The hazards and risks of inhaled poorly soluble particles - where do we stand after 30 years of research?

BACKGROUND: In 2006, titanium dioxide and carbon black were classified by IARC as "possibly carcinogenic to humans" and in 2017 the European Chemicals Agency's (ECHA) Committee for Risk Assessment concluded titanium dioxide meets the criteria to be classified as suspected of causing cancer (category 2, through the inhalation route). These classifications were based primarily on the occurrence of lung cancer in rats exposed chronically to high concentrations of these materials, as no such responses have been observed in other animal species similarly exposed. After the EU classification of titanium dioxide, it was suggested that Poorly Soluble particles of Low Toxicity (PSLTs) can be evaluated as a group. MAIN BODY: To better understand the current state of scientific opinion, we sought perspective from several international experts on topics relevant to the classification of carbon black; titanium dioxide; and, the potential future classification of PSLTs. Areas discussed included: grouping of PSLTs; the relevance of rat lung cancer responses to high concentrations of PSLTs; and, clearance overload and implications for interpretation of inhalation toxicology studies. We found there were several areas where a large majority of experts, including ourselves, agreed. These included concerns on the grouping of PSLT and the definition of clearance overload. Regarding the extrapolation of PSLT associated lung cancer in rats there were some strongly held differences, although most experts questioned the relevance when excessive exposures which overwhelm lung clearance were required. SHORT CONCLUSION: Given the ongoing discussion on PSLT classification and safety, we believe it is important to re-activate the public debate including experts and stakeholders. Such an open discussion would serve to formally document where scientific consensus and differences exist. This could form the basis for design of future safety programs and safety assessments.

An in-depth multi-omics analysis in RLE-6TN rat alveolar epithelial cells allows for nanomaterial categorization.

BACKGROUND: Nanomaterials (NMs) can be fine-tuned in their properties resulting in a high number of variants, each requiring a thorough safety assessment. Grouping and categorization approaches that would reduce the amount of testing are in principle existing for NMs but are still mostly conceptual. One drawback is the limited mechanistic understanding of NM toxicity. Thus, we conducted a multi-omics in vitro study in RLE-6TN rat alveolar epithelial cells involving 12 NMs covering different materials and including a systematic variation of particle size, surface charge and hydrophobicity for SiO2 NMs. Cellular responses were analyzed by global proteomics, targeted metabolomics and SH2 profiling. Results were integrated using Weighted Gene Correlation Network Analysis (WGCNA). RESULTS: Cluster analyses involving all data sets separated Graphene Oxide, TiO2_NM105, SiO2_40 and Phthalocyanine Blue from the other NMs as their cellular responses showed a high degree of similarities, although apical in vivo results may differ. SiO2_7 behaved differently but still induced significant changes. In contrast, the remaining NMs were more similar to untreated controls. WGCNA revealed correlations of specific physico-chemical properties such as agglomerate size and redox potential to cellular responses. A key driver analysis could identify biomolecules being highly correlated to the observed effects, which might be representative biomarker candidates. Key drivers in our study were mainly related to oxidative stress responses and apoptosis. CONCLUSIONS: Our multi-omics approach involving proteomics, metabolomics and SH2 profiling proved useful to obtain insights into NMs Mode of Actions. Integrating results allowed for a more robust NM categorization. Moreover, key physico-chemical properties strongly correlating with NM toxicity were identified. Finally, we suggest several key drivers of toxicity that bear the potential to improve future testing and assessment approaches.

Grouping of nanomaterials to read-across hazard endpoints: from data collection to assessment of the grouping hypothesis by application of chemoinformatic techniques.

BACKGROUND: An increasing number of manufactured nanomaterials (NMs) are being used in industrial products and need to be registered under the REACH legislation. The hazard characterisation of all these forms is not only technically challenging but resource and time demanding. The use of non-testing strategies like read-across is deemed essential to assure the assessment of all NMs in due time and at lower cost. The fact that read-across is based on the structural similarity of substances represents an additional difficulty for NMs as in general their structure is not unequivocally defined. In such a scenario, the identification of physicochemical properties affecting the hazard potential of NMs is crucial to define a grouping hypothesis and predict the toxicological hazards of similar NMs. In order to promote the read-across of NMs, ECHA has recently published "Recommendations for nanomaterials applicable to the guidance on QSARs and Grouping", but no practical examples were provided in the document. Due to the lack of publicly available data and the inherent difficulties of reading-across NMs, only a few examples of read-across of NMs can be found in the literature. This manuscript presents the first case study of the practical process of grouping and read-across of NMs following the workflow proposed by ECHA. METHODS: The workflow proposed by ECHA was used and slightly modified to present the read-across case study. The Read-Across Assessment Framework (RAAF) was used to evaluate the uncertainties of a read-across within NMs. Chemoinformatic techniques were used to support the grouping hypothesis and identify key physicochemical properties. RESULTS: A dataset of 6 nanoforms of TiO2 with more than 100 physicochemical properties each was collected. In vitro comet assay result was selected as the endpoint to read-across due to data availability. A correlation between the presence of coating or large amounts of impurities and negative comet assay results was observed. CONCLUSION: The workflow proposed by ECHA to read-across NMs was applied successfully. Chemoinformatic techniques were shown to provide key evidence for the assessment of the grouping hypothesis and the definition of similar NMs. The RAAF was found to be applicable to NMs.

The "shadow sign": a radiographic differentiation of stainless steel versus titanium spinal instrumentation in spine surgery.

BACKGROUND: Stainless steel spinal instrumentation has been supplanted in recent years by titanium instrumentation. Knowing whether stainless steel or titanium was used in a previous surgery can guide clinical decision making processes, but frequently the clinician has no way to know what type of metal was used. We describe the radiographic "shadow sign," in which superimposed titanium rods and screws remain radiolucent enough that the contour of the underlying components can be seen on a lateral radiograph, whereas superimposed stainless steel rods and screws are completely radiopaque. This technique was evaluated using a retrospective, randomized, and blinded radiographic comparison of titanium and stainless steel spinal instrumentation. The objective was to determine whether the "shadow sign" can reliably differentiate titanium from stainless steel spinal instrumentation. METHODS: Lateral radiographs from 16 cases of posterior spinal instrumentation (6 titanium, 6 stainless steel, and 2 replicates of each to assess intraobserver reliability) were randomly selected from a database of cases performed for pediatric scoliosis in a university setting from 2005 to 2009. The cases were randomized then shown to 19 orthopaedic surgery residents, 1 spine fellow, and 2 spine attendings. After the "shadow sign" was described, the surgeons were asked to determine what type of metal each implant was made of. RESULTS: The κ value for both stainless steel and titanium versus the gold standard was 0.83 [standard error (SE) = 0.053], indicating excellent agreement. The κ value for agreement between raters was 0.71 (SE = 0.016) and the κ value for agreement within raters was 0.70 (SE = 0.016), both of which indicated substantial agreement. CONCLUSIONS: The "shadow sign" can help a clinician differentiate titanium from stainless steel spinal instrumentation based on radiographic appearance alone. Furthermore, our study reveals that the level of experience in diagnosing spinal lateral radiographs also enhances the use of the "shadow sign" indicator. LEVEL OF EVIDENCE: The method proposed to differentiate titanium from stainless steel falls within the diagnostic studies domain. As unaltered randomization was used to enroll radiographs and the procedure was systematic, this study may be classified in the Level II category.

Influence of bending mode on the mechanical properties of nickel-titanium archwires and correlation to differential scanning calorimetry measurements.

INTRODUCTION: Nickel-titanium orthodontic archwires are used with bonded appliances for initial leveling. However, precise bending of these archwires is difficult and can lead to changes within the crystal structure of the alloy, thus changing the mechanical properties unpredictably. The aim of this study was to evaluate different bending methods in relation to the subsequent mechanical characteristics of the alloy. MATERIALS AND METHODS: The mechanical behaviors of 3 archwires (Copper NiTi 35°C [Ormco, Glendora, Calif], Neo Sentalloy F 80 [GAC International, Bohemia, NY], and Titanol Low Force [Forestadent, Pforzheim, Germany]) were investigated after heat-treatment in a dental furnace at 550-650°C, treatment with an electrical current (Memory-Maker, Forestadent), and cold forming. In addition, the change in A(f) temperature was registered by means of differential scanning calorimetry. RESULTS: Heat-treatment in the dental furnace as well as with the Memory-Maker led to widely varying force levels for each product. Cold forming resulted in similar or slightly reduced force levels when compared to the original state of the wires. A(f) temperatures were in general inversely proportional to force levels. CONCLUSIONS: Archwire shape can be modified by using either chair-side technique (Memory-Maker, cold forming) because the superelastic behavior of the archwires is not strongly affected. However it is important to know the specific changes in force levels induced for each individual archwire with heat-treatment. Cold forming resulted in more predictable forces for all products tested. Therefore, cold forming is recommended as a chair-side technique for the shaping of NiTi archwires.

Material-specific properties applied to an environmental risk assessment of engineered nanomaterials - implications on grouping and read-across concepts.

Engineered nanomaterials (ENMs) are intentionally designed in different nano-forms of the same parent material in order to meet application requirements. Different grouping and read-across concepts are proposed to streamline risk assessments by pooling nano-forms in one category. Environmental grouping concepts still are in their infancy and mainly focus on grouping by hazard categories. Complete risk assessments require data on environmental release and exposure not only for ENMs but also for their nano-forms. The key requirement is to identify and to distinguish the production volumes of the ENMs regarding nano-form-specific applications. The aim of our work was to evaluate whether such a grouping is possible with the available data and which influence it has on the environmental risk assessment of ENMs. A functionality-driven approach was applied to match the material-specific property (i.e. crystal form/morphology) with the functions employed in the applications. We demonstrate that for nano-TiO2, carbon nanotubes (CNTs), and nano-Al2O3 the total production volume can be allocated to specific nano-forms based on their functionalities. The differentiated assessments result in a variation of the predicted environmental concentrations for anatase vs. rutile nano-TiO2, single-wall vs. multi-wall CNTs and α- vs. γ-nano-Al2O3 by a factor of 2 to 13. Additionally, the nano-form-specific predicted no-effect concentrations for these ENMs were derived. The risk quotients for all nano-forms indicated no immediate risk in freshwaters. Our results suggest that grouping and read-across concepts should include both a nano-form release potential for estimating the environmental exposure and separately consider the nano-forms in environmental risk assessments.

The effect of surface treatment and clinical use on friction in NiTi orthodontic wires.

OBJECTIVES: Since the low friction of NiTi wires allows a rapid and efficient orthodontic tooth movement, the aim of this research was to investigate the friction and surface roughness of different commercially available superelastic NiTi wires before and after clinical use. The surface of all of the wires had been pre-treated by the manufacturer. MATERIALS: Forty superelastic wires (Titanol Low Force, Titanol Low Force River Finish Gold, Neo Sentalloy, Neo Sentalloy Ionguard) of diameter 0.016 x 0.022 in. were tested. The friction for each type of NiTi archwire ligated into a commercial stainless steel bracket was determined with a universal testing machine. Having ligated the wire into the bracket, it could then be moved forward and backwards along a fixed archwire whilst a torquing moment was applied. The surface roughness was investigated using a profilometric measuring device on defined areas of the wire. Statistical data analysis was conducted by means of the Wilcoxon test. RESULTS: The results showed that initially, the surface treated wires demonstrated significantly (p < 0.01) less friction than the non-treated wires. The surface roughness showed no significant difference between the treated and the non-treated surfaces of the wires. All 40 wires however showed a significant increase in friction and surface roughness during clinical use. SIGNIFICANCE: Whilst the Titanol Low Force River Finish Gold (Forestadent, Pforzheim, Germany) wires showed the least friction of all the samples and consequently should be more conservative on anchorage, the increase in friction of all the surface treated wires during orthodontic treatment almost cancels out this initial effect on friction. It is therefore recommended that surface treated NiTi orthodontic archwires should only be used once.

Micro-X-ray diffraction observation of nickel-titanium orthodontic wires in simulated oral environment.

A micro-X-ray diffraction (micro-XRD) technique has been employed to determine the phases in two superelastic nickel-titanium orthodontic wires that exhibit shape memory in the oral environment and one superelastic nickel-titanium wire that does not exhibit shape memory in vivo. The micro-XRD analyses were performed over the clinically relevant temperature range of 0-55 degrees C, which corresponds to the ingestion of cold and hot liquids, and both straight and bent (135 degrees ) test samples were analyzed. The results showed that for straight (as-received) test samples, the rhombohedral phase (R-phase) was definitely present in one shape memory wire product and perhaps in the other shape memory wire product, but was apparently absent in the superelastic wire product that did not display shape memory. Martensite was observed in all three wire products after bending. Phase transformations occurred with temperature changes simulating the oral environment for straight test samples of the two shape memory wires, but the micro-XRD pattern changed minimally with temperature for straight test samples of the superelastic wire and for bent test samples of all three wire products. The phase transformations revealed by micro-XRD were consistent with results recently found by temperature-modulated differential scanning calorimetry.

Biocompatibility of beta-stabilizing elements of titanium alloys.

In comparison to the presently used alpha + beta titanium alloys for biomedical applications, beta-titanium alloys have many advantageous mechanical properties, such as an improved wear resistance, a high elasticity and an excellent cold and hot formability. This will promote their future increased application as materials for orthopaedic joint replacements. Not all elements with beta-stabilizing properties in titanium alloys are suitable for biomaterial applications-corrosion and wear processes cause a release of these alloying elements to the surrounding tissue. In this investigation, the biocompability of alloying elements for beta- and near beta-titanium alloys was tested in order to estimate their suitability for biomaterial components. Titanium (grade 2) and the implant steel X2CrNiMo18153 (AISI 316 L) were tested as reference materials. The investigation included the corrosion properties of the elements, proliferation, mitochondrial activity, cell morphology and the size of MC3T3-E1 cells and GM7373 cells after 7 days incubation in direct contact with polished slices of the metals. The statistical significance was considered by Weir-test and Lord-test (alpha = 0.05). The biocompatibility range of the investigated metals is (decreasing biocompatibility): niobium-tantalum, titanium, zirconium-aluminium-316 L-molybdenum.

Attachment and proliferation of neonatal rat calvarial osteoblasts on Ti6Al4V: effect of surface chemistries of the alloy.

This study examined the cell attachment and proliferation of neonatal rat calvarial osteoblasts on Ti6Al4V alloy as affected by the surface modifications. The modifications could alter simultaneously the surface chemistries of the alloy (elemental difference of Ti, Al, V, Cu and Ni about 300-600mum thick examined by EDS) as well as the XPS nano-surface characteristics of oxides on the metal surface (chemistries of oxides, amphoteric OH group adsorbed on oxides, and oxide thickness). Three materials including two from modifications and a control were examined. It is argued that a slight change of the nano-surface characteristics of oxides as a result of the modifications neither alters the in vitro capability of Ca and P ion adsorption nor affects the metal ion dissolution behavior of the alloy. This implies that any influence on the cytocompatibility of the materials should only be correlated to the effect of surface chemistries of the alloy and the associated metal ion dissolution behavior of the alloy. The experimental results suggest that the cell response of neonatal rat calvarial osteoblasts on the Ti6Al4V alloy should neither be affected by the variation of surface chemistries of the alloy in a range studied.

In vitro MC3T3 osteoblast adhesion with respect to surface roughness of Ti6Al4V substrates.

This work investigates the role of the surface roughness of Ti6Al4V on the cell morphology, proliferation and adhesion, and in particular on the variation of the expression of cell adhesion proteins. Standardised test samples with five different surface preparations are used: sandblasted, 80, 1200, and 4000 grade polished, mirror polished. Surface roughness is analysed by Scanning Electron Microscopy and LASER Confocal Microscopy. Cell culture experiments are performed with MC3T3-E1 mouse osteoblasts after 3 days culture: proliferation rate, morphology and adhesion are assessed. The variations of expression of cell adhesion proteins are evidenced by indirect immune fluorescence method: actin from the cytoskeleton, vinculin from the focal adhesion complex, fibronectin and collagen I from the extracellular matrix. The results reveal a clear influence of surface roughness of Ti6Al4V on cell proliferation, morphology and adhesion. A significant correlation is established between surface roughness and cell growth. More the surface is smooth more the osteoblasts proliferate and appear spread out on the test samples. In addition, the expression of adhesion proteins varies with respect to the surface roughness. These results indicate a direct relationship between the decrease of cell adhesion and the increase of cell proliferation on mirror polished materials.

Cell orientation and cytoskeleton organisation on ground titanium surfaces.

A stable connection between the biomaterial surface and the surrounding tissue is one of the most important prerequisites for the long-term success of implants. Therefore, a strong adhesion of the cells on the biomaterial surface is required. Beside the surface composition the surface topography influences the properties of the adherent cells. The quality of the connection between the cell and the biomaterial is-among other factors-determined by the dimensions of the surface topography. Osteoblasts and fibroblast-like cells in contact with a ground biomaterial surface spread in the direction of the surface structures. These aligned cells provide a more favourable adhesion behaviour than a spherically shaped cell. To determine the influence of the surface structure on the cell alignment and cytoskeleton organisation or arrangement, substrate discs of cp-titanium were ground, producing different roughness of the substrates. The oriented cells had a higher density of focal contacts when they were in contact with the edges of the grooves and showed a better organisation of the cytoskeleton and stronger actin fibres. These changes of the aligned cells depend on the peak to valley height of the surface structures.

Measurement of the setting and thermal expansion of dental investments used for the superplastic forming of dental implant superstructures.

OBJECTIVES: The study examined the setting and thermal expansions of seven dental casting investments intended for use in the superplastic forming (SPF) of Ti6A14V for dental implant superstructures. The total expansion is compared with the coefficient of thermal expansion of the alloy. METHODS: The unrestricted setting expansion of the investment was measured at room temperature using a lined brass trough and dial gauge. The thermal expansion was measured at a heating rate of 5 degrees C/min up to 900 degrees C. The thermal expansion of Ti6A14V was measured at a heating rate of 15 degrees C/min. RESULTS: The Selevest investment had a small shrinkage on setting. The largest setting expansions were observed with Rema Exakt and Fujivest. Selevest DM and Fujivest had the greatest thermal expansions. Rema Exakt had the greatest overall expansion. The total expansion of Rematitan most closely matched the thermal expansion of Ti6A14V when the manufacturer's recommended special liquid to water ratio for crowns and bridges was used. SIGNIFICANCE: SPF is a novel technique which is being applied to the manufacture of dental prostheses. As dental casting investments are used to make the dies used for SPF the dimensional changes associated with these materials should be matched to the dimensional changes of the Ti6A14V alloy used in order to achieve a passive fit. This study has identified Rematitan as an investment whose total expansion may enable an accurately fitting SPF implant superstructure to be made.

Titanium casting: the surface reaction layer of castings obtained using ultra-low-temperature molds.

To examine whether the surface reaction layer of titanium castings can be reduced by lowering the mold temperature during casting, we cast titanium at three mold temperatures, including an ultra-low temperature produced by cooling the mold with liquid nitrogen, then measured the tensile strength and elongation of the castings. The titanium was cast using a centrifugal casting machine, and the molds were incinerated according to the manufacturers' instructions. Castings were then made with the molds at 200 degrees C, 600 degrees C, and an ultra-low temperature (-196 degrees C). The castability of titanium cast in the mold at the ultra-low temperature was good. The Vickers hardness near the surface layer of castings decreased as the mold temperature decreased.

Surface hardening by anodizing and heat treatments of Ti6Al4V alloys for articular prostheses.

This paper presents a study of the surface hardening of Ti6Al4V alloy produced by electrochemical anodizing and by different heat treatments, in addition to studying the annealing of the martensitic structure. Results of the combination of both methods produce hardening over 1300 HV and an important improvement on the tribological behaviour. These values could improve wear resistance of this alloy in applications like articular prostheses.

Cement bond strengths of titanium plates.

The success of the oral rehabilitation of implant patients depends not only on the osseointegration of implant fixtures but also on maintaining the integrity of the connection of prosthetic superstructures to these fixtures. It was an objective of the present study to evaluate and compare cement bond strengths among rolled (R), cast (C) and metal-injection-molded (M) commercially pure titanium plates which were bonded with Panavia 21 (Kuraray) and Imperva (Shofu) cements. Two plates (15x5x1 mm) of each R, C, and M were lap-jointed (lap length: 5 mm). The joints were stored in 37 degrees C distilled water for 24 h, followed by tensile tests with an INSTRON system under 1 mm/min crosshead speed. It was found that the bond strength of R with Panavia 21 (PAN) was 5.31 (SD:1.5) MPa and 2.30 (0.83) MPa with Imperva (IMP) cement. These were improved by applying an alloy primer to 7.08 (1.31) MPa and 6.72 (1.63) MPa, respectively. Using PAN with primer application, C and M samples showed bond strengths of 7.99 (1.31) and 7.20 (2.50) MPa, while they were 5.83 (2.15) and 6.79 (2.09) MPa using IMP with primer. There was a significant difference (p<0.01) between PAN and IMP cements for C samples. Additionally, samples were pre-oxidized at 100 degrees C in air for 10 min. Bond strengths of PAN with the primer were 5.69 (2.25), 9.14 (1.28), and 5.60 (3.13) MPa for R, C, and M sample groups. If the cement with the primer was applied immediately after the polishing (instead of pre-oxidized surfaces), bond strengths were improved to 9.14 (1.78) for R, 9.29 (1.85) for C, and 9.36 (1.81) MPa for M sample group. At p<0.05 level, there was a significant difference between surface pre-condition of R and M, but no significance with C.

In vitro evaluation of a multispecies oral biofilm on different implant surfaces.

Biofilm accumulation on implant surfaces is one of the most important factors for early and late implant failure. Because of the related clinical implications, the aim of this in vitro study was to compare the bacterial cell attachment of a four-species oral biofilm on titanium discs of purity grade 2 and 4, with machined surfaces and etched-thermochemically modified with Avantblast®. The in vitro biofilm model was composed of early (Actinomyces naeslundii, Streptococcus gordonii), secondary (Veillonella parvula), and intermediate (Fusobacterium nucleatum ssp. polymorphum) colonizers of tooth surfaces. A total of 36 discs were divided into four groups: Tigr2-c (titanium grade 2, machined surface), Tigr2-t (titanium grade 2, modified surface with Avantblast®), Tigr4-c (titanium grade 4, machined surface), Tigr4-t (titanium grade 4, modified surface with Avantblast®). The experiment was repeated three times. Biofilm viability was tested with 1% 2, 3, 5-triphenyltetrazolium chloride solution and bacterial cell quantification by checkerboard DNA-DNA hybridization. Descriptive analysis was performed to evaluate biofilm composition and differences between groups were checked with the Mann-Whitney test (p < 0.05). After one week, multispecies biofilms showed a similar pattern of bacterial composition on all analyzed implant surfaces. The most prevalent bacterium was V. parvula (∼50% of the total biomass), followed by S. gordonii (∼30%), F. nucleatum ssp. polymorphum (∼10%) and A. naeslundii (<5%). Total bacterial biomass was significantly higher in both grade-4-titanium surfaces (p < 0.05). The results demonstrated that not only implant surface treatment, but also titanium purity, influence early bacterial colonization.

Evaluation of the impact of raw materials on the fatigue and mechanical properties of ProFile Vortex rotary instruments.

INTRODUCTION: In this in vitro study, raw materials (including stainless steel, conventional superelastic nickel-titanium [NiTi], M-Wire NiTi, and Vortex Blue NiTi) were used to create ProFile Vortex designed 25/.06 instruments and subject these instruments to testing for fatigue resistance, torsional properties, flexibility, and Vickers microhardness. The comparative results in this study will enable the clinician's understanding of the performance of these materials for better choices in application during endodontic procedures. METHODS: Cyclic fatigue testing was performed by rotating files in an artificially constructed stainless steel canal with a 5-mm radius and a 90° angle of curvature at 500 rpm. Torsional properties and flexibility in bending were assessed according to specification ISO 3630-1. Vickers microhardness was measured on the cross section of instruments with 300-g load and 15-second dwell time. RESULTS: There were significant differences in the average fatigue life and flexibility for instruments made of different materials (P < .05). Vortex Blue was ranked first in both fatigue and flexibility, followed by M-Wire, superelastic wire, and stainless steel. For torsional strength and microhardness, stainless steel and M-Wire were ranked first and second, respectively. There was no statistically significant difference between superelastic wire and Vortex Blue. Vortex Blue showed the greatest distortion angle at break, whereas the other 3 materials showed comparable degree of rotation in the torque test. CONCLUSIONS: Under the limitations of this study, NiTi shape memory alloy appeared to be a superior material option compared with stainless steel for its use in the application of endodontic rotary instruments. Vortex Blue and M-Wire offered functional advantages over conventional superelastic NiTi. Vortex Blue showed improved fatigue resistance and flexibility compared with ProFile Vortex M-Wire.

Effect of environment on fatigue failure of controlled memory wire nickel-titanium rotary instruments.

INTRODUCTION: This study examined the fatigue behavior of 2 types of nickel-titanium (NiTi) instruments made from a novel controlled memory NiTi wire (CM wire) under various environment conditions. METHODS: Three conventional superelastic NiTi instruments of ProFile (Dentsply Maillefer, Ballaigues, Switzerland), Typhoon (Clinician's Choice Dental Products, New Milford, CT), and DS-SS0250425NEYY (Clinician's Choice Dental Products) and 2 new CM wire instruments of Typhoon CM and DS-SS0250425NEYY CM were subjected to rotational bending at the curvature of 35° in air, deionized water, 17% EDTA, or deionized water after immersion in 6% sodium hypochlorite for 25 minutes, and the number of revolutions of fracture (N(f)) was recorded. The fracture surface of all fragments was examined by a scanning electron microscope. The crack-initiation sites and the percentage of dimple area to the whole fracture cross-section were noted. RESULTS: Two new CM Wire instruments yielded an improvement of >4 to 9 times in N(f) than conventional NiTi files with the same design under various environments (P < .05). The fatigue life of 3 conventional superelastic NiTi instruments was similar under various environments, whereas the N(f) of 2 new CM Wire instruments was significantly longer in liquid media than in air (P < .05). The vast majority of CM instruments showed multiple crack origins, whereas most instruments made from conventional NiTi wire had one crack origin. The values of the area fraction occupied by the dimple region were significantly smaller on CM NiTi instruments than in conventional NiTi instruments under various environments (P < .05). CONCLUSIONS: Within the limitations of this study, the type of NiTi metal alloy (CM files vs conventional superelastic NiTi files) influences the cyclic fatigue resistance under various environments. The fatigue life of CM instruments is longer in liquid media than in air.

Research of online automatic titanium grade analyzer and method based on energy dispersive X-ray fluorescence technology.

An online automatic Ti-grade analyzer (OATGA), consisting of a (238)Pu source and a proportional counter, is designed for assuring product quality. The advantage of this system was its time-effectiveness; the entire monitoring process can be finished within approximately 5 min. This system has successfully solved some key analysis issues in titanium ore concentrate production process. The results obtained by feature measurements and chemical analysis were in agreement with each other. After two-year usage of OATGA at PANGANG, southwestern China, it was proved as a reliable method for online quality control in the production process of titanium ore concentrate.