Birgit Bussmann

Linking Microstructure and Nanochemistry in Human Dental Tissues

Mineralized dental tissues and dental pulp were characterized using advanced analytical transmission electron microscopy (TEM) methods. Quantitative X-ray energy dispersive spectroscopy was employed to determine the Ca/P and Mg/P concentration ratios. Significantly lower Ca/P concentration ratios were measured in peritubular dentine compared to intertubular dentine, which is accompanied by higher and variable Mg/P concentration ratios. There is strong evidence that magnesium is partially substituting calcium in the hydroxyapatite structure. Electron energy-loss near-edge structures (ELNES) of C-K and O-K from enamel and dentine are noticeably different. We observe a strong influence of beam damage on mineralized dental tissues and dental pulp, causing changes of the composition and consequently also differences in the ELNES. In this article, the importance of TEM sample preparation and specimen damage through electron irradiation is demonstrated.

Magnesium-Assisted Continuous Growth of Strongly Iron-Enriched Incisors

Teeth are an excellent example where optimally designed nanoarchitectures with precisely constructed components consist of simple compounds. Typically, these simple constituent phases with insignificant properties show mechanical property amplifications when formed into composite architectures. Material properties of functional composites are generally regulated on the nanoscale, which makes their characterization particularly demanding. Using advanced analytical and imaging transmission electron microscopy techniques, we identified innovative microstructural adjustments combined with astonishing compositional adaptations in incisors of coypu. Unique constituents, recognized as an additional amorphous Fe-rich surface layer followed by a transition zone covering pigmented enamel, provide the required structural stability to withstand repeated mechanical load. The chemically diverse Fe-rich surface layer, including ferrihydrite and iron-calcium phosphates, gives the typical orange-brown coloration to the incisors. Within the spaces between elongated hydroxyapatite crystals in the pigmented enamel, only ferrihydrite was found, implying that enamel pigmentation is a very strictly controlled process. Most significantly, an unprecedentedly high amount of Mg was measured in the amorphous flake-like material within the dentinal tubules of the incisors, suggesting the presence of a (Mg,Ca) phosphate phase. This unusually high influx of Mg into the dentin of incisors, but not molars, suggests a substantial functionality of Mg in the initial formation stages and constant growth of incisors. The present results emphasize the strong mutual correlation among the microstructure, chemical composition, and mechanical properties of mineralized dental tissues.

Structural optimization and amorphous calcium phosphate mineralization in sensory setae of a terrestrial crustacean (Isopoda: Oniscidea)

Terrestrial isopods possess large sensory setae on their walking legs. Increased fracture resistance of these elongated structures is of crucial importance, making the exoskeleton forming the setae an interesting durable material that may inspire biomimetic designs. We studied the cuticle of the sensory setae with analytical electron microscopy in order to gain detailed insights into its structure and composition at the nanometer scale and identify features that increase the fracture resistance of these minute skeletal elements. The setae are stiff structures formed by mineralized cuticle that are connected to the leg exoskeleton by a non-mineralized joint membrane. Our results demonstrate that different layers of the setal cuticle display contrasting organizations of the chitin-protein fibers and mineral particles. While in the externally positioned exocuticle organic fibers shift their orientation helicoidally in sequential layers, the fibers are aligned axially in the internally positioned endocuticle. In the setal cuticle, layers of structurally anisotropic cuticle likely providing strength in the axial direction are combined with layers of isotropic cuticle which may allow the setae to better resist perpendicular loading. They are further strengthened with amorphous calcium phosphate, a highly fracture resistant mineral rarely observed in invertebrate skeletons.

Exposing Advanced Building Strategies of Strongly Iron-Enriched Incisors

Teeth are an excellent example of optimally designed hybrid organic-inorganic nanoarchitectures composed of simple compounds. Typically, these simple building phases show exceptional mechanical property amplification when formed into constructions. Many natural materials are complex composites in which synergistic benefits of inorganic and organic components enhance the physical and mechanical properties [1]. The constantly growing incisors of rodents are a perfect example of natural organicinorganic complex composite material. The front part of the incisor is covered by hard and resistant enamel, while softer dentin forms the bulk of the tooth, which is gradually removed due to the heavy gnawing, and hence forms self-sharpening device.

Magnesium-Supported Continuous Growth of Rodents' Incisors

A great variety of functional mineralized composite materials are formed by different living organisms. Typically, simple inorganic and organic components are arranged in optimally designed nanoarchitectures that show outstanding performance and fulfill different functions in animal bodies. The constantly growing incisors of rodents are a perfect example of natural complex organic-inorganic composite material. The front part of the incisors is covered by hard and resistant enamel, while softer dentin forms the bulk of the tooth and provides the mechanical support for enamel. Dentin can be considered as heterogeneous material due to the presence of numerous dentinal tubules (DT) that are separated by intertubular dentin (ID) that is forming the matrix [1]. Dentin is composed of approximately 70 wt% of inorganic material, 10 wt% of water and 20 wt% of organic matrix consisting mainly of type-I collagen fibrils [2].

High Resolution STEM Study of Dy-doped Bi 2 Te 3 Thin Films

Breaking the time-reversal symmetry (TRS) in three-dimensional (3D) topological insulators (TIs) is essential for unlocking exotic physical states and exploring potential device application. Doping of the prototypical 3D-TI [1,2] Bi2Te3 with transition metal ions can lead to ferromagnetic ordering at low temperatures [3,4]. Here we report the study of incorporation of dysprosium (Dy) into Bi2Te3 with the intent to achieve higher ferromagnetic ordering temperatures and higher magnetic moments [5].

Structural Anisotropy in a Crustacean Claw Calcified with Amorphous Calcium Phosphate

Animals form a variety of mineralized biological matrices that perform different functions, ranging from ion storage to protecting animal bodies and enabling movement. From the mechanical point of view, extracellular matrices forming animal skeletons are of particular interest, as they are evolutionary optimized for the function they perform. Understanding structure-function relationships of these natural composite materials can lead to the development of biomimetic designs with industrial applications.

Surprising high iron enrichment in hard dental tissues of rodents

Biominerals formed by living organisms display highly diverse composition and structure. Many of such biominerals are highly complex composite materials with excellent physical and mechanical properties [1, 2] that cannot be mimicked in the laboratory. These unique masterpiece architectures where organic matrix and crystalline or amorphous minerals are linked together are formed under conditions of moderate temperature, pressure and pH.

Revealing the Secrets of Strong Iron Enrichment in Hard Dental Tissues from Feral Coypu ( Myocastor coypus ) by Analytical (S)TEM

The diversity of biominerals produced by living organisms in respect of varying composition and structure is very remarkable. Many of these biominerals are highly complex composite materials with excellent physical and mechanical properties [1,2] which cannot be mimicked in laboratory. The combinations of organic matrix and amorphous and crystalline minerals formed under conditions of moderate temperature, pressure and pH possess masterpiece architectures with superior materials characteristics compared to geological counterparts or their synthetically made analogues [2,3].