The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
M Almotlaq - One of the best experts on this subject based on the ideXlab platform.
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electrochemical behaviour of recasting ni cr and co cr non precious Dental Alloys
Corrosion Science, 2004Co-Authors: Maryam Ali A. Ameer, E Khamis, M AlmotlaqAbstract:Corrosion behaviour of Dental Alloys in artificial saliva was studied using different chemical and electrochemical techniques. The order of corrosion rate for the three Alloys in artificial saliva is: wironit < wirolloy < wiron99. This order agrees with the results of chemical studies for determining the cumulative ion concentration using ICP/MS. The open-circuit potential of wirolloy is more positive than wiron99. The higher corrosion rate of wiron99 compared to wirolloy is due to presence of high concentration of Mo. Increasing casting number leads to decrease Rct value and increasing Cdl. � 2004 Elsevier Ltd. All rights reserved.
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electrochemical behaviour of recasting ni cr and co cr non precious Dental Alloys
Corrosion Science, 2004Co-Authors: Maryam Ali A. Ameer, E Khamis, M AlmotlaqAbstract:Corrosion behaviour of Dental Alloys in artificial saliva was studied using different chemical and electrochemical techniques. The order of corrosion rate for the three Alloys in artificial saliva is: wironit < wirolloy < wiron99. This order agrees with the results of chemical studies for determining the cumulative ion concentration using ICP/MS. The open-circuit potential of wirolloy is more positive than wiron99. The higher corrosion rate of wiron99 compared to wirolloy is due to presence of high concentration of Mo. Increasing casting number leads to decrease Rct value and increasing Cdl. � 2004 Elsevier Ltd. All rights reserved.
Angeline Poulonquintin - One of the best experts on this subject based on the ideXlab platform.
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temporal pulse shaping a key parameter for the laser welding of Dental Alloys
Lasers in Medical Science, 2015Co-Authors: Caroline Bertrand, Angeline PoulonquintinAbstract:This study aims to describe the effect of pulse shaping on the prevention of internal defects during laser welding for two Dental Alloys mainly used in prosthetic dentistry. Single spot, weld beads, and welds with 80 % overlapping were performed on Co-Cr-Mo and Pd-Ag-Sn cast plates with a pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. A specific welding procedure using adapted parameters to each alloy was completed. All the possibilities for pulse shaping were tested: (1) the square pulse shape as a default setting, (2) a rising edge slope for gradual heating, (3) a falling edge slope to slow the cooling process, and (4) a combination of rising and falling edges. The optimization of the pulse shape is supposed to produce defect-free welds (crack, pores, voids). Cross-section SEM observations and Vickers microhardness measurements were made. Pd-Ag-Sn was highly sensitive to hot cracking, and Co-Cr-Mo was more sensitive to voids and small porosities (sometimes combined with cracks). Using a slow cooling ramp allowed a better control on the solidification process for those two Alloys always preventing internal defects. A rapid slope should be preferred for Co-Cr-Mo Alloys due to its low-laser beam reflectivity. On the opposite, for Pd-Ag-Sn alloy, a slow rising slope should be preferred because this alloy has a high-laser beam reflectivity.
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temporal pulse shaping a key parameter for the laser welding of Dental Alloys
Lasers in Medical Science, 2015Co-Authors: Caroline Bertrand, Angeline PoulonquintinAbstract:This study aims to describe the effect of pulse shaping on the prevention of internal defects during laser welding for two Dental Alloys mainly used in prosthetic dentistry. Single spot, weld beads, and welds with 80 % overlapping were performed on Co-Cr-Mo and Pd-Ag-Sn cast plates with a pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. A specific welding procedure using adapted parameters to each alloy was completed. All the possibilities for pulse shaping were tested: (1) the square pulse shape as a default setting, (2) a rising edge slope for gradual heating, (3) a falling edge slope to slow the cooling process, and (4) a combination of rising and falling edges. The optimization of the pulse shape is supposed to produce defect-free welds (crack, pores, voids). Cross-section SEM observations and Vickers microhardness measurements were made. Pd-Ag-Sn was highly sensitive to hot cracking, and Co-Cr-Mo was more sensitive to voids and small porosities (sometimes combined with cracks). Using a slow cooling ramp allowed a better control on the solidification process for those two Alloys always preventing internal defects. A rapid slope should be preferred for Co-Cr-Mo Alloys due to its low-laser beam reflectivity. On the opposite, for Pd-Ag-Sn alloy, a slow rising slope should be preferred because this alloy has a high-laser beam reflectivity.
Maryam Ali A. Ameer - One of the best experts on this subject based on the ideXlab platform.
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electrochemical behaviour of recasting ni cr and co cr non precious Dental Alloys
Corrosion Science, 2004Co-Authors: Maryam Ali A. Ameer, E Khamis, M AlmotlaqAbstract:Corrosion behaviour of Dental Alloys in artificial saliva was studied using different chemical and electrochemical techniques. The order of corrosion rate for the three Alloys in artificial saliva is: wironit < wirolloy < wiron99. This order agrees with the results of chemical studies for determining the cumulative ion concentration using ICP/MS. The open-circuit potential of wirolloy is more positive than wiron99. The higher corrosion rate of wiron99 compared to wirolloy is due to presence of high concentration of Mo. Increasing casting number leads to decrease Rct value and increasing Cdl. � 2004 Elsevier Ltd. All rights reserved.
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electrochemical behaviour of recasting ni cr and co cr non precious Dental Alloys
Corrosion Science, 2004Co-Authors: Maryam Ali A. Ameer, E Khamis, M AlmotlaqAbstract:Corrosion behaviour of Dental Alloys in artificial saliva was studied using different chemical and electrochemical techniques. The order of corrosion rate for the three Alloys in artificial saliva is: wironit < wirolloy < wiron99. This order agrees with the results of chemical studies for determining the cumulative ion concentration using ICP/MS. The open-circuit potential of wirolloy is more positive than wiron99. The higher corrosion rate of wiron99 compared to wirolloy is due to presence of high concentration of Mo. Increasing casting number leads to decrease Rct value and increasing Cdl. � 2004 Elsevier Ltd. All rights reserved.
Caroline Bertrand - One of the best experts on this subject based on the ideXlab platform.
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temporal pulse shaping a key parameter for the laser welding of Dental Alloys
Lasers in Medical Science, 2015Co-Authors: Caroline Bertrand, Angeline PoulonquintinAbstract:This study aims to describe the effect of pulse shaping on the prevention of internal defects during laser welding for two Dental Alloys mainly used in prosthetic dentistry. Single spot, weld beads, and welds with 80 % overlapping were performed on Co-Cr-Mo and Pd-Ag-Sn cast plates with a pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. A specific welding procedure using adapted parameters to each alloy was completed. All the possibilities for pulse shaping were tested: (1) the square pulse shape as a default setting, (2) a rising edge slope for gradual heating, (3) a falling edge slope to slow the cooling process, and (4) a combination of rising and falling edges. The optimization of the pulse shape is supposed to produce defect-free welds (crack, pores, voids). Cross-section SEM observations and Vickers microhardness measurements were made. Pd-Ag-Sn was highly sensitive to hot cracking, and Co-Cr-Mo was more sensitive to voids and small porosities (sometimes combined with cracks). Using a slow cooling ramp allowed a better control on the solidification process for those two Alloys always preventing internal defects. A rapid slope should be preferred for Co-Cr-Mo Alloys due to its low-laser beam reflectivity. On the opposite, for Pd-Ag-Sn alloy, a slow rising slope should be preferred because this alloy has a high-laser beam reflectivity.
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temporal pulse shaping a key parameter for the laser welding of Dental Alloys
Lasers in Medical Science, 2015Co-Authors: Caroline Bertrand, Angeline PoulonquintinAbstract:This study aims to describe the effect of pulse shaping on the prevention of internal defects during laser welding for two Dental Alloys mainly used in prosthetic dentistry. Single spot, weld beads, and welds with 80 % overlapping were performed on Co-Cr-Mo and Pd-Ag-Sn cast plates with a pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. A specific welding procedure using adapted parameters to each alloy was completed. All the possibilities for pulse shaping were tested: (1) the square pulse shape as a default setting, (2) a rising edge slope for gradual heating, (3) a falling edge slope to slow the cooling process, and (4) a combination of rising and falling edges. The optimization of the pulse shape is supposed to produce defect-free welds (crack, pores, voids). Cross-section SEM observations and Vickers microhardness measurements were made. Pd-Ag-Sn was highly sensitive to hot cracking, and Co-Cr-Mo was more sensitive to voids and small porosities (sometimes combined with cracks). Using a slow cooling ramp allowed a better control on the solidification process for those two Alloys always preventing internal defects. A rapid slope should be preferred for Co-Cr-Mo Alloys due to its low-laser beam reflectivity. On the opposite, for Pd-Ag-Sn alloy, a slow rising slope should be preferred because this alloy has a high-laser beam reflectivity.
Lucien Reclaru - One of the best experts on this subject based on the ideXlab platform.
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Investigations on Dental Alloys Using Metallographic Observation, Scanning Electron Microscopy, and Energy- Dispersive X-Ray Spectroscopy
Micro and Nanotechnologies for Biotechnology, 2016Co-Authors: Lavinia Ardelean, Lucien Reclaru, Cristina-maria Bortun, Laura Cristina RusuAbstract:Alloys are used in various areas of dentistry, but mainly in prosthetics. Their proper‐ ties, behavior, and corrosion resistance are of great importance for the success of the prosthetic treatment. Among the investigations used for assessing Dental Alloys, in this chapter, we focus on metallographic observation, scanning electron microscopy, and energy-dispersive X-ray spectroscopy and present the ways we investigated several types of Dental Alloys. We obtained important data concerning their structure and corrosion potential that could explain certain shortcomings which appeared after luting of the fixed partial dentures.
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Ni–Cr based Dental Alloys; Ni release, corrosion and biological evaluation
Materials Science and Engineering: C, 2012Co-Authors: Lucien Reclaru, Ronald E. Unger, Charles James Kirkpatrick, Christian Susz, P.-y. Eschler, M.-h. Zuercher, Iulian Vasile Antoniac, Heinz LüthyAbstract:Abstract 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.
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corrosion behaviour of cobalt chromium Dental Alloys doped with precious metals
Biomaterials, 2005Co-Authors: Lucien Reclaru, Heinz Lüthy, P.-y. Eschler, Andreas Blatter, Christian SuszAbstract:Precious metal based Dental Alloys generally exhibit a superior corrosion resistance, in particular enhanced resistance to pitting and crevice corrosion, compared to non-precious metal based Alloys such as CoCr Alloys. A new generation of Co-Cr Alloys enriched with precious metals (Au, Pt, Ru) have now appeared on the market. The goal of this study was to clarify the effect of the precious metals additions on the corrosion behaviour of such Alloys. Various commercial Alloys with different doping levels were tested by electrochemical techniques in two different milieus based on the Fusayama artificial saliva and an electrolyte containing NaCl. Open circuit potentials, corrosion currents, polarization resistances, and crevices potentials were determined for the various Alloys and completed by a coulometric analysis of the potentiodynamic curves. In addition, the microstructures were characterised by metallography and phase compositions analysed by EDX. The results show that the presence of precious metals can deteriorate the corrosion behaviour of Co-Cr Alloys in a significant way. Gold doping, in particular, produces heterogeneous microstructures that are vulnerable to corrosive attack.
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effects of fluorides on titanium and other Dental Alloys in dentistry
Biomaterials, 1998Co-Authors: Lucien Reclaru, Jeanmarc MeyerAbstract:Abstract Fluoride ions are the only aggressive ions for the protective oxide layer of titanium and titanium Alloys. Thus their presence may possibly start a localized corrosive degradation by pitting and crevice corrosion processes. Since hygiene products like toothpastes and prophylactic gels contain fluoride ions, the present study has been completed to evaluate the effect of fluoride ions on titanium and Dental Alloys used, for example, as Dental implants and superstructures. Two different milieu based on the Fusayama artificial saliva and an electrolyte solution containing NaCl, with and without fluoride ions, have been used for the electrochemical tests, in a pH range of 6.15 to 3.0. Open circuit potentials, potentiodynamic curves, Tafel slopes, galvanic couplings and crevice potentials are the electrochemical procedures selected for this work. Based on the experimental results obtained with these procedures, the mixed potential theory was applied to predict couple potentials and couple currents. It has thus been shown that: (a) with and without fluoride ions, galvanic currents are weak (10E−7 to 10E−8 A cm -2 ) within a pH range of 6.15 to 3.5; (b) titanium submitted to anodic polarization in an electrolyte, even one containing fluoride, merely develops an oxide layer and does not corrode within that same pH range of 6.15 to 3.5; (c) in confined areas where fluoride ions are present, titanium and the Dental Alloys tested undergo a corrosive process, in the form of crevice and pitting, as soon as the pH drops below 3.5.