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The aim was to explore the biological effect of nickel (Ni) and titanium (Ti) ions released from dental alloys. NiTi alloy were exposed to 40 mL of artificial saliva (pH = 4.8, t = 37 °C). The dynamics of Ni and Ti ions release during corrosion were recorded on the 3th, 7th and 14th day. Biological effect of Ni and Ti ions released from alloy was explored on cell lines of human tongue CAL 27, liver Hep G2 and colon Caco-2. Neutral Red uptake assay for the estimation of cell viability/cytotoxicity and 2',7'-dichlorofluorescein diacetate fluorimetric assay for reactive oxygen species were used. Cells were exposed to the following concentration of corrosion products: 5.0×, 1.0×, 0.5 and 0.1× during the period of 24, 48 and 72 h. To check the effect of each metal separately, cells were exposed to nickel-chloride and titanium-dioxide of corresponding concentration. The release of Ni is higher than of Ti (15.1-30.4 μg/L for Ni and 9.0-17.3 μg/L for Ti, respectively) and 5× higher concentrations are needed to induce cytotoxic effect. Ni and Ti ions alone do not induce a major cytotoxic effect, but their combination does indicating their synergistic effect. Increase in concentration of Ni and Ti tends to increase cytotoxicity, Ti more than Ni. Cytotoxicity and induction of free radicals are in strong positive linear correlation. Ions released from NiTi alloy during 14 days do not induce significant cytotoxic effect and would not have a clinically important impact. Cytotoxic effect is largely the result of the induction of free radicals., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Introduction: The aim of this study was to assess the influence of M-Wire (Dentsply Tulsa Dental Specialties, Tulsa, OK) and controlled memory technologies on the fatigue resistance of rotary nickel-titanium (NiTi) files by comparing files made using these 2 technologies with conventional NiTi files., Methods: Files with a similar cross-sectional design and diameter were chosen for the study: new 30/.06 files of the EndoWave (EW; J. Morita Corp, Osaka, Japan), HyFlex (HF; Coltene/Whaledent, Inc, Cuyahoga Falls, OH), ProFile Vortex (PV; Dentsply Tulsa Dental Specialties, Tulsa, OK), and Typhoon (TYP; Clinician's Choice Dental Products, New Milford, CT) systems together with ProTaper Universal F2 instruments (PTU F2; Dentsply Maillefer, Ballaigues, Switzerland). The compositions and transformation temperatures of the instruments were analyzed using x-ray energy-dispersive spectroscopy and differential scanning calorimetry, whereas the mean file diameter values at 3 mm from the tip (D3) were measured using image analysis software. The average number of cycles to failure was determined using a fatigue test device., Results: X-ray energy-dispersive spectroscopy analysis showed that, on average, all the instruments exhibited the same chemical composition, namely, 51% Ni-49% Ti. The PV, TYP, and HF files exhibited increased transformation temperatures. The PTU F2, PV, and TYP files had similar D3 values, which were less than those of the EW and HF files. The average number of cycles to failure values were 150% higher for the TYP files compared with the PV files and 390% higher for the HF files compared with the EW files., Conclusions: M-Wire and controlled memory technologies increase the fatigue resistance of rotary NiTi files., (Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Objectives: To investigate the composition and the microstructural and mechanical characterization of three different types of lingual brackets., Materials and Methods: Incognito™ (3M Unitek), In-Ovation L (DENTSPLY GAC) and STb™ (Light Lingual System, ORMCO) lingual brackets were studied under the scanning electron microscope employing backscattered electron imaging and their elemental composition was analysed by energy-dispersive X-ray microanalysis. Additionally, Vickers hardness was assessed using a universal hardness-testing machine, and the indentation modulus was measured according to instrumented indentation test. Two-way analysis of variance was conducted employing bracket type and location (base and wing) as discriminating variable. Significant differences among groups were allocated by post hoc Student-Newman-Keuls multiple comparison analysis at 95% level of significance., Results: Three different phases were identified for Incognito and In-Ovation L bracket based on mean atomic number contrast. On the contrary, STb did not show mean atomic contrast areas and thus it is recognized as a single phase. Incognito is a one-piece bracket with the same structure in wing and base regions. Incognito consists mainly of noble metals while In-Ovation L and STb show similar formulations of ferrous alloys in wing and base regions. No significant differences were found between ferrous brackets in hardness and modulus values, but there were significant differences between wing and base regions. Incognito illustrated intermediate values with significant differences from base and wing values of ferrous brackets., Conclusions/implications: Significant differences exist in microstructure, elemental composition, and mechanical properties among the brackets tested; these might have a series of clinical implications during mechanotherapy., (© The Author 2013. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Background: Cobalt-chromium alloys are used as casting alloys by dental technicians when producing dental prostheses and implants. Skin exposure and metal release from alloys and tools used by the dental technicians have not been studied previously., Objectives: To study the release of cobalt, nickel and chromium from alloys and tools that come into contact with the skin of dental technicians., Methods: Cobalt and nickel release from tools and alloys was tested with the cobalt spot test and the dimethylglyoxime test for nickel. Also, the release of cobalt, nickel and chromium in artificial sweat (EN1811) at different time-points was assessed. Analysis was performed with inductively coupled plasma-mass spectrometry., Results: Sixty-one tools were spot tested; 20% released nickel and 23% released cobalt. Twenty-one tools and five dental alloys were immersed in artificial sweat. All tools released cobalt, nickel and chromium. The ranges were 0.0047-820, 0.0051-10 and 0.010-160 µg/cm(2) /week for cobalt, nickel and chromium, respectively. All dental alloys released cobalt in artificial sweat, with a range of 0.0010-17 µg/cm(2) /week, and they also released nickel and chromium at low concentrations., Conclusions: Sensitizing metals are released from tools and alloys used by dental technicians. This may cause contact allergy and hand eczema., (© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Statement of Problem: Previous studies have shown casting methodology to influence the as-cast properties of dental casting alloys. It is important to consider clinically important mechanical properties so that the influence of casting can be clarified., Purpose: The purpose of this study was to evaluate how torch/centrifugal and inductively cast and vacuum-pressure casting machines may affect the castability, microhardness, chemical composition, and microstructure of 2 high noble, 1 noble, and 1 base metal dental casting alloys., Material and Methods: Two commonly used methods for casting were selected for comparison: torch/centrifugal casting and inductively heated/ vacuum-pressure casting. One hundred and twenty castability patterns were fabricated and divided into 8 groups. Four groups were torch/centrifugally cast in Olympia (O), Jelenko O (JO), Genesis II (G), and Liberty (L) alloys. Similarly, 4 groups were cast in O, JO, G, and L by an inductively induction/vacuum-pressure casting machine. Each specimen was evaluated for casting completeness to determine a castability value, while porosity was determined by standard x-ray techniques. Each group was metallographically prepared for further evaluation that included chemical composition, Vickers microhardness, and grain analysis of microstructure. Two-way ANOVA was used to determine significant differences among the main effects. Statistically significant effects were examined further with the Tukey HSD procedure for multiple comparisons. Data obtained from the castability experiments were non-normal and the variances were unequal. They were analyzed statistically with the Kruskal-Wallis rank sum test. Significant results were further investigated statistically with the Steel-Dwass method for multiple comparisons (α=.05)., Results: The alloy type had a significant effect on surface microhardness (P<.001). In contrast, the technique used for casting did not affect the microhardness of the test specimen (P=.465). Similarly, the interaction between the alloy and casting technique was not significant (P=.119). A high level of castability (98.5% on average) was achieved overall. The frequency of casting failures as a function of alloy type and casting method was determined. Failure was defined as a castability index score of <100%. Three of 28 possible comparisons between alloy and casting combinations were statistically significant. The results suggested that casting technique affects the castability index of alloys. Radiographic analysis detected large porosities in regions near the edge of the castability pattern and infrequently adjacent to noncast segments. All castings acquired traces of elements found in the casting crucibles. The grain size for each dental casting alloy was generally finer for specimens produced by the induction/vacuum-pressure method. The difference was substantial for JO and L., Conclusions: This study demonstrated a relation between casting techniques and some physical properties of metal ceramic casting alloys., (Copyright © 2013 Editorial Council for the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.)

Background: Titanium is the most widely used metal in dental implantology. The release of particles from metal structures into the biologic milieu may be the result of electrochemical processes (corrosion) and/or mechanical disruption during insertion, abutment connection, or removal of failing implants. The aim of the present study is to evaluate tissue response of human oral mucosa adjacent to titanium cover screws., Methods: One hundred fifty-three biopsies of the supra-implant oral mucosa adjacent to the cover screw of submerged dental implants were analyzed. Histologic studies were performed to analyze epithelial and connective tissue as well as the presence of metal particles, which were identified using microchemical analysis. Langerhans cells, macrophages, and T lymphocytes were studied using immunohistochemical techniques. The surface of the cover screws was evaluated by scanning electron microscopy (SEM)., Results: Forty-one percent of mucosa biopsies exhibited metal particles in different layers of the section thickness. Particle number and size varied greatly among specimens. Immunohistochemical study confirmed the presence of macrophages and T lymphocytes associated with the metal particles. Microchemical analysis revealed the presence of titanium in the particles. On SEM analysis, the surface of the screws exhibited depressions and irregularities., Conclusions: The biologic effects seen in the mucosa in contact with the cover screws might be associated with the presence of titanium or other elements, such as aluminum or vanadium. The potential long-term biologic effects of particles on soft tissues adjacent to metallic devices should be further investigated because these effects might affect the clinical outcome of the implant.

Statement of Problem: Surplus alloy from the initial casting is commonly reused with the addition of new alloy. This recasting procedure could affect the cytotoxicity of dental alloys., Purpose: The purpose of this in vitro study was to evaluate the effect of repeated casting of high-noble and base metal alloys on gingival fibroblast cytotoxicity., Material and Methods: Disk-shaped specimens (5 × 2 mm, n=60) of a high-noble (Au-Pt) and 2 base metal (Ni-Cr and Cr-Co, n=20) alloys were prepared with 100% new alloy and 50%, 65%, and 100% once recast alloy. The elemental composition of specimens was analyzed with X-ray energy-dispersive spectroscopy. Five specimens from each group were conditioned in saline with 3% fetal bovine serum albumin. The conditioning media were analyzed for elemental release with atomic absorption spectroscopy. Cytotoxic effects were assessed on human gingival fibroblast with a 3-(4.5-dimethylthiazol-2-yl)-2.5-diphenyl tetrazolium bromide (MTT) colorimetric assay. The data were analyzed with 1-way and 2-way ANOVA and Tukey's HSD multiple comparison test (α-=.05)., Results: Elemental compositions of Co-Cr and Au-Pt alloys were significantly different among casting protocols. Elemental release of Co-Cr and Ni-Cr alloys was significantly different between new and recast specimens (P<.001). Nickel release increased with recast alloy addition. The 2-way ANOVA showed a significant effect of the casting procedure (P<.001) alloy group (P<.001) and their interaction for cytotoxicity (P<.001). The Ni-Cr alloy groups with 65% and 100% recast alloy had lower cellular activity than all other specimens (P<.001)., Conclusions: The results of this study indicated that alloys containing nickel have increased cytotoxic effects and that composition of the alloys affected the cytotoxicity. Furthermore, recasting nickel-containing alloys with 65% surplus metal addition significantly increased the cytotoxic activity., (Copyright © 2012 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.)

Objective: The purpose of this study was to investigate the effects of oral fluids and archwire-bracket friction on the surface characteristics of NiTi alloy orthodontic archwires with/without aesthetic coating, in vivo for 2-3 months., Materials and Methods: Different cross-sections of NiTi Archwires (DENTSPLY GAC International) and Titanol Cosmetic Archwires (FORESTADENT® USA Inc.) were examined by electron microscopy with dual-beam and spectroscopy analysis, before and after a collecting protocol from patients with multi-technique., Results: Initially, the orthodontic archwires showed microscopic manufacturing and coating defects in the physiognomic layer. After intra-oral exposure, amorphous organic matter deposits were observed on the surface of the NiTi Archwires and the wire coating presented exfoliation on the oral areas of friction with brackets. X-ray microanalysis revealed changes in all atomic and mass percentages of chemical elements from the surface of all retrieved dental archwires, nickel and titanium ion depletion and the occurrence of additional elements due to interactions with saliva., Conclusions: Intra-oral exposure of NiTi Archwires and the archwire-bracket friction of coated wire altered the morphology and changed the elemental composition of the surface due to the process of corrosion, adhesion of organic matters and ionic exchange with oral fluids.

Previous works studied the effect of the material and the dimensions of the post on the biomechanical performance (fracture strength and stress distribution) of restored teeth, under static loads. The aim of this work was to study the effect of the post material (glass fibre and stainless steel) on restored teeth, which have the final crown, under dynamic conditions. The use of a biomechanical model, including a fatigue analysis from FEA, is presented as a powerful method to study the effect of the material of the intraradicular post. The inclusion of the fatigue analysis allows for a more realistic study that takes into account the dynamic nature of masticatory forces. At the same time, the results obtained are easier to interpret by both dentists and mechanical engineers. No differences were found, with the load and number of cycles considered, between glass fibre and stainless steel as material for the intraradicular post used in premolars restorations.

The effect of anodizing on corrosion resistance of Ti-xHf alloys has been investigated. Ti-xHf alloys were prepared and anodized at 120, 170 and 220 V in 1 M H(3)PO(4) solution, and crystallized at 300 and 500°C. Corrosion experiments were carried out using a potentiostat in 0.15 M NaCl solution at 36.5 ± 1°C. The Ti-xHf alloys exhibited the α' and anatase phases. The pore size on the anodized surface increases as the applied voltage is increased, whereas the pore size decreases as the Hf content is increased. The anodized Ti-xHf alloys exhibited better corrosion resistance than non-anodized Ti-xHf alloys.

Aim: To assess the failure mechanism of rotary NiTi instruments by chemical, structural and morphological analyses to provide a rational explanation of the effects of surface and bulk treatments on their resistance to fatigue fracture., Methodology: Thermal treatment (350-500 °C) was performed on electropolished (EP) and non-electropolished (Non-EP) NiTi endodontic instruments. Bulk and surface chemical composition and crystallographic structures were determined by energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) to evaluate the effects of thermal treatment and electropolishing on the NiTi alloy. Fatigue tests of all instruments were performed. Surface morphology before and after the tests, and fractured section were analysed using scanning electron microscopy to determine crack extensions. Results were analysed statistically using analysis of variance (anova) and post hoc Student-Newman-Keuls test., Results: Before thermal treatment, significant differences (P < 0.05) in fatigue resistance between EP and Non-EP instruments (the number of revolutions to failure, N(f) , was 385 and 160, respectively) were attributed to differences in the surface morphology of the instruments. SEM analysis of the fracture surfaces indicated that flexural fatigue fractures occurred in two steps: first by a slow growth of initial cracks and then rapid rupture of the remaining material. Thermal treatment did not affect the surface morphology but resulted in significant changes in the instrument bulk with the appearance of an R-phase and an improved fatigue resistance; indeed after treatment at 500 °C, N(f) increased up to 829 and 474 for EP and Non-EP instruments, respectively., Conclusions: Both thermal treatment and electropolishing improved the resistance of NiTi rotary instruments against fatigue fracture., (© 2010 International Endodontic Journal.)

Band materials are often used in the practice of pediatric dentistry. Nickel and Chromium are the main ingredients of these materials. The potential health hazards of nickel and chromium and their compounds have been the focus of attention for more than 100 years. It has established that these metals could cause hypersensitivity. The study was undertaken to analyze in vitro biodegradation of space maintainers made out of stainless steel band materials from manufacturers Dentaurum and Unitek. The leaching effect simulating the use of one, two, three, and four space maintainers in clinical practice was studied by keeping the respective number of space maintainers in the artificial saliva incubating at 37 degrees C and analyzing for nickel and chromium release after 1,7,14,21 and 28 days using atomic absorption spectrophotometer. Results showed that there was measurable release of both nickel and chromium which reached maximum level at the end of 7 days which was statistically significant (P < 0.05) and was very much below the dietary average intake even for four bands used and was not capable of causing any toxicity.

Introduction: A novel thermomechanical processing procedure has been developed that yields a superelastic (SE) nickel-titanium (NiTi) wire (M-Wire) that laboratory testing shows has improved mechanical properties compared with conventional SE austenitic NiTi wires used for manufacture of rotary instruments. The objective of this study was to determine the origin of the improved mechanical properties., Method: Specimens from 2 batches of M-Wire prepared under different processing conditions and from 1 batch of standard-processed SE wire for rotary instruments were examined by scanning transmission electron microscopy, temperature-modulated differential scanning calorimetry, micro-x-ray diffraction, and scanning electron microscopy with x-ray energy-dispersive spectrometric analyses., Results: The processing for M-Wire yields a microstructure containing martensite, that the proportions of NiTi phases depend on processing conditions, and that the microstructure exhibits pronounced evidence of alloy strengthening., Conclusions: The presence of Ti(2)Ni precipitates in both microstructures indicates that M-Wire and the conventional SE wire for rotary instruments are titanium-rich.

The aims of this study were to modify dental device surface with fluorine and silver and to examine the effectiveness of this new surface modification method. Stainless steel plates were modified by plasma-based fluorine and silver ion implantation-deposition method. The surface characteristics and brushing abrasion resistance were evaluated by XPS, contact angle and brushing abrasion test. XPS spectra of modified specimens showed the peaks of fluoride and silver. These peaks were detected even after brushing abrasion test. Water contact angle significantly increased due to implantation-deposition of both fluorine and silver ions. Moreover, the contact angle of the modified specimen was significantly higher than that of fluorine only deposited specimen with the same number of brushing strokes. This study indicates that this new surface modification method of fluorine and silver ion implantation-deposition improved the brushing abrasion resistance and hydrophobic property making it a potential antimicrobial device.

The present work summarizes data about palladium contents of road tunnel dust from 1994 to 2007 and sewage sludge ash from 1972 to 2006. Since palladium is emitted from automotive catalytic converters as elemental particles, road dust is quiet useful to study traffic-related Pd emissions. Very high Pd values of up to 516 microg Pd kg(-1) were found in the road dust samples collected in 2007. Heavy metals of all urban emissions, also dental practice effluent, are enriched in sewage sludge ash and thus this matrix is useful for the documentation of palladium emission caused by the use of Pd alloys in dental medicine. In sewage sludge ash highest Pd contents of maximum 460 microg Pd kg(-1) were found in the years 1986-1997. In both matrices correlations of Pd content to Pd demand of industry are discussed.

Objective: To evaluate and compare the ultrastructural morphology, surface cleanliness, and roughness of root canal walls of extracted teeth after instrumentation with 2 different rotary nickel-titanium systems (ProTaper and NRT) when associated with the use of sodium hypochlorite and ethylenediaminetetraacetic acid combination as an irrigating regimen., Study Design: A total of 40 freshly extracted single-rooted human mandibular premolars with fully developed apices and straight roots were selected. The roots were randomly divided into 2 experimental groups of 20 samples each according to the rotary system used in the preparation of the canals. In group I, canals were instrumented using the ProTaper file system; in group II, canals were prepared by the NRT file system. For each sample, an overall evaluation of the dentin surface along the whole length of the canal and a specific evaluation of the root dentin at the apical third was carried out regarding presence of debris, quality and amount of smear layer, and roughness using stereomicroscope and scanning electron microscope. Energy-dispersive spectroscopy was further used to detect nickel-titanium alloy remnants on the root dentinal surface of 2 randomly selected samples within each group., Results: Statistical analysis showed no significant difference between the tested systems regarding debris and smear layer. The ProTaper system presented significantly smoother dentinal walls at the apical level than the NRT system. Alloy remnants were detected within the dentinal walls instrumented by both systems., Conclusions: Both systems produced relatively clean and debris-free dentin surfaces in the coronal thirds and to a lesser extent in the middle thirds. In contrast, these instruments were unable to produce a dentin surface free from smear layer and debris in the apical thirds. Smoother prepared walls could be achieved using ProTaper files. Remnants of nickel-titanium alloy were detected on the root dentin surface instrumented by both systems.

The purpose of this study was to investigate the effects of three additives, Sn, Ga, and In, as well as the main constituents, Pd and Cu, of Ag-Pd-Au-Cu alloys on the initial bond strength of 4-META adhesive cement to these alloys. The Ag-Pd-Au-Cu alloys consisted of 20%, 30% or 40% Pd, and 10%, 15% or 20% Cu, 20% Au, and Ag as balance. Besides, additive metals (Sn, Ga, and In) of 2% and 4% were added to these compositions. The addition of three additives, in general, increased the initial bond strength of the cement in comparison to the mother compositions (0% additives), although the degrees of effectiveness of the three additives were different and varied with their contents. Among these additives, a remarkable increase in bond strength was observed with the addition of In. The increase in Cu content, in many cases, resulted in an increase in bond strength at high Pd contents (30% and 40%), but a decrease at low Pd content (20%) in some cases. The positive effects of the three additives and Cu could be due to the formation of a suitable oxide layer for strong bonding with 4-META.

In this study a NiTi alloy was applied as an SPME support due to its superelasticity and shape memory properties. This new metallic support was coated with ZrO(2) by electrodeposition using chronoamperometry. It was then evaluated for extraction of three classes of compounds from gaseous samples: alcohols, BTEX and trihalomethanes (THM). For the optimization of the parameters affecting the extraction efficiency of the target compounds, the univariate approach was used. Five fibers were electrodeposited to evaluate the reproducibility of the coating procedure, resulting in a relative standard deviation lower than 11.9%. The repeatability for one fiber (n=6) was lower than 8.5%. The detection limits were lower than 28.1, 20.8 and 0.18 microgL(-1) for alcohols, BTEX and THM, respectively, and the correlation coefficients were higher than 0.996. Taking into account the amount extracted per unit volume, the NiTi-ZrO(2) fiber showed a better extraction profile in comparison with the commercial fibers 7 microm PDMS, 85 microm PA and 30-50 microm DVB/CAR/PDMS. The new SPME fiber has a lifetime of over 300 extractions. Thus, it is a promising alternative for low-cost analysis, as it is robust, and easily and inexpensively prepared.

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

The objective of this study was to determine the concentration changes of 13 elements in erythrocytes and plasma after the removal of dental amalgam and other metal alloys. Blood samples from 250 patients were collected, separated into erythrocytes and plasma, and analyzed by inductively coupled plasma-mass spectrometry. The 250 patients were divided into 3 groups (Negative, Zero, and Positive) depending on their estimation of quality of life in an earlier study. Magnesium in plasma, selenium and mercury in plasma, and erythrocytes showed decreased concentrations after amalgam removal in all groups (p < 0.05). Titanium in plasma, copper in plasma, and erythrocytes and zinc in plasma exhibited decreased concentrations after amalgam removal in the Negative and Positive groups (p < 0.05). Silver in plasma and gold in erythrocytes decreased in the Zero and Positive groups after amalgam removal (p < 0.05). Copper in erythrocytes and silver and gold in plasma showed higher concentrations after amalgam removal in the Negative compared to the Positive group (p < 0.05), suggesting that patients in the Negative group excrete metals slowly. Moreover, the cobalt levels in plasma were lowest in the Negative group and only this group showed a significant increase in vitamin B12 levels in blood after amalgam removal.

The aim of this study was to investigate the bonding base surface morphology, alloy type, microstructure, and hardness of four types of orthodontic brackets produced by Metal Injection Molding technology (Discovery, Extremo, Freedom, and Topic). The bonding base morphology of the brackets was evaluated by scanning electron microscopy (SEM). Brackets from each manufacturer were embedded in epoxy resin, and after metallographic grinding, polishing and coating were analyzed by x-ray energy-dispersive spectroscopic (EDS) microanalysis to assess their elemental composition. Then, the brackets were subjected to metallographic etching to reveal their metallurgical structure. The same specimen surfaces were repolished and used for Vickers microhardness measurements. The results were statistically analyzed with one-way analysis of variance and Student-Newman-Keuls multiple comparison test at the 0.05 level of significance. The findings of SEM observations showed a great variability in the base morphology design among the brackets tested. The x-ray EDS analysis demonstrated that each bracket was manufactured from different ferrous or Co-based alloys. Metallographic analysis showed the presence of a large grain size for the Discovery, Freedom, and Topic brackets and a much finer grain size for the Extremo bracket. Vickers hardness showed great variations among the brackets (Topic: 287 +/- 16, Freedom: 248 +/- 13, Discovery: 214 +/- 12, and Extremo: 154 +/- 9). The results of this study showed that there are significant differences in the base morphology, composition, microstructure, and microhardness among the brackets tested, which may anticipate significant clinical implications.

Heating titanium structures is assumed to relieve tensions induced by the casting process as well as possibly optimizing some mechanical properties. The aim of this investigation was to evaluate the effect of thermal treatments on tensile strength of commercially pure titanium (CP Ti) and Ti-6Al-4V alloy. Thirty dumbbell rods, with diameters of 3.0 mm at the central segment and lengths of 42 mm, were cast for each metal using the Rematitan System. CP Ti and Ti-6Al-4V specimens were randomly divided into three groups of ten: a control group that received no thermal treatment and two test groups. One (T1) was heated at 750 degrees C for 2 h and the other (T2) was annealed at 955 degrees C for 1 h and aged at 620 degrees C for 2 h. Tensile strength was measured with a universal testing machine (MTS model 810). Tensile strength means and standard deviations were statistically compared using a Kruskal-Wallis test at a alpha=0.05 significance level. No statistically significant differences in tensile strength were observed among CP Ti groups. For the Ti-6Al-4V alloy, the control and T1 groups revealed statistically higher tensile strengths when compared to the T2 group, with no significant difference between the control and T1 groups.

Precious metal based dental alloys generally exhibit a superior corrosion resistance, in particular enhanced resistance to pitting and crevice corrosion, compared to non-precious metal based alloys such as CoCr alloys. A new generation of Co-Cr alloys enriched with precious metals (Au, Pt, Ru) have now appeared on the market. The goal of this study was to clarify the effect of the precious metals additions on the corrosion behaviour of such alloys. Various commercial alloys with different doping levels were tested by electrochemical techniques in two different milieus based on the Fusayama artificial saliva and an electrolyte containing NaCl. Open circuit potentials, corrosion currents, polarization resistances, and crevices potentials were determined for the various alloys and completed by a coulometric analysis of the potentiodynamic curves. In addition, the microstructures were characterised by metallography and phase compositions analysed by EDX. The results show that the presence of precious metals can deteriorate the corrosion behaviour of Co-Cr alloys in a significant way. Gold doping, in particular, produces heterogeneous microstructures that are vulnerable to corrosive attack.

Palladium dental casting alloys are alternatives to gold alloys. The aim of this study was to determine the electrochemical behaviour and the corrosion mechanism of binary silver-palladium alloys. Seven binary silver-palladium alloys and pure palladium and silver were tested in a model saliva solution. Electrochemical tests included corrosion potential, polarization resistance, and potentiodynamic polarization measurements. The corrosion products, which may be theoretically formed, were determined by thermodynamic calculation. The behaviour of silver and silver-rich alloys was dominated by the preferential formation of a thiocyanate surface layer, which controlled the free corrosion potential. Palladium dissolved in the form of a thiocyanate complex, but the surface became passivated by either palladium oxide or solid palladium thiocyanate layer, the thermodynamic calculations indicating preference for the oxide. Palladium-rich alloys showed evidence of silver depletion of the surface, resulting in behaviour similar to palladium. Examination of binary silver-palladium alloys has made possible determination of the role of the components of the alloys and model saliva in the corrosion behaviour. The findings are applicable to the more complex commercial dental alloys containing silver and palladium as major components.

Background: When a dissimilar couple is exposed to corrosive environment, it will normally exhibit a galvanic corrosion. The galvanic corrosion might be influenced by various factors, including type and concentration of electrolyte, surface area ratio between anode and cathode, type of coupling material, and coupling manner., Purpose: The purpose of this study was to investigate and compare the galvanic corrosion behavior of commercially pure titanium when coupled with type IV Au alloy, Au-Ag-Pt alloy, and Ag-Au-Pd alloy by different coupling methods., Materials and Methods: Couples were prepared by a laser welding or a mechanical adhering method. Electrochemical corrosion studies were conducted in a Ringer's solution at a scanning rate of 0.1 mV/sec in a range from -250 mV to +250 mV with respect to E(OCP). Corrosion parameters (E(OCP), I(CORR), E(CORR)) were obtained., Results: It was found that (i) there was a significant difference between LWC and AJC for three couples (p<0.05), (ii) the crevice line caused all three couples more corrosive than weld joint line, (iii) for both joint, it was found that type (IV) Au alloy exhibited discoloration to some extent., Conclusions: It is concluded that among the three couples with two different coupling methods, Ti/Ag-Au-Pd couple exhibited best corrosion resistance in a room temperature Ringer's solution.

Many in vitro studies have confirmed the corrosion of dental alloys. However, in vivo corrosion studies, for example, recording of the release of metal ions into saliva, are scarce, and data on the repeatability of the metal content measurements of saliva are lacking. The present study examined the metal content of saliva of patients with and without metal restorations and assessed the repeatability of these data. The composition of each patient's oral cast alloys was analyzed using the energy-dispersive X-ray analysis of metal biopsy specimens and was compared to the metals found in saliva. Saliva analysis was performed using atomic absorption spectroscopy. Chemical analysis comprised the metals Ag, Au, Co, Cr, Cu, Fe, Ga, In, Ni, Pd, Pt, Sn, and Zn. The metals Ag, Cr, Cu, Fe, Ni, and Zn were found in saliva of patients without metal restorations, but these data showed statistically significant differences in the metal content between consecutively performed samples per patient. The metals Ag, Au, Cr, Cu, Fe, Ni, and Zn were identified in saliva of patients with metal restorations being higher in concentration than in control patients. In 77% of the cases at least one metal of the restoration was found in the patient's saliva. However, the metal content showed statistically significant differences between replicate samples of the same patient taken at different times. The metal content of saliva is affected among other things by intraoral metal restorations, but present data do not support the idea that it is a reliable indicator for the systemic exposure to metals released from dental alloys.

In dentistry studies concerning systemic effects of dental materials are scarce. However, in vitro research showed that from each metal-containing restoration ions will be released. These metal ions can be spread locally but also in the entire human body and initiate an immune response. Nickel and palladium are recognized as the most allergenic elements. In this manuscript a method for evaluation of the alloy composition is described which may help dentists to reveal the relation between alloy compostion and health effects.

Commercial low-gold dental casting alloy composed of Ag-Pd-In-Au-Zn was studied to clarify the age-hardening mechanism and related microstructural changes. The hardness of solution-treated specimen began to increase and reached the maximum value with ageing time, and then the maximum hardness value decreased by further ageing. The changes of X-ray diffraction (XRD) pattern during isothermal ageing revealed that the age hardening was not caused by phase transformation. By comparing the age-hardening curve with the changes in full-width at half-maximum of the XRD peaks at each ageing time, it was revealed that the coherency strains were formed in the Ag-rich matrix, which contributed to the hardness increase during ageing. From scanning electron microscopic observation and electron probe microanalysis, it was clarified that fine particle-like structures composed of InPd containing small amount of Zn gathered by diffusion in the Ag-rich matrix, and the coherency strains which formed during that time caused the hardness increase in the early stage of age-hardening process. The coherency strains were released by the progress of coarsening of Zn-containing InPd dendrite during further ageing, which caused the overaging in the later stage of age-hardening process.

Objectives: The aim of this study was to compare the electrochemical behaviour of two materials used in oral implantology., Methods: The resistance to corrosion of Ti grade 2 and the alloy Ti-6Al-4V was studied in an artificial saliva solution. It has been observed that the passivation of titanium by an oxidised layer can be shown both by cyclic voltametry and by electrochemical impedance spectroscopy. Moreover, this latter technique, rarely used in odontology, opens up interesting perspectives, enabling a more quantitative approach to the resistance of the passive layer to be adopted., Results: Also, the impedance data recorded for Ti grade 2 and the alloy Ti-6Al-4V, in the artificial saliva solution were shown that Ti grade 2 has a higher resistance to corrosion and a thicker oxide layer than the alloy Ti-6Al-4V., Significance: The fact that the electrochemical properties of Ti-6Al-4V are lower than that titanium's ones indicate than a release of ions aluminum and or vanadium ions in the body can occur. This is why we recommend to the dental practitioners to preferably use titanium in implantology.

Purpose: This laboratory study compared the effect of different surface treatments of a medium-gold, high-noble alloy on the shear bond strength of an indirect, highly filled resin composite to the alloy and on the elemental composition of the alloy surface., Materials and Methods: Ninety disks, cast in a medium-gold, high-noble porcelain-fused-to-metal alloy (V-Deltaloy), received three different surface treatments: sandblasting with 50-microm Al2O3 (group 1) or 250-microm Al2O3 (group 2) and chemical agents, or with 250-microm Al2O3 without chemical agents (group 3) prior to bonding of an indirect resin composite (Artglass, and chemical agents Siloc-pre and Siloc-bond). The specimens were tested in shear, half of them after 24-hour dry storage at room temperature and the rest after 10-day storage in normal saline solution at 37 degrees C and thermocycling (2,500 cycles between 5 and 55 degrees C). Morphologic and qualitative changes on the alloy surface after sandblasting with 50- or 250-microm Al2O3 were examined by SEM using EDS analysis and compared with polished specimens. Statistical analysis was performed using two-factor ANOVA., Results: The mean shear bond strengths (in MPa) after dry or wet storage and thermocycling were 29 and 24 for group 1, 21 and 18 for group 2, and 17 and 12 for group 3, respectively; there was a statistically significant difference among the groups. Sandblasting of the alloy surface led to statistically significant changes in elemental composition. These changes were of greater magnitude when 50-microm Al2O3 particles were used., Conclusion: The particle size used for sandblasting influences the shear bond strength between a high-noble alloy and a highly filled indirect resin composite, as well as the elemental composition of the alloy surface.

Interest in the amount of metal ion intake from dental alloys has grown. Fixed orthodontic appliances usually include brackets, bands, and archwires made of stainless steel, nickel-titanium, or nickel-cobalt alloys, and these can release metal ions. The purpose of this study was to investigate the biocompatibility in vivo of fixed orthodontic appliances, evaluating the presence of metal ions in oral mucosa cells, their cytotoxicity, and their possible genotoxic effects. Mucosa samples were collected by gentle brushing of the internal part of the right and left cheeks of 55 orthodontic patients and 30 control subjects who were not receiving orthodontic treatment. The cells were immediately prepared for cell viability and the comet assay. Nickel and cobalt cellular content was quantified by inductively coupled plasma mass spectrometry (ICP-MS). The results indicate that nickel and cobalt concentrations were 3.4-fold and 2.8-fold higher, respectively, in the patients than in the controls; cellular viability was significantly lower in the patients than in the controls, and there was a significant negative correlation with metal levels. The biologic effects, evaluated by alkaline comet assay, indicated that both metals induced DNA damage (more cells with comets and apoptotic cells). There were significant positive correlations between (1) cobalt levels and the number of comets and apoptotic cells, (2) nickel levels and number of comet cells, and (3) cobalt levels and comet tails. This study corroborates that nickel and cobalt released from fixed orthodontic appliances can induce DNA damage in oral mucosa cells.

The potential advantage of magnetic resonance imaging (MRI) has been limited by artifacts due to the presence of metallic materials. For quantitative evaluation of the magnitude of artifacts from dental casting alloys and implant materials in MR imaging, 11 dental casting or implant materials were imaged by means of 1.5 T MRI apparatus with three different sequences. Mean and standard deviation of water signal intensity (SI) around the sample in the region of interest (1200 mm(2)) were determined, and the coefficient of variation was compared for evaluation of the homogeneity of the SI. A variety of artifacts with different magnitudes was observed. Only one of the samples, composed mainly of Pd, In, and Sb, showed no artifacts in all imaging sequences. We concluded that selection of specific dental casting alloys according to their elemental compositions could minimize the metal artifacts in MRI; however, titanium alloys currently pose a problem with respect to causing MRI artifacts.

Single case reports indicate that components of dental alloys accumulate in the adjacent soft tissue of the oral cavity. However, data on a wider range of dental alloys and patient groups are scarce. Therefore, the aim of the present study was to examine the metal content of oral tissues adjacent to dental alloys showing persisting signs of inflammation or other discoloration (affected sites) and of healthy control sites with no adjacent metal restoration in 28 patients. The composition of the adjacent alloys was analyzed and compared to the alloy components in the affected sites. Tissue analysis was performed using atomic absorption spectroscopy. Alloy analysis was performed with energy-dispersive X-ray analysis. In the affected sites, the metals Ag, Au, Cu, and Pd prevailed compared to control sites, reflecting the frequency distribution of single metals in the adjacent alloys. In most cases (84%), at least one of the analyzed metals was a component of the alloy and also detected in the tissue. Metal components from almost all dental cast alloys can be detected in adjacent tissue.

The purpose of this study was to qualitatively and quantitatively assess the nickel, chromium, and ferrous levels in a population of 17 orthodontic patients undergoing treatment, compared with seven untreated individuals, employing a novel methodological approach and a new analytical technique. Salivary samples obtained from patients before and after rinsing with double distilled water were processed for Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) for simultaneous estimation of the concentration of the metallic elements. No statistically significant difference was detected between control and patient groups with respect to salivary metal content, regardless of element. The range of salivary metal levels found did not exceed those of daily intake through food and air. The lack of a continuous monitoring scheme for salivary metal concentrations in real time may impose substantial obstacles to defining the release rate of metals in vivo. The results of this study emphasize the necessity of incorporating the dimension of time in assessing the release potential of orthodontic alloys.

Dental laboratory technicians may be exposed to metal alloys that are used in the production of crowns, bridges and removable partial dentures. These alloys consist of 35-65% cobalt, 20-30% chromium, 0-30% nickel, and small amounts of molybdenum, silica, beryllium, boron and carbon. The aim of this study was to assess whether dental technicians are occupationally exposed to chromium, cobalt and nickel, by analyzing urinary excretion levels of these metals and to investigate the genotoxic effects of occupational exposure associated with dental prostheses production operations by analyzing cytokinesis-blocked micronucleus (CB-MN) frequencies in peripheral lymphocytes and micronucleus (MN) frequencies in exfoliated nasal cells from 27 dental laboratory technicians and 15 control subjects. The differences in the urinary excretion of metals between technicians and controls were statistically significant. The mean (+/-S.D.) CB-MN frequencies ( per thousand ) in peripheral lymphocytes were 4.00 (+/-2.98) among the dental technicians and 1.40 (+/-1.30) among the controls, a statistically significant difference (P<0.005). The mean (+/-S.D.) MN frequencies ( per thousand ) in nasal cells were 3.50 (+/-1.80) among the dental technicians and 1.19 (+/-0.53) among the controls, which was also a statistically significant difference (P<0.005). There was a significant correlation between duration of exposure and MN frequencies in lymphocytes (r=0.642, P<0.01), but not in nasal cells of technicians. Our data reveal that in vivo exposure to chromium, nickel and cobalt metals is evident and that this occupational exposure may contribute to the observed genotoxic damage in two types of cells, e.g. lymphocytes and exfoliated nasal cells. However, it cannot be determined which compound(s) are responsible for the genotoxic damage observed in this study.

Objectives: This study examined dental material degradation product toxicity using the Microtox bacterial bioluminescence assay as well as the effects on toxicity of selective leaching, chelation with protein, the physical form of the products, and synergistic/antagonistic interactions among released ions., Methods: Polarization was used to produce ionically dissolved (ID) and precipitated corrosion products from Litecast B alloy specimens, which were then chemically analyzed to determine their composition and to identify metal valence states. Corrosion product toxicity, as well as that of the individual alloying elements, alone and in the presence of mucin, was analyzed using Microtox. A mathematical approach identified synergistic/antagonistic interactions and determined element contribution to product toxicity. The mechanism by which the Microtox test bacterium interacts with solid products was explored. The toxicity of methyl methacrylate (MMA) monomer was also examined., Results: Precipitated corrosion products were found to be more toxic than ID products. The metals in the precipitate have been shown to be available to the test bacterium. Be and Ni were the most toxic elements in the products and contributed significantly to their toxicity. Synergistic and slightly antagonistic interactions were observed in the ID and precipitated products, respectively. Mucin decreased toxicity of all elements except Be. MMA monomer toxicity was found to be low compared to metal toxicity., Significance: Microtox is useful for evaluating dental degradation product biocompatibility and has significant promise for use in other types of studies, such as determining the effectiveness of antimicrobial treatments.

The phase transformation behavior in three commercial nickel-titanium orthodontic wires having different transformation temperatures was studied by micro X-ray diffraction (micro-XRD). Micro-XRD spectra were obtained at three different included bending angles (135 degrees, 146 degrees and 157 degrees) and three different temperatures (25 degrees C, 37 degrees C and 60 degrees C). The regions analyzed by micro-XRD were within the separate areas of a given wire specimen that experienced only tensile or compressive strain. The intensity ratio (M002/A110) between the 002 peak for martensitic NiTi and the 110 peak for austenitic NiTi was employed as the index to the proportions of the martensite and austenite phases. The ratio of martensite to austenite increased in all three nickel-titanium wires with decreasing included bending angle (greater permanent bending deformation), and was lower within the compression area for all wires at all bending angles than within the tension area. Micro-XRD provides an effective method for quantitative evaluation of the proportions of these two phases in nickel-titanium orthodontic wires, even though considerable preferred crystallographic orientation exists because of the wire drawing process.

Statement of Problem: The biocompatibility of high-palladium alloy restorations has been of some concern due to the release of palladium into the oral environment and sensitivity reactions in patients., Purpose: This study measured the in vitro elemental release from a Pd-Cu-Ga alloy and a Pd-Ga alloy into a corrosion testing medium., Material and Methods: Both alloys were cast into 12-mm-diameter x 1-mm-thick disks, subjected to heat treatment that simulated porcelain firing cycles, polished to a 0.05-mm surface finish, and ultrasonically cleaned in ethanol. Two specimens of each alloy were immersed 3 times (at 7, 70, and 700 hours) in an aqueous lactic acid/NaCl solution used for in vitro corrosion testing and maintained at 37 degrees C. The specimens were removed after each immersion time, and the elemental compositions of the solutions were analyzed with inductively coupled plasma-mass spectroscopy (ICP-MS). Elemental concentrations for the 2 alloys at each immersion time were compared with Student t test (alpha=.05)., Results: No significant differences in palladium release were found for the 7- and 70-hour solutions, but significant differences were found for the 700-hour solutions. Mean concentrations of palladium and gallium in the 700-hour solutions, expressed as mass per unit area of alloy surface, were 97 (Pd) and 46 (Ga) microg/cm(2) for the Pd-Cu-Ga alloy and 5 (Pd) and 18 (Ga) microg/cm(2) for the Pd-Ga alloy., Conclusion: Relative proportions of the elements in the solutions were consistent with the release of palladium and breakdown of microstructural phases found in the alloys. The results suggest that there may be a lower risk of adverse biological reactions with the Pd-Ga alloy than with the Pd-Cu-Ga alloy tested.

Platinum concentrations were determined in 50 urine and 20 saliva samples obtained from 50 subjects who had gold dental restorations. In addition, 42 urine and 35 saliva samples were collected from subjects who did not have gold dental restorations. Subjects with gold alloys had significantly (p < .001) higher urinary platinum excretion (mean = 11.9 +/- 8.5 ng/gm creatinine, range = 1.9-45.8 ng/gm creatinine) than controls (mean = 6.2 +/- 3.2 ng/gm, range = 1.9-14.4 ng/gm creatinine). Mean saliva concentrations were significantly higher in subjects with dental gold alloys (526 pg/gm vs. 8.5 pg/gm; p < .001). A laboratory test with 5 commercially available dental gold/platinum alloys showed that 0.1% sodium chloride mobilized platinum within 1 hr (i.e., 1-18 pg/ml) of its introduction. In conclusion, dental gold/platinum alloys appear to be the main source for urinary platinum excretion from the occupationally unexposed population.

Statement of Problem: The use of dental amalgam as a direct restorative material has been a subject of controversy for many years. The potential safety of amalgam has been questioned because of leakage of elements such as mercury, copper, tin, and silver., Purpose: This study evaluated the elemental leaching from Tytin dental amalgam placed in deionized water for 2 months. Both mercury vapor and elemental (silver, copper, tin, and mercury) analyses were performed., Material and Methods: Two capsules of Tytin amalgam were triturated (one for the precipitate and liquid analysis, and the other for the mercury vapor analysis) and stored in a polypropylene tube with 10 mL deionized water for 60 days at room temperature. The amalgam pellet then was removed and rinsed with deionized water. The resulting liquid was separated from a precipitate, and 2 separate analyses were run: one on the liquid without any precipitate and another on the precipitate. Elemental analyses for copper (Cu), tin (Sn), mercury (Hg), and silver (Ag) were determined by inductively coupled plasma-emission spectroscopy with a Perkin-Elmer P2000 spectrometer. Mercury vapor analyses were performed daily for 60 days with a Jerome 431-X vapor analyzer., Results: The maximum amount of copper (80 microg), silver (2.6 microg), mercury (15 microg), and tin (550 microg) was found in the precipitate. The maximum amount of mercury vapor released was 67 microg/m(3)/d., Conclusion: Under the conditions of this in vitro study, there was a significant amount of elemental leaching and mercury vapor release from the Tytin amalgam over a 60-day period.

Stainless steel wrought wires used as clasp arms for removable partial dentures in Thailand were compared with those used in some other countries (in the as-received condition) in terms of flexibility, Vickers microhardness and composition. The results showed that there were significant differences (P< or =0.05) among the wires. A Japanese stainless steel wire (SK) was obviously different from the others. It had the lowest proportional limit and microhardness, but its flexibility was almost the same. The chemical composition of each wire was not greatly different. The wires were about 18-20 wt% chromium and 8-9 wt% nickel, except for the SK wire, which had about 12 wt% nickel.

The effects of metal combinations on cytotoxicity were examined following dynamic extraction by freely gyrating two spherical metals in a glass vessel. The cell viabilities of an Au alloy, a Ag-Pd-Au alloy and Ti were little affected by combinations among three metals. Cell viability ranged between 60 and 80% when precious alloys were in combination with Co-Cr or Ni-Cr alloys. Ti showed a clear difference in cell viability either in combination with Co-Cr or Ni-Cr alloys. The cell viability of the Ti/Co-Cr alloy combination was the same as that of precious alloys/Co-Cr or Ni-Cr alloy combinations. However, in an analogy with Co-Cr alloy/Ni-Cr alloy combination, the Ti/Ni-Cr alloy combination depressed the cell viability below 20%. This suggested that when new metals are to be used in combination with dissimilar metals, the cytotoxicity of the metals could be evaluated in extraction conditions using the mutual dynamic contact of dissimilar metals.

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

This study evaluated the effect of four methods of metal surface preparation and the use of silane on the bond strength between resin and a Noble metal alloy. SEM Examination and x-ray energy-dispersive spectroscopy (EDS) of the various metal surface treatments was also performed. One-hundred metal disks were cast in a Noble metal alloy (Porcelain #76). Ninety disks were polished flat and the surfaces received one of four abrasive treatments (n = 20). 1) Roughening with a diamond bur at high speed; 2) Air abrasion with an intraoral sandblaster using alumina particles; 3) Air abrasion with KCP-2000 and 4) Air abrasion with an intraoral sandblaster using silanated silica covered alumina particles (CoJet-Sand). Half the specimens from each treatment group (n = 10) were silanated prior to bonding procedures (All-Bond 2 adhesive system, Pertac-Hybrid composite). Specimens were stored in distilled water at 37 degrees C and thermocycled prior to shear strength testing. The 10 remaining metal disks were used for scanning electron microscopy and x-ray energy-dispersive spectroscopy (EDS). Scanning electron microscopy examined the micromorphology of the metal surfaces produced by the four abrasive treatments and x-ray energy-dispersive spectroscopy (EDS) to evaluate changes in surface composition. Two untreated disks served as controls. One-way ANOVA and Tukey's HSD post-hoc test demonstrated that air abrasion with CoJet-Sand and silane resulted in significantly higher resin-to-metal bond strength than all other metal surface treatments, while roughening with a diamond bur produced the lowest bond strength. Resin-to-metal bond strength was similar for all other particle abrasive treatments with or without silane. Using silane significantly improved bond strength only for metal surfaces treated with CoJet-Sand. An increase in Al concentration was observed on metal surfaces sandblasted with aluminum oxide, and an increase in the concentration of both Al and Si was observed on surfaces air-abraded with CoJet-Sand.

Objectives: This study was designed to verify whether nitridation treatment of the cutting surfaces resulted in surface or subsurface changes that produced an increase in the resistance to wear in nickel titanium (NiTi) endodontic files., Study Design: Some experimental samples were exposed to ionic implantation by using 150 keV of nitrogen ions and doses of 1 x 10(17) ions per cm(2). Other samples were exposed to thermal nitridation processes performed for 480 minutes at 500 degrees C temperature. Control samples were not exposed to any process. The chemical composition of the surface layers of each sample was determined by means of x-ray photoelectron spectroscopy. The cutting efficiency was tested on an endotraining bloc., Results: The experimental instruments showed in-depth distributions of chemical composition that were different from those seen in the control group; thermal-nitridated instruments demonstrated a surface ratio of nickel to titanium of 0.5. Implanted samples had a higher N/Ti ratio (1.2); this ratio may be due to the presence of a layer of titanium nitride. Samples in the experimental groups showed an increase in cutting ability as compared with the controls., Conclusions: Thermal nitridation and nitrogen-ionic implantation treatment of nickel-titanium files produced a higher wear resistance and an increased cutting capacity.

Background: Technological progress in the endodontic field has allowed the creation of innovative nickel-titanium endodontic instruments, made with a superelastic alloy with a reduced modulus of elasticity. The elastic properties of the NiTi alloy can undergo significant variations in connection with mechanical movements and cyclic fatigue induced on the instruments caused by their repeated usage, especially in canals which are anatomically difficult to shape. The state of tension of the instrument determines a deformation of the geometry of the files and, therefore, a modification in their properties. Similarly to mechanical stress, thermal treatments can influence the properties of the alloy. The aim of the study is to subject the NiTi alloy to repeated thermomechanical cycles, examining the influence of the mechanical and thermal stress on the temperature at the beginning and end of the martensite transformation, on the increase of recovery of deformation during the cooling phase and on the change in the internal structure of the material., Methods: The instruments (30 ProFile Maillefer) were subdivided into 5 groups: Group I, composed of 6 new ProFiles submitted to 14 sterilization cycles in an autoclave for 30 minutes each; Group II, formed by 6 unused ProFiles subjected to one sterilization cycle in an autoclave; Group III made up of 6 new ProFiles used as controls; Group IV made up of 6 ProFiles submitted to clinical use on endodontic simulators in plexiglas for a total time of 240 seconds; Group V consisting of 6 ProFiles used on endodontic simulators for a total time of 480 seconds. All the above mentioned samples were tested using a thermomechanic dynamic analyzer (DMTA) produced by Rheometric Scientific., Results: The files from Group III (control) show an elastic deformation curve typical of nickel-titanium instruments. The samples from Groups IV and V subjected to sequential use on endodontic simulators evidenced modifications in their elastic behaviour compared to the control instruments. The operative use caused modifications in the original properties of the alloy, with a reduction in elasticity proportional to the number of uses. The instruments that underwent 14 cycles of sterilization in the autoclave (I group) present dynamic analysis curves which are different compared to the new unsterilized ProFiles. After 14 cycles there is a modification in the response of the instruments to thermodynamic stress., Conclusions: Both the samples undergoing repeated mechanical stress on Plexiglas endodontic simulators and those sterilized in the autoclave at thermodynamic analysis show significant modification in modulus of elasti- city. The different taper does not influence the experimental results, there not being any significant differences found in the elastic behaviour between ProFiles.

The corrosion behaviors of four ferric stainless steels and two austenitic stainless steels were examined in a simulated physiological environment (0.9% NaCl solution) to obtain basic data for evaluating the appropriate composition of stainless steels for dental magnetic attachments. The corrosion resistance was evaluated by electrochemical techniques and the analysis of released metal ions by atomic absorption spectrophotometry. The surface of the stainless steels was analyzed by X-ray photoelectron spectroscopy (XPS). The breakdown potential of ferric stainless steels increased and the total amount of released metal ions decreased linearly with increases in the sum of the Cr and Mo contents. The corrosion rate of the ferric stainless steels increased 2 to 6 times when they were galvanically coupled with noble metal alloys but decreased when coupled with commercially pure Ti. For austenitic stainless steels, the breakdown potential of high N-bearing stainless steel was approximately 500 mV higher than that of SUS316L, which is currently used as a component in dental magnetic attachments. The enriched nitrogen at the alloy/passive film interface may be effective in improving the localized corrosion resistance.

Objectives: The objective of this study was to assess the clinical performance of a direct placement gallium alloy sealed with an established dentine adhesive system. In addition, microanalysis of a few gallium restorations that failed in clinical service was performed. Clinical factors such as pulpal sensitivity, fracture of the restoration and of the tooth, marginal deterioration, and tarnish were assessed., Methods: Sixty-five restorations of Galloy and 62 of Tytin (49 and 51 Class II restorations, respectively) were placed according to a predetermined scheme for randomisation in 37 patients by two operators using rubber dam isolation. For the Galloy restorations, the enamel and dentine were etched, and then sealed with PAAMA 2 dentine adhesive according to the manufacturer's instructions. After carving, PAAMA 2 was applied to the Galloy and light-cured. Cavity preparations for Tytin received no adhesive sealer. All restorations were polished at least 24 h post-operatively. Microstructural analysis of retrieved fragments of failed restorations was conducted using electron probe microanalysis., Results: At 1 year, only one Tytin restoration was found to have failed due to an isthmus fracture. The remaining restorations of Tytin were intact with no reported sensitivity. Of the 65 Galloy restorations placed, 28 had to be removed, including restorations in teeth, which were symptomatic, non-vital and/or fractured, and teeth with fractured restorations. Tarnish was present on many of the Galloy restorations. Retrieved fragments of failed Galloy restorations exhibited a dark surface at the pulpal wall interface and small cracks were observed in that surface. Internal cracks and extensive corrosion was observed using the microprobe. Gallium oxides and chlorides were identified as the predominant corrosion products., Conclusions: The gallium alloy, Galloy, sealed with PAAMA 2 dentine adhesive system demonstrated a high clinical failure rate.

The aim of the present study was to develop an automated image analysis method to quantify adherence of Streptococcus sanguinis or Actinomyces viscosus on surfaces of a currently used dental alloy. Counting such bacterial strains was difficult because of their arrangement, thus S. sanguinis being a coccus arranged in chains or pairs, and A. viscosus a long complexly arranged polymorph rod. Direct counting of fluorescently stained adherent bacteria was done visually and with image analysis methods. To differentiate these two morphotypes, two programs were developed: (i) for streptococci, thresholding and selection of the object maxima, and (ii) for actinomyces, two step thresholding and processing of the characteristic points of the object skeletons. The triplicate enumerations for each bacterial strain were not significantly different (p > 0.005) and correlations between visual counting and automated counting were significant (r = 0.91 for S. sanguinis and r = 0.99 for A. viscosus, p <00.0001). These rapid and reproducible methods, allowed us to count either cocci or rods, adherent on an inert substratum, in high density conditions.