X‐ray microdiffraction,TEM characterization and texture analysis of human dentin and enamel

Human tooth is a complex bioceramic composite, which consists of enamel, dentin and the interface, the dentin–enamel junction (DEJ). The crystal properties and ultrastructure of the inorganic phase through the thickness of healthy human molar teeth were investigated using X‐ray microdiffraction (μXRD), electron diffraction and transmission electron microscopy (TEM) techniques. The XRD data were analysed using the Le Bail profile fitting approach. The size and the texture of the crystallites forming enamel and dentin in the crown part of teeth were measured using both techniques and then compared. Results showed that the thickness of dentin crystallites was found to decrease towards the DEJ, whereas the thickness of the enamel crystallites increased from the DEJ towards the outer layers. It was demonstrated that enamel exhibited an increase of texture in 002 lattice planes from the DEJ towards the outer layers. Texture was also detected in 102 lattice planes. The texture effect in 002 planes at the scale of less than 1 μm was also demonstrated in dentin. The variation of lattice parameters as a function of the position within the thickness of dentin and enamel was also observed. The values of the nonuniform microstrain in the dentin and enamel crystallites were from 1.40 × 10^?6% to 4.44 × 10^?5%. The good correlation between XRD and TEM indicated that μXRD is a useful technique to study crystallography and microstructure of heterogeneous enamel and dentin. The observed gradient characteristics of texture and crystallite size in enamel and dentin maybe an evolutionary outcome to resist wear and fracture, thereby contributing to the excellent mechanical properties of teeth.     

Microstructure and mineral composition of dental enamel of permanent and deciduous teeth

Purpose: This study evaluated and compared in vitro the microstructure and mineral composition of permanent and deciduous teeth's dental enamel. Methods: Sound third molars (n = 12) and second primary molars (n = 12) were selected and randomly assigned to the following groups, according to the analysis method performed (n = 4): Scanning electron microscopy (SEM), X‐Ray diffraction (XRD) and Energy dispersive X‐ray spectrometer (EDS). Qualitative and quantitative comparisons of the dental enamel were done. The microscopic findings were analyzed statistically by a nonparametric test (Kruskal‐Wallis). The measurements of the prisms number and thickness were done in SEM photomicrographs. The relative amounts of calcium (Ca) and phosphorus (P) were determined by EDS investigation. Chemical phases present in both types of teeth were observed by the XRD analysis. Results: The mean thickness measurements observed in the deciduous teeth enamel was 1.14 mm and in the permanent teeth enamel was 2.58 mm. The mean rod head diameter in deciduous teeth was statistically similar to that of permanent teeth enamel, and a slightly decrease from the outer enamel surface to the region next to the enamel‐dentine junction was assessed. The numerical density of enamel rods was higher in the deciduous teeth, mainly near EDJ, that showed statistically significant difference. The percentage of Ca and P was higher in the permanent teeth enamel. Conclusions: The primary enamel structure showed a lower level of Ca and P, thinner thickness and higher numerical density of rods. Microsc. Res. Tech., 2010. © 2009 Wiley‐Liss, Inc.     

OM,SEM–EDX,and micro‐FTIR analysis of the Bronze Age pottery from the Băile Figa salt production site (Transylvania,Romania)

This article presents the results of analyses carried out on a lot of 11 fragments of Bronze Age ceramics discovered in the site from B?ile Figa (Beclean town, Transylvania, Romania), where salt exploitation occurred. The samples were analyzed by means of optical microscopy, on the basis of which the morphology and distribution of the inclusions in the ceramic paste was established. Likewise, the samples were analyzed by scanning electron microscopy with energy‐dispersive X‐ray spectrometry, producing microphotographs for each sample, and on the basis of the X‐ray spectra, the elemental composition in gravimetric percentages was established. Through the micro‐Fourier‐transform infrared spectroscopy analysis, on the basis of characteristic group vibrations, it was possible to ascertain the nature of the compounds from the ceramic samples. These analyses will contribute to the reconstruction of the prehistoric technologies for salt exploitation.     

Chemical and crystallographic study of remineralized surface on initial carious enamel treated with Galla chinensis

To investigate the morphologic, chemical and crystallographic characters of remineralized surface on initial carious enamel treated with Galla chinensis, scanning electron microscopy equipped with energy dispersive analysis spectroscopy were used, and X‐ray microdiffraction (microzone XRD) was used for the first time to analyze in situ the microzone crystallite of remineralized surface on carious enamel. Bovine sound enamel slabs were demineralized to produce initial carious lesion in vitro. Then, the lesions were exposed to a pH‐cycling regime for 12 days of remineralization. Each daily cycle included 4×1 min applications with one of the three treatments: distilled and deionized water (DDW); 1 g/L NaF; 4 g/L G. chinensis extract (GCE). After the treatments, some rod‐like deposits and many irregular prominences were found on GCE‐treated enamel surface, and the intensities of Ca and P signals showed a tendency to increase; Ca:P ratio was significantly higher than that of DDW‐treated enamel. X‐ray microdiffraction showed hydroxyapatite was still the main component of GCE‐treated enamel, and the crystallinity was increased, the crystal lattice changed gently with decreased lattice parameter a. These results indicated the potential of GCE in promoting the remineralization of initial enamel carious lesions, and supported the previous hypothesis about GCE mechanism. Combined with the anti‐bacteria and demineralization inhibition properties of GCE, the natural G. chinensis may become one more promising agent for caries prevention. SCANNING 31: 236–245, 2009. © 2010 Wiley Periodicals, Inc.     

Evaluation of contrasting techniques for X‐ray imaging of velvet worms (Onychophora)

Non‐invasive imaging techniques like X‐ray computed tomography have become very popular in zoology, as they allow for simultaneous imaging of the internal and external morphology of organisms. Nevertheless, the effect of different staining approaches required for this method on samples lacking mineralized tissues, such as soft‐bodied invertebrates, remains understudied. Herein, we used synchrotron radiation‐based X‐ray micro‐computed tomography to compare the effects of commonly used contrasting approaches on onychophorans – soft‐bodied invertebrates important for studying animal evolution. Representatives of Euperipatoides rowelli were stained with osmium tetroxide (vapour or solution), ruthenium red, phosphotungstic acid, or iodine. Unstained specimens were imaged using both standard attenuation‐based and differential phase‐contrast setups to simulate analyses with museum material. Our comparative qualitative analyses of several tissue types demonstrate that osmium tetroxide provides the best overall tissue contrast in onychophorans, whereas the remaining staining agents rather favour the visualisation of specific tissues and/or structures. Quantitative analyses using signal‐to‐noise ratio measurements show that the level of image noise may vary according to the staining agent and scanning medium selected. Furthermore, box‐and‐whisker plots revealed substantial overlap in grey values among structures in all datasets, suggesting that a combination of semiautomatic and manual segmentation of structures is required for comprehensive 3D reconstructions of Onychophora, irrespective of the approach selected. Our results show that X‐ray micro‐computed tomography is a promising technique for studying onychophorans and, despite the benefits and disadvantages of different staining agents for specific tissues/structures, this method retrieves informative data that may eventually help address evolutionary questions long associated with Onychophora.     

Characterization of Cobalt Oxide and Calcium‐Aluminum Oxide nano‐catalyst through Scanning Electron Microscopy,X‐ray diffraction,and Energy Dispersive X‐ray Spectroscopy

The Cobalt Oxide and Calcium‐Aluminum Oxide nano‐catalysts were analyzed using Scanning Electronic Microscopy (SEM), X‐ray diffraction (XRD), and dispersive X‐ray spectroscopy (EDX) techniques. Preliminary results showed that the particles of Cobalt Oxide exhibit sponge like morphology and homogenous distribution as per confirmation via SEM. Its average particle size ranges to 30.6 nm demonstrating enormous number of pores and aggregative in nature. Its various peaks were ranging from 19.2 to 65.4 after XRD analysis. The highest intensity was observed at 36.9 position. The energy dispersive spectroscopy techniques were used to calculate the elements present in sample according to their weight and atomic percentage. The cobalt oxide contain cobalt as the most abundant element with 46.85 wt% and 18.01 atomic percent. It contain oxygen with 30.51 wt% and 43.19 atomic percent. Whereas, SEM of calcium aluminum oxide showed random morphology. According to the calculation of Scherrer equation regarding XRD analysis, it was distributed homogenously with particle size ranges from 30 to 40 nm. Its porous morphology was due to the interconnecting gaps between different particles. It result the eight peaks ranging from 18.1 to 62.7 in XRD spectrum. The highest intensity observed at 35.1 with average crystallite particle size of 25.6 nm. The calcium aluminum oxide contain aluminum 7.45 wt% and 6.93 atomic percent. The calcium was the most abundant element with54.7 wt% and 34.24 atomic percent followed by oxygen with 37.26 wt% and 58.42 atomic percent. It was concluded that the SEM, XRD, and EDX are the most significant techniques to characterize nano‐catalysts in particular and other compounds generally.     

Structural investigations on green culms and charcoal of Bambusa multiplex

Green culms of Bambusa multiplex and the bamboo charcoal carbonized from the green culms at 700°C have been studied by means of X‐ray diffraction, X‐ray fluorescent element analysis, analytical scanning electron microscopy, and analytical scanning transmission electron microscopy (STEM), aiming at industrial applications as raw materials for functional devices and substances. It is revealed that the green culms and the charcoal contain a significant amount of Si, in particular, ～18 wt % in the skin. The green culms comprise amorphous and crystalline celluloses. The charcoal has a so‐called amorphous structure which is composed of randomly distributed carbon nanotubes and fibers. The growth of Ag‐doped activated charcoal powders that were produced by two different methods using this charcoal powder has also been studied.     

Imaging connected porosity of crystalline rock by contrast agent‐aided X‐ray microtomography and scanning electron microscopy

We set out to study connected porosity of crystalline rock using X‐ray microtomography and scanning electron microscopy with energy dispersive X‐ray spectroscopy (SEM‐EDS) with caesium chloride as a contrast agent. Caesium is an important radionuclide regarding the final deposition of nuclear waste and also forms dense phases that can be readily distinguished by X‐ray microtomography and SEM‐EDS. Six samples from two sites, Olkiluoto (Finland) and Grimsel (Switzerland), where transport properties of crystalline rock are being studied in situ, were investigated using X‐ray microtomography and SEM‐EDS. The samples were imaged with X‐ray microtomography, immersed in a saturated caesium chloride (CsCl) solution for 141, 249 and 365 days and imaged again with X‐ray microtomography. CsCl inside the samples was successfully detected with X‐ray microtomography and it had completely penetrated all six samples. SEM‐EDS elemental mapping was used to study the location of caesium in the samples in detail with quantitative mineral information. Precipitated CsCl was found in the connected pore space in Olkiluoto veined gneiss and in lesser amounts in Grimsel granodiorite. Only a very small amount of precipitated CsCl was observed in the Grimsel granodiorite samples. In Olkiluoto veined gneiss caesium was found in pinitised areas of cordierite grains. In the pinitised areas caesium was found in notable excess compared to chloride, possibly due to the combination of small pore size and negatively charged surfaces. In addition, elevated concentrations of caesium were found in kaolinite and sphalerite phases. The findings concerning the location of CsCl were congruent with X‐ray microtomography.     

Quantitative imaging of Candida utilis and its organelles by soft X‐ray Nano‐CT

Soft X‐ray microscopy has excellent characteristics for imaging cells and subcellular structures. In this paper, the yeast strain, Candida utilis, was imaged by soft X‐ray microscopy and three‐dimensional volumes were reconstructed with the SART‐TV method. We performed segmentation on the reconstruction in three dimensions and identified several types of subcellular architecture within the specimen cells based on their linear absorption coefficient (LAC) values. Organelles can be identified by the correlation between the soft X‐ray LAC values and the subcellular architectures. Quantitative analyses of the volume ratio of organelles to whole cell in different phases were also carried out according to the three‐dimensional datasets. With such excellent features, soft X‐ray imaging has a great influence in the field of biological cellular and subcellular research.     

Microscopic and spectroscopic characterization of rice and corn starch

Starch granules from rice and corn were isolated, and their molecular mechanism on interaction with α‐amylase was characterized through biochemical test, microscopic imaging, and spectroscopic measurements. The micro‐scale structure of starch granules were observed under an optical microscope and their average size was in the range 1–100 μm. The surface topological structures of starch with micro‐holes due to the effect of α‐ amylase were also visualized under scanning electron microscope. The crystallinity was confirmed by X‐ray diffraction patterns as well as second‐harmonic generation microscopy. The change in chemical bonds before and after hydrolysis of the starch granules by α‐ amylase was determined by Fourier transform infrared spectroscopy. Combination of microscopy and spectroscopy techniques relates structural and chemical features that explain starch enzymatic hydrolysis which will provide a valid basis for future studies in food science and insights into the energy transformation dynamics.     

Exploring the use of soft X‐ray microscopy for imaging subcellular structures of the inner ear1

The soft X‐ray microscope at the Lawrence Berkeley National Laboratory was developed for visualization of biological tissue. Soft X‐ray microscopy provides high‐resolution visualization of hydrated, non‐embedded and non‐sectioned cells and is thus potentially an alternative to transmission electron microscopy. Here we show for the first time soft X‐ray micrographs of structures isolated from the guinea‐pig inner ear. Sensory outer hair cells and supporting pillar cells are readily visualized. In the hair cells, individual stereocilia can easily be identified within the apical hair bundle. The underlying cuticular plate is, however, too densely composed or too thick to be clearly visualized, and thus appears very dark. The cytoplasmic structures protruding from the cuticular plates as well as the fibrillar material surrounding and projecting from the cell nuclei can be seen. In the pillar cells the images reveal individual microtubule bundles. Soft X‐ray images of the acellular tectorial membrane and thin two‐layered Reissner's membrane display a level of resolution comparable to low‐power electron microscopy.     

Fine structure of tooth enamel in the yellowing human teeth: SEM and HRTEM studies

Objective : The aim of this study was to clarify an influence of the fine structure of human tooth enamel to the yellowing teeth. Materials and methods : Sound maxillary first premolars of 15–50‐year‐old females that were extracted for the orthodontic treatment were used as the test samples. The tooth enamel sections of these teeth that prepared by ion polishing were observed by scanning electron microscopy (SEM). Furthermore, the fine structure of substance filling the inter‐rod spaces was analyzed by high resolution transmission electron microscopy (HRTEM). Results : In white tooth, the inter‐rod spaces were observed at the width of about 0.1 μm, while in yellow tooth, the inter‐rod spaces were not clearly observed by SEM. HRTEM observations revealed for the first time that the inter‐rod spaces were filled with fine particles of poorly crystallized hydroxyapatite in the yellow tooth. In yellow tooth, it was considered that the color of the inner dentin was recognized due to the decrease of light scattering by filling the tooth enamel inter‐rod spaces. The generation of particles in the tooth enamel inter‐rod spaces was considered to be caused by the long‐time progression of calcification. Conclusions : These results suggested that the change in fine structure, filling in inter‐rod spaces of tooth enamel, was related to progression of calcification in the inter‐rod spaces with advancing age and one of the factors of yellowness of human tooth. Microsc. Res. Tech. 79:14–22, 2016. © 2015 Wiley Periodicals, Inc.     

X‐ray diffraction of amorphous and crystalline overbased sulphonates

Colloidal dispersions of calcium carbonate stabilised by overbased sulphonates are used as lubricant additives to provide detergency, remove acidity, and prevent wear. In the present work various overbased sulphonate compounds have been analysed using X‐ray diffraction (XRD). The amorphous overbased sulphonates studied displayed broad diffraction patterns while the crystalline overbased sulphonates gave well‐defined diffraction patterns, correlating with the particle size. The XRD distances of the series of Mg, Ca, and Ba overbased sulphonates shifted to greater values and displayed a clear correlation (r = 0.98) with the ionic radius of the cations used.     

Three‐dimensional imaging of whole mouse models: comparing nondestructive X‐ray phase‐contrast micro‐CT with cryotome‐based planar epi‐illumination imaging

In this study, we compare two evolving techniques for obtaining high‐resolution 3D anatomical data of a mouse specimen. On the one hand, we investigate cryotome‐based planar epi‐illumination imaging (cryo‐imaging). On the other hand, we examine X‐ray phase‐contrast micro‐computed tomography (micro‐CT) using synchrotron radiation. Cryo‐imaging is a technique in which an electron multiplying charge coupled camera takes images of a cryo‐frozen specimen during the sectioning process. Subsequent image alignment and virtual stacking result in volumetric data. X‐ray phase‐contrast imaging is based on the minute refraction of X‐rays inside the specimen and features higher soft‐tissue contrast than conventional, attenuation‐based micro‐CT. To explore the potential of both techniques for studying whole mouse disease models, one mouse specimen was imaged using both techniques. Obtained data are compared visually and quantitatively, specifically with regard to the visibility of fine anatomical details. Internal structure of the mouse specimen is visible in great detail with both techniques and the study shows in particular that soft‐tissue contrast is strongly enhanced in the X‐ray phase images compared to the attenuation‐based images. This identifies phase‐contrast micro‐CT as a powerful tool for the study of small animal disease models.     

Adverse effects of respiratory disease medicaments and tooth brushing on teeth: A scanning electron microscopy,X‐ray fluorescence and infrared spectroscopy study

The present study aims to evaluate the effect of brushing with fluoride dentifrice on teeth severely affected by erosion due to respiratory medicaments. Enamel (n = 50) and dentin (n = 50) bovine specimens were prepared and treated with artificial saliva (S‐control), acebrofilin hydrochloride (AC), ambroxol hydrochloride (AM), bromhexine hydrochloride (BR), and salbutamol sulfate (SS) and subjected to cycles of demineralization (immersing in 3 mL, 1 min, three times a day at intervals of 1 hr, for 5 days) followed by remineralization (saliva, 37°C, 1 hr). Simulated brushing with fluoridated toothpaste was performed using 810 strokes in a reciprocal‐action brushing simulator. Scanning electron microscopy, micro energy dispersive X‐ray fluorescence (μ‐EDXRF) spectroscopy and attenuated total reflection Fourier transform infrared (ATR FTIR) spectroscopy were then performed. μ‐EDXRF images showed extensive erosion after treatment with all medicaments. SEM images showed enamel erosion in order SS > BR > AC = AM > S after brushing and fluoridation. FTIR results were in agreement. In case of dentin, μ‐EDXRF measurements showed significant difference in mineral content (percent weight of calcium and phosphate) in SS + brushing + fluoridation treated enamel compared to control, while μ‐EDXRF images showed erosive effects in the order SS > AM>BR > AC = S post brushing + fluoridation. SEM images showed erosion in the order SS > AM = BR > AC > S post brushing + fluoridation. Again, FTIR multivariate results were in agreement. Overall, our study shows that proper oral care is critical when taking certain medication. The study also demonstrates the possible use of FTIR for rapid clinical monitoring of tooth erosion in clinics.     

Characterization of the calcification of cardiac valve bioprostheses by environmental scanning electron microscopy and vibrational spectroscopy

Bioprosthetic heart valve tissue and associated calcification were studied in their natural state, using environmental scanning electron microscopy (ESEM). Energy dispersive X‐ray micro‐analysis, X‐ray diffraction, Fourier‐transform infrared and Raman spectroscopy were used to characterize the various calcific deposits observed with ESEM. The major elements present in calcified valves were also analyzed by inductively coupled plasma–optical emission spectroscopy. To better understand the precursor formation of the calcific deposits, results from the elemental analyses were statistically correlated. ESEM revealed the presence of four broad types of calcium phosphate crystal morphology. In addition, two main patterns of organization of calcific deposits were observed associated with the collagen fibres. Energy dispersive X‐ray micro‐analysis identified the crystals observed by ESEM as salts containing mainly calcium and phosphate with ratios from 1.340 (possibly octacalcium phosphate, which has a Ca/P ratio of 1.336) to 2.045 (possibly hydroxyapatite with incorporation of carbonate and metal ion contaminants, such as silicon and magnesium, in the crystal lattice). Raman and fourier‐transform infrared spectroscopy also identified the presence of carbonate and the analyses showed spectral features very similar to a crystalline hydroxyapatite spectrum, also refuting the presence of precursor phases such as β‐tricalcium phosphate, octacalcium phosphate and dicalcium phosphate dihydrate. The results of this study raised the possibility of the presence of precursor phases associated with the early stages of calcification.     

Evaluation of X‐ray tomography contrast agents: A review of production,protocols, and biological applications

X‐ray computed tomography is a strong tool that finds many applications both in medical applications and in the investigation of biological and nonbiological samples. In the clinics, X‐ray tomography is widely used for diagnostic purposes whose three‐dimensional imaging in high resolution helps physicians to obtain detailed image of investigated regions. Researchers in biological sciences and engineering use X‐ray tomography because it is a nondestructive method to assess the structure of their samples. In both medical and biological applications, visualization of soft tissues and structures requires special treatment, in which special contrast agents are used. In this detailed report, molecule‐based and nanoparticle‐based contrast agents used in biological applications to enhance the image quality were compiled and reported. Special contrast agent applications and protocols to enhance the contrast for the biological applications and works to develop nanoparticle contrast agents to enhance the contrast for targeted drug delivery and general imaging applications were also assessed and listed.     

Deposition of lead and cadmium released by cigarette smoke in dental structures and resin composite

Cigarette smoke is a significant source of cadmium, lead, and toxic elements, which are absorbed into the human organism. In this context, the aim of this study was to investigate in vitro the presence of toxic elements, cadmium, and lead deriving from cigarette smoke in the resin composite, dentine, and dental enamel. Eight cylindrical specimens were fabricated from resin composite, bovine enamel, and root dentin fragments that were wet ground and polished with abrasive paper to obtain sections with 6‐mm diameter and 2‐mm thickness. All specimens were exposed to the smoke of 10 cigarettes/day during 8 days. After the simulation of the cigarette smoke, the specimens were examined with scanning electron microscopy (SEM) and the energy‐dispersive X‐ray analysis. In the photomicrographic analysis in SEM, no morphological alterations were found; however, the microanalysis identified the presence of cadmium, arsenic, and lead in the different specimens. These findings suggest that the deposition of these elements derived from cigarette smoke could be favored by dental structures and resin composite. Microsc. Res. Tech., 2010. © 2010 Wiley‐Liss, Inc.     

Optimizing use of the structural chemical analyser (variable pressure FESEM‐EDX raman spectroscopy) on micro‐size complex historical paintings characterization

The novel Structural Chemical Analyser (hyphenated Raman spectroscopy and scanning electron microscopy equipped with an X‐ray detector) is gaining popularity since it allows 3‐D morphological studies and elemental, molecular, structural and electronic analyses of a single complex micro‐sized sample without transfer between instruments. However, its full potential remains unexploited in painting heritage where simultaneous identification of inorganic and organic materials in paintings is critically yet unresolved. Despite benefits and drawbacks shown in literature, new challenges have to be faced analysing multifaceted paint specimens. SEM?Structural Chemical Analyser systems differ since they are fabricated ad hoc by request. As configuration influences the procedure to optimize analyses, likewise analytical protocols have to be designed ad hoc. This paper deals with the optimization of the analytical procedure of a Variable Pressure Field Emission scanning electron microscopy equipped with an X‐ray detector Raman spectroscopy system to analyse historical paint samples. We address essential parameters, technical challenges and limitations raised from analysing paint stratigraphies, archaeological samples and loose pigments. We show that accurate data interpretation requires comprehensive knowledge of factors affecting Raman spectra. We tackled: (i) the in‐FESEM?Raman spectroscopy analytical sequence, (ii) correlations between FESEM and Structural Chemical Analyser/laser analytical position, (iii) Raman signal intensity under different VP‐FESEM vacuum modes, (iv) carbon deposition on samples under FESEM low‐vacuum mode, (v) crystal nature and morphology, (vi) depth of focus and (vii) surface‐enhanced Raman scattering effect. We recommend careful planning of analysis strategies prior to research which, although time consuming, guarantees reliable results. The ultimate goal of this paper is to help to guide future users of a FESEM‐Structural Chemical Analyser system in order to increase applications.     

人牙釉质的磨损机制研究

以钛合金为对摩材料,考察了人牙釉质在人工唾液介质中的滑动磨损进程,结合微观分析,研究了牙釉质的磨损机制。结果表明:在摩擦过程中,随着釉质表面发生脆性剥落,磨损从两体接触磨损转变为三体磨粒磨损,磨损加剧;随着接触时间增长,硬质磨屑尺寸变小,磨损率降低,进入稳定磨损阶段。牙釉质磨损为机械磨损过程,釉质表面基本无摩擦化学作用。