered carious lesion extended only slightly into enamel, and exhibited a brown pigmentation characteristic of inactive or arrested dental caries. In contrast, the tooth's mesial surface, without a superficial layer of dental calculus, had a large carious lesion going through enamel and deep into dentin. These observations further document the potential protective effects of dental calculus mineralization against dental caries.

  13. Dental Calculus Arrest of Dental Caries

    Science.gov (United States)

    Keyes, Paul H.; Rams, Thomas E.

    2016-01-01

    Background An inverse relationship between dental calculus mineralization and dental caries demineralization on teeth has been noted in some studies. Dental calculus may even form superficial layers over existing dental caries and arrest their progression, but this phenomenon has been only rarely documented and infrequently considered in the field of Cariology. To further assess the occurrence of dental calculus arrest of dental caries, this study evaluated a large number of extracted human teeth for the presence and location of dental caries, dental calculus, and dental plaque biofilms. Materials and methods A total of 1,200 teeth were preserved in 10% buffered formal saline, and viewed while moist by a single experienced examiner using a research stereomicroscope at 15-25× magnification. Representative teeth were sectioned and photographed, and their dental plaque biofilms subjected to gram-stain examination with light microscopy at 100× magnification. Results Dental calculus was observed on 1,140 (95%) of the extracted human teeth, and no dental carious lesions were found underlying dental calculus-covered surfaces on 1,139 of these teeth. However, dental calculus arrest of dental caries was found on one (0.54%) of 187 evaluated teeth that presented with unrestored proximal enamel caries. On the distal surface of a maxillary premolar tooth, dental calculus mineralization filled the outer surface cavitation of an incipient dental caries lesion. The dental calculus-covered carious lesion extended only slightly into enamel, and exhibited a brown pigmentation characteristic of inactive or arrested dental caries. In contrast, the tooth's mesial surface, without a superficial layer of dental calculus, had a large carious lesion going through enamel and deep into dentin. Conclusions These observations further document the potential protective effects of dental calculus mineralization against dental caries. PMID:27446993

  14. [Compressive and bend strength of experimental admixed high copper alloys].

    Science.gov (United States)

    Sourai, P; Paximada, H; Lagouvardos, P; Douvitsas, G

    1988-01-01

    Mixed alloys for dental amalgams have been used mainly in the form of admixed alloys, where eutectic spheres are blend with conventional flakes. In the present study the compressive strength, bend strength and microstructure of two high-copper alloys (Tytin, Ana-2000) is compared with three experimental alloys prepared of the two high copper by mixing them in proportions of 3:1, 1:1 and 1:3 by weight. The results revealed that experimental alloys inherited high early and final strength values without any significant change in their microstructure.

  15. A prospective study of the validity of self-reported use of specific types of dental services.

    OpenAIRE

    Gilbert, Gregg H.; Rose, John S.; Shelton, Brent J.

    2003-01-01

    OBJECTIVE: The purpose of this study was to quantify the validity of self-reported receipt of dental services in 10 categories, using information from dental charts as the "gold standard." METHODS: The Florida Dental Care Study was a prospective cohort study of a diverse sample of adults. In-person interviews were conducted at baseline and at 24 and 48 months following baseline, with telephone interviews at six-month intervals in between. Participants reported new dental visits, reason(s) for...

  16. Unexpected interactions between gold and N-morpholino-sulfonates

    DEFF Research Database (Denmark)

    Nielsen, Frederick Stappen; Engelbrekt, Christian; Elliot, Samuel Gilbert

    Nanoporous gold (NPG) has a high surface area and excellent conductivity. It is an ideal supporting material for the electrocatalysis, e.g. in fuel cell applications. NPG is traditionally produced by etching a gold/silver alloy. This method has significant drawbacks, such as the introduction...... of silver into your NPG, and its multi-step fabrication. A method has been discovered for producing NPG as a thin film chemically. This bottom-up approach entails reduction of Au3+ precursor using morpholinoethanesulfonic acid (MES). This produces a thin and highly porous gold film at the air...

  17. Microstructural study of tungsten influence on Co-Cr alloys

    International Nuclear Information System (INIS)

    Karaali, A.; Mirouh, K.; Hamamda, S.; Guiraldenq, P.

    2005-01-01

    Alloying elements, such as W, Mo, Mn,..., are of a great importance in the preoxidation of dental alloys and, consequently, on the ceramic/metal bond quality. This study deals with the effect of tungsten addition on the microstructural state of Co-Cr dental alloys, before the ceramisation process. These materials were prepared by unidirectional solidification. Their characterization has been carried out, using transmission electron microscopy (TEM) and X-ray diffraction. It shows that the addition of tungsten up to 8 wt.% induces structural transformations, which are believed to be linked to the added amount of tungsten

  18. Frontiers in Gold Chemistry

    OpenAIRE

    Ahmed A. Mohamed

    2015-01-01

    Basic chemistry of gold tells us that it can bond to sulfur, phosphorous, nitrogen, and oxygen donor ligands. The Frontiers in Gold Chemistry Special Issue covers gold complexes bonded to the different donors and their fascinating applications. This issue covers both basic chemistry studies of gold complexes and their contemporary applications in medicine, materials chemistry, and optical sensors. There is a strong belief that aurophilicity plays a major role in the unending applications of g...

  19. Gold in plants

    International Nuclear Information System (INIS)

    Girling, C.A.; Peterson, P.J.

    1980-01-01

    Many plants have the ability to take up gold from the soil and to accumulate it in their tisssue. Advances have been made in understanding these processes to the point where their exploitation in the field of prospecting for gold appears practically feasible. Neutron activation analysis is used for the determination of the small quantities of gold in plants

  20. Artifacts by dental materials on magnetic resonance imaging

    International Nuclear Information System (INIS)

    Hong, Hyun Sook; Choi, Deuk Lin; Kim, Ki Jung; Suh, Won Hyuck

    1992-01-01

    Magnetic resonance imaging (MRI) has proved to be a valuable method for evaluation of the head and neck. Unfortunately, metallic devices associated with certain dental fillings and appliances often cause variable artifacts that can obscure normal or pathologic conditions on MR and computed tomography. In this work, we assessed the MR appearance of dental prosthetic materials in vitro and in vivo including precious alloys, nonprecions alloys, resin, amalgam and titanium alloy. For in vivo studies, these materials were placed in healthy volunteer's mouths and then images were assessed. Analysis of the appearance of shape and extent of artifact, and observed influence of these artifacts on the image interpretation at 0.2 Tesla permanent type MR scanner were valuated. Material used as temporary or permanent filling of crowns such as amalgam, precious alloy and, microfilled resin did not cause artifact on the image. The size of the artifact produced by the nonprecious alloys was influenced by the ferromagnetism of the object and the volume prosthesis, and was related to the scanning sequence. Nonprecious alloys produced minimal local signal distortion, where precious alloys, and dental resin had no effect on the MR images in vivo. These results were mainly from a low field strength MR scanner used in this study

  1. Studies of some alloys using x-ray fluorescence

    International Nuclear Information System (INIS)

    Elmahi, Elamin Musaid

    1997-01-01

    In this project an attempt has been made for the study of alloys commonly used using x-ray fluorescence ( XRF ) technique. The alloys selected for the study included gold jewellery, steels, brasses and coins. The XRF method proved to be simple, fast, non-destructive and reliable as compared to chemical methods. The results showed that most of the gold jewellery used in this country have carat value of 18 and 21. Also most coins used in different countries are alloys of Cu and Ni. A simple spark method was used for the determination of C in steels, since C is not possible to analyze by XRF. ( Author )

  2. Authentication of gold products by nuclear methods

    International Nuclear Information System (INIS)

    De Jesus, A.S.M.

    1985-01-01

    The falsification of valuable gold items is a threat to the authenticity of gold products. To solve this, there is a continuous search for reliable, practicle and cost-effective means of identifying forgeries. Because nuclear techniques as applied to elemental analysis have a high degree of specificity, are non-destructive and permit the availability of results within a relatively short time, a few of these techniques were investigated and reviewed in the article. Work on some promising methods in the author's laboratory is also discussed. Constraints such as those imposed by the time taken by the measurement, negligible residual activity within a relatively short time were also considered. The techniques that were investigated include: the transmission of electromagnetic radiation through a medium; scattering of electromagnetic radiation; x-ray fluorescence analysis; neutron activation analysis; activation by the inelastic scattering of gamma radiation; activation by the inelastic scattering of fast neutrons; absorption and scattering of fast neutrons; self-attenuation of gamma radiation. The shape of the object being investigated, should also be considered. It is concluded that a system based on the inelastic scattering of neutrons emitted by a 241 Am/Be source (halflife = 433 years) is practical and capable of authenticating gold and gold alloy coins such as Krugerrands. The feasibility study on the assaying of gold jewelry by means of nuclear methods also showed it to be impractical

  3. Gold grade variation and particle microchemistry in exploration pits of the Batouri gold district, SE Cameroon

    Science.gov (United States)

    Vishiti, A.; Suh, C. E.; Lehmann, B.; Egbe, J. A.; Shemang, E. M.

    2015-11-01

    The Batouri area hosts lode-gold mineralization under several-m-thick lateritic cover. Pitting to bed rock on a geochemical Au anomaly defined from previous reconnaissance soil sampling identified five horizons ranging from saprock at the base to laterite at the top. Analysis of bulk samples from each horizon by fire assay shows that most of the horizons are barren although 119 ppb and 48 ppb Au values were obtained from one laterite horizon and one saprolite horizon, respectively, from two separate pits. All the horizons were panned and particulate gold was also recovered only from these two horizons. The gold grains from both horizons are morphologically and compositionally indistinguishable with rare quartz, pyrite and galena inclusions. The grains have irregular, sub-rounded, bean to elongated shapes and they show a remarkable core-rim zonation. Electron microprobe analysis of the grains recorded high gold content in the rims (86.3-100 wt%) and along fissures within the grains (95.1-100 wt%). The cores are relatively Ag rich (11.8-14 wt% Ag) while the rims (0.63-13.7 wt% Ag, most of the values fall within the lower limit of this range) and fissures (0.03-5.02 wt% Ag) are poor in Ag. The low Ag concentration in the rims and along fissures is attributed to preferential leaching of Ag; a process recognized in gold grains and platiniferous alloys from alluvia. The core composition of the grains is similar to that of primary gold composition in the bedrock. These results show that gold in the soil is relic particulate gold derived from the primary source with no evidence of secondary gold precipitation in the weathering cycle. In all the pits no horizon was systematically enriched in gold suggesting there has been no chemical remobilization of gold in this environment. Rather the dispersion of gold here is in the particulate form. Therefore combining particulate gold features with assay data is relevant to exploration in such tropical environments.

  4. Correlation between radiographic analysis of alveolar bone density around dental implant and resonance frequency of dental implant

    Science.gov (United States)

    Prawoko, S. S.; Nelwan, L. C.; Odang, R. W.; Kusdhany, L. S.

    2017-08-01

    The histomorphometric test is the gold standard for dental implant stability quantification; however, it is invasive, and therefore, it is inapplicable to clinical patients. Consequently, accurate and objective alternative methods are required. Resonance frequency analysis (RFA) and digital radiographic analysis are noninvasive methods with excellent objectivity and reproducibility. To analyze the correlation between the radiographic analysis of alveolar bone density around a dental implant and the resonance frequency of the dental implant. Digital radiographic images for 35 samples were obtained, and the resonance frequency of the dental implant was acquired using Osstell ISQ immediately after dental implant placement and on third-month follow-up. The alveolar bone density around the dental implant was subsequently analyzed using SIDEXIS-XG software. No significant correlation was reported between the alveolar bone density around the dental implant and the resonance frequency of the dental implant (r = -0.102 at baseline, r = 0.146 at follow-up, p > 0.05). However, the alveolar bone density and resonance frequency showed a significant difference throughout the healing period (p = 0.005 and p = 0.000, respectively). Conclusion: Digital dental radiographs and Osstell ISQ showed excellent objectivity and reproducibility in quantifying dental implant stability. Nonetheless, no significant correlation was observed between the results obtained using these two methods.

  5. Clareamento Dental

    OpenAIRE

    Sossai, Najara; Universidade Paranaense - UNIPAR; Verdinelli, Ellen Carla; Universidade Paranaense - UNIPAR; Bassegio, Wagner; Universidade Paranaense - UNIPAR

    2011-01-01

    O clareamento dental já é utilizado há bastante tempo na Odontologia e atualmente é um dos tratamentos odontológicos mais solicitados para obtenção de um sorriso mais estético. Classificado em clareamento caseiro e/ou de consultório, ambas as técnicas são motivo de polêmica quanto aos seus benefícios, riscos, limitações e efeito clareador, bem como sobre qual é a melhor técnica existente para a promoção de um clareamento dental eficaz e seguro. Neste contexto, o presente estudo tem por objeti...

  6. Low-energy ED-XRF spectrometry application in gold assaying

    International Nuclear Information System (INIS)

    Marucco, Alessandra

    2004-01-01

    The performances of a low-energy dispersive XRF spectrometer in gold assaying are evaluated by a series of analysis on international standards and other certified gold alloys with. Results of standard-free analysis based on fundamental parameters method compared to results of multi-standard method, demonstrate a large gain of accuracy by drawing appropriate calibration curves with use of 1 to 16 matrix-specific standards. The accuracy of gold assaying has improved by a factor of 10, as compared to the conventional touchstone test. This rather economical technique satisfies then numerous precious alloys analyst needs, representing an excellent alternative to the traditional method for quick anti-fraud controls

  7. Dental Implant Surgery

    Science.gov (United States)

    ... here to find out more. Dental Implant Surgery Dental Implant Surgery Dental implant surgery is, of course, ... to find out more. Wisdom Teeth Management Wisdom Teeth Management An impacted wisdom tooth can damage neighboring ...

  8. American Dental Education Association

    Science.gov (United States)

    ... Interest Groups ADEA Governance Documents and Publications ADEA Dental Faculty Code of Conduct ADEA Bylaws ADEAGies Foundation ... Benefits for Faculty ADEA Member Benefits for Allied Dental Programs ADEA Member Benefits for Dental Schools ADEA ...

  9. Gold-Mining

    DEFF Research Database (Denmark)

    Raaballe, J.; Grundy, B.D.

    2002-01-01

      Based on standard option pricing arguments and assumptions (including no convenience yield and sustainable property rights), we will not observe operating gold mines. We find that asymmetric information on the reserves in the gold mine is a necessary and sufficient condition for the existence...... of operating gold mines. Asymmetric information on the reserves in the mine implies that, at a high enough price of gold, the manager of high type finds the extraction value of the company to be higher than the current market value of the non-operating gold mine. Due to this under valuation the maxim of market...

  10. Dental Holography

    Science.gov (United States)

    Dirtoft, Ingegerd

    1983-12-01

    Ten years have passed since the first articles appeared in this new field. The qualities of the laser light together with the need of contactless 3-D measurements for different dental purposes seemed to be extremely promising, but still just a few scientists have used the method and mostly for laboratory studies. For some reason there has been a preponderance for orthodontic measurements. This seems to be a bit peculiar from holographic view compared with measurements for engineering purposes, which usually are made on metals. So naturally holography can become a clinical tool for measurements in the field of fixed bridges, removable partial dentures and implants. One of the problems is that the need for holography in dental research must be fulfilled in collaboration with physicists. Only a two-way communication during an entire experiment can balance both technical and odontological demands and thus give practical and clinical important results. The need for an easy way of handling the evaluation to get all required information is another problem and of course the holographic equipment must be converted to a box easy to handle for everyone. At last the position of dental holography today is going to be carefully examined together with an attempt to look into the hopefully exciting and not to utopic future for this research field.

  11. Machinability of experimental Ti-Ag alloys.

    Science.gov (United States)

    Kikuchi, Masafumi; Takahashi, Masatoshi; Okuno, Osamu

    2008-03-01

    This study investigated the machinability of experimental Ti-Ag alloys (5, 10, 20, and 30 mass% Ag) as a new dental titanium alloy candidate for CAD/CAM use. The alloys were slotted with a vertical milling machine and carbide square end mills under two cutting conditions. Machinability was evaluated through cutting force using a three-component force transducer fixed on the table of the milling machine. The horizontal cutting force of the Ti-Ag alloys tended to decrease as the concentration of silver increased. Values of the component of the horizontal cutting force perpendicular to the feed direction for Ti-20% Ag and Ti-30% Ag were more than 20% lower than those for titanium under both cutting conditions. Alloying with silver significantly improved the machinability of titanium in terms of cutting force under the present cutting conditions.

  12. Danish dental education:

    DEFF Research Database (Denmark)

    Moore, Rod

    1985-01-01

    The effects of Danish cultural traditions on dental education in Denmark are described, as well as the system's current structure and developing issues. Some Danish ideas for future exports of dental education programs and dental personnel are also discussed.......The effects of Danish cultural traditions on dental education in Denmark are described, as well as the system's current structure and developing issues. Some Danish ideas for future exports of dental education programs and dental personnel are also discussed....

  13. Dental students--dental advocates.

    Science.gov (United States)

    Bensch, Brittany

    2010-01-01

    Student advocacy and involvement in the political process is built into the structure of the American Student Dental Association (ASDA), especially in its Legislative Grassroots Network and an internal communication network among students to ensure political awareness. Students are concerned with such issues as a universally accepted, non-patient-based licensure process, mid-level providers, loan availability and tax deductibility, financial support for schools, and service early in one's professional career (giving forward rather than giving back). Through collaboration with the American Dental Education Association and with many state associations, students participate in lobbying, awareness campaigns, and behind the scenes as legislative aids. Although students share the same love for the profession that animates established practitioners, they are perceived by legislators as being different. Students are involved in the legislative process because it represents their future.

  14. A comparison of tensile bond strengths of resin-retained prostheses made using five alloys.

    Science.gov (United States)

    Rubo, J H; Pegoraro, L F; Ferreira, P M

    1996-01-01

    This in vitro study evaluated the bond strength of metal frameworks cast using Ni-Cr, Ni-Cr-Be, Cu-Al, type IV gold, and noble metal ceramic alloy with and without tin electroplating. The castings were luted to human teeth using Panavia Ex resin. It was found that tin electroplating had a negative effect for the Cu-Al and type IV gold alloys and a positive effect for gold for metal ceramic restorations. The best results were obtained using the Ni-Cr alloy.

  15. Moessbauer investigation of gold-bearing pyrite-rich concentrates

    International Nuclear Information System (INIS)

    Wagner, F.E.; Harris, D.C.

    1994-01-01

    A gold-bearing pyrite-rich concentrate of a refractory ore from the Golden Bear mine, northwestern British Columbia, and a pyrite-rich concentrate from Newhawk's west zone, Brucejack Lake area, northern British Columbia, containing 38 and 316 ppm Au and 0.57% and 0.19% As, respectively, have been investigated using 197 Au and 57 Fe Moessbauer spectroscopy. In the Golden Bear sample, the gold is mainly chemically bound in the pyrite with minor amounts present as an Au-Ag alloy, whereas in the Newhawk sample, the gold occurs mainly as an Au-Ag alloy with a composition close to Au 0.5 Ag 0.5 and is only partly bound in the pyrite. Having mean isomer shifts of +3.2 and +4.0 mm/s with respect to a Pt metal source, the gold in pyrite exhibits shifts similar to those observed for gold in arsenopyrite. The nature of the lattice sites occupied by the gold in pyrite is discussed. (orig.)

  16. Magnetic susceptibility and electrical conductivity of metallic dental materials and their impact on MR imaging artifacts

    Czech Academy of Sciences Publication Activity Database

    Starčuková, Jana; Starčuk jr., Zenon; Hubálková, H.; Linetskiy, I.

    2008-01-01

    Roč. 24, č. 6 (2008), s. 715-723 ISSN 0109-5641 R&D Projects: GA MZd NR8110 Institutional research plan: CEZ:AV0Z20650511 Keywords : metallic dental materials * dental alloys * amalgams * MR imaging * magnetic susceptibility * electric conductivity * image artifact Subject RIV: FF - HEENT, Dentistry Impact factor: 2.941, year: 2008

  17. Directed deposition of silicon nanowires using neopentasilane as precursor and gold as catalyst

    Directory of Open Access Journals (Sweden)

    Britta Kämpken

    2012-07-01

    Full Text Available In this work the applicability of neopentasilane (Si(SiH34 as a precursor for the formation of silicon nanowires by using gold nanoparticles as a catalyst has been explored. The growth proceeds via the formation of liquid gold/silicon alloy droplets, which excrete the silicon nanowires upon continued decomposition of the precursor. This mechanism determines the diameter of the Si nanowires. Different sources for the gold nanoparticles have been tested: the spontaneous dewetting of gold films, thermally annealed gold films, deposition of preformed gold nanoparticles, and the use of “liquid bright gold”, a material historically used for the gilding of porcelain and glass. The latter does not only form gold nanoparticles when deposited as a thin film and thermally annealed, but can also be patterned by using UV irradiation, providing access to laterally structured layers of silicon nanowires.

  18. VANADIUM ALLOYS

    Science.gov (United States)

    Smith, K.F.; Van Thyne, R.J.

    1959-05-12

    This patent deals with vanadium based ternary alloys useful as fuel element jackets. According to the invention the ternary vanadium alloys, prepared in an arc furnace, contain from 2.5 to 15% by weight titanium and from 0.5 to 10% by weight niobium. Characteristics of these alloys are good thermal conductivity, low neutron capture cross section, good corrosion resistance, good welding and fabricating properties, low expansion coefficient, and high strength.

  19. A multi-analytical approach to gold in Ancient Egypt: Studies on provenance and corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Tissot, I., E-mail: isabeltissot@gmail.com [LIBPhys – UNL, Faculty of Science and Technology, 2829-516 Caparica (Portugal); Department of Physics, Faculty of Sciences, University of Lisbon, Campo Grande, 1649-004 Lisbon (Portugal); Troalen, L.G. [National Museums Scotland, Collections Services Department, 242 West Granton Road, Edinburgh EH5 1JA (United Kingdom); Manso, M. [LIBPhys – UNL, Faculty of Science and Technology, 2829-516 Caparica (Portugal); Faculdade de Belas-Artes da Universidade de Lisboa, Largo da Academia Nacional de Belas-Artes, 1249-058 Lisbon (Portugal); Ponting, M. [Archaeology, Classics and Egyptology, University of Liverpool, 12-14 Abercromby Square, Liverpool L69 7WZ (United Kingdom); Radtke, M.; Reinholz, U. [BAM Federal Institute for Materials Research and Testing, Richard-Willstaetter-Strasse 11, 12489 Berlin (Germany); Barreiros, M.A. [LNEG, I.P., Estrada do Paço do Lumiar, 22, 1649-038 Lisbon (Portugal); Shaw, I. [Archaeology, Classics and Egyptology, University of Liverpool, 12-14 Abercromby Square, Liverpool L69 7WZ (United Kingdom); Carvalho, M.L. [LIBPhys – UNL, Faculty of Science and Technology, 2829-516 Caparica (Portugal); Guerra, M.F. [ArchAm, UMR 8096 CNRS - Université Paris Sorbonne, MAE, 21 allée de l' Université, 92023 Nanterre (France)

    2015-06-01

    Recent results from a three-year multi-disciplinary project on Ancient Egyptian gold jewellery revealed that items of jewellery from the Middle Kingdom to the New Kingdom were manufactured using a variety of alluvial gold alloys. These alloys cover a wide range of colours and the majority contain Platinum Group Elements inclusions. However, in all the gold foils analysed, these inclusions were found to be absent. In this work a selection of gilded wood and leather items and gold foil fragments, all from the excavations by John Garstang at Abydos (primarily from Middle Kingdom graves), were examined using Scanning Electron Microscopy-Energy Disperse Spectroscopy (SEM-EDS), X-Ray Fluorescence (μXRF), Particle Induced X-Ray Emission (µPIXE) and Double Dispersive X-Ray Fluorescence (D{sup 2}XRF). The work allowed us to characterise the composition of the base-alloys and also to reveal the presence of Pt at trace levels, confirming the use of alluvial gold deposits. Corrosion products were also investigated in the foils where surface tarnish was visually observed. Results showed that the differences in the colour of corrosion observed for the foils are related not only to the thickness of the corrosion layer but also to a multi-layer structure containing the various corrosion products. - Highlights: • Multi-analytical protocol based on techniques with different MDLs and spatial resolution • Application of D{sup 2}XRF developed at synchrotron BESSY II for determination of Pt in Au with a MDL of 1 ppm • Egyptian gold alloys have nanoporous corrosion layers where distinct corrosion phases could be identified. • Egyptian gold foils are made with different gold base alloys, but all containing alluvial gold.

  20. A multi-analytical approach to gold in Ancient Egypt: Studies on provenance and corrosion

    International Nuclear Information System (INIS)

    Tissot, I.; Troalen, L.G.; Manso, M.; Ponting, M.; Radtke, M.; Reinholz, U.; Barreiros, M.A.; Shaw, I.; Carvalho, M.L.; Guerra, M.F.

    2015-01-01

    Recent results from a three-year multi-disciplinary project on Ancient Egyptian gold jewellery revealed that items of jewellery from the Middle Kingdom to the New Kingdom were manufactured using a variety of alluvial gold alloys. These alloys cover a wide range of colours and the majority contain Platinum Group Elements inclusions. However, in all the gold foils analysed, these inclusions were found to be absent. In this work a selection of gilded wood and leather items and gold foil fragments, all from the excavations by John Garstang at Abydos (primarily from Middle Kingdom graves), were examined using Scanning Electron Microscopy-Energy Disperse Spectroscopy (SEM-EDS), X-Ray Fluorescence (μXRF), Particle Induced X-Ray Emission (µPIXE) and Double Dispersive X-Ray Fluorescence (D 2 XRF). The work allowed us to characterise the composition of the base-alloys and also to reveal the presence of Pt at trace levels, confirming the use of alluvial gold deposits. Corrosion products were also investigated in the foils where surface tarnish was visually observed. Results showed that the differences in the colour of corrosion observed for the foils are related not only to the thickness of the corrosion layer but also to a multi-layer structure containing the various corrosion products. - Highlights: • Multi-analytical protocol based on techniques with different MDLs and spatial resolution • Application of D 2 XRF developed at synchrotron BESSY II for determination of Pt in Au with a MDL of 1 ppm • Egyptian gold alloys have nanoporous corrosion layers where distinct corrosion phases could be identified. • Egyptian gold foils are made with different gold base alloys, but all containing alluvial gold

  1. Dental radiography

    International Nuclear Information System (INIS)

    Shekhdar, J.

    1993-01-01

    Dental radiography must comply with the same regulations with which conventional radiography complies. Radiation doses to individual patients are low but, because of the large number of patients X-rayed, the collective dose to the population is not negligible. Care in siting and regular maintenance of the equipment will reduce doses to both staff and patients. To produce X-ray films with a good image quality using a low radiation dose requires attention to film processing; this is often a neglected area. (Author)

  2. Dental erozyon

    NARCIS (Netherlands)

    Özen, B.; Yönel, N.; Çetiner, S.

    2015-01-01

    Dental erozyon, plak içermeyen diş yüzeyleri üzerinde içsel ve dışsal asitlerin veya şelatların etkileriyle oluşan kimyasal bir aşınmadır. İçsel ve/veya dışsal kaynaklar nedensel faktörler olarak tanımlanırken tükürük ve pelikıl gibi biyolojik faktörler, yeme ve içme alışkanlıkları ve ağız hijyeni

  3. Comparison of mechanical and corrosion properties of graphene monolayer on Ti–Al–V and nanometric Nb{sub 2}O{sub 5} layer on Ti–Al–V alloy for dental implants applications

    Energy Technology Data Exchange (ETDEWEB)

    Kalisz, M., E-mail: malgorzata.kalisz@its.waw.pl [Motor Transport Institute, Jagiellońska 80, 03-301 Warsaw (Poland); Grobelny, M. [Motor Transport Institute, Jagiellońska 80, 03-301 Warsaw (Poland); Mazur, M. [Wroclaw University of Technology, Faculty of Microsystem Electronics and Photonics, Janiszewskiego 11/17, 50-372 Wroclaw (Poland); Zdrojek, M. [Faculty of Physics, Warsaw University of Technology, Koszykowa 75, 00-662 Warsaw (Poland); Wojcieszak, D. [Wroclaw University of Technology, Faculty of Microsystem Electronics and Photonics, Janiszewskiego 11/17, 50-372 Wroclaw (Poland); Świniarski, M.; Judek, J. [Faculty of Physics, Warsaw University of Technology, Koszykowa 75, 00-662 Warsaw (Poland); Kaczmarek, D. [Wroclaw University of Technology, Faculty of Microsystem Electronics and Photonics, Janiszewskiego 11/17, 50-372 Wroclaw (Poland)

    2015-08-31

    In this paper the comparative studies on structural, mechanical and corrosion properties of Nb{sub 2}O{sub 5}/Ti–Al–V and graphene/Ti–Al–V alloy systems have been investigated. We show that the hardness of pure niobium pentoxide was ca. 8.64 GPa and graphene deposited on titanium alloy surface was equal 5.63 GPa. However, the graphene monolayer has no effect on surface hardness of titanium alloy and can be easily removed from the surface. On the other hand, the sample with graphene coating has much better corrosion resistance. Our results suggest, that the use of combined layers of niobium pentoxide and graphene, in the hybrid multilayer system can greatly improve the mechanical and corrosion properties of the titanium alloy surface. Such hybrid system can be used in the future, as protection coating for Ti alloy, in biomedical application and in other applications, where Ti alloys work in an aggressive corrosive environment and in engineering applications where friction is involved. - Highlights: • Corrosion properties of Nb{sub 2}O{sub 5}/TiAlV and graphene/TiAlV systems were investigated. • Nb{sub 2}O{sub 5} thin film improves titanium alloy surface hardness from 5.64 GPa to 8.64 GPa. • Nb{sub 2}O{sub 5} thin film improves corrosion resistance of Ti{sub 6}Al{sub 4}V in aggressive environment. • i{sub corr} for graphene monolayer deposited on Ti{sub 6}Al{sub 4}V surface decreases to 0.01 μA/cm{sup 2}. • Graphene monolayer caused decrease in the electrochemical activity of the Ti surface.

  4. Gold and uranium extraction

    International Nuclear Information System (INIS)

    James, G.S.; Davidson, R.J.

    1977-01-01

    A process for extracting gold and uranium from an ore containing them both comprising the steps of pulping the finely comminuted ore with a suitable cyanide solution at an alkaline pH, acidifying the pulp for uranium dissolution, adding carbon activated for gold recovery to the pulp at a suitable stage, separating the loaded activated carbon from the pulp, and recovering gold from the activated carbon and uranium from solution

  5. Gold mineralogy and extraction

    Energy Technology Data Exchange (ETDEWEB)

    Cashion, J.D.; Brown, L.J. [Monash University, Physics Department (Australia)

    1998-12-15

    Several examples are examined in which Moessbauer spectroscopic analysis of gold mineral samples, treated concentrates and extracted species has provided information not obtainable by competing techniques. Descriptions are given of current work on bacterial oxidation of pyritic ores and on the adsorbed species from gold extracted from cyanide and chloride solutions onto activated carbon and polyurethane foams. The potential benefits for the gold mining industry from Moessbauer studies and some limitations on the use of the technique are also discussed.

  6. Gold mineralogy and extraction

    International Nuclear Information System (INIS)

    Cashion, J.D.; Brown, L.J.

    1998-01-01

    Several examples are examined in which Moessbauer spectroscopic analysis of gold mineral samples, treated concentrates and extracted species has provided information not obtainable by competing techniques. Descriptions are given of current work on bacterial oxidation of pyritic ores and on the adsorbed species from gold extracted from cyanide and chloride solutions onto activated carbon and polyurethane foams. The potential benefits for the gold mining industry from Moessbauer studies and some limitations on the use of the technique are also discussed

  7. Molecular dynamics study of atomic displacements in disordered solid alloys

    Science.gov (United States)

    Puzyrev, Yevgeniy S.

    The effects of atomic displacements on the energetics of alloys plays important role in the determining the properties of alloys. We studied the atomic displacements in disordered solid alloys using molecular dynamics and Monte-Carlo methods. The diffuse scattering of pure materials, copper, gold, nickel, and palladium was calculated. The experimental data for pure Cu was obtained from diffuse scattering intensity of synchrotron x-ray radiation. The comparison showed the advantages of molecular dynamics method for calculating the atomic displacements in solid alloys. The individual nearest neighbor separations were calculated for Cu 50Au50 alloy and compared to the result of XAFS experiment. The molecular dynamics method provided theoretical predictions of nearest neighbor pair separations in other binary alloys, Cu-Pd and Cu-Al for wide range of the concentrations. We also experimentally recovered the diffuse scattering maps for the Cu47.3Au52.7 and Cu85.2Al14.8 alloy.

  8. Study of X-ray spectrum of laser-produced gold plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Busquet, M. (CEA Centre d' Etudes de Limeil, 94 - Villeneuve-Saint-Georges (France)); Pain, D.; Bauche, J.; Luc-Koenig, E. (Centre National de la Recherche Scientifique, 91 - Orsay (France). Lab. Aime Cotton)

    1985-02-01

    Aiming at the spectroscopic diagnostic of gold plasmas, we have studied the wavelengths and intensities of X-ray spectral lines emitted in the range 4.4 to 6.2 angstroms by a target made of gold alloyed to a few percent of aluminium irradiated by a laser pulse. Aluminium yields the wavelength calibration and a monitoring of the temperature and the density of the plasma. The main features of the gold spectrum in this spectral range are due to the 3d-4f, 3p-4s and 3d-4p transitions of gold in the Co I through Cu I isoelectronic sequences.

  9. Study of X-ray spectrum of laser-produced gold plasmas

    International Nuclear Information System (INIS)

    Busquet, M.; Pain, D.; Bauche, J.; Luc-Koenig, E.

    1985-01-01

    Aiming at the spectroscopic diagnostic of gold plasmas, we have studied the wavelengths and intensities of X-ray spectral lines emitted in the range 4.4 to 6.2 angstroms by a target made of gold alloyed to a few percent of aluminium irradiated by a laser pulse. Aluminium yields the wavelength calibration and a monitoring of the temperature and the density of the plasma. The main features of the gold spectrum in this spectral range are due to the 3d-4f, 3p-4s and 3d-4p transitions of gold in the Co I through Cu I isoelectronic sequences. (orig.)

  10. Weaker dental enamel explains dental decay.

    Science.gov (United States)

    Vieira, Alexandre R; Gibson, Carolyn W; Deeley, Kathleen; Xue, Hui; Li, Yong

    2015-01-01

    Dental caries continues to be the most prevalent bacteria-mediated non-contagious disease of humankind. Dental professionals assert the disease can be explained by poor oral hygiene and a diet rich in sugars but this does not account for caries free individuals exposed to the same risk factors. In order to test the hypothesis that amount of amelogenin during enamel development can influence caries susceptibility, we generated multiple strains of mice with varying levels of available amelogenin during dental development. Mechanical tests showed that dental enamel developed with less amelogenin is "weaker" while the dental enamel of animals over-expressing amelogenin appears to be more resistant to acid dissolution.

  11. Supercapacitive transport of pharmacologic agents using nanoporous gold electrodes.

    Science.gov (United States)

    Gittard, Shaun D; Pierson, Bonnie E; Ha, Cindy M; Wu, Chung-An Max; Narayan, Roger J; Robinson, David B

    2010-02-01

    In this study, nanoporous gold supercapacitors were produced by electrochemical dealloying of gold-silver alloy. Scanning electron microscopy and energy dispersive X-ray spectroscopy confirmed completion of the dealloying process and generation of a porous gold material with approximately 10 nm diameter pores. Cyclic voltammetry and chronoamperometry of the nanoporous gold electrodes indicated that these materials exhibited supercapacitor behavior. The storage capacity of the electrodes measured by chronoamperometry was approximately 3 mC at 200 mV. Electrochemical storage and voltage-controlled delivery of two model pharmacologic agents, benzylammonium and salicylic acid, was demonstrated. These results suggest that capacitance-based storage and delivery of pharmacologic agents may serve as an alternative to conventional drug delivery methods.

  12. A halogen-free synthesis of gold nanoparticles using gold(III) oxide

    International Nuclear Information System (INIS)

    Sashuk, Volodymyr; Rogaczewski, Konrad

    2016-01-01

    Gold nanoparticles are one of the most used nanomaterials. They are usually synthesized by the reduction of gold(III) chloride. However, the presence of halide ions in the reaction mixture is not always welcome. In some cases, these ions have detrimental influence on the morphology and structure of resulting nanoparticles. Here, we present a simple and halogen-free procedure to prepare gold nanoparticles by reduction of gold(III) oxide in neat oleylamine. The method provides the particles with an average size below 10 nm and dispersity of tens of percent. The process of nanoparticle formation was monitored using UV–Vis spectroscopy. The structure and chemical composition of the nanoparticles was determined by SEM, XPS and EDX. We also proposed the mechanism of reduction of gold(III) oxide based on MS, IR and NMR data. Importantly, the synthetic protocol is general and applicable for the preparation of other coinage metal nanoparticles from the corresponding metal oxides. For instance, we demonstrated that the absence of halogen enables efficient alloying of metals when preparing gold–silver bimetallic nanoparticles.

  13. Nonswelling alloy

    Science.gov (United States)

    Harkness, S.D.

    1975-12-23

    An aluminum alloy containing one weight percent copper has been found to be resistant to void formation and thus is useful in all nuclear applications which currently use aluminum or other aluminum alloys in reactor positions which are subjected to high neutron doses.

  14. Nonswelling alloy

    International Nuclear Information System (INIS)

    Harkness, S.D.

    1975-01-01

    An aluminum alloy containing one weight percent copper has been found to be resistant to void formation and thus is useful in all nuclear applications which currently use aluminum or other aluminum alloys in reactor positions which are subjected to high neutron doses

  15. Impact of Surface Potential on Apatite Formation in Ti Alloys Subjected to Acid and Heat Treatments.

    Science.gov (United States)

    Yamaguchi, Seiji; Hashimoto, Hideki; Nakai, Ryusuke; Takadama, Hiroaki

    2017-09-24

    Titanium metal (Ti) and its alloys are widely used in orthopedic and dental fields. We have previously shown that acid and heat treatment was effective to introduce bone bonding, osteoconduction and osteoinduction on pure Ti. In the present study, acid and heat treatment with or without initial NaOH treatment was performed on typical Ti-based alloys used in orthopedic and dental fields. Dynamic movements of alloying elements were developed, which depended on the kind of treatment and type of alloy. It was found that the simple acid and heat treatment enriched/remained the alloying elements on Ti-6Al-4V, Ti-15Mo-5Zr-3Al and Ti-15Zr-4Nb-4Ta, resulting in neutral surface charges. Thus, the treated alloys did not form apatite in a simulated body fluid (SBF) within 3 days. In contrast, when the alloys were subjected to a NaOH treatment prior to an acid and heat treatment, alloying elements were selectively removed from the alloy surfaces. As a result, the treated alloys became positively charged, and formed apatite in SBF within 3 days. Thus, the treated alloys would be useful in orthopedic and dental fields since they form apatite even in a living body and bond to bone.

  16. Theory of surface enrichment in disordered monophasic binary alloys. Numerical computations for Ag-Au alloys

    NARCIS (Netherlands)

    Santen, van R.A.; Boersma, M.A.M.

    1974-01-01

    The regular solution model is used to compute the surface enrichment in the (111)- and (100)-faces of silver-gold alloys. Surface enrichment by silver is predicted to increase if the surface plane becomes less saturated and decreases if one raises the temperature. The possible implications of these

  17. BROOKHAVEN: High energy gold

    International Nuclear Information System (INIS)

    Bleser, Ed

    1992-01-01

    On April 24, Brookhaven's Alternating Gradient Synchrotron (AGS) started to deliver gold ions at 11.4 GeV per nucleon (2,000 GeV per ion) to experimenters who were delighted not only to receive the world's highest energy gold beam but also to receive it on schedule

  18. Evaluation of MRI artifacts caused by metallic dental implants and classification of the dental materials in use

    Czech Academy of Sciences Publication Activity Database

    Starčuk jr., Zenon; Bartušek, Karel; Hubálková, H.; Bachorec, T.; Starčuková, Jana; Krupa, P.

    2006-01-01

    Roč. 6, č. 2 (2006), s. 24-27 ISSN 1335-8871 R&D Projects: GA MZd NR8110 Institutional research plan: CEZ:AV0Z20650511 Keywords : magnetic resonance imaging * artifacts * metallic implants * dental alloys * magnetic susceptibility Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  19. Evaluation and comparison of castability between an indigenous and imported Ni-Cr alloy.

    Science.gov (United States)

    Ramesh, Ganesh; Padmanabhan, T V; Ariga, Padma; Subramanian, R

    2011-01-01

    Since 1907 casting restorations have been in use in dentistry. Numerous companies have been manufacturing and marketing base metal alloys. Gold was a major component of casting alloys. But alloys with less than 65% gold tarnished easily and the increase in cost of gold post-1970s lead to the revival of base metal alloys such as nickel-chromium and cobalt-chromium alloys which were in use since 1930s. This study was conducted to evaluate and compare the castability between an indigenous alloy and an imported alloy, as imported base metal alloys are considered to be expensive for fabrication of crowns and bridges. This study was conducted to evaluate and compare the castability (for the accurate fabrication of crowns and bridges) between an indigenous base metal alloy-Non-ferrous Materials Technology Development Centre (NFTDC), Hyderabad (Alloy A) -and an imported base metal alloys (Alloy B). Castability measurement was obtained by counting the number of completely formed line segments surrounding the 81 squares in the pattern and later calculating the percentage values. The percentage obtained was taken as the castability value for a particular base metal alloy. The percentage of castability was determined by counting only the number of completely cast segments in a perfect casting (81 × 2 = 162), and then multiplying the resulting fraction by 100 to give the percentage completeness. The Student t-test was used. When the castability of alloys A and B was compared, the calculated value was less than the tabular value (1.171 indigenous alloy is on par with the imported alloy.

  20. Electrical Resistance Alloys and Low-Expansion Alloys

    DEFF Research Database (Denmark)

    Kjer, Torben

    1996-01-01

    The article gives an overview of electrical resistance alloys and alloys with low thermal expansion. The electrical resistance alloys comprise resistance alloys, heating alloys and thermostat alloys. The low expansion alloys comprise alloys with very low expansion coefficients, alloys with very low...... thermoelastic coefficients and age hardenable low expansion alloys....

  1. Dental amalgam and mercury vapor release.

    Science.gov (United States)

    Osborne, J W

    1992-09-01

    Dental diseases are among the most common ailments, and dentists in the United States spend over 50% of their time in dental practice rebuilding carious, malformed, and traumatically injured teeth. It is logical, therefore, that the majority of the dental school curriculum is devoted to the diagnosis, prevention, and treatment of teeth with anomalies. Dentists have several choices of materials they can use to accomplish the task of rebuilding teeth. Besides amalgam, they have ceramic materials, resin composites, base-metal and noble casting alloys, and glass-ionomer cements to use to restore the posterior dentition. Each of these restorative materials has advantages and disadvantages, and the clinical judgment as to when a particular material should be used is given a high priority in dental education. Amalgam is the most widely used of these restorative materials, with 92% of dentists listing it as the material of choice in the posterior of the mouth (Clinical Research Associates, 1990). Dentists have been placing amalgams for over 150 years in the US. They placed 150 million last year, which represents over 75 tons of amalgam alloy. The reasons that dentists use this restorative material so frequently are its durability, ease of manipulation, and low cost. Numerous clinical studies have been conducted on the serviceability of amalgam. Most of these have been on the old, low-copper alloys, and results indicate that they last from 8 to 15 years (Bailit et al., 1979; Osborne et al., 1980; Qvist et al., 1986). In the past 20 years, vast improvements have been made in amalgams with the development of the high-copper systems.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. Fluorescent Thiol-Derivatized Gold Clusters Embedded in Polymers

    Directory of Open Access Journals (Sweden)

    G. Carotenuto

    2013-01-01

    Full Text Available Owing to aurophilic interactions, linear and/or planar Au(I-thiolate molecules spontaneously aggregate, leading to molecular gold clusters passivated by a thiolate monolayer coating. Differently from the thiolate precursors, such cluster compounds show very intensive visible fluorescence characteristics that can be tuned by alloying the gold clusters with silver atoms or by conjugating the electronic structure of the metallic core with unsaturated electronic structures in the organic ligand through the sulphur atom. Here, the photoluminescence features of some examples of these systems are shortly described.

  3. Orthodontic applications of a superelastic shape-memory alloy model

    International Nuclear Information System (INIS)

    Glendenning, R.W.; Enlow, R.L.

    2000-01-01

    During orthodontic treatment, dental appliances (braces) made of shape memory alloys have the potential to provide nearly uniform low level stresses to dentitions during tooth movement over a large range of tooth displacement. In this paper we model superelastic behaviour of dental appliances using the finite element method and constitutive equations developed by F. Auricchio et al. Results of the mathematical model for 3-point bending and several promising 'closing loop' designs are compared with laboratory results for the same configurations. (orig.)

  4. Superfluid density and heat capacity measurements of 4He in porous gold

    International Nuclear Information System (INIS)

    Yoon, J.; Chan, M.

    1995-01-01

    Superfluid density of full pore 4 He as well as thin film 4 He confined in porous gold were measured as a function of temperature. The superfluid transition temperature of full pore was found to be 2.156 K. In both cases power law dependence on reduced temperature was found and the exponent was found to be the same as that of bulk 4 He. Porous gold is made by electrochemically leaching out silver from silver-gold alloy. The porous gold sample the authors fabricated has porosity of 55 with a diameter of 250 angstrom. Electron microscope picture shows that the structure of porous gold is exceedingly similar to that of Vycor. Heat capacity measurement of full pore 4 He in porous gold is in progress

  5. Preparation and bactericide activity of gallic acid stabilized gold nanoparticles

    International Nuclear Information System (INIS)

    Moreno-Alvarez, S. A.; Martinez-Castanon, G. A.; Nino-Martinez, N.; Reyes-Macias, J. F.; Patino-Marin, N.; Loyola-Rodriguez, J. P.; Ruiz, Facundo

    2010-01-01

    In this work, gold nanoparticles with three different sizes (13.7, 39.4, and 76.7 nm) were prepared using a simple aqueous method with gallic acid as the reducing and stabilizing agent, the different sizes were obtained varying some experimental parameters as the pH of the reaction and the amount of the gallic acid. The prepared nanoparticles were characterized using X-ray diffraction, transmission electron microscopy, dynamic light scattering, and UV-Vis spectroscopy. Samples were identified as elemental gold and present spherical morphology, a narrow size distribution and good stabilization according to TEM and DLS results. The antibacterial activity of this gallic acid stabilized gold nanoparticles against S. mutans (the etiologic agent of dental caries) was assessed using a microdilution method obtaining a minimum inhibitory concentration of 12.31, 12.31, and 49.25 μg/mL for 13.7, 39.4, and 76.7 nm gold nanoparticles, respectively. The antibacterial assay showed that gold nanoparticles prepared in this work present a bactericide activity by a synergistic action with gallic acid. The MIC found for this nanoparticles are much lower than those reported for mixtures of gold nanoparticles and antibiotics.

  6. Preparation and bactericide activity of gallic acid stabilized gold nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Moreno-Alvarez, S. A. [UASLP, Doctorado Institucional en Ingenieria y Ciencia de Materiales (Mexico); Martinez-Castanon, G. A., E-mail: mtzcastanon@fciencias.uaslp.m [UASLP, Maestria en Ciencias Odontologicas, Facultad de Estomatologia (Mexico); Nino-Martinez, N. [UASLP, Facultad de Ciencias (Mexico); Reyes-Macias, J. F.; Patino-Marin, N.; Loyola-Rodriguez, J. P. [UASLP, Maestria en Ciencias Odontologicas, Facultad de Estomatologia (Mexico); Ruiz, Facundo [UASLP, Facultad de Ciencias (Mexico)

    2010-10-15

    In this work, gold nanoparticles with three different sizes (13.7, 39.4, and 76.7 nm) were prepared using a simple aqueous method with gallic acid as the reducing and stabilizing agent, the different sizes were obtained varying some experimental parameters as the pH of the reaction and the amount of the gallic acid. The prepared nanoparticles were characterized using X-ray diffraction, transmission electron microscopy, dynamic light scattering, and UV-Vis spectroscopy. Samples were identified as elemental gold and present spherical morphology, a narrow size distribution and good stabilization according to TEM and DLS results. The antibacterial activity of this gallic acid stabilized gold nanoparticles against S. mutans (the etiologic agent of dental caries) was assessed using a microdilution method obtaining a minimum inhibitory concentration of 12.31, 12.31, and 49.25 {mu}g/mL for 13.7, 39.4, and 76.7 nm gold nanoparticles, respectively. The antibacterial assay showed that gold nanoparticles prepared in this work present a bactericide activity by a synergistic action with gallic acid. The MIC found for this nanoparticles are much lower than those reported for mixtures of gold nanoparticles and antibiotics.

  7. Medicinal gold compounds

    International Nuclear Information System (INIS)

    Parish, R.V.; Cottrill, S.M.

    1987-01-01

    A major use of gold compounds in the pharmaceutical industry is for anti-arthritic agents. The disease itself is not understood and little is known about the way in which the drugs act, but detailed pictures of the distribution of gold in the body are available, and some of the relevant biochemistry is beginning to emerge. The purpose of this article is to give a survey of the types of compounds presently employed in medicine, of the distribution of gold in the body which results from their use, and of some relevant chemistry. Emphasis is placed on results obtained in the last few years

  8. Elementary characterization of Ti metal alloys used in implant dentistry

    Energy Technology Data Exchange (ETDEWEB)

    Torres, Catarina A. M. P.; Paschuk, Sergei A.; Rocha, Anna S. S.; Corrêa, Janine Nicolosi [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil); Deniak, Valeriy [Instituto de Pesquisa Pelé Pequeno Príncipe, Curitiba, PR (Brazil); Camargo, Liliane [Universidade Paranaense, Umuarama, PR (Brazil); Assis, J.T, E-mail: cata-montenegro@bol.com.br, E-mail: spaschuk@gmail.com, E-mail: denyak@gmail.com, E-mail: lili_camargo2@hotmail.com, E-mail: joaquim@iprj.uerj.br [Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil)

    2017-07-01

    The main goal of present work is analytical characterization of standard dental implants broadly used by Brazilian dentists. An ideal biological alloy for dental implants must have very high biocompatibility, which means that such material should not provoke any serious adverse tissue response. Dental implants are generally marketed as commercially pure titanium (TiCP) due to their excellent mechanical and physical properties. However, sometimes other alloys are employed and consequently it is essential to study the chemical elements present in those alloys that could bring prejudice for the health. Present work investigated TiCP metal alloys used for dental implant manufacturing and evaluated the presence of elements. For alloy characterization and identification of elements it was used EDXRF technique. This method allows to perform the qualitative and quantitative analysis of the materials using the spectra of the characteristic X-rays emitted by the elements present in the metal samples. The experimental setup was based on two X- ray tubes, Mini X model with Ag and Au targets and X-123SDD detector (AMPTEK) and a 0.5 mm Cu collimator, developed due to specific sample geometrical and topography characteristics. Obtained results showed that implant alloys are not exactly TiCP but were manufactured using Ti-Al-V alloy, which contained Fe, Ni, Cu and Zn. The presence of such metals as Al and V in all studied samples shows very clear that studied implants were not manufactured from TiCP alloy. Moreover, according to the American Society for Testing and Materials (ASTM), these elements should not be present in TiCP. (author)

  9. Electrochemical Characterization of Surface Reactions on Biomedical Titanium alloys

    OpenAIRE

    Alkhateeb, Emad Hashim

    2008-01-01

    Titanium and its alloys are successfully used as implant materials for dental, orthopedic and osteosynthesis applications. The processes that take place at the implant tissue interface are important for the acceptance and integration of the implant. This thesis is divided into two parts: the first part deals with surface modification of titanium to improve the osseointegration, and the second part studies metastable pitting of titanium and its alloys. The weakly attached layer of a bone-like ...

  10. Elementary characterization of Ti metal alloys used in implant dentistry

    International Nuclear Information System (INIS)

    Torres, Catarina A. M. P.; Paschuk, Sergei A.; Rocha, Anna S. S.; Corrêa, Janine Nicolosi; Deniak, Valeriy; Camargo, Liliane; Assis, J.T

    2017-01-01

    The main goal of present work is analytical characterization of standard dental implants broadly used by Brazilian dentists. An ideal biological alloy for dental implants must have very high biocompatibility, which means that such material should not provoke any serious adverse tissue response. Dental implants are generally marketed as commercially pure titanium (TiCP) due to their excellent mechanical and physical properties. However, sometimes other alloys are employed and consequently it is essential to study the chemical elements present in those alloys that could bring prejudice for the health. Present work investigated TiCP metal alloys used for dental implant manufacturing and evaluated the presence of elements. For alloy characterization and identification of elements it was used EDXRF technique. This method allows to perform the qualitative and quantitative analysis of the materials using the spectra of the characteristic X-rays emitted by the elements present in the metal samples. The experimental setup was based on two X- ray tubes, Mini X model with Ag and Au targets and X-123SDD detector (AMPTEK) and a 0.5 mm Cu collimator, developed due to specific sample geometrical and topography characteristics. Obtained results showed that implant alloys are not exactly TiCP but were manufactured using Ti-Al-V alloy, which contained Fe, Ni, Cu and Zn. The presence of such metals as Al and V in all studied samples shows very clear that studied implants were not manufactured from TiCP alloy. Moreover, according to the American Society for Testing and Materials (ASTM), these elements should not be present in TiCP. (author)

  11. Dental Sealants Prevent Cavities

    Science.gov (United States)

    ... Digital Press Kit Read the MMWR Science Clips Dental Sealants Prevent Cavities Effective protection for children Language: ... more use of sealants and reimbursement of services. Dental care providers can Apply sealants to children at ...

  12. Dental Care in Scleroderma

    Science.gov (United States)

    Dental Care in Scleroderma People living with scleroderma face unique challenges while trying to maintain their oral ... They are more likely to be affected by dental conditions such as small mouth, dry mouth, jaw ...

  13. American Dental Association

    Science.gov (United States)

    ... CE providers and find CE courses. Commission on Dental Accreditation Explore CODA's role and find accredited schools and programs Joint Commission on National Dental Examinations Learn about the examinations used in licensing ...

  14. Diabetes: Dental Tips

    Science.gov (United States)

    Diabetes: Dental Tips For more copies contact: National Institute of Dental and Craniofacial Research National Oral Health Information Clearinghouse ... damage the gum and bone that hold your teeth in place and may lead to painful chewing ...

  15. American Dental Hygienists' Association

    Science.gov (United States)

    ... Now Autumn Giving: ‘Fall’ into the Future of Dental Hygiene Support the Institute for Oral Health! Give ... best for your patients! Learn More Sidebar Menu Dental Hygiene Programs Continuing Education Career Center Annual Conference ...

  16. Dental Effluent Guidelines

    Science.gov (United States)

    Overview and documents for Dental Office Category regulation (40 CFR Part 441); comprising pretreatment standards for discharges of dental amalgam pollutants, including mercury, into publicly owned treatment works (POTWs).

  17. Dental Encounter System (DES)

    Data.gov (United States)

    Department of Veterans Affairs — Dental Encounter System (DES) is an automated health care application designed to capture critical data about the operations of VA Dental Services. Information on...

  18. Dental Caries (Tooth Decay)

    Science.gov (United States)

    ... Materials Contact Us Home Research Data & Statistics Dental Caries (Tooth Decay) Dental caries (tooth decay) remains the most prevalent chronic disease ... adults, even though it is largely preventable. Although caries has significantly decreased for most Americans over the ...

  19. Dental Caries (Tooth Decay)

    Science.gov (United States)

    ... Contact Us Home Research Data & Statistics Share Dental Caries (Tooth Decay) Dental caries (tooth decay) remains the most prevalent chronic disease ... adults, even though it is largely preventable. Although caries has significantly decreased for most Americans over the ...

  20. Synthesis, Structure, Stability and Redispersion of Gold-based Nanoparticles

    Science.gov (United States)

    Tiruvalam, Ram Chandra

    Nanoscale gold has been shown to possess an intriguing combination of unexpected optical, photochemical and catalytic properties. The ability to control the size, shape, morphology, composition and dispersion of gold-based nanostructures is key to optimizing their performance for nanotechnology applications. The advanced electron microscopy studies described in this thesis analyze three important aspects of gold and gold-palladium alloy nanoparticles: namely, (i) the ability to synthesize gold nanoparticles of controlled size and shape in an aqueous medium; (ii) the colloidal preparation of designer gold-palladium alloys for selective oxidation catalysis; and (iii) the ability to disperse gold as finely and homogeneously as possible on a metal oxide or carbon support. The ability to exploit the nanoscale properties of gold for various engineering applications often depends on our ability to control size and shape of the nanoscale entity by careful manipulation of the synthesis parameters. We have explored an aqueous based synthesis route, using oleylamine as both a reductant and surfactant, for preparing gold nanostructures. By systematically varying synthesis parameters such as oleylamine concentration, reaction temperature, and aging time it is possible to identify processing regimens that generate Au nanostructures having either pseudo-spherical, faceted polyhedral, nanostar or wire shaped morphologies. Furthermore, by quenching the reaction partway through it is possible to create a class of metastable Au-containing structures such as nanocubes, nanoboxes and nanowires. Possible formation mechanisms for these gold based nano-objects are discussed. There is a growing interest in using supported bimetallic AuPd alloy nanoparticles for selective oxidation reactions. In this study, a systematic series of size controlled AuPd bimetallic particles have been prepared by colloidal synthesis methods. Particles having random alloy structures, as well as `designer

  1. Corrosion Behavior of Ti-13Nb-13Zr and Ti-6Al-4V Alloys for Biomaterial Application

    Energy Technology Data Exchange (ETDEWEB)

    Saji, Viswanathan S.; Jeong, Yong Hoon; Choe, Han Cheol [Chosun University, Gwangju (Korea, Republic of); Yu, Jin Woo [Shingyeong University, Hwaseong (Korea, Republic of)

    2010-02-15

    Ti-13Nb-13Zr (TNZ) alloy has attracted considerable research attention in the last decade as a suitable substitute for the commercially used Ti-6Al-4V (TAV) alloy for orthopedic and dental implant applications. Hence, in the present work, a comparative evaluation has been performed on the electrochemical corrosion behavior of TNZ and TAV alloys in 0.9 wt.% NaCl solution. The result of the study showed that both the alloys had similar electrochemical behavior. The corrosion resistance of TAV alloy is found to be marginally superior to that of TNZ alloy.

  2. Corrosion Behavior of Ti-13Nb-13Zr and Ti-6Al-4V Alloys for Biomaterial Application

    International Nuclear Information System (INIS)

    Saji, Viswanathan S.; Jeong, Yong Hoon; Choe, Han Cheol; Yu, Jin Woo

    2010-01-01

    Ti-13Nb-13Zr (TNZ) alloy has attracted considerable research attention in the last decade as a suitable substitute for the commercially used Ti-6Al-4V (TAV) alloy for orthopedic and dental implant applications. Hence, in the present work, a comparative evaluation has been performed on the electrochemical corrosion behavior of TNZ and TAV alloys in 0.9 wt.% NaCl solution. The result of the study showed that both the alloys had similar electrochemical behavior. The corrosion resistance of TAV alloy is found to be marginally superior to that of TNZ alloy

  3. The Gold Standard Programme

    DEFF Research Database (Denmark)

    Neumann, Tim; Rasmussen, Mette; Ghith, Nermin

    2013-01-01

    To evaluate the real-life effect of an evidence-based Gold Standard Programme (GSP) for smoking cessation interventions in disadvantaged patients and to identify modifiable factors that consistently produce the highest abstinence rates.......To evaluate the real-life effect of an evidence-based Gold Standard Programme (GSP) for smoking cessation interventions in disadvantaged patients and to identify modifiable factors that consistently produce the highest abstinence rates....

  4. Gold nanoprobes for theranostics

    Science.gov (United States)

    Panchapakesan, Balaji; Book-Newell, Brittany; Sethu, Palaniappan; Rao, Madhusudhana; Irudayaraj, Joseph

    2011-01-01

    Gold nanoprobes have become attractive diagnostic and therapeutic agents in medicine and life sciences research owing to their reproducible synthesis with atomic level precision, unique physical and chemical properties, versatility of their morphologies, flexibility in functionalization, ease of targeting, efficiency in drug delivery and opportunities for multimodal therapy. This review highlights some of the recent advances and the potential for gold nanoprobes in theranostics. PMID:22122586

  5. DENTAL SCHOOL PLANNING.

    Science.gov (United States)

    GALAGAN, DONALD J.

    THIS DISCUSSION PRESENTS A COMPLETE PICTURE OF THE CURRENT STATE OF DENTAL EDUCATION WITH SUGGESTIONS FOR MEETING THE DEMANDS FOR DENTAL STAFF AND FACILITIES. THE AREAS INVESTIGATED ARE (1) OBJECTIVES IN DENTAL EDUCATION--COURSES, TEACHING MODES, INNOVATIONS IN CURRICULUM, COORDINATION OF BASIC AND CLINICAL INSTRUCTION, (2) FACILITY…

  6. Stress Among Dental Students

    NARCIS (Netherlands)

    A.M. Alzahem (Abdullah)

    2015-01-01

    markdownabstractAbstract Dental students are facing many stressors in dental education, causing many negative outcomes. The most common are the exams and the clinical requirements. We suggest exposing the dental students to patient care as early as possible in their curriculum. This can help to

  7. Facts and Fantasies about Gold

    OpenAIRE

    Klement, Joachim

    2015-01-01

    Due to the increasing popularity of gold as an investment the demand for effective risk management techniques for gold investments has increased as well. In this paper we analyze several drivers of the price of gold that have been proposed in the past. Our analysis indicates that short-term volatility of the price of gold remains rather unpredictable with many of the explanations like the fund flows in physical gold ETF either unreliable or unstable over time. Our analysis suggests that there...

  8. Marketing Dental Services | Tuominen | Tanzania Dental Journal

    African Journals Online (AJOL)

    Tanzania Dental Journal. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 9, No 1 (2000) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register. Marketing Dental Services. R Tuominen. Abstract. No Abstract.

  9. Dental Radiographs Ordered by Dental Professionals: an ...

    African Journals Online (AJOL)

    Conclusions: Even in resource limited settings dental caries is still the regular indication for taking dental radiographs, and periapical views are the most frequent type of radiograph ordered. Maxillary central incisors and mandibular molars were types of teeth commonly x-rayed mainly due to the aesthetic importance of the ...

  10. Nanoporous Au: an unsupported pure gold catalyst?

    Energy Technology Data Exchange (ETDEWEB)

    Wittstock, A; Neumann, B; Schaefer, A; Dumbuya, K; Kuebel, C; Biener, M; Zielasek, V; Steinrueck, H; Gottfried, M; Biener, J; Hamza, A; B?umer, M

    2008-09-04

    The unique properties of gold especially in low temperature CO oxidation have been ascribed to a combination of various effects. In particular, particle sizes below a few nm and specific particle-support interactions have been shown to play important roles. On the contrary, recent reports revealed that monolithic nanoporous gold (npAu) prepared by leaching a less noble metal, such as Ag, out of the corresponding alloy can also exhibit remarkably high catalytic activity for CO oxidation, even though no support is present. Therefore, it was claimed to be a pure and unsupported gold catalyst. We investigated npAu with respect to its morphology, surface composition and catalytic properties. In particular, we studied the reaction kinetics for low temperature CO oxidation in detail taking mass transport limitation due to the porous structure of the material into account. Our results reveal that Ag, even if removed almost completely from the bulk, segregates to the surface resulting in surface concentrations of up to 10 at%. Our data suggest that this Ag plays a significant role in activation of molecular oxygen. Therefore, npAu should be considered as a bimetallic catalyst rather than a pure Au catalyst.

  11. Antibacterial properties and mechanisms of gold-silver nanocages

    Science.gov (United States)

    Wang, Yulan; Wan, Jiangshan; Miron, Richard J.; Zhao, Yanbin; Zhang, Yufeng

    2016-05-01

    Despite the number of antibiotics used in routine clinical practice, bacterial infections continue to be one of the most important challenges faced in humans. The main concerns arise from the continuing emergence of antibiotic-resistant bacteria and the difficulties faced with the pharmaceutical development of new antibiotics. Thus, advancements in the avenue of novel antibacterial agents are essential. In this study, gold (Au) was combined with silver (Ag), a well-known antibacterial material, to form silver nanoparticles producing a gold-silver alloy structure with hollow interiors and porous walls (gold-silver nanocage). This novel material was promising in antibacterial applications due to its better biocompatibility than Ag nanoparticles, potential in photothermal effects and drug delivery ability. The gold-silver nanocage was then tested for its antibacterial properties and the mechanism involved leading to its antibacterial properties. This study confirms that this novel gold-silver nanocage has broad-spectrum antibacterial properties exerting its effects through the destruction of the cell membrane, production of reactive oxygen species (ROS) and induction of cell apoptosis. Therefore, we introduce a novel gold-silver nanocage that serves as a potential nanocarrier for the future delivery of antibiotics.

  12. Determination of vitamin C in drugs using of an optimized novel TCPO–Amplex red–gold/silver alloy nanoparticles–H2O2 chemiluminescence method by the Box–Behnken design

    International Nuclear Information System (INIS)

    Chaichi, M.J.; Alijanpour, S.O.

    2013-01-01

    Response surface methodology (RSM), based on a Box–Behnken design (BBD) was used to optimize three of the most important operating variables (concentrations of TCPO, Amplex red and pH effect) at peroxyoxalate-chemiluminescence (PO-CL) system. For the first time Amplex red (AR) was introduced as a new fluorescent emitter for predicting the reaction mechanism of PO-CL by means of the fluorescence property of its oxidation product. In optimum conditions, it was found that Au/Ag alloy nanoparticles (NPs) could enhance the CL intensity and the method sensitivity toward the evaluation of trace amount of vitamin C. Based on the antioxidant property of vitamin C noticeably the CL signal of the bis-(2,4,6-trichlorophenyl)oxalate–AR–NPs–hydrogen peroxide–sodium salicylate system was quenched in a low basic medium. A simple, rapid and sensitive CL method for the determination of vitamin C has been developed. The results showed a linear relationship between vitamin C concentration and PO-CL intensity in the range of 0.082–82.7 μg/mL. Detection limit of 0.012 μg/mL and the relative standard deviation (RSD)<4% was obtained. - Highlights: ► The Box-Behnken design was used to optimize peroxyoxalate-chemiluminescence system. ► Amplex red is as new fluorescent emitters for peroxyoxalate chemiluminescence. ► It is introduce a method for determination of vitamin C. ► Detection limit of vitamin C was obtained about 0.012 μg/mL.

  13. Determination of vitamin C in drugs using of an optimized novel TCPO-Amplex red-gold/silver alloy nanoparticles-H{sub 2}O{sub 2} chemiluminescence method by the Box-Behnken design

    Energy Technology Data Exchange (ETDEWEB)

    Chaichi, M.J., E-mail: jchaichi@yahoo.com [Faculty of Chemistry, University of Mazandaran, Babolsar (Iran, Islamic Republic of); Alijanpour, S.O. [Faculty of Chemistry, University of Mazandaran, Babolsar (Iran, Islamic Republic of)

    2013-02-15

    Response surface methodology (RSM), based on a Box-Behnken design (BBD) was used to optimize three of the most important operating variables (concentrations of TCPO, Amplex red and pH effect) at peroxyoxalate-chemiluminescence (PO-CL) system. For the first time Amplex red (AR) was introduced as a new fluorescent emitter for predicting the reaction mechanism of PO-CL by means of the fluorescence property of its oxidation product. In optimum conditions, it was found that Au/Ag alloy nanoparticles (NPs) could enhance the CL intensity and the method sensitivity toward the evaluation of trace amount of vitamin C. Based on the antioxidant property of vitamin C noticeably the CL signal of the bis-(2,4,6-trichlorophenyl)oxalate-AR-NPs-hydrogen peroxide-sodium salicylate system was quenched in a low basic medium. A simple, rapid and sensitive CL method for the determination of vitamin C has been developed. The results showed a linear relationship between vitamin C concentration and PO-CL intensity in the range of 0.082-82.7 {mu}g/mL. Detection limit of 0.012 {mu}g/mL and the relative standard deviation (RSD)<4% was obtained. - Highlights: Black-Right-Pointing-Pointer The Box-Behnken design was used to optimize peroxyoxalate-chemiluminescence system. Black-Right-Pointing-Pointer Amplex red is as new fluorescent emitters for peroxyoxalate chemiluminescence. Black-Right-Pointing-Pointer It is introduce a method for determination of vitamin C. Black-Right-Pointing-Pointer Detection limit of vitamin C was obtained about 0.012 {mu}g/mL.

  14. Biosynthesis of gold nanoparticles using diatoms-silica-gold and EPS-gold bionanocomposite formation

    OpenAIRE

    Schröfel, Adam; Kratošová, Gabriela; Bohunická, Markéta; Dobročka, Edmund; Vávra, Ivo

    2011-01-01

    Novel synthesis of gold nanoparticles, EPS-gold, and silica-gold bionanocomposites by biologically driven processes employing two diatom strains (Navicula atomus, Diadesmis gallica) is described. Transmission electron microscopy (TEM) and electron diffraction analysis (SAED) revealed a presence of gold nanoparticles in the experimental solutions of the diatom culture mixed with tetrachloroaureate. Nature of the gold nanoparticles was confirmed by X-ray diffraction studies. Scanning electron m...

  15. Metallic artifacts caused by dental metal prostheses on PET images. A PET/CT phantom study using different PET/CT scanners

    International Nuclear Information System (INIS)

    Shimamoto, Hiroaki; Kakimoto, Naoya; Murakami, Shumei; Furukawa, Souhei; Fujino, Kouichi; Hamada, Seiki; Shimosegawa, Eku; Hatazawa, Jun

    2009-01-01

    The objective of this study was to investigate the effects of computed tomography (CT) artifacts caused by dental metal prostheses on positron emission tomography (PET) images. A dental arch cast was fixed in a cylindrical water-bath phantom. A spherical phantom positioned in the vicinity of the dental arch cast was used to simulate a tumor. To simulate the tumor imaging, the ratio of the 18 F-fluoro-deoxy-glucose radioactivity concentration of the spherical phantom to that of the water-bath phantom was set at 2.5. A dental bridge composed of a gold-silver-palladium alloy on the right mandibular side was prepared. A spherical phantom was set in the white artifact area on the CT images (site A), in a slightly remote area from the white artifact (site B), and in a black artifact area (site C). A PET/CT scan was performed with and without the metal bridge at each simulated tumor site, and the artifactual influence was evaluated on the axial attenuation-corrected (AC) PET images, in which the simulated tumor produced the strongest accumulation. Measurements were performed using three types of PET/CT scanners (scanners 1 and 2 with CT-based attenuation correction, and 3 with Cesium-137 ( 137 Cs)-based attenuation correction). The influence of the metal bridge was evaluated using the change rate of the SUVmean with and without the metal bridge. At site A, an overestimation was shown (scanner 1: +5.0% and scanner 2: +2.5%), while scanner 3 showed an underestimation of -31.8%. At site B, an overestimation was shown (scanner 1: +2.1% and scanner 2: +2.0%), while scanner 3 showed an underestimation of -2.6%. However, at site C, an underestimation was shown (scanner 1: -25.0%, scanner 2: -32.4%, and scanner 3: -8.4%). When CT is used for attenuation correction in patients with dental metal prostheses, an underestimation of radioactivity of accumulated tracer is anticipated in the dark streak artifact area on the CT images. In this study, the dark streak artifacts of the CT

  16. Backscattering from dental restorations and splint materials during therapeutic radiation

    International Nuclear Information System (INIS)

    Farman, A.G.; Sharma, S.; George, D.I.; Wilson, D.; Dodd, D.; Figa, R.; Haskell, B.

    1985-01-01

    Models were constructed to simulate as closely as possible the human oral cavity. Radiation absorbed doses were determined for controls and various test situations involving the presence of dental restorative and splint materials during cobalt-60 irradiation of the models. Adjacent gold full crowns and adjacent solid dental silver amalgam cores both increased the dose to the interproximal gingivae by 20%. Use of orthodontic full bands for splinting the jaws increased the dose to the buccal tissues by an average of 10%. Augmentation of dose through backscatter radiation was determined to be only slight for intracoronal amalgam fillings and stainless steel or plastic bracket splints

  17. Superconducting alloys

    International Nuclear Information System (INIS)

    Bowers, J.E.

    1976-01-01

    Reference is made to superconductors having high critical currents. The superconductor described comprises an alloy consisting of a matrix of a Type II superconductor which is a homogeneous mixture of 50 to 95 at.% Pb and 5 to 40 at.%Bi and/or 10 to 50 at.%In. Dispersed in the matrix is a material to provide pinning centres comprising from 0.01% to 20% by volume of the alloy; this material is a stable discontinuous phase of discrete crystalline particles of Cu, Mn, Te, Se, Ni, Ca, Cr, Ce, Ge or La, either in the form of the element or a compound with a component of the matrix. These particles should have an average diameter of not more than 2μ. A method for making this alloy is described. (U.K.)

  18. Dental education in Peru.

    Science.gov (United States)

    Komabayashi, Takashi; Sato, Manuel; Rodiguez, Lyly; Sato, Doris; Bird, William F

    2008-09-01

    This paper provides information about Peru's dental history and dental school system, including the curriculum and dental licensure. With the increase in the number of dental schools in Peru, the number of dentists is also increasing. Until 1965, Peru had only three dental schools; currently, there are 14. Four of these dental schools are public, and ten are private. A five- or six-year dental program leads to the B.D.S. degree. After successful completion of a thesis defense or competency examination, the D.D.S. degree is awarded. The D.D.S. is mandatory for practicing dentistry in Peru. Currently, there are approximately 14,000 active dentists, with a dentist-patient ratio of approximately 1:2,000.

  19. Description and Documentation of the Dental School Dental Delivery System.

    Science.gov (United States)

    Chase, Rosen and Wallace, Inc., Alexandria, VA.

    A study was undertaken to describe and document the dental school dental delivery system using an integrated systems approach. In late 1976 and early 1977, a team of systems analysts and dental consultants visited three dental schools to observe the delivery of dental services and patient flow and to interview administrative staff and faculty.…

  20. Pneumoconiosis and exposures of dental laboratory technicians

    International Nuclear Information System (INIS)

    Rom, W.N.; Lockey, J.E.; Lee, J.S.; Kimball, A.C.; Bang, K.M.; Leaman, H.; Johns, R.E. Jr.; Perrota, D.; Gibbons, H.L.

    1984-01-01

    One hundred and seventy-eight dental laboratory technicians and 69 non-exposed controls participated in an epidemiological respiratory study. Eight technicians who had a mean of 28 years grinding nonprecious metal alloys were diagnosed as having a simple pneumoconiosis by chest radiograph. Mean values for per cent predicted FVC and FEV1 were reduced among male nonsmoker technicians compared to male nonsmoker controls; after controlling for age, there was also a reduction in spirometry with increasing work-years. An industrial hygiene survey was conducted in 13 laboratories randomly selected from 42 laboratories stratified by size and type of operation in the Salt Lake City, Utah metropolitan area. Personal exposures to beryllium and cobalt exceeded the Threshold Limit Values (TLVs) in one laboratory. Occupational exposures in dental laboratories need to be controlled to prevent beryllium-related lung disorders as well as simple pneumoconiosis

  1. Silicon Alloying On Aluminium Based Alloy Surface

    International Nuclear Information System (INIS)

    Suryanto

    2002-01-01

    Silicon alloying on surface of aluminium based alloy was carried out using electron beam. This is performed in order to enhance tribological properties of the alloy. Silicon is considered most important alloying element in aluminium alloy, particularly for tribological components. Prior to silicon alloying. aluminium substrate were painted with binder and silicon powder and dried in a furnace. Silicon alloying were carried out in a vacuum chamber. The Silicon alloyed materials were assessed using some techniques. The results show that silicon alloying formed a composite metal-non metal system in which silicon particles are dispersed in the alloyed layer. Silicon content in the alloyed layer is about 40% while in other place is only 10.5 %. The hardness of layer changes significantly. The wear properties of the alloying alloys increase. Silicon surface alloying also reduced the coefficient of friction for sliding against a hardened steel counter face, which could otherwise be higher because of the strong adhesion of aluminium to steel. The hardness of the silicon surface alloyed material dropped when it underwent a heating cycle similar to the ion coating process. Hence, silicon alloying is not a suitable choice for use as an intermediate layer for duplex treatment

  2. GOLD IS EARNED FROM THE PRODUCTION OF THAI GOLD LEAF

    Directory of Open Access Journals (Sweden)

    Dirk Bax

    2010-06-01

    Full Text Available Thai people like to cover sacred objects or things dear to them with gold leaf.. Statues of Buddha are sometimes covered with so many layers of gold leaf that they become formless figures, that can hardly be recognized. Portraits of beloved ancestors, statues of elephants and grave tombs are often covered with gold leaf. If one considers the number of Thai people and the popularity of the habit, the amount of gold involved could be considerable.

  3. Tribological characteristics of dental metal biomaterials

    Directory of Open Access Journals (Sweden)

    Walczak Mariusz

    2016-12-01

    Full Text Available The paper is a report of the examination of the tribological wear characteristics of certain dental metal biomaterials. In the study, tests were undertaken on the following materials: 316L steel, NiCrMo alloy, technically pure titanium (ASTM-grade 2 and Ti6Al4V ELI alloy (ASTM-grade 5. The tribological tests were performed in artificial saliva to determine the coefficient of friction and wear factor; the traces of wear were then ascertained through SEM. The significance of variations in the wear factor, was subsequently assessed by the U Mann-Whitney test. The resistance to wear in the ball-on-disc test under in vitro conditions was observed for the tested materials in the following order: NiCrMo>316L>Ti6Al4V>Ti grade 2.

  4. A useful and non-invasive microanalysis method for dental restoration materials

    International Nuclear Information System (INIS)

    Hosoki, M.; Satsuma, T.; Nishigawa, K.; Takeuchi, H.; Asaoka, K.

    2012-01-01

    Highlights: ► This method for the microanalysis of dental alloys is beneficial for patients with allergies to dental materials. ► This metal sample is easy to mail it for inspection at specialist institutes. ► This method can be also be used in general dental clinics. - Abstract: The elemental analysis of intraoral dental restorations provides considerable information for the treatment of dental metal allergy. Elemental analyses require specific instruments and complicated procedures, so this examination is not commonly carried out in private dental clinics. We describe a novel, simple and useful micro-analytical method for dental metal restorations. Micro metal dust was obtained by polishing the surface of restorative metal material with an unused silicone point (SUPER-SNAP). The metal dust on the silicone point was then rubbed onto adhesive tape, and this tape was covered with polyethylene film. The amount of metal dust material was <20 μg. An energy dispersive X-ray fluorescence spectrometer was used to carry out the elementary analysis of the metal dust on the polyethylene film. Three types of dental metal alloy materials of known components were examined. The results of elementary analyses were compared with the specifications provided by the manufacturer. The same procedure was carried out for three dental metal restorations of an adult female volunteer in vivo. The results of elemental analyses for five alloy materials exactly matched the product specification. Three metal samples obtained from intraoral restoration were also available for elemental analyses. The distinct advantage of this method is that it enables sample extraction without an invasive effect for the restoration. The metal sample is in a polyethylene film, so it is easy to mail it for inspection at specialist institutes yet it can be also be used in general dental clinics.

  5. A useful and non-invasive microanalysis method for dental restoration materials

    Energy Technology Data Exchange (ETDEWEB)

    Hosoki, M., E-mail: hosoki@tokushima-u.ac.jp [Department of Fixed Prosthodontics, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8504 (Japan); Satsuma, T.; Nishigawa, K.; Takeuchi, H. [General Dentistry, Tokushima University Hospital, 3-18-15 Kuramoto-cho, Tokushima 770-8504 (Japan); Asaoka, K. [Department of Biomaterials and Bioengineering, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8504 (Japan)

    2012-12-01

    Highlights: Black-Right-Pointing-Pointer This method for the microanalysis of dental alloys is beneficial for patients with allergies to dental materials. Black-Right-Pointing-Pointer This metal sample is easy to mail it for inspection at specialist institutes. Black-Right-Pointing-Pointer This method can be also be used in general dental clinics. - Abstract: The elemental analysis of intraoral dental restorations provides considerable information for the treatment of dental metal allergy. Elemental analyses require specific instruments and complicated procedures, so this examination is not commonly carried out in private dental clinics. We describe a novel, simple and useful micro-analytical method for dental metal restorations. Micro metal dust was obtained by polishing the surface of restorative metal material with an unused silicone point (SUPER-SNAP). The metal dust on the silicone point was then rubbed onto adhesive tape, and this tape was covered with polyethylene film. The amount of metal dust material was <20 {mu}g. An energy dispersive X-ray fluorescence spectrometer was used to carry out the elementary analysis of the metal dust on the polyethylene film. Three types of dental metal alloy materials of known components were examined. The results of elementary analyses were compared with the specifications provided by the manufacturer. The same procedure was carried out for three dental metal restorations of an adult female volunteer in vivo. The results of elemental analyses for five alloy materials exactly matched the product specification. Three metal samples obtained from intraoral restoration were also available for elemental analyses. The distinct advantage of this method is that it enables sample extraction without an invasive effect for the restoration. The metal sample is in a polyethylene film, so it is easy to mail it for inspection at specialist institutes yet it can be also be used in general dental clinics.

  6. Experimental Investigation of Surface Color Changes in Vacuum Evaporation Process for Gold-like Stainless Steel

    Directory of Open Access Journals (Sweden)

    Yang Baojian

    2016-01-01

    Full Text Available In order to reduce the environmental pollution caused by the three wastes during the process of electroplating of gold-like film on stainless steel, in this paper, the "vacuum evaporation and annealing" composite technologies were adopted to evaporate gold-like film in 16 stainless steel 304 substrates, and electronic color cards and color software were also used for analyzing the color and luster of the gold-like film. Experiments shows that the negative pressure, annealing temperature and mass fraction of the double copper alloys have influence on preparation of imitation in assaying the fineness of gold film, the annealing temperature has significant effects on imitation in assaying the fineness of gold film.

  7. Gold film with gold nitride - A conductor but harder than gold

    International Nuclear Information System (INIS)

    Siller, L.; Peltekis, N.; Krishnamurthy, S.; Chao, Y.; Bull, S.J.; Hunt, M.R.C.

    2005-01-01

    The formation of surface nitrides on gold films is a particularly attractive proposition, addressing the need to produce harder, but still conductive, gold coatings which reduce wear but avoid the pollution associated with conventional additives. Here we report production of large area gold nitride films on silicon substrates, using reactive ion sputtering and plasma etching, without the need for ultrahigh vacuum. Nanoindentation data show that gold nitride films have a hardness ∼50% greater than that of pure gold. These results are important for large-scale applications of gold nitride in coatings and electronics

  8. Activated carbons and gold

    International Nuclear Information System (INIS)

    McDougall, G.J.; Hancock, R.D.

    1980-01-01

    The literature on activated carbon is reviewed so as to provide a general background with respect to the effect of source material and activation procedure on carbon properties, the structure and chemical nature of the surface of the activated carbon, and the nature of absorption processes on carbon. The various theories on the absorption of gold and silver from cyanide solutions are then reviewed, followed by a discussion of processes for the recovery of gold and silver from cyanide solutions using activated carbon, including a comparison with zinc precipitation

  9. 75 FR 33169 - Dental Devices: Classification of Dental Amalgam, Reclassification of Dental Mercury, Designation...

    Science.gov (United States)

    2010-06-11

    .... FDA-2008-N-0163] (formerly Docket No. 2001N-0067) RIN 0910-AG21 Dental Devices: Classification of Dental Amalgam, Reclassification of Dental Mercury, Designation of Special Controls for Dental Amalgam... the Federal Register of August 4, 2009 (74 FR 38686) which classified dental amalgam as a class II...

  10. Mechanical properties and grindability of experimental Ti-Au alloys.

    Science.gov (United States)

    Takahashi, Masatoshi; Kikuchi, Masafumi; Okuno, Osamu

    2004-06-01

    Experimental Ti-Au alloys (5, 10, 20 and 40 mass% Au) were made. Mechanical properties and grindability of the castings of the Ti-Au alloys were examined. As the concentration of gold increased to 20%, the yield strength and the tensile strength of the Ti-Au alloys became higher without markedly deteriorating their ductility. This higher strength can be explained by the solid-solution strengthening of the a titanium. The Ti-40%Au alloy became brittle because the intermetallic compound Ti3Au precipitated intensively near the grain boundaries. There was no significant difference in the grinding rate and grinding ratio among all the Ti-Au alloys and the pure titanium at any speed.

  11. Case based dental radiology.

    Science.gov (United States)

    Niemiec, Brook A

    2009-02-01

    Dental radiology is quickly becoming integral to the standard of care in veterinary dentistry. This is not only because it is critical for proper patient care, but also because client expectations have increased. Furthermore, providing dental radiographs as a routine service can create significant practice income. This article details numerous conditions that are indications for dental radiographs. As you will see, dental radiographs are often critical for proper diagnosis and treatment. These conditions should not be viewed as unusual; they are present within all of our practices. When you choose not to radiograph these teeth, you leave behind painful pathology. Utilizing the knowledge gained from dental radiographs will both improve patient care and increase acceptance of treatment recommendations. Consequently, this leads to increased numbers of dental procedures performed at your practice.

  12. The 'simple' general dental anaesthetic

    African Journals Online (AJOL)

    Dental anaesthesia should not be underestimated. Eddie Oosthuizen .... dental surgeon has limited training in airway management. ... primary teeth to hours for extensive dental conservation .... options after the extraction of permanent teeth ...

  13. Estudo da liga alumínio-zinco como filtração alternativa em aparelhos de raios X odontológicos Study of the aluminum-zinc alloy as an alternative means of filtration in dental X-ray devices

    Directory of Open Access Journals (Sweden)

    Claudia Fátima Silva HAITER

    2002-03-01

    Full Text Available O objetivo neste trabalho foi avaliar os efeitos da filtração alternativa da liga alumínio-zinco em aparelhos de raios X odontológicos, em relação ao espectro de energia dos feixes de raios X, a taxa de kerma no ar, o índice de contraste nas radiografias obtidas e a qualidade das imagens radiográficas. Este estudo foi realizado comparando-se o filtro convencional de alumínio com várias espessuras do filtro de liga alumínio-zinco, em diferentes porcentagens do elemento zinco na liga (2%, 3%, 4% e 5%. Foi utilizado um aparelho de raios X odontológico convencional, operando com 60 kVp e 70 kVp, e filmes radiográficos dos grupos D e E de sensibilidade. Foram realizadas radiografias de um "phantom" e de uma escala de densidade de alumínio. Os resultados mostraram que o uso dos filtros de liga Al-Zn resultou em um não-endurecimento dos feixes. A taxa de kerma no ar diminuiu em até 18,53%, sem alteração no contraste das radiografias e a qualidade das imagens teve uma boa aceitação pelos examinadores. A análise dos resultados nos levou a concluir que o filtro de liga Al-Zn 2%, com 1,99 mm de espessura, tensão de 60 kVp, quando usado com filme D, foi o que obteve melhor desempenho, reduzindo a taxa de kerma no ar sem variar o índice de contraste das radiografias, mantendo a qualidade da imagem aceitável para diagnóstico, sem contudo aumentar o tempo de exposição.The aim of this study was to evaluate the effects of alternative filtration with the aluminum-zinc alloy in dental X-ray devices, regarding the energy spectrum, dose, contrast and image quality. This study was carried out comparing the conventional aluminum filter with aluminum-zinc alloy filters of various thicknesses and with different percentages of zinc in the alloy (2, 3, 4 and 5%. A conventional X-ray device operating with 60 and 70 kVp as well as D- and E-speed films were utilized in order to obtain images of a phantom and an aluminum step wedge. The utilization

  14. Dental pulp stem cells

    DEFF Research Database (Denmark)

    Ashri, N. Y.; Ajlan, S. A.; Aldahmash, Abdullah M.

    2015-01-01

    scaffold, and guided through signaling molecules. Dental pulp stem cells have been used in an increasing number of studies in dental tissue engineering. Those cells show mesenchymal (stromal) stem cell-like properties including self-renewal and multilineage differentiation potentials, aside from...... an updated review on dental pulp stem cells and their applications in periodontal regeneration, in combination with different scaffolds and growth factors....

  15. Dental radiology for children

    International Nuclear Information System (INIS)

    Myers, D.R.

    1984-01-01

    The benefit for the child from the judicious use of diagnostic dental radiography is improved dental health. The risk to the child from dental diagnostic radiation exposure appears to be extremely low. Despite the low risk, the dentist must minimize the child's exposure to ionizing radiation by using sound clinical judgment to determine what radiographs are necessary and to provide children with optimal protection from ionizing radiation

  16. ['Gold standard', not 'golden standard'

    NARCIS (Netherlands)

    Claassen, J.A.H.R.

    2005-01-01

    In medical literature, both 'gold standard' and 'golden standard' are employed to describe a reference test used for comparison with a novel method. The term 'gold standard' in its current sense in medical research was coined by Rudd in 1979, in reference to the monetary gold standard. In the same

  17. Gold Nanoparticle Microwave Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Krantz, Kelsie E. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Christian, Jonathan H. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Coopersmith, Kaitlin [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Washington, II, Aaron L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Murph, Simona H. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-07-27

    At the nanometer scale, numerous compounds display different properties than those found in bulk material that can prove useful in areas such as medicinal chemistry. Gold nanoparticles, for example, display promise in newly developed hyperthermia therapies for cancer treatment. Currently, gold nanoparticle synthesis is performed via the hot injection technique which has large variability in final particle size and a longer reaction time. One underdeveloped area by which these particles could be produced is through microwave synthesis. To initiate heating, microwaves agitate polar molecules creating a vibration that gives off the heat energy needed. Previous studies have used microwaves for gold nanoparticle synthesis; however, polar solvents were used that partially absorbed incident microwaves, leading to partial thermal heating of the sample rather than taking full advantage of the microwave to solely heat the gold nanoparticle precursors in a non-polar solution. Through this project, microwaves were utilized as the sole heat source, and non-polar solvents were used to explore the effects of microwave heating only as pertains to the precursor material. Our findings show that the use of non-polar solvents allows for more rapid heating as compared to polar solvents, and a reduction in reaction time from 10 minutes to 1 minute; this maximizes the efficiency of the reaction, and allows for reproducibility in the size/shape of the fabricated nanoparticles.

  18. Bioassisted Phytomining of Gold

    Science.gov (United States)

    Maluckov, Biljana S.

    2015-05-01

    Bioassisted phytomining implies targeted use of microorganisms and plants for the selective recovery of the metal. Metals from undissolved compounds are dissolved by applying specially chosen microorganisms and therefore become available to the hyperaccumulating plants. In the article, the selective extraction method of base metals and the precious metal gold by using microorganisms and plants is discussed.

  19. Digging for Gold

    Science.gov (United States)

    Waters, John K.

    2012-01-01

    In the case of higher education, the hills are more like mountains of data that "we're accumulating at a ferocious rate," according to Gerry McCartney, CIO of Purdue University (Indiana). "Every higher education institution has this data, but it just sits there like gold in the ground," complains McCartney. Big Data and the new tools people are…

  20. GOLD PRESSURE VESSEL SEAL

    Science.gov (United States)

    Smith, A.E.

    1963-11-26

    An improved seal between the piston and die member of a piston-cylinder type pressure vessel is presented. A layer of gold, of sufficient thickness to provide an interference fit between the piston and die member, is plated on the contacting surface of at least one of the members. (AEC)

  1. Gold Nanoparticle Microwave Synthesis

    International Nuclear Information System (INIS)

    Krantz, Kelsie E.; Christian, Jonathan H.; Coopersmith, Kaitlin; Washington II, Aaron L.; Murph, Simona H.

    2016-01-01

    At the nanometer scale, numerous compounds display different properties than those found in bulk material that can prove useful in areas such as medicinal chemistry. Gold nanoparticles, for example, display promise in newly developed hyperthermia therapies for cancer treatment. Currently, gold nanoparticle synthesis is performed via the hot injection technique which has large variability in final particle size and a longer reaction time. One underdeveloped area by which these particles could be produced is through microwave synthesis. To initiate heating, microwaves agitate polar molecules creating a vibration that gives off the heat energy needed. Previous studies have used microwaves for gold nanoparticle synthesis; however, polar solvents were used that partially absorbed incident microwaves, leading to partial thermal heating of the sample rather than taking full advantage of the microwave to solely heat the gold nanoparticle precursors in a non-polar solution. Through this project, microwaves were utilized as the sole heat source, and non-polar solvents were used to explore the effects of microwave heating only as pertains to the precursor material. Our findings show that the use of non-polar solvents allows for more rapid heating as compared to polar solvents, and a reduction in reaction time from 10 minutes to 1 minute; this maximizes the efficiency of the reaction, and allows for reproducibility in the size/shape of the fabricated nanoparticles.

  2. Dental magnetic resonance imaging

    International Nuclear Information System (INIS)

    Hilgenfeld, Tim; Bendszus, Martin; Haehnel, Stefan

    2016-01-01

    Growing distribution and utilization of digital volume tomography (DVT) extend the spectrum of clinical dental imaging. Additional diagnostic value, however, comes along with an increasing amount of radiation. In contrast, magnetic resonance imaging is a radiation free imaging technique. Furthermore, it offers a high soft tissue contrast. Morphological and numerical dental anomalies, differentiation of periapical lesions and exclusion of complications of dental diseases are field of applications for dental MRI. In addition, detection of caries and periodontal lesions and injury of inferior alveolar nerve are promising application areas in the future.

  3. Gold and gold working in Late Bronze Age Northern Greece

    Science.gov (United States)

    Vavelidis, M.; Andreou, S.

    2008-04-01

    Numerous objects of gold displaying an impressive variety of types and manufacturing techniques are known from the Late Bronze Age (LBA) contexts of Mycenaean Greece, but very little is known about the origin and processing of gold during the second millennium b.c. Ancient literature and recent research indicate that northern Greece is probably the richest gold-bearing region in Greece, and yet, very little evidence exists regarding the exploitation of its deposits and the production as well as use of gold in the area during prehistory. The unusual find of a group of small stone crucibles at the prehistoric settlement of Thessaloniki Toumba, one with visible traces of gold melting, proves local production and offers a rare opportunity to examine the process of on-site gold working. Furthermore, the comparison of the chemical composition of prehistoric artefacts from two settlements with those of gold deposits in their immediate areas supports the local extraction of gold and opens up the prospect for some of the Mycenaean gold to have originated in northern Greece. The scarcity of gold items in northern Greek LBA contexts may not represent the actual amount of gold produced and consumed, but could be a result of the local social attitudes towards the circulation and deposition of artefacts from precious metals.

  4. Metal-ceramic alloys in dentistry: a review.

    Science.gov (United States)

    Roberts, Howard W; Berzins, David W; Moore, B Keith; Charlton, David G

    2009-02-01

    The purpose of this article is to review basic information about the alloys used for fabricating metal-ceramic restorations in dentistry. Their compositions, properties, advantages, and disadvantages are presented and compared. In addition to reviewing traditional noble-metal and base-metal metal-ceramic alloys, titanium and gold composite alloys are also discussed. A broad search of the published literature was performed using Medline to identify pertinent current articles on metal-ceramic alloys as well as articles providing a historical background about the development of these alloys. Textbooks, the internet, and manufacturers' literature were also used to supplement this information. The review discusses traditional as well as more recently-developed alloys and technologies used in dentistry for fabricating metal-ceramic restorations. Clear advantages and disadvantages for these alloy types are provided and discussed as well as the role that compositional variations have on the alloys' performance. This information should enable clinicians and technicians to easily identify the important physical properties of each type and their primary clinical indications. A number of alloys and metals are available for metal-ceramic use in dentistry. Each has its advantages and disadvantages, primarily based on its specific composition. Continuing research and development are resulting in the production of new technologies and products, giving clinicians even more choices in designing and fabricating metal-ceramic restorations.

  5. Corrosion Characteristics of Ti-29Nb-xHf Ternary Alloy for Biomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Pak, Sun Young; Choi, Han Chul [Chosun Univ., Kwangju (Korea, Republic of)

    2015-12-15

    The Cp-Ti and Ti-6Al-4V alloys were widely used for dental materials due to their mechanical properties and good corrosion resistance. However, Cp-Ti was known as bio-inert materials, Ti-6Al-4V alloy has a problem such as high Young modulus, potential loss of the surrounding bone, and to the release of potentially toxic ions from the alloy. To overcome this problem, Ti alloys containing Nb and Hf elements have been used for biomaterials due to low toxicity and high corrosion resistance. Especially, alloying element of Nb was known as β phase stabilizer. The β phase alloy was widely used to replace currently used implant materials. The corrosion resistances of Ti-29Nb-xHf ternary alloys were dependent on Hf content in oral environment solution.

  6. Education About Dental Hygienists' Roles in Public Dental Prevention Programs: Dental and Dental Hygiene Students' and Faculty Members' and Dental Hygienists' Perspectives.

    Science.gov (United States)

    Pervez, Anushey; Kinney, Janet S; Gwozdek, Anne; Farrell, Christine M; Inglehart, Marita R

    2016-09-01

    In 2005, Public Act No. 161 (PA 161) was passed in Michigan, allowing dental hygienists to practice in approved public dental prevention programs to provide services for underserved populations while utilizing a collaborative agreement with a supervising dentist. The aims of this study were to assess how well dental and dental hygiene students and faculty members and practicing dental hygienists have been educated about PA 161, what attitudes and knowledge about the act they have, and how interested they are in additional education about it. University of Michigan dental and dental hygiene students and faculty members, students in other Michigan dental hygiene programs, and dental hygienists in the state were surveyed. Respondents (response rate) were 160 dental students (50%), 63 dental hygiene students (82%), 30 dental faculty members (26%), and 12 dental hygiene faculty members (52%) at the University of Michigan; 143 dental hygiene students in other programs (20%); and 95 members of the Michigan Dental Hygienists' Association (10%). The results showed that the dental students were less educated about PA 161 than the dental hygiene students, and the dental faculty members were less informed than the dental hygiene faculty members and dental hygienists. Responding dental hygiene faculty members and dental hygienists had more positive attitudes about PA 161 than did the students and dental faculty members. Most of the dental hygiene faculty members and dental hygienists knew a person providing services in a PA 161 program. Most dental hygiene students, faculty members, and dental hygienists wanted more education about PA 161. Overall, the better educated about the program the respondents were, the more positive their attitudes, and the more interested they were in learning more.

  7. Moessbauerspectroscopy on Gold Ruby Glass

    International Nuclear Information System (INIS)

    Haslbeck, S.

    2005-01-01

    In this thesis, the chemical states of gold and the physical mechanisms of the growing process of the particles under the influence of additional ingredients like tin, lead, antimony and selenium before, during and after the colouring process are investigated by using the Moessbauer spectroscopy on 197 Au, 119 Sn and 121 Sb, optical spectroscopy and X-ray-diffraction. Gold in an unnealed, colourless state of the glasses consists of monovalent forming linear bonds to two neighbouring oxygen atoms. The Lamb-Moessbauer factor of these gold oxide bondings is observed as 0.095 at 4.2 K. The gold in it's oxide state transforms to gold particles with a diameter of 3 nm to 60 nm. The size of the gold particles is quite definable within the optical spectra and certain sizes are also discernable within the Moessbauer spectra. One component of the Moessbauer spectra is assigned to the surface layer of the gold particles. By comparing this surface component with the amount of the bulk metallic core, one can calculate the size of the gold particles. In the Moessbauer spectra of the colourless glass one also can find parts of bulk metallic gold. Investigations with X-ray diffraction show that these are gold particles with a diameter of 100 nm to 300 nm and therefore have no additional colouring effect within the visible spectrum. The Moessbauer spectra on gold of the remelt glasses are similar to those which have been measured on the initial colourless glasses

  8. Radioisotopes in the study of the adaptation of dental amalgam fillings

    International Nuclear Information System (INIS)

    Bermawi, A.

    1995-02-01

    Adaptation expresses the significance of the relationship between the dental filling and its cavity, and forms a special challenge for the dentist when he performs dental restorative procedures. Therefore, I have done a study on the adaptation of dental amalgam fillings and their marginal leakage using radioactive iodine (I sup 1 sup 3 sup 1) and radioactive carbon (C sup 1 sup 4) on three alloys: Viva cap-Contour-Sybraloy. Marginal leakage has been established by the use of I sup 1 sup 3 sup 1, and the leakage points located by C sup 1 sup 4, by means of radioautography. This study was carried out on: - 45 dental specimens to examine marginal leakage. - 9 dental specimens to examine the time of leakage as it reached the occlusal surface. - 6 dental specimens to examine the effect of lining the cavity walls with NO sup 3 Ag varnish on marginal leakage. - 5 dental specimens to examine the effect of form (bevel) of pulpal axial point angle on marginal leakage. - 3 dental specimens as controls. - 25 dental specimens for radioautography, and to determine leakage points. The following results were observed: - Leakage occurred around the contours of all fillings under study, and spread from their basal parts to the angle of their occlusal margin. - Quantitative increase of leakage with time. - The type of the alloy played an active role in determining the pattern of leakage. - Metallic amalgam alloys with spheroidal regular atoms showed the least leakage. - The occlusal sulci exhibited more leakage than the other parts. - Beveling the pulpal axial point angle decreased leakage. - Lining the cavity walls with NO sup 3 Ag varnish inhibited leakage. - The radioactive element, to which the specimens were exposed, was unable to infiltrated and penetrate dentinal and enamel tissues. (author). 55 refs, 52 figs., 68 tabs

  9. Radioisotopes in the study of the adaptation of dental amalgam fillings

    Energy Technology Data Exchange (ETDEWEB)

    Bermawi, A [Atomic Energy Commission, Damascus (Syrian Arab Republic). Dept. of Radiation Protection and Nuclear Safety

    1995-02-01

    Adaptation expresses the significance of the relationship between the dental filling and its cavity, and forms a special challenge for the dentist when he performs dental restorative procedures. Therefore, I have done a study on the adaptation of dental amalgam fillings and their marginal leakage using radioactive iodine (I sup 1 sup 3 sup 1) and radioactive carbon (C sup 1 sup 4) on three alloys: Viva cap-Contour-Sybraloy. Marginal leakage has been established by the use of I sup 1 sup 3 sup 1, and the leakage points located by C sup 1 sup 4, by means of radioautography. This study was carried out on: - 45 dental specimens to examine marginal leakage. - 9 dental specimens to examine the time of leakage as it reached the occlusal surface. - 6 dental specimens to examine the effect of lining the cavity walls with NO sup 3 Ag varnish on marginal leakage. - 5 dental specimens to examine the effect of form (bevel) of pulpal axial point angle on marginal leakage. - 3 dental specimens as controls. - 25 dental specimens for radioautography, and to determine leakage points. The following results were observed: - Leakage occurred around the contours of all fillings under study, and spread from their basal parts to the angle of their occlusal margin. - Quantitative increase of leakage with time. - The type of the alloy played an active role in determining the pattern of leakage. - Metallic amalgam alloys with spheroidal regular atoms showed the least leakage. - The occlusal sulci exhibited more leakage than the other parts. - Beveling the pulpal axial point angle decreased leakage. - Lining the cavity walls with NO sup 3 Ag varnish inhibited leakage. - The radioactive element, to which the specimens were exposed, was unable to infiltrated and penetrate dentinal and enamel tissues. (author). 55 refs, 52 figs., 68 tabs.

  10. For the love of gold

    International Nuclear Information System (INIS)

    Young, J.E.

    1993-01-01

    Gold is found in minute quantities and gold mining generates enormous amounts of waste materials and long history of environmental destruction: mercury in tailing, eroded land, and acid mine drainage are legacies of the past. The problem has become worse in recent years in North America, Australia, the Amazon basin, Philippines. This paper describes the economics of gold and the changes in the world economy which has precipitated the new gold rushes. Current technology uses a cyanide solution for leaching small amounts of gold from tons of waste, and mercury remains a toxic waste of gold mining. Both short and long term results of gold mining, on the environment and on indiginous populations are described

  11. Tanzania Dental Association

    African Journals Online (AJOL)

    Committee of Tanzania Dental. Association would like to Thank. [fUfNJfNJU[[j)~ for its magnanimity towards meeting the cost of this Journal ... ceps is token out of the dental kit and the tooth is removed out of its socket. The tooth is dropped into the waste bucket. The fareceps is placed in the water basin. The socket site is ...

  12. Nigerian Dental Journal

    African Journals Online (AJOL)

    ... needs of dental practitioners in Nigeria, Africa and international community interested in the dental practice in the developing world. The NDJ is published biannually and accepts reports of original research, review articles, clinical case reports and innovations in surgical techniques related to dentistry and allied subjects ...

  13. Acute dental pain II

    DEFF Research Database (Denmark)

    Jonasson, Peter; Kirkevang, Lise-Lotte; Rosen, Annika

    2016-01-01

    Acute dental pain most often occurs in relation to inflammatory conditions in the dental pulp or in the periradicular tissues surrounding a tooth, but it is not always easy to reach a diagnose and determine what treatment to perform. The anamnesis and the clinical examination provide valuable...

  14. Patients' satisfaction with dental care provided by public dental ...

    African Journals Online (AJOL)

    Background: In Tanzania, patient satisfaction with dental services has received only minor attention. Objective: To assess patients' satisfaction with public dental health services in Dar es Salaam. Design: A cross-sectional study. Setting: Five public dental clinics randomly selected from a list of all the nine public dental ...

  15. Dental fluorosis and dental caries prevalence among 12 and 15 ...

    African Journals Online (AJOL)

    Background: Fluoride is a double edged sword. The assessment of dental caries and fluorosis in endemic fluoride areas will facilitate in assessing the relation between fluoride concentrations in water with dental caries, dental fluorosis simultaneously. Aim: The objective of the following study is to assess the dental caries ...

  16. Awareness of dental implants among dental patients in Nigeria ...

    African Journals Online (AJOL)

    The aim of this study was to determine the level of awareness of dental implant in Nigerian patients and their willingness to choose dental implant as a tooth replacement option. A survey was conducted among patients presenting for dental treatment in 3 teaching hospitals and private dental clinics in 3 urban cities of ...

  17. Role of dental restoration materials in oral mucosal lichenoid lesions

    Directory of Open Access Journals (Sweden)

    Rajneesh Sharma

    2015-01-01

    Full Text Available Background: Dental restorative materials containing silver-mercury compounds have been known to induce oral lichenoid lesions. Objectives: To determine the frequency of contact allergy to dental restoration materials in patients with oral lichenoid lesions and to study the effect of removal of the materials on the lesions. Results: Forty-five patients were recruited in three groups of 15 each: Group A (lesions in close contact with dental materials, Group B (lesions extending 1 cm beyond the area of contact and Group C (no topographic relationship. Thirty controls were recruited in two groups of 15 individuals each: Group D (oral lichenoid lesions but no dental material and Group E (dental material but no oral lichenoid lesions. Patch tests were positive in 20 (44.5% patients. Mercury was the most common allergen to elicit a positive reaction in eight patients, followed by nickel (7, palladium (5, potassium dichromate (3, balsam of Peru, gold sodium thiosulphate 2 and tinuvin (2 and eugenol (1, cobalt chloride (1 and carvone (1. Seven patients elicited positive response to more than one allergen. In 13 of 20 patients who consented to removal of the dental material, complete healing was observed in 6 (30%, marked improvement in 7 (35% and no improvement in 7 (35% patients. Relief of symptoms was usually observed 3 months after removal. Limitations: Limited number of study subjects and short follow up after removal/replacement of dental restoration materials are the main limitations of this study. Conclusion: Contact allergy to amalgam is an important etiologic factor in oral lichenoid lesions and removal of restorative material should be offered to patients who have lesions in close proximity to the dental material.

  18. Rushing for gold

    DEFF Research Database (Denmark)

    Jønsson, Jesper Bosse; Bryceson, Deborah Fahy

    2009-01-01

    African rural dwellers have faced depressed economic prospects for several decades. Now, in a number of mineral-rich countries, multiple discoveries of gold and precious stones have attracted large numbers of prospective small-scale miners. While their 'rush' to, and activities within, mining sit...... affluent than the others, suggesting that movement can be rewarding for those willing to 'try their luck' with the hard work and social networking demands of mining another site.......African rural dwellers have faced depressed economic prospects for several decades. Now, in a number of mineral-rich countries, multiple discoveries of gold and precious stones have attracted large numbers of prospective small-scale miners. While their 'rush' to, and activities within, mining sites...

  19. Gold' 82 - technical sessions

    International Nuclear Information System (INIS)

    Viewing, K.

    1983-01-01

    Sulphur-isotope studies had been applied by Dr. I. Lambert to a number of deposits in Western Australia and also to certain samples from Vubachickwe and other deposits in Zimbabwe. A study of the sulphur isotopes at the Dickenson Mine, revealed a wide spread of values in the mineralised zones. Metamorphic processes were likely to be significant in the concentration of gold. The iron formations at the Old Jardine Mine had been unfolded by Dr. W.S. Hallager and the pattern of sedimentation was unraveled. A gold-rich zone was separated by a barren gap from the other part of the mineralised zone. Research was also done on the effects of the metamorphic processes, and the ages of mineralisation

  20. What is dental ecology?

    Science.gov (United States)

    Cuozzo, Frank P; Sauther, Michelle L

    2012-06-01

    Teeth have long been used as indicators of primate ecology. Early work focused on the links between dental morphology, diet, and behavior, with more recent years emphasizing dental wear, microstructure, development, and biogeochemistry, to understand primate ecology. Our study of Lemur catta at the Beza Mahafaly Special Reserve, Madagascar, has revealed an unusual pattern of severe tooth wear and frequent tooth loss, primarily the result of consuming a fallback food for which these primates are not dentally adapted. Interpreting these data was only possible by combining our areas of expertise (dental anatomy [FC] and primate ecology [MS]). By integrating theoretical, methodological, and applied aspects of both areas of research, we adopted the term "dental ecology"-defined as the broad study of how teeth respond to the environment. Specifically, we view dental ecology as an interpretive framework using teeth as a vehicle for understanding an organism's ecology, which builds upon earlier work, but creates a new synthesis of anatomy and ecology that is only possible with detailed knowledge of living primates. This framework includes (1) identifying patterns of dental pathology and tooth use-wear, within the context of feeding ecology, behavior, habitat variation, and anthropogenic change, (2) assessing ways in which dental development and biogeochemical signals can reflect habitat, environmental change and/or stress, and (3) how dental microstructure and macro-morphology are adapted to, and reflect feeding ecology. Here we define dental ecology, provide a short summary of the development of this perspective, and place our new work into this context. Copyright © 2012 Wiley Periodicals, Inc.

  1. Various Effects of Sandblasting of Dental Restorative Materials.

    Directory of Open Access Journals (Sweden)

    Goro Nishigawa

    Full Text Available Sandblasting particles which remain on the surfaces of dental restorations are removed prior to cementation. It is probable that adhesive strength between luting material and sandblasting particle remnants might exceed that with restorative material. If that being the case, blasting particles adhere to sandblasted material surface could be instrumental to increasing adhesive strength like underlying bonding mechanism between luting material and silanized particles of tribochemical silica coating-treated surface. We hypothesize that ultrasonic cleaning of bonding surfaces, which were pretreated with sandblasting, may affect adhesive strength of a resin luting material to dental restorative materials.We therefore observed adhesive strength of resin luting material to aluminum oxide was greater than those to zirconia ceramic and cobalt-chromium alloy beforehand. To measure the shear bond strengths of resin luting material to zirconia ceramic and cobalt-chromium alloy, forty specimens of each restorative material were prepared. Bonding surfaces were polished with silicon abrasive paper and then treated with sandblasting. For each restorative material, 40 sandblasted specimens were equally divided into two groups: ultrasonic cleaning (USC group and non-ultrasonic cleaning (NUSC group. After resin luting material was polymerized on bonding surface, shear test was performed to evaluate effect of ultrasonic cleaning of bonding surfaces pretreated with sandblasting on bond strength.For both zirconia ceramic and cobalt-chromium alloy, NUSC group showed significantly higher shear bond strength than USC group.Ultrasonic cleaning of dental restorations after sandblasting should be avoided to retain improved bonding between these materials.

  2. Experimental constraints on gold and silver solubility in iron sulfides

    Energy Technology Data Exchange (ETDEWEB)

    Pal' yanova, Galina [Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, 3, Koptyuga, Novosibirsk, 630090 (Russian Federation); Novosibirsk State University, Russia, 2, Pirogova, Novosibirsk, 630090 (Russian Federation); Mikhlin, Yuri [Institute of Chemistry and Chemical Technology, Siberian Branch of the Russian Academy of Sciences, Akademgorodok, 50/24, Krasnoyarsk, 660036 (Russian Federation); Kokh, Konstantin, E-mail: k.a.kokh@gmail.com [Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, 3, Koptyuga, Novosibirsk, 630090 (Russian Federation); Novosibirsk State University, Russia, 2, Pirogova, Novosibirsk, 630090 (Russian Federation); Siberian Physical–Technical Institute of Tomsk State University, 1, Novosobornaya, Tomsk, 634050 (Russian Federation); Karmanov, Nick [Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, 3, Koptyuga, Novosibirsk, 630090 (Russian Federation); Seryotkin, Yurii [Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, 3, Koptyuga, Novosibirsk, 630090 (Russian Federation); Novosibirsk State University, Russia, 2, Pirogova, Novosibirsk, 630090 (Russian Federation)

    2015-11-15

    Experiments were performed to determine crystallization of Fe,S-melts (pyriti≿ and troilitic with molar ratio S/Fe ratios of 2 and 1, respectively) containing traces of gold and silver at (Ag/Au){sub wt} ratios varying from 10 to 0.1. The solid products were studied by optical microscopy, scanning electron microscopy, X-ray powder diffraction (XRD), microprobe analysis, and X-ray photoelectron spectroscopy (XPS) in order to reveal the concentration limits of “invisible” gold and silver in magmatic iron sulfides, and to determine the influence of sulfur on forms of precious metals in the Fe–S system with different Ag/Au ratios. Au–Ag phases do not form inclusions but instead concentrate on the grain boundaries in the synthetic pyrrhotite and troilite, while pyrite comprises micro- (1–5 μm) and macroinclusions of Au–Ag alloys and Au–Ag sulfides. In “pyriti≿” systems, the fineness of alloys increases from 650 to 970‰ and the composition of sulfides changes from acanthite (Ag{sub 2}S) to uytenbogaardtite (Ag{sub 3}AuS{sub 2}) and petrovskaite (AgAuS) as the Ag/Au ratio decreases. The concentrations of “invisible” precious metals revealed in troilite were 0.040 ± 0.013 wt.% Au and 0.079 ± 0.016 wt.% Ag. Measured concentrations in pyrite and pyrrhotite were <0.024 wt.% Au and <0.030 wt.% Ag. The surface layers of iron sulfides probed with XPS were enriched in the precious metals, and in silver relative to gold, especially in the systems with Fe/S = 1, probably, due to depletion of the metallic alloy surfaces with gold. Au- and Ag-bearing iron sulfides crystallized primarily from melts may be the source of redeposited phases in hydrothermal and hypergene processes. - Highlights: • The samples of Fe–S–Au–Ag system were synthesized. • Coupled solubility of gold and silver in iron sulfides was specified. • Ag–Au inclusions on surfaces of iron sulfides are likely to be enriched in silver. • Au–Ag sulfides can exist along with

  3. Radioactive gold ring dermatitis

    International Nuclear Information System (INIS)

    Miller, R.A.; Aldrich, J.E.

    1990-01-01

    A superficial squamous cell carcinoma developed in a woman who wore a radioactive gold ring for more than 30 years. Only part of the ring was radioactive. Radiation dose measurements indicated that the dose to basal skin layer was 2.4 Gy (240 rad) per week. If it is assumed that the woman continually wore her wedding ring for 37 years since purchase, she would have received a maximum dose of approximately 4600 Gy

  4. A useful and non-invasive microanalysis method for dental restoration materials

    Science.gov (United States)

    Hosoki, M.; Satsuma, T.; Nishigawa, K.; Takeuchi, H.; Asaoka, K.

    2012-12-01

    The elemental analysis of intraoral dental restorations provides considerable information for the treatment of dental metal allergy. Elemental analyses require specific instruments and complicated procedures, so this examination is not commonly carried out in private dental clinics. We describe a novel, simple and useful micro-analytical method for dental metal restorations. Micro metal dust was obtained by polishing the surface of restorative metal material with an unused silicone point (SUPER-SNAP). The metal dust on the silicone point was then rubbed onto adhesive tape, and this tape was covered with polyethylene film. The amount of metal dust material was film. Three types of dental metal alloy materials of known components were examined. The results of elementary analyses were compared with the specifications provided by the manufacturer. The same procedure was carried out for three dental metal restorations of an adult female volunteer in vivo. The results of elemental analyses for five alloy materials exactly matched the product specification. Three metal samples obtained from intraoral restoration were also available for elemental analyses. The distinct advantage of this method is that it enables sample extraction without an invasive effect for the restoration. The metal sample is in a polyethylene film, so it is easy to mail it for inspection at specialist institutes yet it can be also be used in general dental clinics.

  5. Porous Titanium for Dental Implant Applications

    Directory of Open Access Journals (Sweden)

    Zena J. Wally

    2015-10-01

    Full Text Available Recently, an increasing amount of research has focused on the biological and mechanical behavior of highly porous structures of metallic biomaterials, as implant materials for dental implants. Particularly, pure titanium and its alloys are typically used due to their outstanding mechanical and biological properties. However, these materials have high stiffness (Young’s modulus in comparison to that of the host bone, which necessitates careful implant design to ensure appropriate distribution of stresses to the adjoining bone, to avoid stress-shielding or overloading, both of which lead to bone resorption. Additionally, many coating and roughening techniques are used to improve cell and bone-bonding to the implant surface. To date, several studies have revealed that porous geometry may be a promising alternative to bulk structures for dental implant applications. This review aims to summarize the evidence in the literature for the importance of porosity in the integration of dental implants with bone tissue and the different fabrication methods currently being investigated. In particular, additive manufacturing shows promise as a technique to control pore size and shape for optimum biological properties.

  6. 75 FR 16511 - Pentron Clinical Technologies, a Wholly-Owned Subsidiary of Kerr Dental/Sybron Dental...

    Science.gov (United States)

    2010-04-01

    ... produce dental materials such as dental prosthetics, dental composites, dental impressions, dental... materials such as dental prosthetics, dental composites, dental impressions, dental adhesives, and other... Technologies, a Wholly-Owned Subsidiary of Kerr Dental/Sybron Dental Specialities, Formally Known as Customedix...

  7. Finite element analysis (FEA) of dental implant fixture for mechanical stability and rapid osseointegration

    Science.gov (United States)

    Tabassum, Shafia; Murtaza, Ahmar; Ali, Hasan; Uddin, Zia Mohy; Zehra, Syedah Sadaf

    2017-10-01

    For rapid osseointegration of dental implant fixtures, various surface treatments including plasma spraying, hydroxyapatite coating, acid-etching, and surface grooving are used. However undesirable effects such as chemical modifications, loss of mechanical properties, prolonged processing times and post production treatment steps are often associated with these techniques. The osseointegration rate of the dental implants can be promoted by increasing the surface area of the dental implant, thus increasing the bone cells - implant material contact and allow bone tissues to grow rapidly. Additive Manufacturing (AM) techniques can be used to fabricate dental implant fixtures with desirable surface area in a single step manufacturing process. AM allows the use of Computer Aided Designing (CAD) for customised rapid prototyping of components with precise control over geometry. In this study, the dental implant fixture that replaces the tooth root was designed on commercially available software COMSOL. Nickel - titanium alloy was selected as build materials for dental implant. The geometry of the dental fixture was varied by changing the interspacing distance (thread pitch) and number of threads to increase the total surface area. Three different microstructures were introduced on the surface of dental implant. The designed models were used to examine the effect of changing geometries on the total surface area. Finite Element Analysis (FEA) was performed to investigate the effect of changing geometries on the mechanical properties of the dental implant fixtures using stress analysis.

  8. Grindability of cast Ti-Hf alloys.

    Science.gov (United States)

    Kikuchi, Masafumi; Takahashi, Masatoshi; Sato, Hideki; Okuno, Osamu; Nunn, Martha E; Okabe, Toru

    2006-04-01

    As part of our systematic studies characterizing the properties of titanium alloys, we investigated the grindability of a series of cast Ti-Hf alloys. Alloy buttons with hafnium concentrations up to 40 mass% were made using an argon-arc melting furnace. Each button was cast into a magnesia-based mold using a dental titanium casting machine; three specimens were made for each metal. Prior to testing, the hardened surface layer was removed. The specimens were ground at five different speeds for 1 min at 0.98 N using a carborundum wheel on an electric dental handpiece. Grindability was evaluated as the volume of metal removed per minute (grinding rate) and the volume ratio of metal removed compared to the wheel material lost (grinding ratio). The data were analyzed using ANOVA. A trend of increasing grindability was found with increasing amounts of hafnium, although there was no statistical difference in the grindability with increasing hafnium contents. We also found that hafnium may be used to harden or strengthen titanium without deteriorating the grindability.

  9. Antibacterial effect of copper-bearing titanium alloy (Ti-Cu) against Streptococcus mutans and Porphyromonas gingivalis

    Science.gov (United States)

    Liu, Rui; Memarzadeh, Kaveh; Chang, Bei; Zhang, Yumei; Ma, Zheng; Allaker, Robert P.; Ren, Ling; Yang, Ke

    2016-07-01

    Formation of bacterial biofilms on dental implant material surfaces (titanium) may lead to the development of peri-implant diseases influencing the long term success of dental implants. In this study, a novel Cu-bearing titanium alloy (Ti-Cu) was designed and fabricated in order to efficiently kill bacteria and discourage formation of biofilms, and then inhibit bacterial infection and prevent implant failure, in comparison with pure Ti. Results from biofilm based gene expression studies, biofilm growth observation, bacterial viability measurements and morphological examination of bacteria, revealed antimicrobial/antibiofilm activities of Ti-Cu alloy against the oral specific bacterial species, Streptococcus mutans and Porphyromonas gingivalis. Proliferation and adhesion assays with mesenchymal stem cells, and measurement of the mean daily amount of Cu ion release demonstrated Ti-Cu alloy to be biocompatible. In conclusion, Ti-Cu alloy is a promising dental implant material with antimicrobial/antibiofilm activities and acceptable biocompatibility.

  10. Translating VDM to Alloy

    DEFF Research Database (Denmark)

    Lausdahl, Kenneth

    2013-01-01

    specifications. However, to take advantage of the automated analysis of Alloy, the model-oriented VDM specifications must be translated into a constraint-based Alloy specifications. We describe how a sub- set of VDM can be translated into Alloy and how assertions can be expressed in VDM and checked by the Alloy...

  11. Dental Anomalies: An Update

    Directory of Open Access Journals (Sweden)

    Fatemeh Jahanimoghadam

    2016-01-01

    Full Text Available Dental anomalies are usual congenital malformation that can happen either as isolated findings or as a part of a syndrome. Developmental anomalies influencing the morphology exists in both deciduous and permanent dentition and shows different forms such as gemination, fusion, concrescence, dilaceration, dens evaginatus (DE, enamel pearls, taurodontism or peg-shaped laterals. All These anomalies have clinical significance concerning aesthetics, malocclusion and more necessary preparing of the development of dental decays and oral diseases. Through a search in PubMed, Google, Scopus and Medline, a total of eighty original research papers during 1928-2016 were found with the keywords such as dental anomaly, syndrome, tooth and hypodontia. One hundred review titles were identified, eighty reviews were retrieved that were finally included as being relevant and of sufficient quality. In this review, dental anomalies including gemination, fusion, concrescence, dilaceration, dens invaginatus, DE, taurodontism, enamel pearls, fluorosis, peg-shaped laterals, dentinal dysplasia, regional odontodysplasia and hypodontia are discussed. Diagnosing dental abnormality needs a thorough evaluation of the patient, involving a medical, dental, familial and clinical history. Clinical examination and radiographic evaluation and in some of the cases, specific laboratory tests are also needed. Developmental dental anomalies require careful examination and treatment planning. Where one anomaly is present, clinicians should suspect that other anomalies may also be present. Moreover, careful clinical and radiographical examination is required. Furthermore, more complex cases need multidisciplinary planning and treatment.

  12. Alternative materials study for dental magnetics attachments applications

    International Nuclear Information System (INIS)

    Marques, Rogerio Albuquerque

    2009-01-01

    Ferromagnetic alloys have been investigated as potential candidates for dental prosthesis applications in replacement for magnetic attachments made of noble and expensive alloys. Three stainless steels were investigated: 17-4 PH produced by powder injection (PIM), PM2000 obtained by mechanical alloying and oxide dispersion strengthened, and nickel free stainless steel 1802. In the in vitro cytotoxicity analysis, none of the three steels tested showed cytotoxic effects. The corrosion resistance of stainless steels was evaluated by electrochemical impedance spectroscopy (EIS) and anodic potentiodynamic polarization, in sodium phosphate buffer solutions (PBS) at 25 degree C. The AISI 316L stainless steel was also tested under the same conditions for comparison reasons. All the stainless steel samples were passive in the electrolyte used and presented susceptibility to pitting. The steel that showed the highest pitting resistance was the PM2000, whereas the 1802 had the lowest resistance to pitting among the tested ones. The Mott-Schottky diagrams suggested that the passive film over the surface of PM2000 steel is at least one decade less doped compared to 316L stainless steel, so less defective in its structure. The results pointed out to the PM2000 as a potential candidate for substitution of high cost magnetic alloys used in dental prosthesis. (author)

  13. Equine dental advances.

    Science.gov (United States)

    Greene, S K

    2001-08-01

    The reintroduction and development of safe motorized instruments, the increased availability of continuing education, and the understanding and implementation of appropriate procedures allow practitioners to provide better dental care. Veterinarians realize that sedation, analgesia, a full-mouth speculum, and proper instrumentation are necessary to provide these services. Continued instrument design, future research, and new treatment and prophylactic protocols should have a positive impact on the future of equine dental health. New and rediscovered procedures for equilibrating equine occlusion are allowing horses to masticate more efficiently, carry a bit more comfortably, and experience improved performance. The horse, the horse owner, and the veterinary profession all benefit from providing complete equine dental care.

  14. Dental biofilm infections

    DEFF Research Database (Denmark)

    Larsen, Tove; Fiehn, Nils-Erik

    2017-01-01

    and cause gingival inflammation and breakdown of supporting periodontal fibers and bone and ultimately tooth loss, i.e., gingivitis, chronic or aggressive periodontitis, and around dental implants, peri-implantitis. Furthermore, bacteria from the dental biofilm may spread to other parts of the body......-fermenting bacteria causing demineralization of teeth, dental caries, which may further lead to inflammation and necrosis in the pulp and periapical region, i.e., pulpitis and periapical periodontitis. In supra- and subgingival biofilms, predominantly gram-negative, anaerobic proteolytic bacteria will colonize...

  15. Dental Trauma Guide

    DEFF Research Database (Denmark)

    Andreasen, Jens Ove; Lauridsen, Eva; Gerds, Thomas Alexander

    2012-01-01

    Diagnosis and treatment for traumatic dental injuries are very complex owing to the multiple trauma entities represented by six luxation types and nine fracture types affecting both the primary and the permanent dentition. When it is further considered that fracture and luxation injuries are often...... problems in selecting proper treatment for some of these trauma types. To remedy this situation, an Internet-based knowledge base consisting of 4000 dental trauma cases with long-term follow up is now available to the public and the professions on the Internet using the address http://www.Dental...

  16. Optimization of dental implantation

    Science.gov (United States)

    Dol, Aleksandr V.; Ivanov, Dmitriy V.

    2017-02-01

    Modern dentistry can not exist without dental implantation. This work is devoted to study of the "bone-implant" system and to optimization of dental prostheses installation. Modern non-invasive methods such as MRI an 3D-scanning as well as numerical calculations and 3D-prototyping allow to optimize all of stages of dental prosthetics. An integrated approach to the planning of implant surgery can significantly reduce the risk of complications in the first few days after treatment, and throughout the period of operation of the prosthesis.

  17. Immunological properties of gold nanoparticles.

    Science.gov (United States)

    Dykman, Lev A; Khlebtsov, Nikolai G

    2017-03-01

    In the past decade, gold nanoparticles have attracted strong interest from the nanobiotechnological community owing to the significant progress made in robust and easy-to-make synthesis technologies, in surface functionalization, and in promising biomedical applications. These include bioimaging, gene diagnostics, analytical sensing, photothermal treatment of tumors, and targeted delivery of various biomolecular and chemical cargos. For the last-named application, gold nanoparticles should be properly fabricated to deliver the cargo into the targeted cells through effective endocytosis. In this review, we discuss recent progress in understanding the selective penetration of gold nanoparticles into immune cells. The interaction of gold nanoparticles with immune cell receptors is discussed. As distinct from other published reviews, we present a summary of the immunological properties of gold nanoparticles. This review also summarizes what is known about the application of gold nanoparticles as an antigen carrier and adjuvant in immunization for the preparation of antibodies in vivo . For each of the above topics, the basic principles, recent advances, and current challenges are discussed. Thus, this review presents a detailed analysis of data on interaction of gold nanoparticles with immune cells. Emphasis is placed on the systematization of data over production of antibodies by using gold nanoparticles and adjuvant properties of gold nanoparticles. Specifically, we start our discussion with current data on interaction of various gold nanoparticles with immune cells. The next section describes existing technologies to improve production of antibodies in vivo by using gold nanoparticles conjugated with specific ligands. Finally, we describe what is known about adjuvant properties of bare gold or functionalized nanoparticles. In the Conclusion section, we present a short summary of reported data and some challenges and perspectives.

  18. The extractive metallurgy of gold

    Energy Technology Data Exchange (ETDEWEB)

    Kongolo, K.; Mwema, M.D. [University of Lubumbashi, Zaire, Gecamines Metallurgical Research Centre, Likasi, Zaire, c/o Gecamines Brussels (Belgium)

    1998-12-15

    Moessbauer spectroscopy has been successfully used in investigation of the gold compounds present in ores and the gold species which occur during the process metallurgy of this metal. This paper is a survey of the basic recovery methods and techniques used in extractive metallurgy of gold. Process fundamentals on mineral processing, ore leaching, zinc dust cementation, adsorption on activated carbon, electrowinning and refining are examined. The recovery of gold as a by-product of the copper industry is also described. Alternative processing methods are indicated in order to shed light on new interesting research topics where Moessbauer spectroscopy could be applied.

  19. The extractive metallurgy of gold

    Science.gov (United States)

    Kongolo, K.; Mwema, M. D.

    1998-12-01

    Mössbauer spectroscopy has been successfully used in investigation of the gold compounds present in ores and the gold species which occur during the process metallurgy of this metal. This paper is a survey of the basic recovery methods and techniques used in extractive metallurgy of gold. Process fundamentals on mineral processing, ore leaching, zinc dust cementation, adsorption on activated carbon, electrowinning and refining are examined. The recovery of gold as a by-product of the copper industry is also described. Alternative processing methods are indicated in order to shed light on new interesting research topics where Mössbauer spectroscopy could be applied.

  20. The extractive metallurgy of gold

    International Nuclear Information System (INIS)

    Kongolo, K.; Mwema, M.D.

    1998-01-01

    Moessbauer spectroscopy has been successfully used in investigation of the gold compounds present in ores and the gold species which occur during the process metallurgy of this metal. This paper is a survey of the basic recovery methods and techniques used in extractive metallurgy of gold. Process fundamentals on mineral processing, ore leaching, zinc dust cementation, adsorption on activated carbon, electrowinning and refining are examined. The recovery of gold as a by-product of the copper industry is also described. Alternative processing methods are indicated in order to shed light on new interesting research topics where Moessbauer spectroscopy could be applied

  1. Surface-stabilized gold nanocatalysts

    Science.gov (United States)

    Dai, Sheng [Knoxville, TN; Yan, Wenfu [Oak Ridge, TN

    2009-12-08

    A surface-stabilized gold nanocatalyst includes a solid support having stabilizing surfaces for supporting gold nanoparticles, and a plurality of gold nanoparticles having an average particle size of less than 8 nm disposed on the stabilizing surfaces. The surface-stabilized gold nanocatalyst provides enhanced stability, such as at high temperature under oxygen containing environments. In one embodiment, the solid support is a multi-layer support comprising at least a first layer having a second layer providing the stabilizing surfaces disposed thereon, the first and second layer being chemically distinct.

  2. Twinning in fcc lattice creates low-coordinated catalytically active sites in porous gold

    Energy Technology Data Exchange (ETDEWEB)

    Krajčí, Marian [Institute of Physics, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84511 Bratislava (Slovakia); Kameoka, Satoshi; Tsai, An-Pang [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan)

    2016-08-28

    We describe a new mechanism for creation of catalytically active sites in porous gold. Samples of porous gold prepared by de-alloying Al{sub 2}Au exhibit a clear correlation between the catalytic reactivity towards CO oxidation and structural defects in the fcc lattice of Au. We have found that on the stepped (211) surfaces quite common twin boundary defects in the bulk structure of porous gold can form long close-packed rows of atoms with the coordination number CN = 6. DFT calculations confirm that on these low-coordinated Au sites dioxygen chemisorbs and CO oxidation can proceed via the Langmuir–Hinshelwood mechanism with the activation energy of 37 kJ/mol or via the CO–OO intermediate with the energy barrier of 19 kJ/mol. The existence of the twins in porous gold is stabilized by the surface energy.

  3. Economic impact of dental hygienists on solo dental practices.

    Science.gov (United States)

    Lazar, Vickie F; Guay, Albert H; Beazoglou, Tryfon J

    2012-08-01

    The fact that a significant percentage of dentists employ dental hygienists raises an important question: Are dental practices that utilize a dental hygienist structurally and operationally different from practices that do not? This article explores differences among dental practices that operate with and without dental hygienists. Using data from the American Dental Association's 2003 Survey of Dental Practice, a random sample survey of U.S. dentists, descriptive statistics were used to compare selected characteristics of solo general practitioners with and without dental hygienists. Multivariate regression analysis was used to estimate the effect of dental hygienists on the gross billings and net incomes of solo general practitioners. Differences in practice characteristics--such as hours spent in the practice and hours spent treating patients, wait time for a recall visit, number of operatories, square feet of office space, net income, and gross billings--were found between solo general practitioners who had dental hygienists and those who did not. Solo general practitioners with dental hygienists had higher gross billings. Higher gross billings would be expected, as would higher expenses. However, net incomes of those with dental hygienists were also higher. In contrast, the mean waiting time for a recall visit was higher among dentists who employed dental hygienists. Depending on personal preferences, availability of qualified personnel, etc., dentists who do not employ dental hygienists but have been contemplating that path may want to further research the benefits and opportunities that may be realized.

  4. 31 CFR 100.4 - Gold coin and gold certificates in general.

    Science.gov (United States)

    2010-07-01

    ... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Gold coin and gold certificates in... EXCHANGE OF PAPER CURRENCY AND COIN In General § 100.4 Gold coin and gold certificates in general. Gold coins, and gold certificates of the type issued before January 30, 1934, are exchangeable, as provided...

  5. Determining gold content

    International Nuclear Information System (INIS)

    Clayton, C.G.; Wormald, M.R.

    1981-01-01

    A method for determining the gold content of a material, comprises irradiating a body of the material with neutrons and determining the intensity of γ-rays having an energy of 279 keV arising from the reaction 179 Au(nn') 179 Au → 279 keV. The apparatus has means for conveying the materials past an assembly, which has a neutron source, which does not produce neutrons having sufficient energy to excite fast neutron reactions in non-auriferous constituents. (author)

  6. Turning lead into gold

    DEFF Research Database (Denmark)

    Jensen, Steffen Moltrup Ernø

    For years the field of entrepreneurship has been blinded by the alchemical promise of turning lead into gold, of finding the ones most likely to become the next Branson, Zuckerberg or Gates. The promise has been created in the midst of political and scientific agendas where certain individuals...... is not to accumulate state or market wealth, but for entrepreneurial skills to become tools towards the liberation of the individual from oppressive systems of control – essentially to add public value rather than economic value. In this presentation I will sketch an anarchist perspective on entrepreneurship, looking...

  7. Orthodontic applications of a superelastic shape-memory alloy model

    Energy Technology Data Exchange (ETDEWEB)

    Glendenning, R.W.; Enlow, R.L. [Otago Univ., Dunedin (New Zealand). Dept. of Math. and Stat.; Hood, J.A.A. [Dept. of Oral Sciences and Orthodontics, Univ. of Otago, Dunedin (New Zealand)

    2000-07-01

    During orthodontic treatment, dental appliances (braces) made of shape memory alloys have the potential to provide nearly uniform low level stresses to dentitions during tooth movement over a large range of tooth displacement. In this paper we model superelastic behaviour of dental appliances using the finite element method and constitutive equations developed by F. Auricchio et al. Results of the mathematical model for 3-point bending and several promising 'closing loop' designs are compared with laboratory results for the same configurations. (orig.)

  8. Dental education in Kuwait.

    Science.gov (United States)

    Behbehani, J M

    2003-01-01

    For a long time there has been a need to establish a dental school in Kuwait, due to the fact that the majority of dentists working in Kuwait are expatriates from various countries. An Amiri decree in 1996 made it possible, and the first dental students were admitted to the Kuwait University Faculty of Dentistry in 1998. The mission of the Faculty of Dentistry is 'to promote oral health in Kuwait through education, research and cooperation with other professional health care institutions as well as the community at large'. A 6.5-year dental curriculum was completed after 2 years of committee work and was accepted by the University Council in 2001. This curriculum incorporates current trends in medical and dental education, such as the evidence-based and community-based approaches, problem-solving methodology for outcome-based learning, and competency achieved through comprehensive patient care. Copyright 2003 S. Karger AG, Basel

  9. Xilitol and dental caries.

    NARCIS (Netherlands)

    Smits, Marten Titus

    1987-01-01

    Dental caries is a widespread multifactoral disease. The main sympthons are minaral loss from tooth enemal and dentine, eventually leading to total destruction of the teeth, pain, impairment of mastication and problems with facial esthetics. ... Zie: Summary

  10. Advances in dental imaging.

    Science.gov (United States)

    Brown, J E

    2001-04-01

    The number of dental radiographs taken in the UK has steadily increased over the past 20 years--recently estimating around 18 million taken in the general dental services alone, and dental radiographs now account for nearly 25% of all medical radiographic exposures. Radiographs remain our most useful diagnostic aid. Their strength is in demonstrating hard tissue pathology, which makes radiographs particularly effective in the maxillofacial region. Although well accepted in this capacity, there remain a number of limitations and drawbacks to conventional radiographs which recent developments have begun to overcome. There have been improvements in the scope and capabilities of dental imaging equipment. There has also been a continuing effort to reduce radiation-induced harm by limiting our exposure to it. This has been possible both through the introduction of new methods and protocols for reducing individual radiation exposures and by the creation of guidelines for selecting radiographs more effectively and thereby reducing the total number of radiographs taken.

  11. Dental care - child

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/002213.htm Dental care - child To use the sharing features on ... please enable JavaScript. Proper care of your child's teeth and gums includes brushing and rinsing daily. It ...

  12. Dental Exam for Children

    Science.gov (United States)

    ... risks associated with tobacco, substance abuse and oral piercings. Why it's done Regular dental exams help protect ... sugary beverages Smoking Chewing tobacco Eating disorders Oral piercings Not wearing a mouthguard during contact sports The ...

  13. Nigerian Dental Journal: Submissions

    African Journals Online (AJOL)

    INSTRUCTIONS FOR AUTHORS AND CONTRIBUTORS The Nigerian Dental ... review articles, clinical case reports and innovations in surgical techniques ... figures and illustrations, including one copy stored in a 3.5” floppy should be sent to ...

  14. Dental Assisting Program Standards.

    Science.gov (United States)

    Georgia Univ., Athens. Dept. of Vocational Education.

    This publication contains statewide standards for the dental assisting program in Georgia. The standards are divided into 12 categories: foundations (philosophy, purpose, goals, program objectives, availability, evaluation); admissions (admission requirements, provisional admission requirements, recruitment, evaluation and planning); program…

  15. Determination of Gold from Gold Matrix of North Western Nigeria ...

    African Journals Online (AJOL)

    The research paper presents analytical results of Au, Mn and V concentrations of some Nigerian gold ores using two techniques: epithermal neutron activation analysis (ENAA) and proton induced X-ray emission (PIXE). Fourteen samples were collected from gold fields of North Western Nigeria, prepared separately to a ...

  16. Comparative investigation of smooth polycrystalline diamond films on dental burs by chemical vapor deposition

    Science.gov (United States)

    Sein, Htet; Ahmed, Waqar; Rego, Christopher; Jackson, Mark; Polini, Riccardo

    2006-04-01

    Depositions of hot filament chemical vapor-deposited diamond on cobalt-cemented tungsten carbide (WC-Co) rotary cutting dental burs are presented. Conventional dental tools made of sintered polycrystalline diamond have a number of problems associated with the heterogeneity of the crystallite, decreased cutting efficiency, and short life. A preferential (111) faceted diamond was obtained after 15 h of deposition at a growth rate of 1.1 µm/h. Diamond-coated WC-Co dental burs and conventional sintered burs are mainly used in turning, milling, and drilling operations for machining metal ceramic hard alloys such as CoCr, composite teeth, and aluminum alloy in the dental laboratory. The influence of structure, the mechanical characteristics of both diamond grains and hard alloys on the wear behavior, as well as the regimen of grinding on diamond wear are considered. Erosion wear properties are also investigated under air-sand erosion testing. After machining with excessive cutting performance, calculations can be made on flank and crater wear areas. Diamond-coated WC-Co dental burs offered significantly better erosion and wear resistance compared with uncoated WC-Co tools and sintered burs.

  17. Steel alloys

    International Nuclear Information System (INIS)

    Bloom, E.E.; Stiegler, J.O.; Rowcliffe, A.F.; Leitnaker, J.M.

    1977-01-01

    The invention deals with a fuel element for fast breeder reactors. It consits essentially of a uranium oxide, nitride, or carbide or a mixture of these fuels with a plutonium or thorium oxide, nitride, or carbide. The fuel elements are coated with an austenitic stainless steel alloy. Inside the fuel elements, vacancies or small cavities are produced by neutron effects which causes the steel coating to swell. According to the invention, swelling is prevented by a modification of type 304, 316, 321, or 12 K 72HV commercial steels. They consist mainly of Fe, Cr, and Ni in a ratio determined by a temary diagram. They may also contain 1.8 to 2.3% by weight of Mo and a fraction of Si (0.7 to 2% by weight) and Ti(0.10 to 0.5% by weight) to prevent cavity formation. They are structurally modified by cold working. (IHOE) [de

  18. An artifical neural network for detection of simulated dental caries

    Energy Technology Data Exchange (ETDEWEB)

    Kositbowornchai, S. [Khon Kaen Univ. (Thailand). Dept. of Oral Diagnosis; Siriteptawee, S.; Plermkamon, S.; Bureerat, S. [Khon Kaen Univ. (Thailand). Dept. of Mechanical Engineering; Chetchotsak, D. [Khon Kaen Univ. (Thailand). Dept. of Industrial Engineering

    2006-08-15

    Objects: A neural network was developed to diagnose artificial dental caries using images from a charged-coupled device (CCD)camera and intra-oral digital radiography. The diagnostic performance of this neural network was evaluated against a gold standard. Materials and methods: The neural network design was the Learning Vector Quantization (LVQ) used to classify a tooth surface as sound or as having dental caries. The depth of the dental caries was indicated on a graphic user interface (GUI) screen developed by Matlab programming. Forty-nine images of both sound and simulated dental caries, derived from a CCD camera and by digital radiography, were used to 'train' an artificial neural network. After the 'training' process, a separate test-set comprising 322 unseen images was evaluated. Tooth sections and microscopic examinations were used to confirm the actual dental caries status.The performance of neural network was evaluated using diagnostic test. Results: The sensitivity (95%CI)/specificity (95%CI) of dental caries detection by the CCD camera and digital radiography were 0.77(0.68-0.85)/0.85(0.75-0.92) and 0.81(0.72-0.88)/0.93(0.84-0.97), respectively. The accuracy of caries depth-detection by the CCD camera and digital radiography was 58 and 40%, respectively. Conclusions: The model neural network used in this study could be a prototype for caries detection but should be improved for classifying caries depth. Our study suggests an artificial neural network can be trained to make the correct interpretations of dental caries. (orig.)

  19. An artifical neural network for detection of simulated dental caries

    International Nuclear Information System (INIS)

    Kositbowornchai, S.; Siriteptawee, S.; Plermkamon, S.; Bureerat, S.; Chetchotsak, D.

    2006-01-01

    Objects: A neural network was developed to diagnose artificial dental caries using images from a charged-coupled device (CCD)camera and intra-oral digital radiography. The diagnostic performance of this neural network was evaluated against a gold standard. Materials and methods: The neural network design was the Learning Vector Quantization (LVQ) used to classify a tooth surface as sound or as having dental caries. The depth of the dental caries was indicated on a graphic user interface (GUI) screen developed by Matlab programming. Forty-nine images of both sound and simulated dental caries, derived from a CCD camera and by digital radiography, were used to 'train' an artificial neural network. After the 'training' process, a separate test-set comprising 322 unseen images was evaluated. Tooth sections and microscopic examinations were used to confirm the actual dental caries status.The performance of neural network was evaluated using diagnostic test. Results: The sensitivity (95%CI)/specificity (95%CI) of dental caries detection by the CCD camera and digital radiography were 0.77(0.68-0.85)/0.85(0.75-0.92) and 0.81(0.72-0.88)/0.93(0.84-0.97), respectively. The accuracy of caries depth-detection by the CCD camera and digital radiography was 58 and 40%, respectively. Conclusions: The model neural network used in this study could be a prototype for caries detection but should be improved for classifying caries depth. Our study suggests an artificial neural network can be trained to make the correct interpretations of dental caries. (orig.)

  20. Panoramic dental radiography

    International Nuclear Information System (INIS)

    Cushman, R.H.; Kircher, D.R.; Hart, F.W.; Ciavattoni, A.

    1980-01-01

    Apparatus is described for improving the handling rate of patients in panoramic dental radiography when tube head-camera assembly of a low silhouette panoramic dental X-ray machine is rotated for a scan in one direction only. This is effected by fast return of the tube head-camera assembly with its simultaneous elevation, thus facilitating the radiographed patient's exit from the machine and the entrance of another patient. Fast speed is about twice the scanning speed. (author)

  1. Spiral patterns of gold nanoclusters in silicon (100) produced by metal vapour vacuum arc implantation of gold ions

    International Nuclear Information System (INIS)

    Venkatachalam, Dinesh Kumar; Sood, Dinesh Kumar; Bhargava, Suresh Kumar

    2008-01-01

    Self-assembled gold nanoclusters are attractive building blocks for future nanoscale sensors and optical devices due to their exciting catalytic properties. In this work, we report direct bottom-up synthesis of spiral patterns of gold nanoclusters in silicon (100) substrates by Au ion implantation followed by thermal annealing. This unique phenomenon is observed only above a critical threshold implantation dose and annealing temperature. Systematic study by electron microscopy, analytical x-ray diffraction and atomic force microscopy shows the temperature- and time-dependent nucleation, growth of Au nanoclusters and evolution of the spiral patterns. The observed patterns of gold nanoclusters bear a resemblance to the spiral growth prevalent in some directionally solidified eutectic alloys. Based on this systematic study of the growth and morphology of nanoclusters, a tentative model has been proposed for the formation mechanism of this unusual self-assembled pattern in an amorphous Si/Au system. This model shows that melting of the implanted layer is essential and without which no spiral patterns are observed. A better understanding of this self-assembly process will open up new ways to fabricate ordered arrays of gold nanoclusters in silicon substrates for seeding selective growth of one-dimensional nanostructures

  2. Saliva and dental erosion

    Directory of Open Access Journals (Sweden)

    Marília Afonso Rabelo Buzalaf

    2012-10-01

    Full Text Available Dental erosion is a multifactorial condition. The consideration of chemical, biological and behavioral factors is fundamental for its prevention and therapy. Among the biological factors, saliva is one of the most important parameters in the protection against erosive wear. Objective: This review discusses the role of salivary factors on the development of dental erosion. Material and Methods: A search was undertaken on MeDLINe website for papers from 1969 to 2010. The keywords used in the research were "saliva", "acquired pellicle", "salivary flow", "salivary buffering capacity" and "dental erosion". Inclusion of studies, data extraction and quality assessment were undertaken independently and in duplicate by two members of the review team. Disagreements were solved by discussion and consensus or by a third party. Results: Several characteristics and properties of saliva play an important role in dental erosion. Salivary clearance gradually eliminates the acids through swallowing and saliva presents buffering capacity causing neutralization and buffering of dietary acids. Salivary flow allows dilution of the acids. In addition, saliva is supersaturated with respect to tooth mineral, providing calcium, phosphate and fluoride necessary for remineralization after an erosive challenge. Furthermore, many proteins present in saliva and acquired pellicle play an important role in dental erosion. Conclusions: Saliva is the most important biological factor affecting the progression of dental erosion. Knowledge of its components and properties involved in this protective role can drive the development of preventive measures targeting to enhance its known beneficial effects.

  3. Saliva and dental erosion.

    Science.gov (United States)

    Buzalaf, Marília Afonso Rabelo; Hannas, Angélicas Reis; Kato, Melissa Thiemi

    2012-01-01

    Dental erosion is a multifactorial condition. The consideration of chemical, biological and behavioral factors is fundamental for its prevention and therapy. Among the biological factors, saliva is one of the most important parameters in the protection against erosive wear. This review discusses the role of salivary factors on the development of dental erosion. A search was undertaken on MeDLINe website for papers from 1969 to 2010. The keywords used in the research were "saliva", "acquired pellicle", "salivary flow", "salivary buffering capacity" and "dental erosion". Inclusion of studies, data extraction and quality assessment were undertaken independently and in duplicate by two members of the review team. Disagreements were solved by discussion and consensus or by a third party. Several characteristics and properties of saliva play an important role in dental erosion. Salivary clearance gradually eliminates the acids through swallowing and saliva presents buffering capacity causing neutralization and buffering of dietary acids. Salivary flow allows dilution of the acids. In addition, saliva is supersaturated with respect to tooth mineral, providing calcium, phosphate and fluoride necessary for remineralization after an erosive challenge. Furthermore, many proteins present in saliva and acquired pellicle play an important role in dental erosion. Saliva is the most important biological factor affecting the progression of dental erosion. Knowledge of its components and properties involved in this protective role can drive the development of preventive measures targeting to enhance its known beneficial effects.

  4. Managing dental erosion.

    Science.gov (United States)

    Curtis, Donald A; Jayanetti, Jay; Chu, Raymond; Staninec, Michal

    2012-01-01

    The clinical signs of dental erosion are initially subtle, yet often progress because the patient remains asymptomatic, unaware and uninformed. Erosion typically works synergistically with abrasion and attrition to cause loss of tooth structure, making diagnosis and management complex. The purpose of this article is to outline clinical examples of patients with dental erosion that highlight the strategy of early identification, patient education and conservative restorative management. Dental erosion is defined as the pathologic chronic loss of dental hard tissues as a result of the chemical influence of exogenous or endogenous acids without bacterial involvement. Like caries or periodontal disease, erosion has a multifactorial etiology and requires a thorough history and examination for diagnosis. It also requires patient understanding and compliance for improved outcomes. Erosion can affect the loss of tooth structure in isolation of other cofactors, but most often works in synergy with abrasion and attrition in the loss of tooth structure (Table 1). Although erosion is thought to be an underlying etiology of dentin sensitivity, erosion and loss of tooth structure often occurs with few symptoms. The purpose of this article is threefold: first, to outline existing barriers that may limit early management of dental erosion. Second, to review the clinical assessment required to establish a diagnosis of erosion. And third, to outline clinical examples that review options to restore lost tooth structure. The authors have included illustrations they hope will be used to improve patient understanding and motivation in the early management of dental erosion.

  5. Recent Advances in Material and Geometrical Modelling in Dental Applications

    Directory of Open Access Journals (Sweden)

    Waleed M. S. Al Qahtani

    2018-06-01

    Full Text Available This article touched, in brief, the recent advances in dental materials and geometric modelling in dental applications. Most common categories of dental materials as metallic alloys, composites, ceramics and nanomaterials were briefly demonstrated. Nanotechnology improved the quality of dental biomaterials. This new technology improves many existing materials properties, also, to introduce new materials with superior properties that covered a wide range of applications in dentistry. Geometric modelling was discussed as a concept and examples within this article. The geometric modelling with engineering Computer-Aided-Design (CAD system(s is highly satisfactory for further analysis or Computer-Aided-Manufacturing (CAM processes. The geometric modelling extracted from Computed-Tomography (CT images (or its similar techniques for the sake of CAM also reached a sufficient level of accuracy, while, obtaining efficient solid modelling without huge efforts on body surfaces, faces, and gaps healing is still doubtable. This article is merely a compilation of knowledge learned from lectures, workshops, books, and journal articles, articles from the internet, dental forum, and scientific groups' discussions.

  6. Automated classification and visualization of healthy and pathological dental tissues based on near-infrared hyper-spectral imaging

    Science.gov (United States)

    Usenik, Peter; Bürmen, Miran; Vrtovec, Tomaž; Fidler, Aleš; Pernuš, Franjo; Likar, Boštjan

    2011-03-01

    Despite major improvements in dental healthcare and technology, dental caries remains one of the most prevalent chronic diseases of modern society. The initial stages of dental caries are characterized by demineralization of enamel crystals, commonly known as white spots which are difficult to diagnose. If detected early enough, such demineralization can be arrested and reversed by non-surgical means through well established dental treatments (fluoride therapy, anti-bacterial therapy, low intensity laser irradiation). Near-infrared (NIR) hyper-spectral imaging is a new promising technique for early detection of demineralization based on distinct spectral features of healthy and pathological dental tissues. In this study, we apply NIR hyper-spectral imaging to classify and visualize healthy and pathological dental tissues including enamel, dentin, calculus, dentin caries, enamel caries and demineralized areas. For this purpose, a standardized teeth database was constructed consisting of 12 extracted human teeth with different degrees of natural dental lesions imaged by NIR hyper-spectral system, X-ray and digital color camera. The color and X-ray images of teeth were presented to a clinical expert for localization and classification of the dental tissues, thereby obtaining the gold standard. Principal component analysis was used for multivariate local modeling of healthy and pathological dental tissues. Finally, the dental tissues were classified by employing multiple discriminant analysis. High agreement was observed between the resulting classification and the gold standard with the classification sensitivity and specificity exceeding 85 % and 97 %, respectively. This study demonstrates that NIR hyper-spectral imaging has considerable diagnostic potential for imaging hard dental tissues.

  7. A new indicator mineral methodology based on a generic Bi-Pb-Te-S mineral inclusion signature in detrital gold from porphyry and low/intermediate sulfidation epithermal environments in Yukon Territory, Canada

    Science.gov (United States)

    Chapman, R. J.; Allan, M. M.; Mortensen, J. K.; Wrighton, T. M.; Grimshaw, M. R.

    2017-12-01

    Porphyry-epithermal and orogenic gold are two of the most important styles of gold-bearing mineralization within orogenic belts. Populations of detrital gold resulting from bulk erosion of such regions may exhibit a compositional continuum wherein Ag, Cu, and Hg in the gold alloy may vary across the full range exhibited by natural gold. This paper describes a new methodology whereby orogenic and porphyry-epithermal gold may be distinguished according to the mineralogy of microscopic inclusions observed within detrital gold particles. A total of 1459 gold grains from hypogene, eluvial, and placer environments around calc-alkaline porphyry deposits in Yukon (Nucleus-Revenue, Casino, Sonora Gulch, and Cyprus-Klaza) have been characterized in terms of their alloy compositions (Au, Ag, Cu, and Hg) and their inclusion mineralogy. Despite differences in the evolution of the different magmatic hydrothermal systems, the gold exhibits a clear Bi-Pb-Te-S mineralogy in the inclusion suite, a signature which is either extremely weak or (most commonly) absent in both Yukon orogenic gold and gold from orogenic settings worldwide. Generic systematic compositional changes in ore mineralogy previously identified across the porphyry-epithermal transition have been identified in the corresponding inclusion suites observed in samples from Yukon. However, the Bi-Te association repeatedly observed in gold from the porphyry mineralization persists into the epithermal environment. Ranges of P-T-X conditions are replicated in the geological environments which define generic styles of mineralization. These parameters influence both gold alloy composition and ore mineralogy, of which inclusion suites are a manifestation. Consequently, we propose that this methodology approach can underpin a widely applicable indicator methodology based on detrital gold.

  8. American Academy of Dental Sleep Medicine

    Science.gov (United States)

    ... New Research AADSM Highlights Members More news... Dental Sleep Medicine: An area of dental practice that focuses on ... SomnoMed Silver Sponsors Copyright © American Academy of Dental Sleep Medicine, All Rights Reserved. American Academy of Dental Sleep ...

  9. Dental patients' use of the Internet.

    LENUS (Irish Health Repository)

    2009-12-19

    To determine the use of the Internet by patients attending a range of dental clinics to search for information regarding dental procedures, and also to investigate their interest in online dental consultations and \\'dental tourism\\'.

  10. 42 CFR Appendix G to Part 75 - Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography

    Science.gov (United States)

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography G Appendix G to Part 75 Public Health PUBLIC HEALTH SERVICE...—Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography The following section...

  11. Activation analysis in gold industry

    International Nuclear Information System (INIS)

    Kist, A. A.

    2003-01-01

    Nuclear techniques and methods were, are, and will be very important for many fields of science, agriculture, industry, etc. Among other examples one can remember role of the nuclear medicine (radiotherapy and radiodiagnostic methods) or semiconductors (communication, computing, information, etc.) which industrial production has been on initial stage based on activation analysis. One of very illustrative examples is application of nuclear methods in gold industry. This is given by favorable nuclear properties of gold. Uzbekistan is one of the main producers of gold. Open-cast mining and hydro metallurgic extraction (using leaching by cyanide and sorption by ion-exchange resin) is the mostly used technology. The typical gold ores are sulfide and contain elevated concentration of As and Sb. That needs special technology of gold extraction. Importance of gold for Uzbekistan economy is a reason why for many years there are carried out studies concerning to gold production. These studies include also nuclear methods and their results are successfully used in gold industry. The present paper gives a brief overview for period of 25 years. For many reasons most of these studies were not published before completely. Despite some results are obtained decades ago we decided to present the overview as an example how nuclear methods can cover requirements of the whole process. We are trying to sort these studies according to methods and applications

  12. Dental school finances: current status.

    Science.gov (United States)

    Crawford, W H

    1986-05-01

    Total expenditures and revenues of 58 US dental school were derived from reports of the ADA Division of Educational Measurements. These financial data were studied by type of dental school (public, state-related private, and private) and by expenditure/revenue categories. Dental schools showed little diversity in expenditures: most were directed toward instruction; few were directed toward research or continuing education. Several distinctive patterns among the three types of dental schools in revenues were observed. Two configurations emerged: public and state-related private dental schools receive more than 75% of their revenues from government and tuition, and private dental schools, more than 50%.

  13. Neurological symptoms among dental assistants: a cross-sectional study.

    Science.gov (United States)

    Moen, Be; Hollund, Be; Riise, T

    2008-05-18

    Dental assistants help the dentist in preparing material for filling teeth. Amalgam was the filling material mostly commonly used in Norway before 1980, and declined to about 5% of all fillings in 2005. Amalgam is usually an alloy of silver, copper, tin and mercury. Copper amalgam, giving particularly high exposure to mercury was used in Norway until 1994. Metallic mercury is neurotoxic. Few studies of the health of dental assistants exist, despite their exposure to mercury. There are questions about the existence of possible chronic neurological symptoms today within this working group, due to this exposure. The aim of this study was to compare the occurrence of neurological symptoms among dental assistants likely to be exposed to mercury from work with dental filling material, compared to similar health personnel with no such exposure. All dental assistants still at work and born before 1970 registered in the archives of a trade union in Hordaland county of Norway were invited to participate (response rate 68%, n = 41), as well as a similar number of randomly selected assistant nurses (response rate 87%, n = 64) in the same age group. The participants completed a self-administered, mailed questionnaire, with questions about demographic variables, life-style factors, musculoskeletal, neurological and psychosomatic symptoms (Euroquest). The dental assistants reported significant higher occurrence of neurological symptoms; psychosomatic symptoms, problems with memory, concentration, fatigue and sleep disturbance, but not for mood. This was found by analyses of variance, adjusting for age, education, alcohol consumption, smoking and personality traits. For each specific neurological symptom, adjusted logistic regression analyses were performed, showing that these symptoms were mainly from arms, hands, legs and balance organs. There is a possibility that the higher occurrence of neurological symptoms among the dental assistants may be related to their previous work

  14. Neurological symptoms among dental assistants: a cross-sectional study

    Directory of Open Access Journals (Sweden)

    Hollund BE

    2008-05-01

    Full Text Available Abstract Background Dental assistants help the dentist in preparing material for filling teeth. Amalgam was the filling material mostly commonly used in Norway before 1980, and declined to about 5% of all fillings in 2005. Amalgam is usually an alloy of silver, copper, tin and mercury. Copper amalgam, giving particularly high exposure to mercury was used in Norway until 1994. Metallic mercury is neurotoxic. Few studies of the health of dental assistants exist, despite their exposure to mercury. There are questions about the existence of possible chronic neurological symptoms today within this working group, due to this exposure. The aim of this study was to compare the occurrence of neurological symptoms among dental assistants likely to be exposed to mercury from work with dental filling material, compared to similar health personnel with no such exposure. Methods All dental assistants still at work and born before 1970 registered in the archives of a trade union in Hordaland county of Norway were invited to participate (response rate 68%, n = 41, as well as a similar number of randomly selected assistant nurses (response rate 87%, n = 64 in the same age group. The participants completed a self-administered, mailed questionnaire, with questions about demographic variables, life-style factors, musculoskeletal, neurological and psychosomatic symptoms (Euroquest. Results The dental assistants reported significant higher occurrence of neurological symptoms; psychosomatic symptoms, problems with memory, concentration, fatigue and sleep disturbance, but not for mood. This was found by analyses of variance, adjusting for age, education, alcohol consumption, smoking and personality traits. For each specific neurological symptom, adjusted logistic regression analyses were performed, showing that these symptoms were mainly from arms, hands, legs and balance organs. Conclusion There is a possibility that the higher occurrence of neurological symptoms

  15. Direct Filling Golds: An In-Vitro Study of Microleakage as a Function of Condensation Force: An In-Vivo Study of Marginal Quality

    Science.gov (United States)

    1979-01-01

    three teeth in vivo in dogs . All three showed penetration surrounding the restorations. No mention was made as to whether a cavity varnish was...gingival reactions to gold foil restorations. J Periodontal 46:614, 1975. 12. Christensen, C.J.: -iologic implications of dental restorations. J -m Acad...1ack, C.17.: An investignr-ian of the physical characters of thle huna. tee--: in relation to their diseases and to practical dental o-ierations

  16. Patient Satisfaction in Military Dental Treatment Facilities

    Science.gov (United States)

    2006-03-07

    the variance in regards to overall satisfaction. 15. SUBJECT TERMS Dentistry, Patient Satisfaction, Military, Consumer Satisfaction, Dental... patient satisfaction in military dental treatment facilities. Dental health is extremely important for the military as dental assets are not always... customer satisfaction is an important component of military dental care. Quarterly patient satisfaction reports are generated for each dental treatment

  17. History of dental hygiene research.

    Science.gov (United States)

    Bowen, Denise M

    2013-01-01

    Dental hygiene is defined as the science and practice of the recognition, treatment and prevention of oral diseases. The history of dental hygiene research is considered in the context of the development of the discipline and an emerging infrastructure. Research-related events supporting the growth and maturation of the profession are considered from the early years to the most recent. The benefits of preventive oral health services provided by dental hygienists have been supported by research, and the practice of dental hygiene has expanded as a result of research findings since its inception 100 years ago. Dental hygienists' engagement in research, however, did not begin until the 1960s as research associates or administrators, primarily with dental researchers as primary investigators. The Journal of Dental Hygiene (JDH) has provided information for dental hygiene practice since 1927, and has been the primary venue for dissemination of dental hygiene research since 1945. Graduate education in dental hygiene at the master's degree level and the work of early dental hygiene researchers led to the first conference on dental hygiene research in 1982. Over 30 years later, dental hygiene has established a meta-paradigm and defined conceptual models, built an initial infrastructure to support research endeavors and contributed much to the development of dental hygiene as a unique discipline. A doctoral degree in the discipline, continued theory-based research, initiatives to foster collaborations between dental hygiene and other researchers and enhanced capabilities to attract funding to support large scale studies are goals that must be attained through the efforts of future researchers to address the needs for additional development in the discipline of dental hygiene. Dental hygiene research supports the growing discipline and its value to society.

  18. Components made of corrosion-resistent zirconium alloy and method for its production

    International Nuclear Information System (INIS)

    Hanneman, R.E.; Urquhart, A.W.; Vermilyea, D.A.

    1977-01-01

    The invention deals with a method to increase the resistance of zirconium alloys to blister corrosion which mainly occurs in boiling-water nuclear reactors. According to the method described, the surface of the alloy body is coated with a thin film of a suitable electronically conducting material. Gold, silver, platinum, nickel, chromium, iron and niobium are suitable as coating materials. The invention is more closely explained by means of examples. (GSC) [de

  19. Bulimia and Anorexia Nervosa in Dental and Dental Hygiene Curricula.

    Science.gov (United States)

    Gross, Karen B. W.; And Others

    1990-01-01

    Dentists and dental hygienists are in a unique position to identify an eating disorder patient from observed oral manifestations and to refer the patient for psychological therapy. The inclusion of information on general and oral complications of bulimia and anorexia nervosa in dental and dental hygiene curriculum was examined. (MLW)

  20. Hand hygiene amongst dental professionals in a tertiary dental clinic ...

    African Journals Online (AJOL)

    Objective: To evaluate hand washing attitude and practices among Dentists and Dental Students treating patients in a Nigerian Tertiary Dental Clinic. Materials and Methods: A cross-sectional survey of Dentists and Dental Students treating patients in University of Benin Teaching Hospital was conducted between February ...

  1. Reasons for late seeking of dental care among dental patients ...

    African Journals Online (AJOL)

    Reasons for delayed reporting for oral care were negligence (53.5%); poor dental services or visited but not treated (19.4%); financial reasons (14.8%); and dental fear (12.3%). Seventy seven percent of respondents who had toothache due to advanced dental caries were aware that the aching tooth was decayed, of which, ...

  2. Diagnostic methods for dental caries used by private dental ...

    African Journals Online (AJOL)

    Objectives: This study aimed to investigate the preference profiles of various types of diagnostic tools and methods used by private dental practitioners in Ankara for detecting dental caries. Methods: Private dental practitioners, in five districts of Ankara, were provided with questionnaires comprising demographic ...

  3. Elemental analysis of gold coins by particle induced X-ray emission (PIXE)

    International Nuclear Information System (INIS)

    Ferreira, G.P.; Gil, F.B.

    1981-01-01

    A Van de Graaff accelerator of 2 MeV energy was used for quantitative analysis of gold coins of the eighteenth and nineteenth centuries by the PIXE method. The results reproduce well the known legal title of the coins. However, for confirmation, a small set of Au-Ag-Cu and Au-Cu standards was also analysed. Again, the known composition of the standards was reasonably reproduced. In this way the authors think that the PIXE method is quite adequate for absolutely non-destructive analysis of gold alloy artifacts with no need of standards. (author)

  4. Fire-assay determination of small amounts of gold in mineral raw materials

    International Nuclear Information System (INIS)

    Kuligin, V.M.; Zdorova, Eh.P.; Popova, N.N.; Rakovskij, Eh.V.

    1976-01-01

    Gold is concentrated in 0.1-1.0 g of a lead alloy obtained in fire assay and cupellation and can be used for the analysis of a number of geological samples. The procedure makes it possible to determine gold with a limit of detection of 0.02 g/ton from a representative sample of 50-100 g. The use of lead acetate ensures the limit of detection of 0.002 g/ton, the relative standard deviation being greater than 0.01

  5. Histological evaluations and inflammatory responses of different dental implant abutment materials: A human histology pilot study.

    Science.gov (United States)

    Sampatanukul, Teeratida; Serichetaphongse, Pravej; Pimkhaokham, Atiphan

    2018-04-01

    Improvements of soft tissue to the abutment surface results in more stable peri-implant conditions, however, few human histological studies have compared soft tissue responses around different abutment materials. To describe the peri-implant tissue around 3 abutment materials; titanium, zirconia, and gold alloy, over an 8-week healing period. Fifteen edentulous sites were treated with implants. Eight weeks later, peri-implant tissue was harvested and processed using a nonseparation resin embedded technique. The tissue attachment characteristics were assessed at clinical stages using the gingival index (GI) score, surgical stage (surgical score), and histological stage (histological attachment percentage). Additionally, the inflammatory responses were evaluated using inflammatory extent and inflammatory cellularity grades. Nonparametrical statistics were used to describe the GI and surgical scores, and analytical statistics were used to analyze the histological attachment percentages as well as the inflammatory extent and cellularity grades amongst the 3 groups. There were no statistically significant differences among the groups for GI score (P = .071) and surgical score (P = .262). Titanium and zirconia exhibited nearly similar mean histological attachment percentages while gold alloy had a significantly lower percentage (P = .004). For the inflammatory extent and cellularity grades, the odds of being one grade higher for gold alloy abutment was 5.18 and 17.8 times that of titanium abutment, respectively. However, for the zirconia abutment, the odds were 0.87 and 7.5 times higher than the titanium group. The tissue around the gold alloy abutments resulted in worse attachment conditions compared with the titanium and zirconia abutments. Inflammation tended to be higher in the tissue around the gold alloy abutments than the titanium and zirconia abutments. © 2017 Wiley Periodicals, Inc.

  6. Stealing the Gold

    International Nuclear Information System (INIS)

    Whittington, S G

    2005-01-01

    Stealing the Gold presents a survey of some of the most exciting topics in condensed matter physics today, from the perspective of the pioneering work of Sam Edwards. Original articles from leaders in the field, including several Nobel laureates, highlight the historical development as well as new and emerging areas. This book would be of interest to graduate students and researchers in condensed matter physics, statistical physics and theoretical physics. Over the course of nearly half a century, Sam Edwards has led the field of condensed matter physics in new directions, ranging from the electronic and statistical properties of disordered materials to the mechanical properties of granular materials. Along the way he has provided seminal contributions to fluid mechanics, polymer science, surface science and statistical mechanics. This volume celebrates the immense scope of his influence by presenting a collection of original articles by recognized leaders in theoretical physics, including two Nobel laureates and a Fields medalist, which describe the genesis, evolution and future prospects of the various sub-fields of condensed matter theory, along with reprints of a selection of Edwards' seminal papers that helped give birth to the subject. Stealing the Gold, Edwards' favourite caricature of the relationship between theoretical physicists and nature, will be of singular interest to graduate students looking for an overview of some of the most exciting areas of theoretical physics, as well as to researchers in condensed matter physics looking for a comprehensive, broad and uniquely incisive snapshot of their subject at the dawn of the 21st century. (book review)

  7. Dental Education in the Netherlands.

    Science.gov (United States)

    Nash, David A.; And Others

    1981-01-01

    Dental education in the Netherlands is reviewed in terms of dental practice, overall development, structure and functioning of a typical school of dentistry, admissions, student finances, curriculum, certification, postgraduate education, and education for related professions. (MSE)

  8. Medical and Dental Patient Issues

    Science.gov (United States)

    ... A RadiationAnswers.org Ask the Experts Medical and Dental Patient Issues What's My Risk? The risks of ... developed by our topic editors for this category: Dental-Patient Issues Medical CT Reference Books and Articles ...

  9. Dental Care - Medicaid and Chip

    Data.gov (United States)

    U.S. Department of Health & Human Services — Dental health is an important part of peoples overall health. States are required to provide dental benefits to children covered by Medicaid and the Childrens Health...

  10. Dental modification in the past

    DEFF Research Database (Denmark)

    Bennike, Pia; Alexandersen, Verner

    2003-01-01

    Skeleton remains from Denmark, Greenland, Faeroe Islands, dental care, drillling in the past, tooth extraction......Skeleton remains from Denmark, Greenland, Faeroe Islands, dental care, drillling in the past, tooth extraction...

  11. Dental Health: The Basic Facts

    Science.gov (United States)

    Dental Health THE BASIC FACTS MULTIPLE SCLEROSIS Kim, diagnosed in 1986 People with a chronic disease may neglect their general health and wellness, research shows. Dental care is no exception. A tendency to focus ...

  12. Dental plaque identification at home

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/003426.htm Dental plaque identification at home To use the sharing ... a sticky substance that collects around and between teeth. The home dental plaque identification test shows where ...

  13. Radiation protection in dental practice

    International Nuclear Information System (INIS)

    This guide provides the dentist and dental support personnel with basic information on the safe use of x-rays in dental radiography. Included in this CODE are specific recommendations for eliminating unnecessary radiation exposure of both patients and staff

  14. Alloy Fabrication Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — At NETL’s Alloy Fabrication Facility in Albany, OR, researchers conduct DOE research projects to produce new alloys suited to a variety of applications, from gas...

  15. Controlled Thermal Expansion Alloys

    Data.gov (United States)

    National Aeronautics and Space Administration — There has always been a need for controlled thermal expansion alloys suitable for mounting optics and detectors in spacecraft applications.  These alloys help...

  16. Visualisation of dental images

    International Nuclear Information System (INIS)

    Md Saion Salikin; Azuhar Ripin; Wan Hazlinda Ismail; Asmaliza Hashim; Norriza Mohd Isa; Suriany Sarmid

    2005-01-01

    Since the invention and the discovery of x-rays, physicians, surgeons and life scientists have been using images to diagnose and subsequently treat diseases. X-ray is also widely used in many imaging techniques to better understand basics anatomy, physiology and biology as well as testing and analytical work in physical science. In dentistry, x-ray technique has been employed to get a panoramic view of the whole teeth of a particular patient. A panoramic dental radiograph is very useful in dentistry for diagnostic purpose, denture preparation, as well as for orthodontic. Image visualisation is an important aspect especially for the dentists to analyse and proceed with a particulate dental treatment. In this project panoramic dental image obtained by using a standard phantom is visualised by using Interactive Data Language (IDL) software. A panoramic dental x-ray machine, Cranex3, is used to get a panoramic radiograph, which is subsequently digitized, by using Vidar digitizer (Sierra Plus). The 2D digitized image is enhance and apply other visualising techniques such as surface rendering and volume rendering technique using Interactive Data Language (IDL) software as a first step in 3D visualisation. In this paper, visualising of panoramic dental radiograph by using IDL is discussed in brief. (Author)

  17. Cosmogenic 3He in detrital gold

    Science.gov (United States)

    Stuart, Finlay; Yakubovich, Olga; Caracedo, Ana; Nesterenok, Alexander

    2017-04-01

    Since the measurement of cosmogenic He in an alluvial diamond by McConville and Reynolds (1996) the application of cosmogenic noble gases to individual detrital grains to quantify surface processes has not been vigorously pursued. The likely low rate of diffusion of cosmogenic He in native metals, and their resistance to weathering and disintegration during erosion and transport, makes them a potential record of long-term Earth surface processes. In an effort to assess the extent that detrital refractory metals record the exposure history during transport and storage we have undertaken a reconnaissance study of the He isotope composition in 18 grains (2-200 mg) of native gold, copper, silver, and PtPd, Pt3Fe and OsIr alloys from alluvial placer deposits from around the world. 4He is dominantly the result of U and Th decay within the grains, or decay of 190Pt in the Pt-rich alloys. 3He is measurable in 13 grains, concentrations range up to 2.7E+6 atoms/g. 3He/4He are always in excess of the crustal radiogenic ratio, up to 306 Ra. Although nucleogenic 3He produced by (n,α) reactions on 6Li, and 3He from trapped hydrothermal fluids, are present, the majority of the 3He is cosmogenic in origin. Using newly calculated cosmogenic 3He production rates in heavy metals, and a determination of the effect of implantation based on the stopping distances of spallogenic 3He and 3H, the grains have 3Hecos concentrations that are equivalent to 0.35 to 1.5 Ma exposure at Earth's surface. In a study of detrital gold grains from several sites in Scotland we have found that 10 % have 3He concentrations that are significantly in excess of that generated since the Last Glacial Maximum. These studies demonstrate that, with refinement, cosmogenic 3He in refractory detrital minerals can be used to quantify sediment transport and storage on the 1-10 Ma timescale. P. McConville & J.H. Reynolds (1989). Geochim. Cosmochim. Acta, 53, 2365-75.

  18. Stretchable microelectrode array using room-temperature liquid alloy interconnects

    International Nuclear Information System (INIS)

    Wei, P; Ziaie, B; Taylor, R; Chung, C; Higgs, G; Pruitt, B L; Ding, Z; Abilez, O J

    2011-01-01

    In this paper, we present a stretchable microelectrode array for studying cell behavior under mechanical strain. The electrode array consists of gold-plated nail-head pins (250 µm tip diameter) or tungsten micro-wires (25.4 µm in diameter) inserted into a polydimethylsiloxane (PDMS) platform (25.4 × 25.4 mm 2 ). Stretchable interconnects to the outside were provided by fusible indium-alloy-filled microchannels. The alloy is liquid at room temperature, thus providing the necessary stretchability and electrical conductivity. The electrode platform can withstand strains of up to 40% and repeated (100 times) strains of up to 35% did not cause any failure in the electrodes or the PDMS substrate. We confirmed biocompatibility of short-term culture, and using the gold pin device, we demonstrated electric field pacing of adult murine heart cells. Further, using the tungsten microelectrode device, we successfully measured depolarizations of differentiated murine heart cells from embryoid body clusters

  19. Electronic structure of alloys

    International Nuclear Information System (INIS)

    Ehrenreich, H.; Schwartz, L.M.

    1976-01-01

    The description of electronic properties of binary substitutional alloys within the single particle approximation is reviewed. Emphasis is placed on a didactic exposition of the equilibrium properties of the transport and magnetic properties of such alloys. Topics covered include: multiple scattering theory; the single band alloy; formal extensions of the theory; the alloy potential; realistic model state densities; the s-d model; and the muffin tin model. 43 figures, 3 tables, 151 references

  20. Does dental caries affect dental development in children and adolescents?

    Science.gov (United States)

    Dhamo, Brunilda; Elezi, Besiana; Kragt, Lea; Wolvius, Eppo B; Ongkosuwito, Edwin M

    2018-01-01

    Although a link between dietary changes, caries, and dental development has been observed, the literature provides little insight about this relationship. The aim of our study was to investigate the association between dental caries and dental development in a clinical sample of Albanian children and adolescents. In total, 118 children and adolescents, born between 1995 and 2004 and aged 6–15 years, were included. Dental caries in the deciduous dentition was assessed using the Decayed, Filled Teeth (dft) index and dental caries in the permanent dentition was assessed using the Decayed, Missing, Filled Teeth (DMFT) index. Dental development during the permanent dentition was determined using the Demirjian method. Linear and ordinal regression models were applied to analyze the associations of dental caries with dental age and developmental stages of each left mandibular tooth. Dental caries in the deciduous dentition, estimated as a median dft of 2.0 (90% range, 0.0–9.1), was significantly associated with lower dental age (β = -0.21; 90% CI: -0.29, -0.12) and with delayed development of the canine, both premolars, and the second molar. Untreated dental caries (dt) was associated with lower dental age (β = -0.19; 90% CI: -0.28, -0.10). Dental caries in the permanent dentition, estimated as a median DMFT of 1.0 (90% range, 0.0–8.0), was not significantly associated with dental age (β = 0.05; 90% CI: -0.04, 0.14). However, the DMFT was associated with the advanced stages of development of both premolars and the second molar. The untreated dental caries in the deciduous dentition delays the development of permanent teeth. PMID:29659350