The knowledge about the orientation of the prisms in human dental enamel is mainly based on morphological observations (light optical, SEM etc.). Hence there are many schematic drawings, showing the orientation as seen in the microscope. Locally resolved direct measurements of the orientations, proofing the observations, have not been done in detail up to now. X-ray diffraction methods adapted from material science are used in this study, providing directly the orientation of the crystallites in the examined positions. Hereby new and better detailed information was obtained, showing the orientation of the prisms and giving information about their intrinsic structure. Based on the measurements, existing prism orientation models can be enhanced and two structural suggestions can be made, showing possible inner building principles for the prisms. Future planned measurements will even allow deciding which of the two models is more likely.
In materials science or applied crystallography, X‐ray diffraction represents a versatile and useful method with which one can obtain the orientation of single crystals or even the texture of a polycrystalline material. When the investigated sample consists of many phases, or phases of low symmetry, it becomes difficult to measure pole figures from single diffraction peaks. A combined Rietveld–texture analysis with the program MAUD is perfectly suitable to deal with conditions of overlapping diffraction peaks, including those arising from different phases. Even though nearly no alternative to MAUD exists, it is not always easy to use. The input of a file series of two‐dimensional diffraction images, for example from a texture measurement, can be time consuming since each individual image must be loaded manually, and only the newest beta version of MAUD allows semi‐automated file input. The new program input4MAUD, which is presented in this paper, offers a much more efficient way to automate both single and batch file series input into MAUD as well as the preparation of basic batch refinements with MAUD. input4MAUD is written in Visual C++ and is currently available as a 32‐bit statically compiled binary executable file for Windows.
Obtaining information about the intrinsic structure of polycrystalline materials is of prime importance owing to the anisotropic behaviour of individual crystallites. Grain orientation and its statistical distribution, i.e. the texture, have an important influence on the material properties. Crystallographic orientations play an important role in all kinds of polycrystalline materials such as metallic, geological and biological. Using synchrotron diffraction techniques the texture can be measured with high local and angular resolving power. Here methods are presented which allow the spatial orientation of the crystallites to be determined and information about the anisotropy of mechanical properties, such as elastic modulus or thermal expansion, to obtained. The methods are adapted to all crystal and several sample symmetries as well as to different phases, for example with overlapping diffraction peaks. To demonstrate the abilities of the methods, human dental enamel has been chosen, showing even overlapping diffraction peaks. Likewise it is of special interest to learn more about the orientation and anisotropic properties of dental enamel, since only basic information is available up to now. The texture of enamel has been found to be a tilted fibre texture of high strength (up to 12.5×). The calculated elastic modulus is up to 155 GPa and the thermal expansion up to 22.3 × 10(-6)°C(-1).
Dental enamel is the most highly mineralised and hardest biological tissue in human body [1]. Dental enamel is made of hydroxylapatite (HAP) - Ca5(PO4)3(OH), which is hexagonal (6/m). The lattice parameters are a = b = 0.9418 nm und c = 0.6875 nm [1]. Although HAP is a very hard mineral, it can be dissolved easily in a process which is known as enamel demineralization by lactic acid produced by bacteria. Also the direct consumption of acid (e.g. citric, lactic or phosphoric acid in soft drinks) can harm the dental enamel in a similar way. These processes can damage the dental enamel. It will be dissolved completely and a cavity occurs. The cavity must then be cleaned and filled. It exists a lot of dental fillings, like gold, amalgam, ceramics or polymeric materials. After filling other dangers can occur: The mechanical properties of the materials used to fill cavities can differ strongly from the ones of the dental enamel itself. In the worst case, the filling of a tooth can damage the enamel of the opposite tooth by chewing if the interaction of enamel and filling is not equivalent, so that the harder fillings can abrade the softer enamel of the healthy tooth at the opposite side. This could be avoided if the anisotropic mechanical properties of dental enamel would be known in detail, hence then another filling could be searched or fabricated as an equivalent opponent for the dental enamel with equal properties. To find such a material, one has to characterise the properties of dental enamel first in detail for the different types of teeth (incisor, canine, premolar and molar). This is here exemplary done for a human incisor tooth by texture analysis with the program MAUD from 2D synchrotron transmission images [2,3,4].
The exoskeleton of the crustacean Homarus americanus, the American lobster, is a biological multiphase composite consisting of a crystalline organic matrix (chitin), crystalline biominerals (calcite), amorphous calcium carbonate and proteins. One special structural aspect is the occurrence of pronounced crystallographic orientations and resulting directional anisotropic mechanical properties. The crystallographic textures of chitin and calcite have been measured by wide-angle Bragg diffraction, calculating the Orientation Distribution Function (ODF) from pole figures by using the series expansion method according to Bunge. A general strong relationship can be established between the crystallographic and the resulting mechanical and physical properties.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.