TY - JOUR A1 - Zabler, S. A1 - Riesemeier, Heinrich A1 - Fratzl, P. A1 - Zaslansky, P. T1 - Fresnel-propagated imaging for the study of human tooth dentin by partially coherent x-ray tomography JF - Optics express N2 - Recent methods of phase imaging in x-ray tomography allow the visualization of features that are not resolved in conventional absorption microtomography. Of these, the relatively simple setup needed to produce Fresnel-propagated tomograms appears to be well suited to probe tooth-dentin where composition as well as microstructure vary in a graded manner. By adapting analytical propagation approximations we provide predictions of the form of the interference patterns in the 3D images, which we compare to numerical simulations as well as data obtained from measurements of water immersed samples. Our observations reveal details of the tubular structure of dentin, and may be evaluated similarly to conventional absorption tomograms. We believe this exemplifies the power of Fresnel-propagated imaging as a form of 3D microscopy, well suited to quantify gradual microstructural-variations in teeth and similar tissues. KW - Fourier optics KW - Partial coherence in imaging KW - Tomography KW - X-ray imaging KW - Phase modulation KW - Dentistry KW - High resolution Sy-CT KW - Microstructure in human Teeth PY - 2006 DO - https://doi.org/10.1364/OE.14.008584 SN - 1094-4087 VL - 14 IS - 19 SP - 8584 EP - 8597 PB - Optical Society of America CY - Washington, DC AN - OPUS4-13869 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rack, T. A1 - Zabler, S. A1 - Rack, C. A1 - Stiller, M. A1 - Riesemeier, Heinrich A1 - Cecilia, A. A1 - Nelson, K. T1 - Coherent synchrotron-based micro-imaging employed for studies of micro-gap formation in dental implants T2 - 10th International conference on X-ray microscopy (AIP conference proceedings) N2 - Biocompatible materials such as titanium are regularly applied in oral surgery. Titanium-based implants for the replacement of missing teeth demand a high mechanical precision in order to minimize micro-bacterial leakage, especially when two-piece concepts are used. Synchrotron-based hard x-ray radiography, unlike conventional laboratory radiography, allows high spatial resolution in combination with high contrast even when micro-sized features in such highly attenuating objects are visualized. Therefore, micro-gap formation at interfaces in two-piece dental implants with the sample under different mechanical loads can be studied. We show the existence of micro-gaps in implants with conical connections and study the mechanical behavior of the mating zone of conical implants during loading. The micro-gap is a potential source of implant failure, i.e., bacterial leakage, which can be a stimulus for an inflammatory process. T2 - 10th International conference on X-ray microscopy CY - Chicago, Illinois, USA DA - 15.08.2010 KW - X-ray imaging KW - Dental implants KW - Digital radiography KW - Implant-abutment interface KW - Synchrotron radiation KW - X-ray phase contrast PY - 2011 SN - 978-0-7354-0925-5 DO - https://doi.org/10.1063/1.3625398 N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings VL - 1365 SP - 445 EP - 448 AN - OPUS4-25347 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zabler, S. A1 - Rack, A. A1 - Manke, I. A1 - Thermann, K. A1 - Tiedemann, J. A1 - Harthill, N. A1 - Riesemeier, Heinrich T1 - High-resolution tomography of cracks, voids and micro-structure in greywacke and limestone JF - Journal of structural geology N2 - Rocks are commonly very heterogeneous materials. Randomly distributed micro-flaws inside the rock are believed to initiate tensile cracks from which shear fractures develop and coalescence through en echelon interactions leads to fracture. In this paper, we describe the results of applying high-resolution X-ray tomography to samples of greywacke and limestone experimentally deformed under unconfined axial shortening at various loads equivalent to different fractions of the sample strength. Mineral grains, pores, micro-cracks and other voids were imaged with a resolution of 10 µm. 3D image analysis enabled us to monitor the initial state of the samples and the changes in them due to compression. Crack morphology is characterized and compared to the micro-structure of the sample before and after deformation. In the greywacke, formation of a macro-crack ~10° oblique to the stress direction is observed. It initiated in fine intergranular material at the top tip of the sample and is composed of tensile fractures connected by wing cracks. None of the voids defined in the initial state fractured, and the crack is interpreted to have started either as a micro-crack which was smaller than the resolution of the tomography, or, as a completely new crack. In the limestone, cracks are observed to initiate in features that are too small to be imaged by the tomography, or also in newly created cracks. KW - Rock porosity KW - Crack formation KW - X-ray imaging KW - Micro-tomography KW - 3D image analysis PY - 2008 DO - https://doi.org/10.1016/j.jsg.2008.03.002 SN - 0191-8141 SN - 1873-1201 VL - 30 IS - 7 SP - 876 EP - 887 PB - Pergamon Press CY - Oxford AN - OPUS4-18566 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rack, A. A1 - Rack, T. A1 - Stiller, M. A1 - Riesemeier, Heinrich A1 - Zabler, S. A1 - Nelson, K. T1 - In vitro synchrotron-based radiography of micro-gap formation at the implant-abutment interface of two-piece dental implants JF - Journal of synchrotron radiation N2 - Micro-gap formation at the implant-abutment interface of two-piece dental implants was investigated in vitro using high-resolution radiography in combination with hard X-ray synchrotron radiation. Images were taken with the specimen under different mechanical loads of up to 100 N. The aim of this investigation was to prove the existence of micro-gaps for implants with conical connections as well as to study the mechanical behavior of the mating zone of conical implants during loading. Synchrotron-based radiography in comparison with classical laboratory radiography yields high spatial resolution in combination with high contrast even when exploiting micro-sized features in highly attenuating objects. The first illustration of a micro-gap which was previously indistinguishable by laboratory methods underlines that the complex micro-mechanical behavior of implants requires further in vitro investigations where synchrotron-based micro-imaging is one of the prerequisites. KW - X-ray imaging KW - Dental implants KW - Digital radiography KW - Implant-abutment interface PY - 2010 DO - https://doi.org/10.1107/S0909049510001834 SN - 0909-0495 SN - 1600-5775 VL - 17 IS - 2 SP - 289 EP - 294 PB - Blackwell Publishing CY - Oxford AN - OPUS4-22121 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -