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Proceedings of the National Science... Oct 1989Since a good retention of direct bonded retainers onto abutment teeth is the primary requirement for the fabrication of etched fixed partial dentures, successful...
Since a good retention of direct bonded retainers onto abutment teeth is the primary requirement for the fabrication of etched fixed partial dentures, successful formation of a micromechanical retentive architecture on the bonding surface is one of the most important procedures. For creating such a retentive dendritic pattern on nonprecious metal, a 2-electrode electrolytic method has been used. This equipment consists of a low-voltage DC power supply and two electrodes, namely, a working and a counter one. However, the current and voltage should be monitored during the entire processing time and the etching area must be pre-estimated. A potentiostat has been used to automatically stabilize the voltage across the working electrode and reference electrode by adjusting the current, as commonly employed in electro-chemical technology. A 3-electrode corrosion device originally developed for laboratory research was adapted for dental retainer etching in this study. The results revealed that the etching of dental nonprecious metal (Ni-Cr-Be alloy) could successfully be performed by using the system with a potentiostat. Moreover, the working potential was found to be approximately 1.3 volts by taking the midpoint between the breakdown and the critical potentials for passivation on the potentiostatic anode polarization curves. The optimal exposure time has been found to be in a range of 3 to 5 minutes and 4 minutes to be ideal as determined by SEM microphotographic observation which showed a uniform dendritic pattern with regular lattice form of alternating ridges and valleys.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Acid Etching, Dental; Dental Alloys; Dental Bonding; Electrodes; Microscopy, Electron, Scanning; Tensile Strength
PubMed: 2700236
DOI: No ID Found -
Scandinavian Journal of Dental Research Jul 1975The steady-state creep rates of dental amalgams were measured and the creep rates were correlated with the microstructure of the amalgams. The influence of manipulation...
The steady-state creep rates of dental amalgams were measured and the creep rates were correlated with the microstructure of the amalgams. The influence of manipulation variables on creep rate and microstructure are evaluated. The samples were either mechanically or hand triturated, hand condensed, and stored at 20 degrees C for 7 d. The specimens were subjected to a constant tensile load for 24 h, and the elongation was measured with a displacement transducer. The smallest creep rate was found on a spherical amalgam, and the highest on an amalgam made from a preamalgamated fine grain alloy. A correlation between microstructure and creep rate could be demonstrated. The amount of gamma2 phase did not seem to influence the creep rate. Amalgams that had large closely packed gamma particles surrounded by a small volume fraction of gamma1 phase exhibited a low creep rate. Amalgams that had small broken up gamma particles surrounded by a large volume fraction of gamma1 exhibited a high creep rate. Abusive manipulation of lathe-cut amalgam alloys resulted in high creep rates, small broken up gamma particles and a high volume fraction of gamma1.
Topics: Dental Alloys; Dental Amalgam; Dental Stress Analysis; Microscopy, Electron; Rheology
PubMed: 1057789
DOI: 10.1111/j.1600-0722.1975.tb00433.x -
Dental Materials : Official Publication... Dec 2015CrCoMo alloy specimens were successfully fabricated using selective laser melting (SLM). The aim of this study was to carefully investigate microstructure of the SLM...
OBJECTIVES
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.
METHODS
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.
RESULTS
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), fine cracks at grain boundaries (<10 μm) and cracks at weld line boundaries (>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.
SIGNIFICANCE
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".
Topics: Chromium; Cobalt; Dental Alloys; Dental Casting Investment; Hardness; Hot Temperature; Lasers; Materials Testing; Microscopy, Electron, Scanning; Molybdenum; Nanostructures; Spectrometry, X-Ray Emission; Stress, Mechanical; Surface Properties; Tensile Strength; X-Ray Diffraction
PubMed: 26452598
DOI: 10.1016/j.dental.2015.09.003 -
The Journal of Prosthetic Dentistry Mar 2022The complex oral environment leads to the corrosion of dental alloy materials and the release of metal ions that may have a negative impact on health. Digital...
STATEMENT OF PROBLEMS
The complex oral environment leads to the corrosion of dental alloy materials and the release of metal ions that may have a negative impact on health. Digital manufacturing is increasingly being used in dentistry, but whether digitally manufactured prostheses have better resistance to corrosion than traditional cast prostheses is unclear.
PURPOSE
The purpose of this in vitro study was to determine the surface properties and corrosion resistance of dental cobalt-chromium (Co-Cr) alloys fabricated by lost-wax casting (CAST), selective laser melting (SLM), and computer numerical control milling (CNC).
MATERIAL AND METHODS
The surface characteristics of the specimens were analyzed via scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS), metallurgical observation, and X-ray diffraction (XRD). For corrosion resistance, the specimens were immersed in artificial saliva at a pH 2.3 and 6.8 for 1, 4, and 7 weeks. Then, inductively coupled plasma-mass spectrometry (ICP-MS) was used to detect the main metal ion. Electrochemical impedance spectroscopy (EIS) was conducted based on a 3-electrode system to assess the electrochemical corrosion resistance. An ANOVA test was used to evaluate statistically significant differences among the groups (α=.05).
RESULTS
The SLM and CNC specimens showed more homogenous microstructures, less ion release at different times and pH, and more charge transfer resistance than CAST specimens.
CONCLUSIONS
Compared with casting, SLM-printing and CNC-milling have advantages in terms of surface properties and corrosion resistance.
Topics: Alloys; Chromium Alloys; Corrosion; Dental Alloys; Lasers; Materials Testing; Surface Properties
PubMed: 34998583
DOI: 10.1016/j.prosdent.2021.11.019 -
Dental Materials Journal May 2010Artifacts in MR(Magnetic Resonance) images of oral cavity produced from non-magnetic metal restorations was verified by measuring the image of index finger and a...
Artifacts in MR(Magnetic Resonance) images of oral cavity produced from non-magnetic metal restorations was verified by measuring the image of index finger and a cylinder of fat test piece with a type 4 gold alloy ring using a compact MRI equipment. In the images of finger, portion around the ring disappeared. However, it was nearly restored with a cut ring. In the cylinder of fat test piece, obvious artifacts appeared when circumferential surface of the ring was placed perpendicular to RF(Radio Frequency) field of MRI equipment's excitation/detection coil. However, in other directions or with a cut ring, artifact disappeared. The cause was simulated with FEM(Finite Element Method) electromagnetic field analysis, and alternating magnetic field was shown to induce surface current on the continuous gold ring. Magnetic field produced by that current interfered with the field from excitation coil. This demonstrated the characteristics and cause of artifacts by non-magnetic dental metals.
Topics: Adipose Tissue; Artifacts; Dental Alloys; Electromagnetic Fields; Finite Element Analysis; Gold Alloys; Humans; Magnetic Resonance Imaging; Radio Waves
PubMed: 20448408
DOI: 10.4012/dmj.2009-116 -
Journal of the Mechanical Behavior of... Apr 2014Dental 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...
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 (p<.05). There is a positive correlation between weight and height loss (p<.05), but weight (p=.204) and height (p=.05) loss are not correlated to microhardness. The results suggest that pressable low-fusing ceramic presents different wear according to the dental alloy used as antagonist and the wear is not affected by antagonist microhardness.
Topics: Ceramics; Dental Alloys; Hardness; Materials Testing; Mechanical Phenomena
PubMed: 24412716
DOI: 10.1016/j.jmbbm.2013.12.018 -
Journal of Dental Research Jun 1992A new, simple surface modification method for adherend metals has been developed. It gives high bond strength and superior water durability to dental precious-metal... (Comparative Study)
Comparative Study
A new, simple surface modification method for adherend metals has been developed. It gives high bond strength and superior water durability to dental precious-metal alloys bonded with 4-META/MMA-TBB resin. However, there was no effect on the bonding of Ag-In-Zn alloy and base-metal alloys. In the present study, the alloy surfaces modified by the new method were analyzed by ESCA and SEM for determination of details of the modification effect. A new alloying layer containing Ga and Sn was formed on the precious-metal alloys. The main factor for excellent adhesion to be achieved was the formation of a very thin layer of Ga2O3 and SnO2, less than 1-2nm thick, on the alloy surface. A thicker modified layer, as formed on the Ag-In-Zn and Ni-Cr alloys, led to low bonding ability.
Topics: Acrylic Resins; Adhesiveness; Alloys; Boron Compounds; Chromium Alloys; Dental Alloys; Dental Bonding; Electron Probe Microanalysis; Gallium; Gold Alloys; Indium; Materials Testing; Microscopy, Electron, Scanning; Oxidation-Reduction; Silver; Surface Properties; Tensile Strength; Tin; Tin Compounds
PubMed: 1613184
DOI: 10.1177/00220345920710061101 -
Journal of Prosthodontics : Official... Dec 2019To investigate the effect of bonding agent on the bonding strength between Co-Cr dental alloy, prepared by selective laser melting (SLM), and feldspathic porcelain.
PURPOSE
To investigate the effect of bonding agent on the bonding strength between Co-Cr dental alloy, prepared by selective laser melting (SLM), and feldspathic porcelain.
MATERIALS AND METHODS
The experiments were conducted according to ISO 9693 and the conventional protocols for the production of metal-ceramic dental restorations. After Al O air-particle abrasion, metal substrates of Co-Cr dental alloy specimens were bonded, using bonding agent (25 specimens), with dental porcelain positioned in layers (opaque, dentin, enamel). Control specimens (25) were also produced without bonding agent. Bonding strength was measured using 3-point bending tests, and the results were statistically analyzed using the t-test and Weibull statistics. Elemental (by SEM/EDS) and crystallographic analyses (by XRD) were conducted on the bonding agent, along cross sections of alloy-porcelain interfaces, and on fracture surfaces.
RESULTS
Cohesive fracture occurred (on the porcelain side). The application of the bonding agent decreased the average bonding strength (from 42.27 ± 5.85 to 36.25 ± 3.26 MPa, P = 0.00006), attributed to the nonexisting reaction between the TiO -rich bonding agent and the Co-Cr alloy, but it increased the Weibull modulus (from 7.84 to 12.16), which reflects the reliability of the bond in the tested metal-ceramic specimens.
CONCLUSIONS
Although the application of bonding agent slightly decreased the bonding strength, all the measured values of the metal-ceramic specimens produced by the SLM technique, with or without the bonding agent, are markedly higher than the minimum value required by ISO 9693 (25 MPa). Moreover, the use of bonding agent favors the increase of the Weibull modulus.
Topics: Ceramics; Chromium Alloys; Dental Bonding; Dental Porcelain; Materials Testing; Metal Ceramic Alloys; Reproducibility of Results; Surface Properties
PubMed: 30912204
DOI: 10.1111/jopr.13058 -
Dental Materials Journal 2011The purpose of present investigation was to compare the cyto-genotoxicity induced by five dental alloys in vitro. The cyto-genotoxicity induced by five dental alloy... (Comparative Study)
Comparative Study
The purpose of present investigation was to compare the cyto-genotoxicity induced by five dental alloys in vitro. The cyto-genotoxicity induced by five dental alloy extracts on human B lymphoblast cells was assessed with neutral red uptake (NRU) , CCK-8, comet and micronucleus (CBMN) assays in vitro, respectively. The results of in vitro comet and CBMN assays indicated that DNA damage (% tail DNA) and micronucleus frequencies (MNFs) in all exposure groups did not significantly increase, as compared with the control group. However, the results of NRU and CCK-8 assays demonstrated that there were to some extent differences in the cytotoxicity among 5 dental alloy extracts in vitro. The cytotoxicity may be relevant to the Ni and Be ions released in the alloy extract.
Topics: B-Lymphocytes; Beryllium; Cell Survival; Cells, Cultured; Chromium; Cobalt; Comet Assay; DNA Damage; Dental Alloys; Humans; Materials Testing; Micronucleus Tests; Nickel
PubMed: 22123010
DOI: 10.4012/dmj.2011-127 -
The Bulletin of Tokyo Dental College May 2000Dental alloy surface finishing procedures of may influence their electrochemical behavior, which is used to evaluate their corrosion resistance. We examined the... (Comparative Study)
Comparative Study
Dental alloy surface finishing procedures of may influence their electrochemical behavior, which is used to evaluate their corrosion resistance. We examined the polarization resistance and potentiodynamic polarization profile of the precious-metal alloys, Type 4 gold alloy and silver-palladium alloy, and the base-metal alloys, nickel-chromium alloy, cobalt-chromium alloy, and CP-titanium. Three types of finishing procedure were examined: mirror-finishing using 0.05 micron alumina particles, polishing using #600 abrasive paper and sandblasting. Dissolution of the alloy elements in 0.9% NaCl solution was also measured and compared with the electrochemical evaluation. The corrosion resistance of the dental alloys was found to relate to finishing as follows: The polarization resistance and potentiodynamic polarization behavior revealed that the corrosion resistance improved in the order of sandblasting, #600-abrasive-paper polishing, and mirror-finishing. While the corrosion potential, critical current density and passive current density varied depending on the type of finishing, the transpassive potential remained unchanged. The influence of finishing on the corrosion resistance of precious-metal alloys was less significant than on that of base-metal alloys. A mirror-finishing specimen was recommended for use in evaluation of the corrosion resistance of various dental alloys.
Topics: Alloys; Aluminum Oxide; Chromium Alloys; Corrosion; Dental Alloys; Dental Polishing; Electric Impedance; Electrochemistry; Gold Alloys; Humans; Materials Testing; Palladium; Paper; Potentiometry; Silicon Dioxide; Silver; Sodium Chloride; Solubility; Surface Properties; Titanium
PubMed: 11212579
DOI: 10.2209/tdcpublication.41.49