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Statement of problem Angle-correcting options allow the use of screw-retained implant prostheses in situations where an implant has been placed with a facial inclination. However, manufacturers have different recommended torque values, and it is unclear whether the performance of these designs is equivalent to that of the traditional screw-retained crowns (SRCs) when subjected to cyclic loading forces. Purpose The purpose of this in vitro study was to compare torque differences between conventional straight-line screw access and angulated access SRCs before and after simulated functional loading. Material and methods Five groups consisting of 10 SRCs and implants were formed: Nobel Biocare zirconia crowns with 20-degree access channels (NB-20); Dynamic Abutment Solution zirconia crowns (DA-20) with 20-degree access channels; Core3dcentre angle correction zirconia crowns with 20-degree access channels (C3D-20); Nobel Biocare zirconia crowns with 0-degree access channels (NB-0); and gold alloy crowns cast to Nobel Biocare Gold-Adapt abutments (GA-0). Each specimen underwent thermocycling before cyclic loading. A preload torque based on the manufacturer’s recommendation was applied to each crown placed on an implant. Reverse torque measurements were obtained for each specimen before cyclic loading. Each implant-abutment assembly was then cyclic loaded at 0 to 100 N at 10 Hz for 1 million cycles. Reverse torque measurements were obtained after cyclic loading and the percentage difference calculated. Results No significant percentage torque loss differences were observed between the 0-degree and 20-degree SRCs after cyclic loading. No significant differences were seen among the angulated access channel crowns. DA-20 and C3D-20 specimens had significantly higher torque loss compared with the NB-0 group. The C3D-20 group reported the largest percentage torque loss (34.5%) among the angulated access screw channel groups. The GA-0 group reported the largest percentage torque loss of all the groups (35.9%). No crown mobility or other complications were observed in any of the groups after cyclic loading. Conclusions Angulated access channel crowns performed comparably with conventional straight-line screw access SRCs with regard to percentage torque values after cyclic loading. Angulated access channel crowns with lower manufacturer recommended torque values had higher percentage torque differences.

In this work, the use of gold and gold alloy plaques is proposed for the first time, to reduce the dose to healthy organs in brachytherapy with Ir-192 sources. For dose simulations in tumour and healthy tissue, the MCNPX Monte Carlo code was used. The radiation source implemented in those simulations was benchmarked with well-known TG-43 criteria of dose rate constant, air-kerma strength, radial dose function, and 2D anisotropy function. For various arrangements of iridium sources and plaques of gold and gold alloy of various thicknesses, the dose distributions in an esophagus tumour and in surrounding healthy organs were simulated. The results showed that while the dose to the tumour is not much affected by the presence of gold plaques with a thickness of 3.5 mm in an optimized 192Ir sources’ configuration, a relative reduction in average organ dose of 64%, 65%, 73%, 67%, and 35% was observed, for esophagus, thyroid, heart, stomach, and liver, respectively. Moreover, it was found that a gold plaque leads to smaller doses to healthy organs than a gold alloy plaque. It is concluded that gold plaques can be used to improve the treatment of esophageal cancer by HDR brachytherapy and to protect surrounding non-target organs.

Introduction: This study compares the cyclic fatigue resistance of files made of gold technology, such as ProTaper Gold F2 and WaveOne Gold Primary files, and files made of M-Wire technology, such as ProTaper Next X2 and WaveOne files. Materials and Methods: A total of 45 files were used in this study, which were classified into 4 groups. Cyclic fatigue tests were conducted using a cyclic loading testing machine, with an artificial canal made of stainless steel (angle of curvature: 45°; curvature radius: 5 mm). All rotary instruments were allowed to reciprocate and rotate until complete fracture, and the fracture time was recorded in seconds using a stop watch. To prevent human error, the experiments were also video-recorded. Results: Gold-Wire files (WaveOne Gold and ProTaper Gold) demonstrated longer time to fracture than that M-Wire files (WaveOne and ProTaper Next) (P < 0.005). In addition, WaveOne files showed more time to fracture than ProTaper Next files (P < 0.005). Fracture surface evaluation coincide with our results. Conclusions: Under the conditions of this study, the gold alloy files resisted cyclic fatigue better than the M-Wire alloy files, In addition, WaveOne files resist cyclic fatigue better than ProTaper Next files.

Aim: This study aimed to comparatively evaluate the fracture resistance of different metallic post and core materials. Materials and Methods: Twenty-four maxillary–central incisors were selected, standardized, and segregated into three groups (GP I–III) (n = 8) based on the type of alloy used for post and core preparation. GP I (gold alloy [Au]), GP II (chrome–cobalt alloy [Co–Cr]), and GP III (titanium alloy [Ti]) were comparatively evaluated for use as post and core materials. The teeth were endodontically treated and tooth preparation for post core was done.Metal post and cores were fabricated using indirect wax pattern and luted. Teeth were mounted on resin bases, fracture testing was done, and type of fractures were analyzed. Results: Mesiodistal type of fracture was the most common among experimental groups with a percentage incidence of 54.20%. The comminuted type of fracture was the next most common with a percentage incidence of 29.2%. The incidence of buccolingual, transverse, and other type of fracture was not common and had a percentage incidence of 29.2%, 4.2%, 8.3% and 4.2% respectively. Group II had the highest fracture resistance with a mean value of 742.89N. Group III and Group I had mean values of 482.33 and 361.1123N. Statistically significant difference between experimental groups (I and II) and (II and III) was observed in load values of root fracture (P < 0.05). Conclusion: On the basis of the protocols used and limitations of this study, among metallic post and core materials tested, GP II had the highest fracture resistance values. Further evaluation of these different post and core systems, new alloy formulations designed specifically for use as post and core materials, and assessment in a clinical setting is recommended.

Background The objective of this study was to assess the bending and torsional properties of two nickel-titanium endodontic files with equivalent sizes and various designs and alloys using finite element analysis, ProTaper Next®X2 (PTN) size 25 with 0.06 taper and WaveOne Gold® (WOG) primary size 25 with 0.07 taper. Methodology Two-dimensional models of the two files PTN and WOG were created using computer tomography scanning and stereomicroscope to produce a three-dimensional digital model. Instrument behavior under bending or torsional conditions was numerically analyzed in SolidWorks software package. Result ProTaper Next® revealed higher flexibility than WaveOne Gold® when exposed to cantilever bending but showed higher stress accumulation than WOG. In terms of torsional resistance, PTN also revealed higher torsional resistance than WOG. Conclusion The geometry of the instrument, thermomechanical treatment of the alloy, and its composition affect the mechanical behavior (bending and torsion) of nickel titanium rotary files. Hence, being aware of these behavioral differences, each clinician will be able to use the adequate file according to the clinical situation in addition to the manufacturer’s instructions.

Background The appearance of high-density root obturating materials, such as gutta-percha and intracanal posts, on cone-beam computed tomography (CBCT) scans is substantially different from that seen in the specimen. This study evaluated the effectiveness of different CBCT software in the reduction of blooming artifacts when examining teeth with intracanal posts. Method The sample included 42 human single-rooted teeth with two types of posts: G1 – low-fusion alloy posts; G2 – gold alloy posts. CBCT scans were obtained using two scanners, PreXion 3D Elite® and Carestream 9000C 3D®. First, the posts were measured using a digital micrometer (standard reference, control). Post diameters were determined using the Blooming Artifact Reduction (BAR) tool of the e-Vol DX software and of the PreXion3D Image Analysis System. Statistical data were evaluated using the van Der Waerden nonparametric analysis of variance and, after that, normalized data were analyzed using the Tukey test. The level of significance was set at α = 5 %. Results There were no significant differences (p > 0.05) between the diameters of intracanal posts on the CT scans when the e-Vol DX was used, or when these results were compared with those obtained using a micrometer. There were significant differences in post diameters determined using the PreXion3D Image Analysis System when compared with the e-Vol DX and the micrometer values (p Conclusions The use of the e-Vol DX BAR filter eliminated blooming artifacts. There were no dimensional changes in the CBCT images of the low-fusion and gold alloy intracanal posts using the e-Vol DX BAR filter.

Gold nanoparticles have been used as imaging probes to track the motions of single biomolecules. To investigate behaviors of various biomolecules simultaneously, increase of the color palette is ne...

Polytetrafluoroethylene (PTFE) is chemically stable, non-toxic to humans, highly resistant to heat and chemicals, and has an extremely low coefficient of friction. Therefore, PTFE is used in medical applications. We focused on the physical properties of PTFE in relation to its application as a material for use in prostheses and dental devices/instruments. PTFE exhibited low wear (approximately 1/3 that of bovine tooth, and 1/2 that of type III gold alloy), low dynamic friction (approximately 1/5 that of the other specimens), low hardness (4.8HV1.0), low coloration, and low bacterial adhesion, compared to other specimens except porcelain in wear and coloration test (p

Aqueous extract of Opuntia ficus-indica (OF) was employed to reduce salt solutions of silver nitrate, gold chloride and silver nitrate/gold chloride to OFAgNPs, OFAuNPs, and OFAg-AuNPs respectively. Characterization of the particles was carried out using different standard methods, and their antimicrobial and antioxidant activities were also evaluated. The UV-vis spectroscopy showed silver, gold and silver-gold alloys nanoparticles with surface plasmon resonance at 462, 545 and 539 nm, respectively. The significant FTIR peaks: OFAgNPs (3300 and 1635 cm−1), OFAuNPs (3288 and 1635 cm−1) and OFAg-AuNPs (3307 and 1637 cm−1) for synthesized nanoparticles pointed to protein as both capping and stabilizing agent. Generally, particles were spherical with size range of 27-38 nm, 11-28 nm and 15-54 nm for silver, gold and silver-gold alloys nanoparticles respectively. OFAgNPs gave highest antagonistic effects against tested bacteria (35-82%), followed by OFAg-AuNPs (12-75%) and AuNPs (11-48%). The fungal inhibition of 44-70% for OFAgNPs, 42-79% for OFAuNPs and 52-92% for OFAg-AuNPs were obtained. DPPH scavenging activities were obtained as follows: OFAgNPs (52.25–57.50%), OFAuNPs (37.07-59.07%) and OFAg-AuNPs (37.07-63.00%) at tested concentrations of 20–100 µg/ml, which were dose-dependent in comparison with standard BHA (42.57–91.27%) and ascorbic acid (52.13–84.20%). The bleaching inhibition assay of ABTS showed activities of 41.33–61.83% (OFAgNPs), 27.37-50.60% (OFAuNPs) and 32.83-44.33% (OFAg-AuNPs). The synthesized nanoparticles demonstrated an excellent antioxidant and antimicrobial activity. The current study, to the best of our knowledge, is the first time to use Opuntia ficus-indica to synthesize silver, gold and silver-gold alloys nanoparticles.

Purpose To evaluate the influence of polymerization methods and a metal priming agent on the bond strength between gold alloy for metal ceramic restorations and dual-cure-type resin luting agents, and on the strength and hardness of the luting agents. Methods A total of 154 disks cast by a gold alloy were treated with or without a metal priming agent. One of the three luting agents was applied on the disk. The luting agent was either chemically or dual-polymerized. The shear bond strength was measured both before and after thermocycling. In addition, scanning electron microscope (SEM) observation, flexural strength test, and Knoop hardness test were performed. Results Significant differences among the luting agents were observed in terms of bond strength and flexural strength. Significant differences between chemically and dual-polymerized luting agents were observed regarding shear bond strength, flexural strength, and Knoop hardness before thermocycling. The application of the priming agent was effective only for a luting agent. Conclusion Both bond strength and flexural strength differed among three luting agents. The effect of the priming agent on bond strength differed among the luting agents. Both the bond and flexural strength of a chemically polymerized luting agent differed before or after thermocycling.

In this study, retentive forces were compared between telescopic crowns (TSC) made with poly(ether ether ketone) (PEEK) using computer-aided design and manufacturing and type 4 gold alloy using the conventional method. The retentive forces of TSCs were evaluated by performing a pull-out test with primary and secondary crowns. Initial retentive force was approximately 12 N for both PEEK and gold alloy TSCs. The retentive force of PEEK TSC was approximately 6.5 N after 10,000 cycles of insertion and removal. The reduction rate in retentive force was smaller for gold alloy TSC. PEEK TSC displayed greater surface roughness on the primary crown compared to the gold alloy TSC. Surface roughness slightly increased at the cervical margin after repetitive insertion and removal. The retentive force of PEEK TSC was smaller than gold alloy TSC, however the retentive force of PEEK TSC was adequate for stabilizing dental prostheses even after 10,000 cycles.

Objective This study aimed to investigate the effects of long-term use on the retention force and wear behavior of double crown systems. Methods Based on a common double crown design sixty pairs of telescopic crowns were fabricated and divided into six groups, each consisting ten samples: “Gold standard” cast gold alloy primary and secondary crown (GG) and cast non-precious alloy (NN), computer-aided design (CAD)/computer-aided manufacturing (CAM)-milled zirconia primary crown and galvanoformed secondary crown (ZG), CAD/CAM-milled non-precious alloy primary and secondary crown (CC NN), CAD/CAM-milled zirconia primary crown and non-precious alloy secondary crown (CC ZN) and CAD/CAM-milled zirconia primary crown and polyetheretherketone (PEEK) secondary crown (CC ZP). In the constant presence of artificial saliva, all samples were subjected to 10,000 joining-separation cycles at a velocity of 120 mm/min. Wear was analyzed by reflected light microscopy and confocal microscopy before and after artificial aging. Results Retention force losses were observed in each group after long-term use, with significant losses in the groups ZG and CC ZP (pZG = 0.01, pCC ZP = 0.049). During artificial aging, no significant differences in pull-off force were recorded for groups GG, NN and CC ZN. Regarding wear, merely the Y-TZP primary crowns of the CC ZP group displayed no surface changes. Significance All tested production methods and material combinations seem to be suitable for clinical practice. CAD/CAM technology allows similarly predictable results to be achieved as the gold standard. Confocal microscopy is recommended for surface examinations of double crowns.

The purpose of this study was to evaluate the effect of monolithic zirconia vs. gold alloy type IV on the wear of human enamel under different occlusal loads. Materials and Methods: Forty square plate specimens, 6×6×2 mm, were prepared from monolithic zirconia (Bruxzir, n=20) and type IV gold (Begostar, n=20) and divided into two groups. Forty freshly extracted premolar teeth for orthodontic purpose were sectioned mesio-distally and only the cusp tips of the buccal halves were used as antagonists in the testing procedures. All of the specimens were mounted to chewing simulator with the cusp antagonists, half of them were subjected to(50000 chewing cycles under 50N load), the other were subjected to (50000 chewing cycles under 150N load)cyclic loading (50 N load, 3700 cycles ). Data were submitted to two-way ANOVA, and statistical significance was set at p < 0.05. Results: Type IV gold alloy based restorations had significantly little wear effect on human enamel than that of monolithic zirconia (Bruxzir) based restorations in high load. However in low load it was non-significant.

The aim of the present study is developing a simple, commercially available, and inexpensive method for detecting the presence of Ir in gold alloys during the cupellation process to avoid errors in gold assays. In the presence of Ir, the reported gold karat is higher than its actual amount. It is, therefore, economically important to detect Ir in gold alloys because of its lower price than gold. The present study was implemented to investigate the effects of Ir in a gold alloy both on its assay during the cupellation process and on its appearance and microstructural transformations. Visual inspection revealed that the upper surface of Ir-containing beads is typically matte and coarse with black rough cavities of an irregular oval-like shape. Also, the observation of dark spots and lines on just one side of rolled beads, as well as blister-like appendages on parted and annealed cornets, were found to signify the presence of Ir in gold alloys. X-ray analysis along the vertical section of the bead indicated that the amount of Ir on the surface was negligible as it was mainly concentrated at a distance of about 75% from the top of the bead. After the parting and annealing steps, Ir forms cubic-like structures surrounded by fcc Au sponge-like structures. As a consequence, both visual and microstructural examinations of gold alloys during the cupellation process might be used as simple and useful strategies to identify the presence of Ir in gold alloys to prevent incorrect karat reports.

Made available in DSpace on 2019-09-12T16:53:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2018 The aim of this study was compare the effect of two in vitro ageing protocols to intraoral aging on the flexural strength of a lithium disilicate (LD) ceramic bars with clamped ends. After polishing and crystallization, the both ends of the bars were cemented to a metallic device and subjected to mechanical cycling, thermomechanical cycling, or intraoral ageing. Ten volunteers used an intraoral device - similar to an occlusal splint with a balanced contact condition on the occlusal surface of the ceramic bar - during 8 h night time / 30 days. Both in vitro and intraoral ageing decreased the flexural residual strength of LD, with the lowest values obtained after intraoral ageing. Thus, the in vitro ageing protocols tested in this study revealed to be less deleterious than intraoral ageing of LD. [de Pinho Barcellos, Aline Serrado; Marinho, Caroline Cotes; Miranda, Jean Soares; Shiino, Marcos Yutaka] Univ Estadual Paulista, Inst Sci & Technol, Sao Paulo, Brazil [Amaral, Marina; Kimpara, Estevao Tomomitsu] Universidade de Taubaté (Unitau), Dept Dent, Sao Paulo, Brazil

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 (meta)stable 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 (semi)product. 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%.

Few and fragmentary is the information regarding the &ldquo, oro di met&agrave, &rdquo, (halfway gold) gilding due to the low probability of finding it in paintings as well as its short durability because of tarnishing. However, the very rare, excellent state of conservation of the gilding found in the fifteenth-century wood panel painting of the Master of St. Ivo studied in this work along with a multi-analytical approach allowed shedding light on the structure, the composition and the conservation state of this type of gilding. An Ultra-High Resolution Scanning Electron Microscope (UHR-SEM) along with Energy Dispersive X-Ray (EDX) analysis and polarised light Optical Microscopy (OM) were employed in order to image and analyse a cross-section of a sample taken from the wood panel painting. Results highlighted a divided structure of the gilding which is constituted by two separated layers of gold and silver with different thickness. This is the first time that scientific evidence on this issue is provided. Moreover, considerations on the tarnishing process of the gilding were made. Finally, complementary vibrational spectroscopic techniques such as micro-Raman and micro-ATR-FTIR were employed in order to identify the molecular composition of the &ldquo, bole&rdquo, (gilding preparation layer) and the ground layers.

A crucial criterion for the quality of the additively manufactured parts is the porosity content for achieving an acceptable final relative density. In addition, for jewelry applications, visible pores are unacceptable at or in the vicinity of the surface. In this study, non-destructive 3D neutron microtomography is applied to map the spatial distribution of pores in additively manufactured red-gold samples. The 3D imaging assessment underlines the high relative density of the printed red-gold sample and indicates residual pore sizes are predominantly below the limit of concern for jewelry applications. The 3D maps of pores within printed samples highlight the effect of the scanning strategy on the final quality and location of pores in the printed samples. These results confirm that neutron microtomography is a novel and precise tool to characterize residual porosity in additively manufactured gold alloys and other higher-Z materials where such investigation using other non-destructive methods (such as X-rays) is challenging due to the limited penetration depth.

Selective Laser Melting (SLM) or Laser Powder Bed Fusion (L-PBF) is the most studied laser-based additive manufacturing process for metals and alloys. One important issue in SLM is the time-consuming identification of a process window leading to quasi fully dense parts (> 99.8%), usually based on trials and errors. As some metal powders may be very expensive, and therefore not suitable for a whole battery of tests, a method to infer optimal parameters from one material to another would be highly beneficial. In this study, we use bronze as a test material for optimizing SLM parameters, before translating these parameters to red gold and 316 L steel. The concept of normalized enthalpy is used to take into account the differences in thermal and optical properties among the different materials. A translation rule is derived for the prediction of optimal processing conditions, based on the ones found for the test material. One important input for this translation rule is the powder absorptivity, which is measured at the appropriate laser wavelength and at room temperature. This approach eventually leads to the highest reported density for an additive manufactured 18-carat gold alloy (99.81% relative density), to the authors' knowledge. Finite element (FEM) simulations justify the translation rule formulation by showing the importance of the laser/powder interactions during the SLM process, leading to a finite penetration depth of the laser in the powder bed due to multiple reflections. The FEM calculations indicate that a significant part of the laser energy is directly absorbed by the powder during the manufacturing process when operating in near-optimal conditions.

Statement of problem Few studies have compared the marginal and internal fits of crowns fabricated from machinable palladium-silver-indium (Pd-Ag-In) semiprecious metal alloy. Purpose The purpose of this clinical study was to evaluate and compare the marginal and internal fits of machined Pd-Ag-In alloy, zirconia, and cast gold crowns. Material and methods A prospective clinical trial was performed on 35 participants and 52 abutment teeth at 2 centers. Individuals requiring prosthetic restorations were treated with gold alloy or zirconia crowns (2 control groups) or Pd-Ag-In alloy crowns (experimental group). A replica technique was used to evaluate the marginal and internal fits. The buccolingual and mesiodistal cross-sections were measured, and a noninferiority comparison was conducted. Results The mean marginal gaps were 68.2 μm for the gold crowns, 75.4 μm for the zirconia crowns, and 76.9 μm for the Pd-Ag-In alloy crowns. In the 5 cross-sections other than the distal cross-section, the 2-sided 95% confidence limits for the differences between the Pd-Ag-In alloy crowns and the 2 control groups were not larger than the 25-μm noninferiority margin. The control groups displayed smaller internal gaps in the line angle and occlusal spaces compared with the Pd-Ag-In crown group. Conclusion The marginal gaps of machinable Pd-Ag-In alloy crowns did not meet the noninferiority criterion in the distal margin compared with zirconia and gold alloy crowns. Nonetheless, all 3 crowns had clinically applicable precision.

With the development of science and technology, in the late 19th century, began the research and application of new alloys for making jewelry. By adding different amounts of Cu and Ag alloy of Au, as well as adding some new elements (Zn), alloys were obtained with different color spectrum (from red to yellow) and different technological and metallurgical characteristics. This paper aims to show thermomechanical behavior of commercial yellow Au alloys for making jewelry.

Purpose This in vitro study evaluated and compared the vertical marginal gap of cast and milled full coverage gold copings using two margin designs (chamfer and chamfer bevel) before and after fitting adjustments. Materials and Methods Ten impressions were made of two metal master dies (one chamfer margin, one chamfer-bevel margin) and poured twice in Type IV stone. The 20 subsequent casts with 40 dies were split into four groups (n = 10); cast gold bevel, cast gold chamfer, milled gold bevel, and milled gold chamfer groups. The cast specimens received approximately 40 μm die relief no closer than 1 mm from the finish line. Cast copings were hand waxed, cast in a high noble gold alloy, chemically divested, and the sprues were removed. For milled gold copings, casts were scanned and copings designed using 3shape D900 scanner and software. Parameters were set to approximate analog fabrication (cement gap = 0.01 mm; extra cement gap = 0.04 mm, drill radius = 0.65 mm). Copings were milled from the same high noble alloy. All copings were seated on their respective master die in a custom scanning jig and measured using a measuring microscope at 90× (60 measurements per specimen, 15 per surface). Following initial measurements, all copings were adjusted on stone dies. The number of adjustment cycles was recorded and post-adjustment measurements were made using the same method. Data were analyzed using independent and paired t-tests. Results Milled gold copings with a beveled margin (11.7 ± 20.4 μm) had a significantly (p < 0.05) smaller marginal gap than cast gold copings with a beveled margin (43.6 ± 46.8 μm) after adjustment. Cast gold copings with a chamfer margin (22.7 ± 24.7 μm) had a significantly (p < 0.05) smaller marginal gap than milled gold copings with a chamfer margin (27.9 ± 31.6 μm) following adjustments. Adjustments significantly decreased marginal gap for both cast groups (p < 0.05) and the milled chamfer bevel group (p < 0.05) but had no significant effect on the milled chamfer group. Conclusions Within the limitations of this study, results indicate that gold restorations milled with the tested parameters provide a vertical marginal gap that is an acceptable alternative to traditional gold crown casting techniques.

One of the most widely used techniques in present-day in order to save teeth is endodontic treatment (ET). Nowadays, a post or a dowel is widely used in the tooth treatment process. The aims of the current investigation are to: (1) evaluate the stress distribution surrounding the endodontic prefabricated parallel post (EPPP), gutta-percha, and dentin with six types of post materials, and (2) determine the optimum material of an EPPP. Six post materials: (1) carbon fibre post (CFP), (2) gold (G), (3) gold alloy (GA), (4) titanium (T), (5) titanium alloy (TA), and (6) stainless steel (SS) were selected in the present work. In order to evaluate the stress distribution surrounding the EPPP, gutta-percha, and dentin with different post materials, the finite element analysis (FEA) is adopted. After that, the sub-problem approximation method was used in order to investigate the optimum material of an EPPP. The results obtained indicate that the optimum elastic characteristics for the EPPP, elastic modulus (E), and Poisson’s ratio (υ) equal to 185 GPa and 0.245, respectively.

In many cases, the differentiation between an artefact on gold alloy, or on tumbaga (the last being a poor gold alloy subject to depletion gilding), and, sometimes, on gilded copper, is not easy. Their aspect is often similar, and energy-dispersive X-ray fluorescence analysis, which is one of the few non-destructive and non-invasive technique suited to analyze gold sheets, is sometimes not able to solve the question on the basis of altered Au-L, Cu-K, Cu-K/Au-L- ratios, as in other similar cases. For that reason, X-rays from a Sn secondary target, and 26.4 and 59.6 keV γ-rays emitted by an Am-241 radioactive source were employed in transmission mode as an additional differentiation method.

Correction for ‘Gold alloy-based nanozyme sensor arrays for biothiol detection’ by Junshu Lin et al., Analyst, 2020, DOI: 10.1039/d0an00451k.

The objective was to evaluate the fracture resistance properties of maxillary incisors with flared canals restored with computer aided design and computer aided manufacture (CAD/CAM) integrated glass fiber post-and-core. Thirty prepared flared root canals were selected in vitro and restored with CAD/CAM integrated fiber post-and-core (Group A), prefabricated fiber posts (Group B), and cast gold alloy (Group C), respectively. After submitted to fatigue loading, each specimen was subjected to a static loading until fracture. Analysis of variance (ANOVA) tests were used to determine statistical differences. The mean fracture strengths of Groups A and C were significantly higher than those of Group B, whereas no differences were observed between Groups A and C. In addition, reparable fracture modes were mostly observed in Group A while irreparable and catastrophic fractures were mostly found in Groups B and C. These results demonstrate that, in comparison to traditional treatments, CAD/CAM integrated glass fiber post-and-core restoration significantly enhances the fracture resistance of flared root canals.

Purpose: The objective of the study was to investigate one-piece CAD/CAM abutments made of titanium and gold-cast UCLA-type abutments for contamination, processing marks and microgaps via scanning electron microscope.Material and Methods: Three groups with five identical abutments each were examined with a scanning electron microscope (LEO 1530 VP; Oberkochen, Germany) after cleaning using a steam jet and ethanol. Group 1 included custom CAD/CAM abutments (Atlantis™; Dentsply Implants, Molndal, Sweden). Group 2 included UCLA-type cast bases prior to casting (Astra Tech Cast Design 4.5; Dentsply Implants). Group 3 included the identical cast bases with a cast-on abutment (gold alloy).Results: Contaminants were found on all abutments of group 1, on 3 of 5 samples in group 2 and on 1 of 5 samples in group 3. Processing marks were visible on samples of groups 2 and 3. No microgaps were present in groups 1 and 2. For all group 3 cast-on abutments, large unfilled shrinking cavities with a horizontal extent between

Au–Ag–Cu–Zn yellow gold alloy is one of the most popular jewellery materials. Rare earth element cerium is an efficient grain refiner. In this paper, four different cerium contents are added to 18-carat Au–Ag–Cu–Zn alloys. The microstructures of these kinds of as-cast 18-carat gold alloys are investigated. Experimental results indicate that the addition of Ce can help grain refinement; as the percentage of cerium in alloy grows, the alloy becomes refined. The morphology of the as-cast structure changed as well. The mechanism is discussed in the literature.

With the introduction of commercially available handheld XRF analysers, there is a growing problem that the results, simply taken at face value, are regarded as representative of the bulk gold alloys of the objects analysed in museums and used for treasure analysis. It is well known that surface analysis is problematic, and the aim of this study was to test whether non-destructive surface analysis could be useful in grouping the very large numbers of fragmentary pieces in the Anglo-Saxon Staffordshire Hoard. Surface and subsurface analyses of 16 objects from the Hoard were carried out by X-ray fluorescence (XRF) and scanning electron microscopy with energy-dispersive X-ray analysis (SEM–EDX). The results indicate that there are significant but inconsistent levels of enrichment of the gold at the surface of many of these objects, due to the loss of both copper and silver. The significant loss of silver (up to 50% relative in some cases) suggests that some form of deliberately induced depletion gilding was carried out during manufacture to remove both silver and copper from the surface. In three cases, an increase in silver at the surface compared to the core metal was detected: this might tentatively be explained by redeposition from contact with silver objects during burial. These results have clear implications for the reliability and interpretation of surface analysis data of gold alloys from this period.

Micromechanical testing of electroplated gold alloy films has been conducted using theta-like specimens. Specimens were formed by a standard combination of photolithography, electroplating, and deep reactive ion etching. Testing was performed using an instrumented indenter and the results interpreted using a finite-element model with a Ramberg-Osgood constitutive law to extract elastic and plastic material properties. The observed results were highly repeatable and appear to be sensitive to variations in both sample dimensions and material properties. These qualities suggest that the testing methodology may have significant value as a quality control technique in the fabrication of metal micro-electromechanical systems.

This paper reports the particle induced X-ray emission (PIXE) and particle induced gamma-ray emission (PIGE) analyses of 78 glass bracelet fragments discovered in the Byzantine fortified settlement of Isaccea, Romania (10th–13th centuries AD). The chemical composition of the glass was used to identify the raw materials and manufacturing techniques. Most of the bracelets turned out to be soda-lime-silica glasses, but lead and soda-lime-lead glasses were also identified. The PIXE–PIGE data revealed the glass chromophores and provided clues about the pigments used to decorate the external surfaces of some bracelets—lead stannate and gold alloy. The analytical results showed that the bracelets were manufactured by recycling different types of coloured glass, probably in a local workshop.

The mechanical loss spectrum of a yellow gold bi-crystal is presented and analyzed in detail. The relaxation strength is monitored as a function of several geometrical parameters such as sample width, length and thickness. It is found that the relaxation strength is proportional to the GB density (the inverse width), whereas it depends linearly on the sample thickness. The experimental findings are compared to finite elements (FE) simulations, where the material can glide frictionless along the grain boundary. The simulations show the same dependencies as the mechanical loss measurements. The relaxation peak in the loss spectrum can be interpreted as due to GB sliding accommodated by the elastic deformation of the grains. (C) 2015 Elsevier B.V. All rights reserved.

Aim: To isolate the effect of metallurgy in lateral and axial cutting efficacy against plastic and bovine dentine substrates by comparing two rotary systems with identical design but manufactured with either conventional nickel-titanium or heat-treated gold alloy. Methodology: A total of 258 ProTaper Universal (PTU) and ProTaper Gold (PTG) Shaping instruments were used. Bending behaviour was assessed to determine the appropriate displacement associated with a 2 N force in lateral cutting. Ten instruments of each type were used in lateral action for 60 s against bovine dentine or plastic substrates four consecutive times producing four notches in each specimen. Ten further instruments of each type were used in on axial action in four standardized simulated root canals fabricated from 4-mm thick plastic or dentine discs. Both tests were performed at 300 rpm in a computer-controlled testing platform. Notch area and torsional load were compared with Student's t-tests. Repeated measures ANOVA was used to compare cutting efficiency across the four different time-points. Pearson correlation coefficients between substrates were also determined. Results: For lateral action, all three PTG instruments cut significantly more effectively (P < 0.05) than PTU on the plastic substrate. S1 and S2 PTG cut significantly more after 120 and 180 s (P < 0.05) on bovine dentine substrate. For axial action, S1 and S2 PTG were significantly more efficient in cutting at 180 s on plastic and 120 s on bovine dentine (P < 0.05). Conclusion: Instruments made from heat-treated nickel-titanium gold alloy had equal or greater cutting efficiency when compared to those made from conventional nickel-titanium.

Purpose: The aim of this study was to compare the 5-year outcomes of glass fiber composite with cast posts and cores for the restoration of endodontically treated teeth. Materials and Methods: A total of 143 patients in need of 203 full ceramic restorations on endodontically treated teeth were included. After primary stratification based on the need for post or no post, teeth were randomly allotted to test group 1 (prefabricated glass fiber posts), 2 (custom-made glass fiber posts), or 3 (composite cores without posts). The control group was treated with gold alloy-based wrought posts and cast cores. Success (original present) and survival (present after intervention) probability lifetime curves, corrected for clustering, were drawn over the entire data set. Results: The mean follow-up time was 5.8 years (range: 0.5 to 7.2 years). At 5 years, the success and survival probabilities were 85.2% and 91.5%, respectively. Lifetime curves did not show any significant differences between the test and control groups for success (P = .85) or survival (P = .57). Moreover, no significant differences for success or survival could be found among the four groups (the three test groups and the control group). Conclusion: After 5 years of follow-up, cast gold and composite post-and-core systems on teeth with ceramic full restorations provided with a ferrule performed equally well.

OBJECTIVES To evaluate the discoloration of the mucosa caused by different ceramic and metal-based materials. MATERIAL AND METHODS On six pig maxillae, trap-door flaps were prepared bilaterally. Different ceramic and metal-based specimens were placed underneath the flap. To simulate increasing mucosal thicknesses (MC), connective tissue grafts (CTGs) were harvested. Spectrophotometric measurements were performed prior to flap elevation (TBL ) and for each material under the flap alone (1 mm MC) (TMC1 ), with a 1-mm CTG (2-mm MC) (TMC2 ) and with a 2-mm CTG (3-mm MC) (TMC3 ). Tested materials were as follows: Zr1 (zirconia), Zr2 (zirconia + pink ceramic), Zr3 (zirconia), Zr4 (fluorescent zirconia), Zr5 (zirconia), Zr6 (high translucent zirconia), Zr7 (low translucent zirconia) and Zr8 (low translucent zirconia), Gol (gold alloy), Ti1 (titanium alloy), Ti2 (anodized gold-shaded titanium alloy) and Ti3 (anodized pink-shaded titanium alloy). Color differences (ΔE) were calculated comparing the measurement of the native tissue (TBL ) and the measurements with varying mucosal thicknesses (TMC1-3 ). RESULTS For ceramic materials, the median ΔE values for the different time-point comparison ranged as follows: 3.80 (Zr4) - 7.47 (Zr2) (pooled); 3.15 (Zr4) - 8.13 (Zr2) (TBL -TMC1 ); 3.39 (Zr4) - 7.24 (Zr2) (TBL -TMC2 ); 4.31 (Zr8) - 6.99 (Zr2) (TBL -TMC3 ). For metal-based materials, the median ΔE values were as follows: 4.20 (Gol) - 5.82 (Ti3) (pooled); 3.21 (Gol) - 13.56 (Ti1) (TBL -TCM1 ); 4.0 (Ti1) - 5.27 (Gol) (TBL -TCM2 ); 3.11 (Ti1) - 5.11 (Gol) (TBL -TCM2 ). The comparison of the materials and the time points showed in the nonparametric linear mixed model a significant interaction effect between material and time point (P < 0.001). The side was not a significant main effect, nor as term in an interaction with the other two effects. CONCLUSIONS Reconstructive materials result in an evident discoloration of the mucosal tissue, tending to decrease with increasing mucosal thickness. The use of fluorescent zirconia (ceramic materials) or gold alloy (metal-based materials) lead to the least discoloration.

Many different types of alloys are now available in the market to be used for dental restorations and fixed prostheses. The common criterion for all these fixed prosthodontic materials is the permanent existence of them in the oral cavity for prolonged time without the ability to be removed by the patient. Therefore, knowledge about the biocompatibility of dental alloys is of great importance. This article presents a literature review on the biocompatibility of dental alloys. A PubMed database search was conducted for studies pertaining to the biocompatibility of dental alloys. The search was limited to peer-reviewed articles published in English between 1985 and 2013. Available data revealed that substances are released from alloys into the surrounding tissues; mainly nickel, zinc, and copper. Some alloys such as nickel–chromium alloy have shown to be cytotoxic in vitro . Also, elements released from gold alloy showed in vitro cytotoxic effect. Therefore, clinicians should give up assuming that gold alloy is completely inert and biocompatible with oral tissues. The clinical relevance of these findings remains unclear. Further in vitro studies, as well as controlled clinical trials, are needed due to possible exceptions.

The optical properties are determined and presented in an adequate references for common pure noble metals (Au, Ag, Cu, etc.) but not for almost their alloys. This was a reason for investigation of specific optical properties amplitude diminutions at gold alloy of 585 finess, as an often used alloy in jewelry. This alloy for jewel making in practice usually is composed from three - or four metals. The jewels, as their nature need, ordinary must possess pretty high level of brilliance. Variuos metals will produce changes in optical properties of an alloy, indeed. Here are represented some ellipsometric measuring of tg(ψ) for annealed and cold rolled strips from golden alloy 585. Cold rolling is provided by height reduction of 10, 20 and 30%. Typical microstructures at annealed and cold rolled (30%) deformation were shown.

Sn-based solder is used for soldering a gold alloy and a brass sheet. Subsequently thermal aging tests are performed. The influence of thermal aging on the interfacial microstructure evolution of gold alloy/Sn-based solder and its mechanical properties was analysed. The results show that the aging time and aging temperature have large influence on the growth of interfacial compounds, and the interfacial compounds show a multiply-sublayers structure, the main components are AuNi2Sn4, AuSn4, Ni3Sn4 and Ni3Sn. The hardness of the interfacial compounds show a distinct layered phenomenon, in which the hardness of the first layer is the highest. Shear tests indicated that the failure happened at the gold alloy/Sn-based solder interface close to the gold alloy, showing obvious brittle fracture features. Shear strength decreases with increasing aging time at the aging temperature of 150°C and 175°C.

The suggested use of nanoporous gold for functional and structural applications requires uniform and specifically crack-free monolithic bodies, ideally with a structure size in the range of 10 nm or below. Here we investigate electrochemical dealloying of two different starting alloys, Au25Ag75 and Au25Cu75, as pathways towards that goal. With an emphasis on the processes that lead to crack formation, we discuss the role of the parameters (i) lattice parameter change, (ii) dealloying potential and rate, and (iii) thermo-mechanical treatment of the master alloys. The Cu-based alloys are found to give superior homogeneity at very small structure sizes, provided that intermediate temperature treatments are avoided. A complete suppression of crack formation was achieved by application of a dealloying potential of 1.1 V versus Ag/AgCl, at a ligament size of 11 nm.

phase diagram is known as Maps of Materials Science. However, the existing precious metal phase diagrams are far from able to meet the needs of the development of the precious metal materials science and technology. In this paper, the recent research achievements of Au-Ag-Y ternary phase diagram by experimental method and Au-Pd-Zr ternary phase diagram by multi-phase equilibrium thermodynamic calculation software were introduced.

A point defect relaxation peak has been observed in a ternary 18-carat gold alloy with the composition Au62.5Pd32.5In5. It shows a Curie Weiss dependence on the temperature, as is commonly observed for a Zener peak. However, the peak is absent in the binary alloys AuPd and AuIn and therefore it is a new type of relaxation that is due to In-Pd pairs. The relaxation strength shows a linear dependence on the indium concentration. We have developed a model of elastic dipoles containing one palladium and one indium atom in a gold matrix. The model is based on the reorientation under stress of InPd dipoles in a gold matrix and takes into account the atom ordering. The model accounts for a linear dependence of the relaxation strength on the indium concentration in a dilute alloy and is also valid for more concentrated alloys. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.