White Light Confocal Microscopy Research Articles

Clinical comparison of marginal fit of ceramic inlays between digital and conventional impressions.

The aim of this stuldy was to compare the clinical marginal fit of CAD-CAM inlays obtained from intraoral digital impression or addition silicone impression techniques. The study included 31 inlays for prosthodontics purposes of 31 patients: 15 based on intraoral digital impressions (DI group); and 16 based on a conventional impression technique (CI group). Inlays included occlusal and a non-occlusal surface. Inlays were milled in ceramic. The inlay-teeth interface was replicated by placing each inlay in its corresponding uncemented clinical preparation and taking interface impressions with silicone material from occlusal and free surfaces. Interface analysis was made using white light confocal microscopy (WLCM) (scanning area: 694 × 510 µm2) from the impression samples. The gap size and the inlay overextension were measured from the microscopy topographies. For analytical purposes (i.e., 95-%-confidence intervals calculations and P-value calculations), the procedure REGRESS in SUDAAN was used to account for clustering (i.e., multiple measurements). For p-value calculation, the log transformation of the dependent variables was used to normalize the distributions. Marginal fit values for occlusal and free surfaces were affected by the type of impression. There were no differences between surfaces (occlusal vs. free). Gap obtained for DI group was 164 ± 84 µm and that for CI group was 209 ± 104 µm, and there were statistical differences between them (p = .041). Mean overextension values were 60 ± 59 µm for DI group and 67 ± 73 µm for CI group, and there were no differences between then (p = .553). Digital impression achieved inlays with higher clinical marginal fit and performed better than the conventional silicone materials.

Observation of Catalyst Layer Structure Formation from Electrode Slurry By White Light Confocal Microscopy

Mass transport in the catalyst layers (CLs) is an important factor to improve the cell performance of polymer electrolyte fuel cells (PEFCs). Transport properties in the CLs are determined by their structure and material distributions. The CLs are usually fabricated from electrode slurry in which Pt/C and ionomer are contained through applying and drying processes. Therefore, the structure and material distributions in the CLs are determined in these fabrication processes. However, these fabrication processes have been developed through trial-and-error approaches. A fundamental understanding of the structure formation mechanisms during the fabrication processes is required.The authors have performed impedance measurement and surface displacement measurement of electrode slurry during the drying process at the same time and detected the particle packing process (1, 2). For a further understanding of the fabrication process, observation of the structure formation of electrode slurry during drying by white light confocal microscopy was conducted in this study to break down the structure formation regimes. The observation of flow mode on the surface of the slurry and measurement of surface displacement were performed at the same time.Figure 1 shows confocal images of the electrode slurry during drying. Three different regimes were observed. At the initial state of drying, convection flow was observed. Then, the shrinking of the slurry was observed. After shrinking stopped, the solvent was evaporated from the porous media and finally, the structure of the catalyst layer was formed. Understanding the relationships between the variation of the flow regimes during the drying of electrode slurry and fabrication conditions including materials and process parameters can contribute to revealing the methodology for controlling porous structure and material distributions in the catalyst layers.AcknowledgmentsA part of this work was supported by JST PRESTO JPMJPR22O4.References(1) T. Suzuki et al., ECS Trans., 67(17), 465 (2015).(2) T. Suzuki et al., J. Therm. Sci. Technol., 16(1), 20-00259 (2021). Figure 1

Behavioral strategies of prehistoric and historic children from dental microwear texture analysis

IntroductionReconstructing the dietary and behavioral strategies of our hominin ancestors is crucial to understanding their evolution, adaptation, and overall way of life. Teeth in general, and dental microwear specifically, provide a means to examine these strategies, with posterior teeth well positioned to tell us about diet, and anterior teeth helping us examine non-dietary tooth-use behaviors. Past research predominantly focused on strategies of adult individuals, leaving us to wonder the role children may have played in the community at large. Here we begin to address this by analyzing prehistoric and historic children through dental microwear texture analysis of deciduous anterior teeth.Materials and MethodsFour sample groups were used: Neandertals (N = 8), early modern humans (N = 14), historic Egyptians from Amarna (N = 19) and historic high-Arctic Inuit from Point Hope, Alaska (N = 6). Anterior deciduous teeth were carefully cleaned, molded, and cast with high-resolution materials. Labial surfaces were scanned for dental microwear textures using two white-light confocal microscopes at the University of Arkansas, and a soft filter applied to facilitate data comparisons.Results and DiscussionResults show that dental microwear texture analysis successfully differentiated the samples by all texture variables examined (anisotropy, complexity, scale of maximum complexity, and two variants of heterogeneity). Interestingly, the Neandertal and Point Hope children had similar mean values across all the texture variables, and both groups were significantly different from the Amarna, Egyptian children. These differences suggest diversity in abrasive load exposure and participation in non-dietary anterior tooth-use behaviors. Further analyses and an expanded sample size will help to strengthen the data presented here, but our results show that some prehistoric and historic children took part in similar behaviors as their adult counterparts.

Microstructure, surface topography and mechanical properties of slip cast and powder injection moulded microspecimens made of zirconia

Abstract Investigations on ceramic microspecimens made of Y2O3- stabilized ZrO2 produced by slip casting or micro powder injection moulding are introduced. During the production of the microspecimens, feedstocks and sintering conditions were varied. Differently moulded specimens were examined with respect to their microstructure and surface topography using light microscopy, scanning electron microscopy (SEM) and confocal white light microscopy. Additionally, the mechanical characteristics were investigated by three-point bending tests using a micro universal testing device. The statistical analysis was realised by means of the Weibull theory and interpreted by the aid of SEM images of fracture surfaces. This research allowed to understand correlations between different feedstocks used, process parameters like the sintering conditions applied and the resulting characteristics as well as material properties of the microspecimens. These results could be used to improve the production process.

Application of microreactor technology to dehydration of bio-ethanol

Dehydration and etherification of bio-ethanol was studied in a microreactor using γ-alumina, H-Beta-38 and Sn-Beta-38 as catalysts. An extensive series of kinetic experiments was carried out in the microreactor device operating at ambient pressure and temperatures 225–325 °C.The H-Beta-38 catalyst coated microplates exhibited the highest production rate of ethene. While the fresh H-Beta-38 catalyst allowed complete conversion of ethanol and 98% selectivity towards ethene, the catalyst deactivated significantly with time-on-stream. Diethyl ether was the dominating co-product, whereas trace amounts of acetaldehyde were detected in the experiments.Based on the kinetic studies, thermodynamic analysis and catalyst characterization results obtained with SEM-EDX, TEM, nitrogen physisorption, FTIR-Pyridine and white light confocal microscopy, a surface reaction mechanism was proposed. The fundamental hypothesis of the reaction mechanism was the co-existence of two kinds of active sites on the catalyst surface, namely the Brønsted sites promoting dehydration and the Lewis sites responsible for etherification. The Brønsted sites deactivate, whereas the Lewis sites are more stable, which leads to a shift of the product distribution during long-term experiments, from ethene to diethyl ether. The rate equations were implemented in the microreactor model. The kinetic and adsorption parameters included in the model were estimated by non-linear regression analysis. The experimental data were satisfactorily described by the proposed mechanism. The work demonstrated that microreactors are strong tools in the determination of catalytic kinetics and catalyst durability.

Fabrication of super-hydrophobic and highly oleophobic Ti-6Al-4 V surfaces by a hybrid method

In this study, the super-hydrophobic and highly oleophobic surfaces were fabricated on Ti-6Al-4V substrate by a hybrid method, which combined laser texturing followed by silanization treatment. To fabricate super-hydrophobic and oleophobic surfaces more accurately and effectively, three series of experiments have been carried out to determine the laser parameters for the fabrication of surfaces with the best wettability. Surface wettability was assessed by water contact angle, glycerin contact angle and the n-hexadecane contact angle. To investigate the laser texturing microstructure features and effects thereof on wettability, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and white light confocal scanning microscopy measurements were utilized to characterize the modifications of morphologic, chemical compositions and 3D profiles. The surface with best wettability presented a water contact angle of 153.3°, glycerin contact angle of 149.7°, and n-hexadecane contact angle of 136.6° was successfully achieved by setting the laser parameters to: distance between adjacent laser passes at 60 μm, output power at 12 W and scanning speed at 300 mm/s. The effect of corrosion and abrasion on wettability was also evaluated. Stability tests prove that the super-hydrophobic and oleophobic surfaces possess corrosion/abrasion resistance and good chemical and mechanical stability.

Investigation of Effects of Acid, Alkali, and Salt Solutions on Fluorinated Superhydrophobic Surfaces

Extensive studies have been carried out to investigate the stability of superhydrophobic surfaces under acid, alkali, and salt solutions. It is noted that previous literature studies just demonstrated a variety of experimental phenomena. However, very few works have focused on the protection mechanism or failure mechanism of fluorinated superhydrophobic surfaces from the perspective of chemical aspects. Herein, this paper aims to investigate the effects of acid, alkali, and salt solutions on the stability of fluorinated superhydrophobic surfaces, and the anticorrosion/corrosion mechanism will be further proposed. The superhydrophobic coating was obtained on silicon substrates by laser surface texturing followed by fluoroalkyl silane modification. The resultant surfaces presented a water contact angle (WCA) of 157.6 ± 0.4° with a small water sliding angle (WSA) of 1.3 ± 0.3°. The newly fabricated superhydrophobic surfaces were then immersed in different concentrations of corrosive solutions (acid, alkali, and salt solutions). The revolution of surface wettability and surface morphology on treated silicon surfaces was evaluated through WCAs, scanning electron microscopy, and white light confocal microscopy. The results indicate that the hydrogen ions (H+) played a positive role in the retention of superhydrophobicity. However, the hydroxyl (OH-) and chloride ions (Cl-) presented the negative influence. The protection mechanism or corrosion mechanism under different solutions was proposed based on the X-ray photoelectron spectroscopy results. In addition, the potentiodynamic polarization and electrochemical impedance spectroscopy measurements provided strong support in data and were conducted to verify the rationality of the proposed mechanism.

Modelling the surface roughness influence on the hole expansion ratio of multiphase steel

There exist both extrinsic manufacturing process-related and intrinsic material-immanent effects on the edge crack sensitivity of dualphase steels. Extrinsic influences can be further divided into effects of residual damage as well as roughness-induced effects. A new simulation framework is applied to quantitatively assess the surface roughness-induced influences on the edge crack sensitivity of cold rolled dualphase steel of grade DP1000. Hole expansion ratios are numerically predicted for four different edge manufacturing processes, including drilling, milling, waterjet cutting, and wire cutting. The simulation framework applies the idea to make use of a ductile damage mechanics model. It employs realistic material parameters for all elements situated in the bulk, whereas those elements situated at the edge to be expanded during the test apply artificial model parameters. These are identified with the help of sub-models with geometrical surface representation. For the sub-model construction, roughness profiles are experimentally characterized by white light confocal microscopy. With the new simulation framework, numerical predictions of hole expansion ratios can be significantly improved, even though a remarkable overestimation still remains. Among others, this general overestimation can be attributed to local strain hardening, residual stresses, and microstructural modifications.

Influence of topography on the scratch and mar visibility resistance of randomly micro-textured surfaces

In this research, the influence of the macro- and micro-topography on randomly micro-textured polypropylene surfaces has been studied. An initial characterization of the underlying surface was carried out using three-dimensional (3D) technologies such as chromatic and white light confocal microscopy. A multi-scale analysis methodology was employed for analysing the surface at either macro- or micro-scales. Among others, topographic characteristics such as peak-to-valley symmetry and the amount of micro-asperities were analysed to quantitatively determine the scratch and mar visibility resistance. The results show that surfaces with higher symmetry in their functional height distributions yield lower lightness variation (ΔL*) between the scratch pattern and its residual background height (RBH). This allows for a better suitability in hiding the scratch damage. On the other hand, topographies with less amount of micro-asperities on top of the texture provided a better mar resistance. In these cases, deformation mechanisms such as ironing are minimized, resulting in a lower gloss variation and lower contrast between the damaged area and its surroundings.

Fabrication of controllable wettability of crystalline silicon surfaces by laser surface texturing and silanization

This paper aims to explore the effects of laser surface texturing and chemical modifications by silanization on the wettability of silicon surfaces. To effectively prepare super-hydrophobic surfaces on silicon, a process using laser texturing with following silanization treatment is used to modify the surface. The surface wettability is evaluated by water contact angle (WCA). To ascertain the effect of laser texturing on wettability, the morphological and metallurgical modifications of the surface were investigated by scanning electron microscopy (SEM), white light confocal microscope and X-ray photoelectron spectroscopy (XPS). It is found that the fresh laser-processed silicon surface is super-hydrophilic, which is in line with the Wenzel model. A super-hydrophobic surface with a WCA >150° was successfully obtained after silanization treatment. Silanization by a concentration of 0.72 wt% 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane with 2 h of immersion time was found to be the most effective condition for achieving super-hydrophobic silicon surfaces. The effects of acids, alkalis and salts on wettability have also been assessed. The results indicate that as-prepared silicon samples with a fluoride coating can be normally used in acid condition but not suitable for use in alkaline and salty environments.

Water-Repellent Fluoropolymer-Based Coatings

Fluoropolymer-based coatings are widely used for release applications. However, these hydrophobic surfaces do not reveal a significantly low adhesion. Water repellency incorporated to fluoropolymer coatings might enhance their release performance. In this work, we focused on the surface texturing of a well-known polytetrafluoroethylene (PTFE)-based coating. We explored as texturing routes: sanding, sandblasting and laser ablation. We examined the surface roughness with white light confocal microscopy and the surface morphology with environmental scanning electron microscopy (ESEM). Water-repellent fluoropolymer coatings were reproduced in all cases, although with different degree, parametrized with bounces of water drops (4–5 μL). Laser ablation enabled the lowest adhesion of coatings with 24 ± 2 bounces. This result and the current development of laser patterning for industry assure the incipient use of laser ablation for release coatings.

Micro-Magnetic and Microstructural Characterization of Wear Progress on Case-Hardened 16MnCr5 Gear Wheels.

The evaluation of wear progress of gear tooth flanks made of 16MnCr5 was performed using non-destructive micro-magnetic testing, specifically Barkhausen noise (BN) and incremental permeability (IP). Based on the physical interaction of the microstructure with the magnetic field, the micro-magnetic characterization allowed the analysis of changes of microstructure caused by wear, including phase transformation and development of residual stresses. Due to wide parameter variation and application of bandpass filter frequencies of micro-magnetic signals, it was possible to indicate and separate the main damage mechanisms considering the wear development. It could be shown that the maximum amplitude of BN correlates directly with the profile form deviation and increases with the progress of wear. Surface investigations via optical and scanning electron microscopy indicated strong surface fatigue wear with micro-pitting and micro-cracks, evident in cross-section after 3 × 105 cycles. The result of fatigue on the surface layer was the decrease of residual compression stresses, which was indicated by means of coercivity by BN-analysis. The different topographies of the surfaces, characterized via confocal white light microscopy, were also reflected in maximum BN-amplitude. Using complementary microscopic characterization in the cross-section, a strong correlation between micro-magnetic parameters and microstructure was confirmed and wear progress was characterized in dependence of depth under the wear surface. The phase transformation of retained austenite into martensite according to wear development, measured by means of X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) was also detected by micro-magnetic testing by IP-analysis.

A numerical approach to evaluate roughness effects on localization and damage in sheet materials

In dualphase steels damage initiation can be triggered by interface debonding between ferrite and ferrite or ferrite and martensite, by martensite breaking, or by strain localization in the ferritic matrix. The roughness of sheet materials strongly influences the damage initiation and accumulation of dualphase steel, because roughness provokes local strain concentrations which accelerate the evolution of ductile damage. The presented study quantifies the effect of surface roughness on strain localization and ductile damage evolution in a numerical simulation framework established on different scales. On the macro-scale, an uncoupled phenomenological ductile damage mechanics model is applied to ductile material failure. On the microscale, sub-models are investigated that contain information on surface roughness profiles. Two different conditions are investigated: i.) samples that have been only grinded, ii.) samples that have been grinded and polished. In both cases, the surface roughness is characterized by white light confocal microscopy, and the raw data of these experimental measurements are used as input data for a numerical algorithm that reproduces surfaces with the same statistical roughness profiles. The numerical studies reveal the pronounced influence of surface roughness on material resistance against ductile failure.

Dental microwear texture analysis of Neandertals from Hortus cave, France

The dental microwear textures of six individuals from Hortus cave, France are compared to Neandertals from different ecological zones and time periods. Molar Phase II facets were scanned using white-light confocal microscopy and scale sensitive fractal analysis yielded enamel surface textural characteristics. The juvenile Hortus III and the older adult Hortus XI exhibit relatively low anisotropy (epLsar) and textural fill volume (Tfv) and are distinct from young adults with higher values. These differences may be related to age, such that only young adults were engaged in the mastication of tough, fibrous vegetation, whereas Hortus XI (50+ years) and Hortus III (6.5–7.9 years) did not. Sub-Phase Vb Hortus individuals exhibit reduced dietary hardness (Asfc) suggesting a greater reliance on soft foods, like meat. Differences between individuals from Hortus cave correspond to both sub-phase variation in climate and intrinsic lifeways.

Fabrication of bio-inspired nitinol alloy surface with tunable anisotropic wetting and high adhesive ability

In this paper, micro/nano-scale structures were fabricated on nitinol alloy (NiTi) to realize tunable anisotropic wetting and high adhesive capability. Laser texturing and silanization process are utilized to change the morphological and chemical properties of substrates. It is noted that these treated substrates exhibit the joint characteristics of anisotropic wetting and high adhesive capability. In order to investigate the influences of laser-texturing and silanization processes on NiTi, these surfaces were evaluated using scanning electron microscope (SEM), a white light confocal microscope, X-ray photoelectron spectroscopy (XPS) and goniometer. The relationship between water volume and anisotropic wetting was also established. From the experimental testing, we can obtain the following conclusions: (1) the anisotropic wetting characterized by the difference between the water contact angles (WCAs) in the vertical and parallel directions ranges from 0° to 20.3°, which is far more than the value of natural rice leaves. (2) the water sliding angles (WSAs) kept stable at 180°, successfully mimicking the adhesive ability of rose petals. (3) the silanization process could strengthen the hydrophobicity but weaken anisotropic wetting. These bio-inspired NiTi surfaces have a tremendous potential applications such as microfluidic devices, bio-mimetic materials fabrication and lab on chip.

Buccal dental microwear texture and catarrhine diets.

Two-dimensional dental microwear analyses on occlusal and nonocclusal enamel surfaces have been widely applied to reconstruct the feeding behaviors of extant primates and to infer ecological adaptations in fossil hominins. To date, analyses of dental microwear texture, using three-dimensional, Scale-Sensitive Fractal Analysis approaches has only been applied to occlusal surfaces. Here, for the first time, we apply this 3D proxy to buccal enamel surfaces of catarrhine primates of known feeding ecologies to assess the utility of nonocclusal microwear texture variables as indicators of dietary habits. Buccal microwear texture attributes were collected from high-resolution second molar casts in a sample of seven extant African catarrhine taxa with differing dietary behaviors. A white-light confocal microscope with a 100× objective lens was used to record six microwear texture variables that assess complexity, anisotropy, heterogeneity, and textural fill volume. The physical properties and variation in hardness of ingested foods is reflected by significant differences in the microwear variables on buccal enamel surfaces between species, which is in agreement with early reports using 2D microwear signatures of the same samples. Species that consume hard brittle items showed high buccal enamel complexity and low anisotropy values, while folivorous species that consume tough foods revealed high anisotropy and low complexity enamel patterns. Buccal microwear texture analysis on enamel surfaces clearly reflects diet-related variation in nonhuman primates. Our findings indicate that microwear texture attributes on nonworking enamel surfaces provide an alternative procedure for reconstructing dietary behavior when wear facets on occlusal surfaces are lacking.

Canine and incisor microwear in pitheciids and Ateles reflects documented patterns of tooth use.

Platyrrhine species differ in the extent to and the manner in which they use their incisors and canines during food ingestion. For example, Ateles uses its anterior teeth to process mechanically nondemanding soft fruits, while the sclerocarp-harvesting pitheciids rely extensively on these teeth to acquire and process more demanding foods. Pitheciids themselves vary in anterior tooth use, with the pitheciines (Cacajao, Chiropotes, and Pithecia) noted to use their robust canines in a variety of ways to predate seeds, while Callicebus, which rarely predates seeds, uses its incisors and exceptionally short canines to scrape tough mesocarp from fruits. To investigate the relationship between tooth use and dental wear, microwear textures were investigated for the anterior teeth of these five genera of platyrrhine primates. Using a white light confocal microscope, 12 microwear texture attributes that reflect feature size, anisotropy, density, and complexity were recorded from high-resolution epoxy casts of the incisors and canines of adult wild-collected Brazilian specimens of Ateles, Callicebus, Cacajao, Chiropotes, and Pithecia. Pitheciine canines tend to have deep microwear features and complex, anisotropic microwear textures, while Ateles anterior teeth tend to have very small features, low feature density, and less complex and anisotropic surfaces. Callicebus incisor and canine microwear is generally intermediate in size and complexity between those extremes. These findings align with expectations from reported field observations of tooth use and illustrate the potential for using microwear texture analysis to infer patterns of anterior tooth use in extinct primates. Am J Phys Anthropol 161:6-25, 2016. © 2016 Wiley Periodicals, Inc.

Influence of molecular weight of modified ultrahigh-molecular-weight polyethylene with Cu(II) chelate of bissalicylaldehydeethylenediamine on wear-resistant materials

Abstract Reciprocating friction and wear performances of pure ultrahigh-molecular-weight polyethylenes (UHMWPEs) with molecular weights (MWs) of 2, 3, 5, and 9 million and their modified UHMWPEs with 15 wt.% Cu(II) chelate of bissalicylaldehyde-ethylenediamine (add1) against titanium alloy (Ti6Al4V) were investigated under boundary lubrication with 25 vol.% calf serum deionized water solution. Differential scanning calorimetry (DSC) of purchased UHMWPE powders was performed. The enthalpy changed with an increase in MW. UH300 had the lowest temperature of an extrapolated peak and the best peak symmetry in DSC analysis. The friction coefficient curves of molded pure and modified UHMWPEs/Ti6Al4V were compared, and the volume loss by the wear of polymers was measured. 3D topographies of the worn surfaces of polymers and images of the worn surfaces of polymers and titanium alloy against polymers were analyzed by confocal white light microscopy and scanning electron microscopy, respectively. Results showed that the influence of MW of UHMWPE was obvious on the friction and wear characteristics of pure UHMWPEs and 15% add1 UHMWPEs. An MW of 3 million was the best to reduce the friction of rubbing pairs, enhance the wear resistance of pure UHMWPEs and 15% add1-UHMWPEs, and improve the mating properties of Ti6Al4V.

Influences of grinding with Toric CBN grinding tools on surface and subsurface of 1.3344 PM steel

Residual stresses have an important role concerning service life of forming tools. The grinding of the tool is one of the major manufacturing steps inducing residual stresses into the subsurface of the tool. Tool and process parameters for grinding with toric grinding pins have been investigated for their influences on residual stresses and surface finish. Residual stresses were measured using the sin2ψ method, while the surface finish was analyzed using white light confocal microscopy. Results show that the grinding strategy has a major influence on residual stress generation for both principle directions of the process. In addition cutting grain size has the major impact on residual stresses transverse to cutting direction, while feed rate has the main influence on residual stresses in cutting direction. A bigger grain size results in more compressive residual stresses, while a higher feed rate shifts stresses towards the tensile regime. A good surface finish is achieved with small cutting grain size, low feed rates and frontal grinding strategy.

Influences of surface structures on polarization properties

The surface structure is an important factor that affects the polarization properties, which is useful information for object detection. This paper studies the influences of surface structures on polarization properties by the examination of man-made objects and nature objects using a scanning electron microscope (SEM) and white light confocal microscope. In the work, polarization imaging was discussed, and a system was set up to obtain polarization images. Comparing the degree of linear polarization (DOLP) images with traditional spectral images, there are obvious differences between man-made objects and nature objects on the micro- and nano-scales. The experiment results indicate that surface structures have significant influences on polarization properties, and such characteristic can be used to identify the differences between objects or materials.