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This study aimed to evaluate the effect of three pretreatment conditioners and surface preparations on a composite resin adhesive for a gold alloy. Cast disk specimens were made and bonded with RelyX Unicem luting agent under six surface conditions: 1) polished with No.600 carbide paper, 2) air-abraded with alumina, 3) Alloy Primer metal conditioner was applied after alumina-abrasion, 4) Monobond Plus multipurpose conditioner was applied after alumina-abrasion, 5) M. L. Primer metal conditioner was applied after alumina-abrasion, and 6) Rocatec multipurpose silica-coating system was applied. The bond strengths were determined before and after thermocycling (50,000 cycles). The bond strengths of the alumina-abrasion group were significantly decreased after thermocycling. The Rocatec and M. L. Primer exhibited higher bond strengths than other treatments. The application of metal conditioners and multipurpose surface preparations was recommended for improved bonding between the evaluated adhesive resin and gold alloy.

A series of iterative wear and corrosion tests were conducted on two 950 platinum alloys, two 585 white gold alloys and two 750 white gold alloys. Testing followed standardised industrial procedures in order to provide comparable and reproducible conditions. Wear testing comprised a sequence including abrasion testing, corrosion testing and polish testing. Mass loss was recorded after each test cycle. Five complete test cycles were followed by two long-term polish tests. The total testing time was ca. 250 h. A pronounced difference in the mass and volume loss between the platinum and the gold alloys was observed. The absolute volume loss per surface area of the platinum alloys was a factor of two to three times lower than that of the gold alloys. The highest volume loss was observed for 750AuPd, followed by 585AuPd, 585AuNi and 750AuNi with the latter three showing similar wear behaviours. The mass loss increased linearly with testing time. No measurable mass loss was observed by corrosion testing in our limited duration test cycle and the only alloy exhibiting significant corrosion was 585AuNi. Hardness of the alloys was determined by Vickers microhardness testing at a 100 g load. Notably, higher hardness levels were not found to be an indicator for low mass or volume loss.

Objective The purpose of this study was to assess the effects of an experimental primer containing acetone solution and a sulfur-containing functional monomer, 10-methacryloyloxydecyl-(2-thiohydantoin-4-yl)propionate (MDTHP), on the bonds between noble metals and acrylic resin. Methods The experimental primer used as the control for comparison consisted of 6-(4-vinylbenzyl-n-propyl)amino-1,3,5-triazine-2,4-dithione (VBATDT) in acetone. These primers were prepared as equimolar functional monomers (0.1 mol%). A self-polymerizing acrylic resin initiated with tri-n-butylborane (TBB) was used as the luting agent. Four elemental metal disks (silver, copper, palladium, and gold) were used as adherend specimens. All the disks were wet-ground with silicon carbide paper (#1500). Bonding reactions were performed on 12 combinations of the four metals, and the disks were either primed with MDTHP or VBATDT or were unprimed (control). Shear bond strengths were determined pre- and post-thermocycling (5–55 °C, dwell time 60 s, 20,000 cycles). The results were statistically analyzed via a non-parametric test (α = 0.05). Results The post-thermocycling shear bond strengths of the MDTHP primer were as follows (median, n = 11): 13.2 MPa on silver, 25.9 MPa on copper, 4.1 MPa on palladium, and 11.3 MPa on gold. The MDTHP primer showed higher post-thermocycling shear bond strength on all the four metals. Additionally, on silver and copper, the MDTHP bond strengths were higher than on the other metals. Significance Within the limitation of current of experimental setting, the MDTHP compound may be applicable as a functional monomer for bonding noble metal alloys.

The results of numerical experiments upon modeling thermodynamic parameters such as value of pressure and compression of germanium and its alloys with gold are presented. The calculations were performed using the model TEC (thermodynamic equilibrium components). The model allows us to take into account the phase transition of germanium under shock-wave action. The interest in investigating of the compressibility for such materials is related both to the possibility of creating materials with the necessary properties and to the properties of the materials themselves. The results of calculations are compared with the known experimental results of different authors. The value of pressure and compression for shock wave loading of pure germanium and alloys with germanium as a component of various compositions are calculated.

A stripping solution with thiourea, iron(III) sulfate, and sodium dodecyl sulfate(SDS) was employed to strip Ni-based 14 karat white gold alloys, and the formation of the NiS byproduct and elimination of passivation were investigated in the presence of 0.0-0.2 g/L SDS. White gold alloy samples with a flat shape were cast by gypsum investment and were stripped using the prepared stripping solution. Subsequently, the surface morphology, elimination of the passivation layer, weight loss, microstructure, elemental composition, and electrochemical properties of the samples were analyzed by optical microscopy, Raman spectroscopy, precision scale, scanning electron microscopy, energy dispersive X-ray spectroscopy, and linear sweep voltammetry, respectively. It was found that passivation layers of the as-cast samples were removed by the suggested stripping solution. Upon the addition of SDS, the stripped sample showed a bright silver color without NiS, while the sample showed a dark tarnished appearance due to NiS formation without SDS. The weight loss ratio decreased with increasing SDS content and stabilized at 0.2 % for SDS concentrations exceeding 0.15 g/L, and the sample showed a uniformly etched microstructure. EDS results showed that NiS was formed without SDS addition, while linear sweep voltammetry results indicated that NiS formation was restrained upon SDS addition because SDS suppresses the formation of formamidine disulfide from thiourea. Thus, the suggested thiourea stripping with SDS addition was successfully applied to Ni-based 14 karat white gold alloys.

Portable devices for energy-dispersive X-ray fluorescence analysis and X and γ-ray transmission measurements were employed to analyze pre-Columbian metals from the North of Peru. Gold and silver are generally composed of gold, silver, and copper and silver, copper, and gold (and more rarely lead), respectively. Besides gold and silver, artisans from these cultures also produced artifacts with gilded copper, gilded silver, tumbaga (gold alloys enriched at the surface by depletion gilding), silvered copper, and silvered gold. Furthermore, “strange” elements like arsenic, bromine, and mercury were also sometimes detected by energy-dispersive X-ray fluorescence, rarely in gold alloys (mercury) and more frequently in silver alloys (arsenic, bromine and mercury). Arsenic is associated with copper, always present in silver alloys, while bromine and lead are typically associated to silver. Finally, mercury, in form of cinnabar powder, was employed to cover gold masks, and, possibly in form of liquid mercury, for a process called “mercury amalgam” to sold together gold and silver sheets.

International audience; Adaptive coordination-driven supramolecular chemistry based on conformationally flexible pre-organized luminescent Cu(I) precursors paves the way to the ready formation of intricate supramolecular scaffold possessing intrinsic luminescence properties. A formal ring extension of a tetrametallic Cu(I) metallacycle bearing Thermally Activated Delayed Fluorescence (TADF) properties can thus be carried out, affording a new hexametallic Cu(I) metallacycle 1 bearing modulated solid-state TADF properties. Attempts to adapt this ring extension process to the formation of targeted heterometallic Au2Cu4 and Pt2Cu8 assemblies led to the unexpected and ready formation of the Au2Cu10 and Pt4Cu11 derivatives 2 and 3, respectively. These outcomes strengthen the scope and perspectives of adaptive coordination-driven supramolecular chemistry compared to those of conventional coordination-driven supramolecular chemistry. Indeed, it guides concerted intramolecular fragmentation and redistribution of the particular building blocks used, affording selectively supramolecular scaffolds of higher nuclearity and complexity. The study of the solid-state photophysical properties of the assemblies 2 and 3 highlights enhanced and original behaviors, in which the heavy metal spin-orbit coupling values significantly influence the relaxation processes centered on the Cu(I) metal centers.

Surface-enhanced Raman scattering (SERS) spectroscopy has become a powerful and sensitive analytical tool for the detection and assessment of chemical/biological molecules in special scenarios. Herein we propose a flexible hygroscopic SERS biocompatible sensor based on the silk fibroin fibers (SFF) decorated with urchin-like Au/Ag nanoalloys (NAs). The hybrid SFF-Au/Ag NAs with a stronger absorbance capacity (500∼1100 nm) and excellent hygroscopicity provide a remarkable higher near-infrared (NIR)-SERS activity than that of bare urchin-like Au/Ag NAs. The interesting NIR-SERS sensor enables the limit of detection (LOD) of folic acid (FA) to be achieved at nanomolar (nM, 10−9 M) level, facilitating the ultrasensitive monitoring of FA in human sweat and offering reliable real-time personal health management in the near future.

The purpose of the present study was to examine the effects of silane coupling treatment and airborne-particle abrasion (APA) on shear bond strength (SBS) between photo-cured bulk-fill flowable composite resin and 12% silver-palladium-copper-gold (Ag-Pd-CuAu) alloy using self-adhesive resin cement. The six experimental groups were compared using two-way analysis of variance (ANOVA) followed by Tukey Kramer's post-hoc test to compare SBS values among the six groups at a 95% confidence level. The SBS of APA groups was significantly higher than non-APA groups. The SBS of the specimens with silane coupling treatment increased slightly compared with specimens without silane coupling treatment. The combination of resin coating with bulk-fill resin and self-adhesive resin cement could be clinically useful when restoring a cavity with a noble metal.

We report testing the yellow and white jewelry alloys based on gold that contains nickel, zinc, palladium, using a touchstone by applying various chemical reagents and XFA (X-ray fluorescence analysis). We have improved the procedure for assessing the conformity of assay of the precious alloys based on gold, considering the content of component composition by using the results from rubbing the alloys on a touchstone. It was established that the magnitude of gold assay for precious alloys in the system AuAgZnCu, determined under the action of the reagent "chloric gold" on the touchstone, depends on the manifestation of contrast in the course of quality reaction against a standard sample (touch-needle). Under the influence of the reagent, the "yellow" gold alloys demonstrate chloride compounds with silver and copper, being reduced to a metal powder of black and brown color. In this case, copper dissolves while gold, together with silver, forms an intensive residue on a strip that depends on the ligature composition of the alloy. It was established that the lower the assay of a tested sample, the greater the amount of "chlorine gold" that decomposes, the larger the sediment of silver chloride and the pure gold reduced from the reagent, and hence the darker the sediment. It has been proven that testing the precious alloys of red color from the system AuAgZnCu 585 with a content of zinc (over 2 %), nickel, indium by using a reagent based on potassium dichromate and copper chloride is not effective. The results of our analysis indicate the increased gold assay compared with a standard touch-needle. To eliminate this phenomenon, it is recommended that one should first determine the composition of an alloy by the XFA method and construct an algorithm for testing in accordance with the content of the alloy by other reagents. It was determined that the gold assay defined on a touchstone for alloys from the system AuAgZnCu 585 (a content of zinc is over 2 %) is more contrast under the influence of acidic reagents and depends on the component composition of the alloy. It has been proven that the alloy of "white gold", composed of palladium and silver (AuAgPd585), is not affected by the acid reagent for gold assay 585. Testing the alloy of "white gold" (AuAgPd585) using an acid reagent for gold assay 750 yields the dark sediment of a bluish tint. We have established a more contrast effect on the alloys of "white gold" and "yellow gold" of assay 750 from the acid reagent for gold alloys of assay 750

Statement of problem Components have been introduced that allow the screw channel of an implant crown to be angled lingually and the screws to be tightened in a non-axial direction to the implant. Information is lacking as to how the removal torque value (RTV) and force to failure (FTF) of these components compare with those of conventional screws. Purpose The purpose of this in vitro study was to evaluate and compare the RTV and FTF values of cyclically loaded implant-supported restorations. Specifically, values for conventional axially tightened gold screws were compared with those for non-axially tightened screws aligned at 3 different angulations. Material and methods A total of 28 external hexagon implants were embedded in acrylic resin and divided into 4 groups. Simulated restorations were fabricated on abutments capable of different screw channel angulations. Dynamic abutments (DA) were waxed at different angulations and then cast. Simulated restorations were placed on the implants and tightened: group 0GS: 0-degree angulation gold screw tightened to 35 Ncm (control group); group 0DAS, 0-degree angulation with dynamic abutment (DAS) screw; group 20DAS: 20-degree angulation with DA screw; group 28DAS: 28-degree angulation with DAS screw. In groups 0DAS, 20DAS, and 28DAS, the DAS screw was used and tightened to 25 Ncm. Screw removal torque values were recorded by using a digital torque gauge at baseline and, after reaching cyclic fatigue, by using a dual-axis mastication simulator for 1 200 000 cycles. The fracture strength (FS) of the implant restorations was tested under compression until failure by using a universal testing machine. Differences between baseline and removal torque (ΔRT) were calculated. Statistical analysis was performed by using 1-way ANOVA for ΔRT and FS separately (α=.05). Results ΔRT and FS values were not significantly different among the groups (P>.05). The screw fractured in 5 of 28 specimens (17.8%); the remaining specimens failed with fracture of the implant. Conclusions The removal torque and FS values of the angulated abutment screw were comparable to those of the gold screw. Angulation of the abutment had no significant influence on the screw removal torque values.

Purpose This study investigated the influence of an interaction between sulfur-containing monomers and other monomers in multipurpose primers on the bond durability of a tri-n-butylborane (TBB)-initiated acrylic resin to a gold alloy. Methods The disk-shaped adherend materials were prepared from a gold alloy (Casting Gold M.C. Type IV). Two multipurpose-primers (Universal Primer, Monobond Plus), four metal primers containing an organic sulfur compound (M.L. Primer, Alloy Primer, Metaltite, and V-Primer), and three acidic primers (Estenia Opaque Primer, Acryl Bond, and Super-Bond Liquid) were used. The shear bond strengths were determined pre- and post-thermocycling to evaluate the bond durability. A statistical analysis of the results was performed using a non-parametric procedure, and the cohesive failure ratios of the debonded surfaces were compared. Results Among the pre-thermocycling groups, M.L. Primer, Metaltite, Monobond Plus, Universal Primer, and Alloy Primer showed the greatest bond strengths. Among the post-thermocycling groups, M.L. Primer, Metaltite, Monobond Plus, and Universal Primer showed the greatest bond strengths, whereas Acryl Bond, Super-Bond Liquid, Estenia Opaque Primer, and the unprimed control showed the lowest. Similarly, the primers that did not contain either a sulfur compound showed an obvious reduction in the cohesive failure ratio. Conclusions Multi-purpose primers containing a sulfur-containing monomer increased the bond strength of a TBB-initiated acrylic resin to a gold alloy. The proportion of the area of cohesive failure to the bonded area showed an interrelationship with the shear bond strength testing results.

This article aims to outline the characteristics of the blood flow conveying copper (Cu) and gold (Au) nanoparticles (NPs) through a non-uniform endoscopic annulus with wall slip under the action of electromagnetic force and Hall currents. The flow of blood with the suspension of hybrid nanoparticles in the annulus is induced by the peristaltic pumping. The governing equations are modeled and then simplified with the postulate of lubrication theory. The resulting non-dimensional momentum equation after simplification is solved analytically by employing the He's homotopy perturbation method (HPM) with the computational software Mathematica program (version 11). The influential role of emerging physical parameters on the physiological features related to the blood flow is inferred graphically and physically. The analytical outcomes reveal that Hall parameter has a diminishing behavior on the blood flow while the inverse impact is endured for mounting Hartmann number. Electromagnetic field and Hall currents offer a superlative mode for regulating blood flow at the time of surgery. An increment in the volume fraction of nanoparticles causes a drop in the blood temperature profile. The trapping phenomenon is also explored with the help of contours. An expansion in Hartmann number reduces the size of entrapped bolus and ultimately vanishes when Hartmann number is very large. This prospective model may be applicable in electromagnetic micro-pumps, medical simulation devices, heart-lung machine (HLM), drug carrying and drug transport systems, cancer diagnosis, tumor selective photothermal therapy, etc.

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.

Herein, we report the preparation of mesoporous gold (Au)-silver (Ag) alloy films through the electrochemical micelle assembly process and their applications as microRNA (miRNA) sensors. Following electrochemical deposition and subsequent removal of the templates, the polymeric micelles can create uniformly sized mesoporous architectures with high surface areas. The resulting mesoporous Au-Ag alloy films show high current densities (electrocatalytic activities) towards the redox reaction between potassium ferrocyanide and potassium ferricyanide. Following magnetic isolation and purification, the target miRNA is adsorbed directly on the mesoporous Au-Ag film. Electrochemical detection is then enabled by differential pulse voltammetry (DPV) using the [Fe(CN)6]3-/4- redox system (the faradaic current for the miRNA-adsorbed Au-Ag film decreases compared to the bare film). The films demonstrate great advantages towards miRNA sensing platforms to enhance the detection limit down to attomolar levels of miR-21 (limit of detection (LOD) = 100 aM, s/n = 3). The developed enzymatic amplification-free miniaturized analytical sensor has promising potential for RNA-based diagnosis of diseases.

Power electronic modules require multi-layer architectures, where the layers provide dedicated functions, e.g. active semiconductor chip, electric conduction layer, heat spreader, insulation layer. All the layers have different material properties, like coefficients of thermal expansion. Due to their mismatch, local stresses are induced, which can cause electronic failure in packaging technologies. In this regard, new materials need to be developed, which provide high thermo-mechanical stability. In addition, innovative interconnect processes are required, which minimize the formation of stresses. Silicon nitride (Si 3 N 4 ) chips with polycrystalline and multi-phase morphology are investigated. The chips are sintered to copper substrates using a Cu(II)formate/polyethylene glycol sinter paste. In reference to the sintered copper interconnect, SAC and AuSn solder interconnects are also analysed. The final assemblies are studied using micro-Raman spectroscopy. The frequency changes of the E 1g vibrational mode at ca. 860 cm−1 are observed to detect intrinsic tensile and compressive local stresses. Stress values between 640 and 400 MPa are detected in the Si 3 N 4/ AuSn/Cu assemblies, while in all other assemblies stress relaxation appears very efficient.

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.

SUMMARY The purpose of this laboratory study was to compare the two-body wear resistance of different restorative materials commonly used for the indirect restoration of posterior teeth. The tested materials, based on ceramic (Imagine Press X, IPS e.max CAD, Milled Celtra Duo, Glaze-Fired Celtra Duo, Vita Mark II) and composite (Enamel Plus HRi, Enamel Plus HRi Bio-Function, Filtek Supreme XTE, Lava Ultimate), were compared with the wear properties of a type III gold alloy (Aurocast 8). Flat samples were prepared with a 6-mm thickness (n=10). Composite samples were tested after a heat polymerization cycle. All samples were exposed to a two-body wear test in a dual axis chewing simulator performing over 120,000 loading cycles. The opposing abrader cusps were fabricated from yttria-stabilized tetragonal zirconia polycrystal. The vertical substance loss (mm) and the volume loss (mm3) were recorded, as was the wear of the antagonist cusp (mm). Mean values were analyzed by one-way analysis of variance. Significant differences among materials were detected. The heat-cured resin-based composite material Enamel Plus Bio-Function and the type III gold alloy demonstrated similar mean values for wear depth and volumetric loss.

The conducted studies revealed the influence of the methods of cupellation and the XFA on the accuracy of determining the millesimal fineness in the system of the assay control. The effect of the alloy composition of jewelry alloys on determining millesimal fineness was established. In particular, it was experimentally proved that nickel in combination with zinc as an integrated alloying component substantially changes the cupellation process of gold alloys. This leads to deviation of the millesimal fineness of a gold alloy, determined by cupellation compared with the X-ray fluorescent analysis (XFA) towards a decrease ranging from 0.10 to 0.15 %. The research of gold alloys with the content of nickel with the help of the XFA revealed microalloying by modifiers and actively acting deoxidizing agents (indium, palladium, platinum, etc.). It was established that modifiers are used both separately and in complex, but they do not make a significant impact on determining the millesimal fineness. A number of systemic and random errors in techniques, which affect the results of determining and are related to the technique of performing preparatory operations, as well as analyses operation, were detected. Based on the obtained results, the permanent temperature mode was developed and the procedure of the process of cupellation of gold alloys with the content of nickel was improved with a view to further improvement and metrological certification of the procedure. It was proved that the use of the XFA method for control of millesimal fineness and the content of the component composition of modern gold-based pieces of jewelry and museum values (antiques) is possible not only as the method of screening. The method can replace the touchstone (with obvious advantages), and be an alternative to cupellation. Application of the XFA for current control of millesimal fineness and the content of an alloy of jewelry pieces is advisable to increase up to 30 % (against 2 % in accordance with the current legislation). Its use will make it possible to increase the number of analyzed samples without worsening the trading presentation of the jewelry pieces of a customer

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.

The reduced marginal bone loss observed when using the platform-switching concept may be the result of reduced amounts of tribocorrosion products released to the peri-implant tissues. Therefore, the purpose of this study was to compare the tribocorrosion product release from various platform-matched and platform-switched implant-abutment couplings under cyclic loading. Forty-eight titanium implants were coupled with pure titanium, gold alloy, cobalt-chrome alloy, and zirconia abutments forming either platform-switched or platform-matched groups ( n = 6). The specimens were subjected to cyclic occlusal forces in a wet acidic environment for 24 h followed by static aqueous immersion for 6 d. The amount of metal ions released was measured using inductively coupled plasma mass spectrometry. Microscopic evaluations were performed pre- and postimmersion under scanning electron microscope (SEM) equipped with energy-dispersive spectroscopy X-ray for corrosion assessment at the interface and wear particle characterization. All platform-switched groups showed less metal ion release compared with their platform-matched counterparts within each abutment material group ( P < 0.001). Implants connected to platform-matched cobalt-chrome abutments demonstrated the highest total mean metal ion release (218 ppb), while the least total mean ion release (11 ppb) was observed in the implants connected to platform-switched titanium abutments ( P ≤ 0.001). Titanium was released from all test groups, with its highest mean release (108 ppb) observed in the implants connected to platform-matched gold abutments ( P < 0.001). SEM images showed surface tribocorrosion features such as pitting and bands of fretting scars. Wear particles were mostly titanium, ranging from submicron to 48 µm in length. The platform-matched groups demonstrated a higher amount of metal ion release and more surface damage. These findings highlight the positive effect of the platform-switching concept in the reduction of tribocorrosion products released from dental implants, which consequently may minimize the adverse tissue reactions that lead to peri-implant bone loss.

Objectives: The aim of this research was to assess galvanic behavior of lingual orthodontic brackets coupled with representative types of orthodontic wires. Materials and Methods: 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. Results: 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. Conclusions: 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.

RESUMEN: Históricamente el oro ha sido usado debido a las especiales propiedades que posee, entre las que se pueden resaltar su resistencia a medios agresivos (por ser altamente inerte), su buena conducción térmica y eléctrica, y porque además presenta un color llamativo. Sus principales aplicaciones se han dado en áreas como la economía (en el uso de monedas), en joyería, en electrónica y en odontología. Con el fin de mejorar las propiedades que presenta el oro, se fabrican aleaciones de éste con otros metales. Dentro de las nuevas aleaciones que se están desarrollando, se encuentra el sistema de aleaciones Au-Fe. En esta investigación se pretende profundizar en el estudio de la microestructura de las aleaciones Au-Fe y Au-Fe-Co, para lo cual, se fabricaron aleaciones base oro aleadas con 25% (p/p) Fe y se han comparado a nivel de estructura y conformabilidad con la aleación Au-24.5Fe-0.5Co (% p/p), con el fin de determinar la influencia de este último aleante (el cobalto). Las aleaciones se obtuvieron en horno de inducción con atmósfera controlada de argón, utilizando crisoles conductores revestidos con silicato de zirconio. Las muestras se caracterizaron en tres diferentes procesos: as-cast con tratamiento térmico a temperaturas de 900°C a una y tres horas respectivamente y as-cast centrifugada. Los resultados de conformabilidad al finalizar el proceso son 62% de deformación (en laminador) para la aleación Au-24.5Fe-0.5Co contra el 23% para el sistema Au-25Fe para las muestras obtenidas as-cast y con tratamiento térmico a 900°C por 1 hora. Las muestras as-cast centrifugadas presentaron una deformación de 75% con fractura dúctil en Au-25Fe y de 82% sin fractura en Au-24.5Fe-0.5Co. El anterior resultado es satisfactorio para el sistema con adición de cobalto, lo cual es altamente benéfico para diversas aplicaciones, sobretodo la joyería. ABSTRACT: Since ancient times, gold has been used due to its especial properties. Among those properties are the resistance to corrosion (for being noble), its high electrical and thermal conductivity, and also its conspicuous coloration. Gold has been applied in a diversity of subjects such as economy, jewelry, electronic circuits and odontology. The fascinating properties of gold are likely to improve with the preparation of alloys; among those, the Au-Fe alloys constitute some of the most studied nowadays. In this research, we present our results concerning the microstructure of the Au-Fe and Au-Fe-Co alloys. We fabricated gold based alloys with 25% (weight) Fe and then compared their structure and formability to Au-24.5Fe-0.5Co (% weight) to determine the role of cobalt in the alloy. An induction furnace with controlled atmosphere (argon) and conductor crucibles coated with zirconium silicate was used. The samples were characterized by three processes: as-cast, with heat treatment (HT) at T=900°C (1h and 3h) and as-cast centrifuged. The formability results for the as-cast samples revealed a 23% deformation (rolling mill) for the Au-25Fe versus a 62% for the Au-24.5Fe-0.5Co alloy (HT-1h; T=900°C), whilst for the as-cast centrifuged sample revealed a 75% deformation with ductile fracture for the Au-25Fe versus an 82% without fracture for the Au-24.5Fe-0.5Co alloy. This result is particularly promissory for the applications in jewelry, showing that the addition of cobalt increases the formability of Au-Fe alloys.

AIM Since fiber posts are not recommended for teeth under lateral loads, a new alloy containing >80% copper (nonprecious gold or NPG) was introduced with a modulus of elasticity closer to that of dentin and easier preparation. This study aimed to compare the fracture strength of endodontically treated maxillary central incisors restored with nickel chromium (Ni-Cr) and NPG alloys. MATERIALS AND METHODS Casting post and cores were fabricated of Ni-Cr and NPG alloys for 24 maxillary central incisors (n = 12). Full-metal crowns were also fabricated and placed under cyclin loading in 30 N load and 45° angle, for 250,000 cycles with 2.6 Hz frequency. The fracture strength was measured at a crosshead speed of 0.5 mm/min and 135° angle in a universal testing machine. Data were analyzed using independent t-test. RESULTS The mean fracture strength was 731.179 ± 327.47 and 1411.89 ± 313.56 N in the Ni-Cr and NPG groups respectively; this difference was statistically significant (p < 0.001). The fracture was irreparable in all teeth since the fracture line was below the cementoenamel junction (CEJ). CONCLUSION The fracture strength of teeth restored with cast NPG post and cores was significantly higher than that of teeth restored with cast Ni-Cr post and cores. CLINICAL SIGNIFICANCE Due to proper mechanical properties, NPG post and cores seem to be a suitable choice for restoration of severely damaged anterior teeth, provided that other properties are proven to be acceptable.

SUMMARY The purpose of the present in vitro study was to compare the two-body wear resistance of a type 3 gold alloy (Aurocast8), two lithium disilicate glass ceramics (IPS e.max CAD and IPS e.max Press), a heat-pressed feldspathic porcelain (Cerabien ZR Press), an yttria-stabilized tetragonal zirconia polycrystal ceramic (Katana Zirconia ML), and three heat-cured composite resins (Ceram.X Universal, Enamel Plus Function, and Enamel Plus HRi) opposing antagonistic cusps made out of the same restorative materials. Ten 6-mm-thick samples and 10 cusp-shaped abraders were manufactured with each test material (n=10) according to standard laboratory procedures. All sample/antagonist pairs made out of the same material were subjected to a two-body wear test in a dual-axis chewing simulator for up to 120,000 loading cycles. The total vertical wear (mm) and the total volumetric loss (mm3) for each sample/antagonist pair were calculated. Data were statistically analyzed using one-way analysis of variance tests. The total vertical wear for the gold alloy was not significantly different compared to Ceram.X Universal, Enamel Plus Function, IPS e.max CAD, and Cerabien ZR Press. Significantly increased wear values were observed for Enamel Plus HRi and IPS e.max Press. The lowest values for total vertical wear and volumetric loss were recorded on the monolithic zirconia.

Background/purpose: Pure titanium (Ti) has many advantages, such as high corrosion resistance and excellent biocompatibility. The mechanical properties of pure Ti are like those of type IV gold alloys. Furthermore, gold alloys can be successfully recast in dental clinics. The aim of this study was to investigate the possibility of recasting pure Ti. Materials and methods: Magnesium oxide (MgO)-based investment that contained a 5 wt. % zirconium dioxide (ZrO2) additive was used. An argon-casting machine (Castmatic-S, Iwatani) was used to recast pure Ti. The first generation and second generation pure Ti (50 wt. % new Ti+50 wt. % surplus Ti) were used. Five specimens were fabricated and tested. The data were evaluated using two-sample t-test analysis (P

Statement of problem The recent application of printing for the fabrication of dental restorations has not been compared and evaluated for margin discrepancy (margin fit) with restorations fabricated using milling and conventional hand-waxing techniques. Purpose The purpose of this in vitro study was to evaluate and compare margin discrepancy of complete gold crowns (CGCs) fabricated from printed, milled, and conventional hand-waxed patterns. Material and methods Thirty crown patterns were produced by each of 3 different methods: printed by ProJet DP 3000, milled by LAVA CNC 500, and hand waxed, then invested and cast into CGCs. Each crown was evaluated at 10 positions around the margin on the corresponding epoxy die under ×50 light microscopy to determine the mean and maximum margin discrepancy. Measurements were made using a micrometer positioning stage. The results were compared by ANOVA (α=.05). Results Milled and hand-waxed patterns were not statistically different from each other ( P >.05), while printed patterns produced significantly higher mean and maximum margin discrepancy than milled and hand-waxed patterns ( P Conclusions Relative to margin discrepancy, the LAVA CNC 500 milled and hand-waxed patterns were not significantly different from each other. The ProJet DP 3000 printed patterns were significantly different from LAVA CNC 500 milled and hand-waxed patterns, with an overall poorer result. Fabricating CGCs from printed patterns produced a significantly higher number of crowns with unacceptable margin discrepancy (>120 μm).

In this work, a novel electrochemical detection platform was established by integrating molecularly imprinting technique with microfluidic chip and applied for trace measurement of three therapeutic drugs. The chip foundation is acrylic panel with designed grooves. In the detection cell of the chip, a Pt wire is used as the counter electrode and reference electrode, and a Au-Ag alloy microwire (NPAMW) with 3D nanoporous surface modified with electro-polymerized molecularly imprinted polymer (MIP) film as the working electrode. Detailed characterization of the chip and the working electrode was performed, and the properties were explored by cyclic voltammetry and electrochemical impedance spectroscopy. Two methods, respectively based on electrochemical catalysis and MIP/gate effect were employed for detecting warfarin sodium by using the prepared chip. The linearity of electrochemical catalysis method was in the range of 5×10-6-4×10-4M, which fails to meet clinical testing demand. By contrast, the linearity of gate effect was 2×10-11-4×10-9M with remarkably low detection limit of 8×10-12M (S/N=3), which is able to satisfy clinical assay. Then the system was applied for 24-h monitoring of drug concentration in plasma after administration of warfarin sodium in rabbit, and the corresponding pharmacokinetic parameters were obtained. In addition, the microfluidic chip was successfully adopted to analyze cyclophosphamide and carbamazepine, implying its good versatile ability. It is expected that this novel electrochemical microfluidic chip can act as a promising format for point-of-care testing via monitoring different analytes sensitively and conveniently.

Fabricating accurate cast gold restorations can be challenging for both clinicians and laboratory technicians. Removing the wax pattern from the master die often distorts the pattern, which, in turn, compromises the overall fit and marginal adaptation of the casting. This article demonstrates a laboratory technique in which the final restoration is cast directly on the refractory die without removing the wax pattern. Thus, distortion of the wax pattern is avoided, enabling the production of superbly fitting gold castings for both intracoronal and extracoronal restorations.

The aims of nano oncology are to detect, target and treat cancer cells without any side effects. The present study describes the microbial synthesis of biocompatible nanoparticles of silver (AgNPs), gold (AuNPs) and their alloy (Ag/AuNPs) for hepatoprotective activity against diethylnitrosamine (DEN)-induced liver cancer in a Sprague Dawley (SD) rat model. The crystalline nature and physicochemical features of the nanoparticles were identified by Fourier transform infra-red (FT-IR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) analysis. Based on the instrumental analysis, the synthesised nanomaterials were found to be spherical in shape and have an average size in the nano region. Nitrate reductase was characterized after partial purification of the culture filtrate via polyacrylamide gel electrophoresis and its molecular weight was determined as ∼45 kDa. Furthermore, the IC50 values of the AgNPs, AuNPs and Ag/AuNPs on HepG2 cells were determined as 38.42 μg ml-1, 43.25 μg ml-1 and 39.20 μg ml-1, respectively, and the antioxidant potential of the nanoparticles was also systematically analyzed. The No-Observed-Adverse-Effect-Level (NOAEL) for the AgNPs was determined to be 2000 mg per kg of body weight (bw) from an acute toxicity test. Similarly, the NOAEL of AuNPs and Ag/AuNPs were calculated as 1000 mg per kg bw. Based on the in vivo studies, a significant tumour reduction (∼45 to 65%) was observed in the nanoparticle-treated animals, which was further confirmed by hematological, biochemical, TEM and histopathological analysis. Immunohistochemistry analysis confirmed the presence of BAX antibodies, up to immunoreactive (3+) level in treated animals. These results strongly suggest the potential anticancer activities of AgNPs, AuNPs and Ag/AuNPs against DEN-induced liver cancer and they could be potential candidates for effective nano drug development.

The aim of this study was to evaluate the wear properties of resin teeth with different opposing dental restorative materials. One type of resin tooth (Trubyte Biotone) was tested against six types of restorative materials including type III gold alloy (GO), monolithic zirconia (MZ), lithium disilicate glass ceramic (LD), nickel&ndash, chromium alloy (NC), feldspathic ceramic (FC), and steatite (ST). Two-body wear tests were performed under a vertical load of 5 kgf and thermo-cycling at 5/55 &deg, C with a total of 120,000 cycles. The wear amount was quantified by measuring the volume loss of the resin teeth and the vertical substance loss of the opposing materials using three-dimensional images. The FC group showed a significantly greater amount of wear of the resin teeth, followed by the ST, NC, LD, MZ, and GO groups. The GO group showed significantly less wear of resin teeth than the other groups. There were no statistically significant differences in the wear of opposing restorative materials between groups. Within the limits of this study, it is recommended that zirconia, rather than feldspathic ceramic, should be used for restorations in the esthetic zone, and gold alloy should be used for areas with little or no esthetic demand.

Microhardness of eolian gold – new morphologic type of placer gold, is studied. Flaky gold particles with a elevation at the periphery, as well as gold of toroidal and globular-hollow forms belong to eolian gold. Genesis of eolian gold is related to mechanical transformation of flaky gold particles into toroidal, and then into globular-hollow form in eolian conditions, that is experimentally proven. Previous studies determined changes of microhardness, mainly from 47 kg/mm2 to 100 kg/mm2, lower limit – 40 kg/mm2. But, low microhardness was identified in globular-hollow gold for the first time, which stood at 21 kg/mm2. This is due to the fact that, as a result of transformation of flaky gold in eolian conditions, under mechanical and chemical processes, silver and trace elements were removed, that led to fineness increase up to 1000‰, and to decompaction of inner structure of gold, that influenced microhardness indices. Identified patterns in nature, microhardness changes under mechanogenic and chemical process impact in eolian conditions, can be successfully used in gold metallurgy to produce gold alloys with very low microhardness.

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.

The objectives of the present study is to determine the differences in peri-implant soft tissue color with the utilization of titanium, titanium gold-plated, white zirconia, Vita Classical (VC) A4-shaded zirconia, and fluorescent white zirconia abutments and to establish the influence of gingival thickness on the resulting color.Four implants were contralaterally inserted in 19 fresh pig mandibles, and the color of the peri-implant mucosa with the different abutments was spectrophotometrically measured at 1-, 2-, and 3-mm height from the margin.At 1-mm height, titanium significantly differed from all zirconia abutments in lightness (L*), chroma along red axis (a*), and chroma along yellow-blue axis (b*) parameters. At 2 mm, all zirconia abutments differed from titanium in b* but only fluorescent zirconia in a*. At 3 mm, titanium differed from VC A4-shaded and fluorescent zirconia abutments in b*. At soft tissue thicknesses1 and 1-2 mm, titanium differed from fluorescent zirconia in a* and b* and from VC A4-shaded zirconia in b*; at thickness2 mm, no differences were found among abutments. All abutments differed from natural teeth in a* and b* at all heights and thicknesses except for fluorescent zirconia at thickness2 mm. The Euclidean distance (ΔΕ) differed between titanium abutments and gold, VC A4, and fluorescent zirconia at1- and 1-2-mm thicknesses.The natural gingival color was not reproduced with any abutment at gingival thicknesses2 mm. The worst color match was with titanium abutments and the best with fluorescent zirconia, followed by VC A4-shaded zirconia. At gingival thicknesses2 mm, no differences were detected among abutments.This study demonstrates that the type of abutment and the gingival thickness affect the resulting peri-implant gingival color.

Patient A 69-year-old Japanese male visited Nihon University Dental Hospital for refabrication of his mandibular implant-supported complete fixed prosthesis (ISCFPD) and maxillary complete denture, which had been fabricated 15 years previously. In this case, Ce-TZP/Al 2 O 3 nanocomposite (Ce-TZP/A) was applied to the framework of the mandibular ISCFPD and maxillary complete denture. Three years after deliver of the framework, no particularly notable biological or prosthetic complications were observed, and a high level of patient satisfaction had been achieved. Discussion Conventional ISCFPD frameworks were fabricated by casting gold alloys; however, with the recent advancement of CAD/CAM technology, titanium (Ti) or yttria tetragonal zirconia polycrystal (Y-TZP) frameworks have become more common. In contrast, the main fabrication method for Ti or Co-Cr frameworks of removable dental prostheses has shifted from the conventional casting method to CAD/CAM fabrication. Ce-TZP/A, which was chosen as the framework material this time, shows higher strength and greater toughness than Y-TZP. However, since it has a low light-transmitting property and exhibits an opaque white color, the range of its application in fixed prostheses, particularly in the esthetic area, is limited. Conclusion We described a case in which Ce-TZP/A was applied to the frameworks of a mandibular ISCFPD and a maxillary complete denture. No particularly notable biological or prosthetic complications were observed in the mandibular ISCFPD or the maxillary complete denture, and a high level of patient satisfaction was achieved. Medium- and long-term observations with a greater number of cases are essential to obtain information concerning various phenomena related to this procedure.

The operability of low-voltage sliding electrical contacts made of ZlM-80 and ZlKh-05 alloys has been investigated. The temperature-time parameters of thermal treatment, which ensures the improvement of the physicomechanical properties of alloys and the rise in the operability indices of low-voltage sliding contacts (LVSC), have been investigated. Applying the friction pair of ZlM-80 and ZlKh-05 alloys ensured operation under the conditions of the implementation of the elastic unconcentrated contact in the friction zone and the decrease in the wear rate of low-voltage sliding contacts