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Abstract: Carious lesions exhibit a complex structural organization composed of zones of higher and lower mineralization, formed by successive periods of cyclic de- and re-mineralization. A thorough understanding of the lesion morphology is necessary for the development of suitable treatments aiming to repair rather than replace the damaged tissue. This detailed understanding includes the entire lesion down to individual crystallites and nanopores within the natural organization of the crown. A moderate lesion, with surface loss and reaching dentin, and a very early lesion were studied. Scanning small-angle X-ray scattering (SAXS) with a pixel size of 20×20μm2 was used to characterize these lesions, allowing for the identification of distinct zones with varied absorption and scattering behavior, indicative of varied porosity and pore morphology. Despite these differences, the overall orientation and anisotropy of the SAXS signal was unaltered throughout both lesions, indicating that an anisotropic scaffold is still present in the lesion. The finding that crystallite orientation is preserved throughout the lesions facilitates the identification of preventive re-mineralizing strategies with the potential to recreate the original nanostructure. [Copyright &y& Elsevier]

The anatomy of human teeth reflects its usage. Spatially resolved X-ray scattering permits quantitative studies of the characteristic arrangement of the anisotropic calcium phosphate crystallites and the collagen fibers within the hard tissues of the crown. The present study summarizes the distinctive nanometer-sized anatomical features of the tooth hard tissues including their interface taking advantage of spatially resolved synchrotron radiation-based small-angle X-ray scattering. The comparison of slices from eight teeth indicates a long-range organization of tooth nanostructures. [ABSTRACT FROM AUTHOR]

Abstract: Spatially resolved small-angle x-ray scattering based on synchrotron radiation combines the quantitative assessment of nanometer-sized components using scattering with the real-space imaging by means of scanning. The method enables us to study the effect of caries-induced damages on the inorganic and organic nanoscopic components in human teeth. We demonstrate for several 200- to 500-μm-thin tooth slices that the bacterial processes dissolve the ceramic components in enamel and dentin, but the dentinal collagen network remains practically unaffected with respect to its abundance and orientation in early stages of caries and in parts of extended carious lesions. Consequently, we speculate that future caries treatments can be developed reversing the effect of bacterial attacks by means of suitable remineralization of the dentin. From the Clinical Editor: In this groundbreaking study of caries pathology using synchrotron-based X-ray scattering, the authors demonstrated that while bacterial processes do dissolve the ceramic components in enamel and dentin; however, the dentinal collagen network remains unaffected, enabling the development of future caries treatments that re-mineralize the dentin. [Copyright &y& Elsevier]

It is demonstrated that X-ray beam positions can be extracted from two-dimensional profiles with sub-pixel resolution. Beam-position measurements utilizing a self-designed low-cost two-dimensional detector have been performed at two synchrotron radiation beamlines of the Swiss Light Source. The effective detector pixel size was 4.8 µm and the resolution achieved for the beam position was about 5 nm. At a data rate of 25 frames per second, periodic variations of the beam position could be detected with a frequency resolution below 0.1 Hz. This allowed, for example, the influence of a turbo-pump in the X-ray optics hutch on the beam position to be quantified, and even minute variations related to the electron beam in the storage ring could be detected. [ABSTRACT FROM AUTHOR]

Understanding and controlling the structural anisotropies of injection-molded polymers is vital for designing products such as cantilever-based sensors. Such micro-cantilevers are considered as cost-effective alternatives to single-crystalline silicon-based sensors. In order to achieve similar sensing characteristics, structure and morphology have to be controlled by means of processing parameters including mold temperature and injection speed. Synchrotron radiation-based scanning small- (SAXS) and wide-angle x-ray scattering techniques were used to quantify crystallinity and anisotropy in polymer micro-cantilevers with micrometer resolution in real space. SAXS measurements confirmed the lamellar nature of the injection-molded semi-crystalline micro-cantilevers. The homogenous cantilever material exhibits a lamellar periodicity increasing with mold temperature but not with injection speed. We demonstrate that micro-cantilevers made of semi-crystalline polymers such as polyvinylidenefluoride, polyoxymethylene, and polypropylene show the expected strong degree of anisotropy along the injection direction. [ABSTRACT FROM AUTHOR]

In this work, we used scanning electron microscopy (SEM), in situ coherent small angle x-ray scattering (SAXS), and Monte Carlo molecular simulation to gain insights into the dynamics of block copolymer directed assembly with density multiplication on chemically patterned surfaces. During directed assembly, it was observed with SEM that poly(styrene-block-methyl methacrylate) initially formed discrete polystyrene domains that lacked long-range order at the free surface. After further annealing, the polystyrene domains gradually coalesced into linear domains that were not registered fully with the underlying chemical pattern. The linear domains could be trapped in metastable morphologies. Finally, the linear polystyrene domains formed perpendicular lamellae in full registration with the underlying chemical pattern. It was revealed with SAXS that scattering peaks characteristic of the period of the chemical pattern appeared and disappeared at the early stages of assembly. Finally, the morphological evolution of directed assembly of block copolymer on chemically patterned surfaces was modeled by molecular simulations. [ABSTRACT FROM AUTHOR]

Abstract: X-ray phase and absorption radiographs and tomograms of the heart of a rat were taken with an X-ray grating interferometer with monochromatic synchrotron radiation at a photon energy of 17.5keV. The phase images show largely superior quality with respect to the absorption images taken with the same dose, particularly much better contrast and contrast-to-noise ratio. Different tissues can clearly be distinguished. The results demonstrate the potential of grating interferometry for two- and three-dimensional X-ray imaging of biological soft tissue in an aqueous environment. [Copyright &y& Elsevier]

The arrangement and orientation of the ultrastructure plays an important role for the mechanical properties of inhomogeneous and anisotropic materials, such as polymers, wood, or bone. However, there is a lack of techniques to spatially resolve and quantify the material's ultrastructure orientation in a macroscopic context. In this study, a new method is presented, which allows deriving the ultrastructural 3D orientation in a quantitative and spatially resolved manner. The proposed 3D scanning small-angle X-ray scattering (3D sSAXS) method was demonstrated on a thin trabecular bone specimen of a human vertebra. A micro-focus X-ray beam from a synchrotron radiation source was used to raster scan the sample for different rotation angles. Furthermore, a mathematical framework was developed, validated and employed to describe the relation between the SAXS data for the different rotation angles and the local 3D orientation and degree of orientation (DO) of the bone ultrastructure. The resulting local 3D orientation was visualized by a 3D orientation map using vector fields. Finally, by applying the proposed 3D scanning SAXS method on consecutive bone sections, a 3D map of the local orientation of a complete trabecular element could be reconstructed for the first time. The obtained 3D orientation map provided information on the bone ultrastructure organization and revealed links between trabecular bone microarchitecture and local bone ultrastructure. More specifically, we observed that trabecular bone ultrastructure is organized in orientation domains of tens of micrometers in size. In addition, it was observed that domains with a high DO were more likely to be found near the surface of the trabecular structure, and domains with lower DO (or transition zones) were located in-between the domains with high DO. The method reproducibility was validated by comparing the results obtained when scanning the sample under different sample tilt angles. 3D orientation maps such as the ones created using 3D scanning SAXS will help to quantify and understand structure–function relationships between bone ultrastructure and bone mechanics. Beyond that, the proposed method can also be used in other research fields such as material sciences, with the aim to locally determine the 3D orientation of material components. [ABSTRACT FROM AUTHOR]