Surface Roughness and Microhardness of Two Recent CAD/CAM-Materials After Storage

Objectives: To investigate surface roughness and microhardness of two recent resin-ceramic materials for computer-aided design/computer-aided manufacturing (CAD/CAM) after polishing with three polishing systems. Surface roughness and microhardness were measured immediately after polishing and after six months storage including monthly artificial toothbrushing. Methods: Sixty specimens of Lava Ultimate (3M ESPE) and 60 specimens of VITA ENAMIC (VITA Zahnfabrik) were roughened in a standardized manner and polished with one of three polishing systems (n=20/group): Sof-Lex XT discs (SOFLEX; three-step (medium-superfine); 3M ESPE), VITA Polishing Set Clinical (VITA; two-step; VITA Zahnfabrik), or KENDA Unicus (KENDA; one-step; KENDA Dental). Surface roughness (Ra; μm) was measured with a profilometer and microhardness (Vickers; VHN) with a surface hardness indentation device. Ra and VHN were measured immediately after polishing and after six months storage (tap water, 37°C) including monthly artificial toothbrushing (500 cycles/month, toothpaste RDA ~70). Ra- and VHN-values were analysed with nonparametric ANOVA followed by Wilcoxon rank sum tests (α=0.05). Results: For Lava Ultimate, Ra (mean [standard deviation] before/after storage) remained the same when polished with SOFLEX (0.18 [0.09]/0.19 [0.10]; p=0.18), increased significantly with VITA (1.10 [0.44]/1.27 [0.39]; p=0.0001), and decreased significantly with KENDA (0.35 [0.07]/0.33 [0.08]; p=0.03). VHN (mean [standard deviation] before/after storage) decreased significantly regardless of polishing system (SOFLEX: 134.1 [5.6]/116.4 [3.6], VITA: 138.2 [10.5]/115.4 [5.9], KENDA: 135.1 [6.2]/116.7 [6.3]; all p<0.0001). For VITA ENAMIC, Ra (mean [standard deviation] before/after storage) increased significantly when polished with SOFLEX (0.37 [0.18]/0.41 [0.14]; p=0.01) and remained the same with VITA (1.32 [0.37]/1.31 [0.40]; p=0.58) and with KENDA (0.81 [0.35]/0.78 [0.32]; p=0.21). VHN (mean [standard deviation] before/after storage) remained the same regardless of polishing system (SOFLEX: 284.9 [24.6]/282.4 [31.8], VITA: 284.6 [28.5]/276.4 [25.8], KENDA: 292.6 [26.9]/282.9 [24.3]; p=0.42-1.00). Conclusion: Surface roughness and microhardness of Lava Ultimate was more affected by storage and artificial toothbrushing than was VITA ENAMIC.

Microstructural and mechanical characterization of contemporary lingual orthodontic brackets.

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 Quiet Eye in Motor Performance and Learning – Functional and Theoretical Considerations

High precision in motor skill performance, in both sport and other domains (e.g. surgery and aviation), requires the efficient coupling of perceptual inputs (e.g. vision) and motor actions. A particular gaze strategy, which has received much attention within the literature, has been shown to predict both inter- (expert vs. novice) and intra-individual (successful vs. unsuccessful) motor performance (see Vine et al., 2014). Vickers (1996) labelled this phenomenon the quiet eye (QE) which is defined as the final fixation before the initiation of the crucial phase of movement. While the positive influence of a long QE on accuracy has been revealed in a range of different motor skills, there is a growing number of studies suggesting that the relationship between QE and motor performance is not entirely monotonic. This raises interesting questions regarding the QE’s purview, and the theoretical approaches explaining its functionality. This talk aims to present an overview of the issues described above, and to discuss contemporary research and experimental approaches to examining the QE phenomenon. In the first part of the talk Dr. Vine will provide a brief and critical review of the literature, highlighting recent empirical advancements and potential directions for future research. In the second part, Dr. Klostermann will communicate three different theoretical approaches to explain the relationship between QE and motor performance. Drawing upon aspects of all three of these theoretical approaches, a functional inhibition role for the QE (related to movement parameterisation) will be proposed.

Analyses of the Erosive Effect of Dietary Substances and Medications on Deciduous Teeth.

This study aimed at analysing the erosive potential of 30 substances (drinks, candies, and medicaments) on deciduous enamel, and analyse the associated chemical factors with enamel dissolution. We analysed the initial pH, titratable acidity (TA) to pH 5.5, calcium (Ca), inorganic phosphate (Pi), and fluoride (F) concentration, and degree of saturation ((pK -pI)HAP, (pK -pI)FAP, and (pK-pI)CaF2) of all substances. Then, we randomly distributed 300 specimens of human deciduous enamel into 30 groups (n = 10 for each of the substances tested. We also prepared 20 specimens of permanent enamel for the sake of comparison between the two types of teeth, and we tested them in mineral water and Coca-Cola®. In all specimens, we measured surface hardness (VHN: Vickers hardness numbers) and surface reflection intensity (SRI) at baseline (SHbaseline and SRIbaseline), after a total of 2 min (SH2min) and after 4 min (SH4min and SRI4min) erosive challenges (60 ml of substance for 6 enamel samples; 30°C, under constant agitation at 95 rpm). There was no significant difference in SHbaseline between deciduous and permanent enamel. Comparing both teeth, we observed that after the first erosive challenge with Coca-Cola®, a significantly greater hardness loss was seen in deciduous (-90.2±11.3 VHN) than in permanent enamel (-44.3±12.2 VHN; p = 0.007), but no differences between the two types of teeth were observed after two challenges (SH4min). After both erosive challenges, all substances except for mineral water caused a significant loss in relative surface reflectivity intensity, and most substances caused a significant loss in surface hardness. Multiple regression analyses showed that pH, TA and Ca concentration play a significant role in initial erosion of deciduous enamel. We conclude that drinks, foodstuffs and medications commonly consumed by children can cause erosion of deciduous teeth and erosion is mainly associated with pH, titratable acidity and calcium concentration in the solution.

Einfluss von Politursystemen auf Oberflächenrauigkeit und mechanische Eigenschaften von CAD/CAM-Materialien

Zielsetzung: Das Ziel dieser Studie war, den Einfluss von drei Politursystemen auf die Oberflächenrauigkeit von verschiedenen Materialien für computer-aided design/computer-aided manufacturing (CAD/CAM) Restaurationen mittels Profilometrie sowie die mikromechanischen Eigenschaften der Materialien mittels Mikrohärtemessgerät zu analysieren. Materialien und Methoden: Von dem CAD/CAM-Kompositmaterial Paradigm MZ100 (3M ESPE), der CAD/CAM-Feldspatkeramik VITABLOCS Mark II (VITA Zahnfabrik) und den CAD/CAM-Hybridmaterialien Lava Ultimate (3M ESPE), VITA ENAMIC (VITA Zahnfabrik) und AMBARINO High-Class (Creamed) wurden je 60 Prüfkörper zugeschnitten, gekennzeichnet und standardisiert aufgerauht. Die standardisierte Aufrauhung wurde mit Baseline-Rauigkeitsmessungen überprüft (Ra und Rz; µm). Die Prüfkörper wurden mit einem von drei Politursystemen poliert (n=20 pro CAD/CAM-Material): 1) Sof-Lex Scheiben (Disc-System, 3 Politurschritte: medium, fein und superfein; 3M ESPE), 2) VITA Polishing Set Clinical (Silikonpolitursystem, 2 Politurschritte: medium und fein; VITA Zahnfabrik) oder 3) KENDA Nobilis (Silikonpolierer, 1 Politurschritt (universal); KENDA Dental). Nach Politur der Prüfkörper wurden Ra und Rz sowie die mikromechanischen Eigenschaften Oberflächenhärte (VHN; Vickers Härte) und Elastizitätsmodul (EM; GPa) gemessen. In den darauf folgenden sechs Monaten wurden die Prüfkörper in Leitungswasser gelagert und insgesamt sechs Mal einem maschinellem Zahnbürsten zugeführt. Anschliessend wurden erneut Ra und Rz sowie VHN und EM gemessen. Ra-, Rz-, VHN- und EM-Werte wurden mittels nichtparametrischer ANOVA global analysiert und die p-Werte mittels Bonferroni-Holm Korrektur für multiples Testen korrigiert. Als post-hoc Tests wurden Kruskal-Wallis-Tests sowie exakte Wilcoxon Rangsummen-Tests verwendet und die p-Werte wurden nicht korrigiert. Das Signifikanzniveau wurde auf α=0,05 festgelegt. Resultate: Für alle drei CAD/CAM-Hybridmaterialien ergaben Sof-Lex Scheiben nach der Politur die tiefste Oberflächenrauigkeit (d. h. die tiefsten Ra- und Rz-Werte), gefolgt von KENDA Nobilis und von dem VITA Polishing Set Clinical. Bei dem CAD/CAM-Kompositmaterial sowie bei der CAD/CAM-Feldspatkeramik ergaben Sof-Lex Scheiben und KENDA Nobilis ähnliche Resultate, gefolgt von dem VITA Polishing Set Clinical. Bei einigen CAD/CAM-Materialien zeigten sich – zum Teil in Abhängigkeit des Politursystems – nach maschinellem Zahnbürsten und Lagerung signifikant höhere Ra- und Rz-Werte. Die CAD/CAM-Materialien zeigten unabhängig des Politursystems und der Lagerung signifikant verschiedene VHN- und EM-Werte. Bei einigen CAD/CAM-Materialien zeigten sich – zum Teil ebenfalls in Abhängigkeit des Politursystems – nach maschinellem Zahn-bürsten und Lagerung signifikant tiefere VHN- und EM-Werte. Schlussfolgerungen: Die Wahl des Politursystems beeinflusste die Oberflächenrauigkeit der CAD/CAM-Materialien markant, wobei Sof-Lex Scheiben insgesamt die besten Politurresultate zeigten, gefolgt von dem Silikonpolierer KENDA Nobilis. Von der Verwendung des Silikonpolitursystems VITA Polishing Set Clinical muss eher abgeraten werden. Das CAD/CAM-Kompositmaterial Paradigm MZ100 und die CAD/CAM-Hybridmaterialien Lava Ultimate und AMBARINO High-Class als weichere und elastischere Materialien liessen sich insgesamt besser polieren, waren aber bezüglich mechanischer Eigenschaften anfälliger auf Lagerung als die härtere CAD/CAM-Feldspatkeramik VITABLOCS Mark II und das CAD/CAM-Hybridmaterial VITA ENAMIC.

Determinación de la microdureza de la dentina coronaria previamente acondicionada

La dureza es una de las propiedades utilizadas para comparar tanto los materiales restauradores como los tejidos biológicos. El objetivo de este trabajo es determinar la microdureza de la dentina coronaria en dientes sin acondicionar y luego acondicionados con EDTA al 17%. Para este estudio se seleccionaron 30 muestras de dentina de dientes recientemente extraídos. Los elementos fueron seccionados longitudinalmente con discos de diamante de doble corte (Horico), con abundante refrigeración acuosa, a nivel coronario, y serán conservados en saliva artificial (laboratorio NAF) a 37°C. La medición de la microdureza dentinaria se realizó con un microdurómetro Vickers, con una carga de 50g durante 30 s. Los datos fueron recolectados en una planilla ad hoc y procesados estadísticamente mediante el Test de Student.

Shotgun proteomics reveals physiological response to ocean acidification in Crassostrea gigas

Background. Ocean acidification as a result of increased anthropogenic CO2 emissions is occurring in marine and estuarine environments worldwide. The coastal ocean experiences additional daily and seasonal fluctuations in pH that can be lower than projected end of century open ocean pH reductions. Projected and current ocean acidification have wide-ranging effects on many aquatic organisms, however the exact mechanisms of the impacts of ocean acidification on many of these animals remains to be characterized. Methods. In order to assess the impact of ocean acidification on marine invertebrates, Pacific oysters (Crassostrea gigas) were exposed to one of four different pCO2 levels for four weeks: 400 µatm (pH 8.0), 800 µatm (pH 7.7), 1000 µatm (pH 7.6), or 2800 µatm (pH 7.3). At the end of 4 weeks a variety of physiological parameters were measured to assess the impacts of ocean acidification: tissue glycogen content and fatty acid profile, shell micromechanical properties, and response to acute heat shock. To determine the effects of ocean acidification on the underlying molecular physiology of oysters and their stress response, some of the oysters from 400 µatm and 2800 µatm were exposed to an additional mechanical stress and shotgun proteomics were done on oysters from high and low pCO2 and from with and without mechanical stress. Results. At the end of the four week exposure period, oysters in all four pCO2 environments deposited new shell, but growth rate was not different among the treatments. However, micromechanical properties of the new shell were compromised by elevated pCO2. Elevated pCO2 affected neither whole body fatty acid composition, nor glycogen content, nor mortality rate associated with acute heat shock. Shotgun proteomics revealed that several physiological pathways were significantly affected by ocean acidification, including antioxidant response, carbohydrate metabolism, and transcription and translation. Additionally, the proteomic response to a second stress differed with pCO2, with numerous processes significantly affected by mechanical stimulation at high versus low pCO2 (all proteomics data are available in the ProteomeXchange under the identifier PXD000835). Discussion. Oyster physiology is significantly altered by exposure to elevated pCO2, indicating changes in energy resource use. This is especially apparent in the assessment of the effects of pCO2 on the proteomic response to a second stress. The altered stress response illustrates that ocean acidification may impact how oysters respond to other changes in their environment. These data contribute to an integrative view of the effects of ocean acidification on oysters as well as physiological trade-offs during environmental stress.

Seawater carbonate chemistry and biological processes of oysters Crassostrea virginica during experiments, 2010

Estuarine organisms are exposed to periodic strong fluctuations in seawater pH driven by biological carbon dioxide (CO2) production, which may in the future be further exacerbated by the ocean acidification associated with the global rise in CO2. Calcium carbonate-producing marine species such as mollusks are expected to be vulnerable to acidification of estuarine waters, since elevated CO2 concentration and lower pH lead to a decrease in the degree of saturation of water with respect to calcium carbonate, potentially affecting biomineralization. Our study demonstrates that the increase in CO2 partial pressure (pCO2) in seawater and associated decrease in pH within the environmentally relevant range for estuaries have negative effects on physiology, rates of shell deposition and mechanical properties of the shells of eastern oysters Crassostrea virginica (Gmelin). High CO2 levels (pH ~7.5, pCO2 ~3500 µatm) caused significant increases in juvenile mortality rates and inhibited both shell and soft-body growth compared to the control conditions (pH ~8.2, pCO2 ~380 µatm). Furthermore, elevated CO2 concentrations resulted in higher standard metabolic rates in oyster juveniles, likely due to the higher energy cost of homeostasis. The high CO2 conditions also led to changes in the ultrastructure and mechanical properties of shells, including increased thickness of the calcite laths within the hypostracum and reduced hardness and fracture toughness of the shells, indicating that elevated CO2 levels have negative effects on the biomineralization process. These data strongly suggest that the rise in CO2 can impact physiology and biomineralization in marine calcifiers such as eastern oysters, threatening their survival and potentially leading to profound ecological and economic impacts in estuarine ecosystems.

Ground-penetrating radar (GPR) point measurements of ice thickness in Austria

Glacier thickness is an important factor in the course of glacier retreat in a warming climate. Thiese study data presents the results (point data) of GPR surveys on 66 Austrian mountain glaciers carried out between 1995 and 2014. The glacier areas range from 0.001 to 18.4 km**2, and their ice thickness has been surveyed with an average density of 36 points/km**2 . The glacier areas and surface elevations refer to the second Austrian glacier inventory (mapped between 1996 and 2002). According to the glacier state recorded in the second glacier inventory, the 64 glaciers cover an area of 223.3±3.6 km**3. Maps of glacier thickness have been calculated by Fischer and Kuhn (2013) with a mean thickness of 50±3 m and contain an glacier volume of 11.9±1.1 km**3. The mean maximum ice thickness is 119±5 m. The ice thickness measurements have been carried out with the transmitter of Narod and Clarke (1994) combined with restively loaded dipole antennas (Wu and King, 1965; Rose and Vickers, 1974) at central wavelengths of 6.5 (30 m antenna length) and 4.0 MHz (50 m antenna length). The signal was recorded trace by trace with an oscilloscope. 168 m/µs as used by Haeberli et al. (1982), Bauder (2001), and Narod and Clarke (1994), the signal velocity in air is assumed to be 300 m/µs. Details on the method can be are found in Fischer and Kuhn (2013), as well as Span et al. (2005) and Fischer et al. (2007).

Nanoindentation of Bridgman YBCO samples

In this study, the mechanical properties of YBa2Cu3O7−x, obtained by the Bridgman technique, were examined using a Berkovich tip indenter on the basal plane (0 0 1). Intrinsic hardness was measured by nanoindentation tests and corrected using the Nix and Gao model for this material. Furthermore, Vickers hardness tests were performed, in order to determine the possible size effect on these measurements. The results showed an underestimation of the hardness value when the tests were performed with large loads. Moreover, the elastic modulus of the Bridgman samples was 128 ± 5 GPa. Different residual imprints were visualised by atomic force microscopy and a focused ion beam, in order to observe superficial and internal fracturing. Mechanical properties presented a considerable reduction at the interface. This effect could be attributed to internal stress generated during the texturing process. In order to corroborate this hypothesis, an observation using transmission electron microscopy was performed.

Flow and fracture behaviour of FV535 steel at different triaxialities, strain rates and temperatures

The new generation jet engines operate at highly demanding working conditions. Such conditions need very precise design which implies an exhaustive study of the engine materials and behaviour in their extreme working conditions. With this purpose, this work intends to describe a numerically-based calibration of the widely-used Johnson–Cook fracture model, as well as its validation through high temperature ballistic impact tests. To do so, a widely-used turbine casing material is studied. This material is the Firth Vickers 535 martensitic stainless steel. Quasi-static tensile tests at various temperatures in a universal testing machine, as well as dynamic tests in a Split Hopkinson Pressure Bar, are carried out at different triaxialities. Using ABAQUS/Standard and LS-DYNA numerical codes, experimental data are matched. This method allows the researcher to obtain critical data of equivalent plastic strain and triaxility, which allows for more precise calibration of the Johnson–Cook fracture model. Such enhancement allows study of the fracture behaviour of the material across its usage temperature range.

Comportamiento mecánico de la aleación W+1%Y2O3 en función de la atmósfera y la temperatura

Mediante ensayos de flexión en tres puntos se compara y evalúa el comportamiento mecánico de la aleación W- 1wt%Y2O3 con el W puro fabricados ambos mediante HIP. Se ha obtenido la tenacidad de fractura, la resistencia a flexión y el límite elástico en atmósfera oxidante y de vacío en un intervalo de temperaturas comprendido entre -196 ºC, ensayos de inmersión en nitrógeno líquido, y 1200 ºC. Previamente, se ha medido la densidad, la dureza mediante ensayos Vickers y el módulo de elasticidad dinámico de los materiales. Además, la dureza y el módulo de elasticidad se han comparado con los obtenidos mediante ensayos instrumentados de nanoindentación. Finalmente se ha realizado un pequeño estudio de las superficies de fractura de las muestras ensayadas mediante microscopía electrónica de barrido para poder relacionar el modo de rotura de los materiales y las propiedades mecánicas macroscópicas con los micromecanismos de fallo involucrados en función de la temperatura.

Microestructura y propiedades mecánicas del material masivo superconductor YBCO a 300 Y 77 K.

En este trabajo se realiza una caracterización mecánica y microestructural del material masivo superconductor YBCO. El material ha sido procesado mediante dos técnicas distintas, Top-Seeding Melt Growth (TSMG) y Bridgman, y este estudio profundiza en el efecto de la microestructura, el método de procesado y la temperatura de ensayo en el comportamiento mecánico de material. Con el fin de conseguir un amplio conocimiento de sus propiedades mecánicas se han realizado ensayos de resistencia a flexión, tenacidad de fractura y dureza Vickers a 300 y 77 K. Asimismo, se llevaron a cabo ensayos de nanoindentación y el tamaño crítico del defecto semielíptico. Los resultados obtenidos muestran que el comportamiento mecánico de los dos materiales está controlado por defectos y grietas, introducidas durante el procesado. También se ha encontrado un buen acuerdo entre el tamaño del defecto critico detectado experimentalmente con los valores obtenidos mediante de análisis de mecánica de fractura.

Laser shock peening without absorbent coating (LSPwC) effect on 3D surface topography and mechanical properties of 6082-T651 Al alloy

The influence of nanosecond laser pulses applied by laser shock peening without absorbent coating (LSPwC) with a Q-switched Nd:YAG laser operating at a wavelength of λ = 1064 nm on 6082-T651 Al alloy has been investigated. The first portion of the present study assesses laser shock peening effect at two pulse densities on three-dimensional (3D) surface topography characteristics. In the second part of the study, the peening effect on surface texture orientation and micro-structure modification, i.e. the effect of surface craters due to plasma and shock waves, were investigated in both longitudinal (L) and transverse (T) directions of the laser-beam movement. In the final portion of the study, the changes of mechanical properties were evaluated with a residual stress profile and Vickers micro-hardness through depth variation in the near surface layer, whereas factorial design with a response surface methodology (RSM) was applied. The surface topographic and micro-structural effect of laser shock peening were characterised with optical microscopy, InfiniteFocus® microscopy and scanning electron microscopy (SEM). Residual stress evaluation based on a hole-drilling integral method confirmed higher compression at the near surface layer (33 μm) in the transverse direction (σmin) of laser-beam movement, i.e. − 407 ± 81 MPa and − 346 ± 124 MPa, after 900 and 2500 pulses/cm2, respectively. Moreover, RSM analysis of micro-hardness through depth distribution confirmed an increase at both pulse densities, whereas LSPwC-generated shock waves showed the impact effect of up to 800 μm below the surface. Furthermore, ANOVA results confirmed the insignificant influence of LSPwC treatment direction on micro-hardness distribution indicating essentially homogeneous conditions, in both L and T directions.