ISBN 978-3-8439-5081-7

978-3-8439-5081-7, Reihe Materialwissenschaften

Jasmin Koldehoff
Structural, Compositional and Mechanical Characterization of Bovine Dental Enamel

203 Seiten, Dissertation Technische Universität Hamburg (2022), Softcover, A5

Zusammenfassung / Abstract

In this work a thorough structural and mechanical characterization of untreated and deproteinized bovine dental enamel was carried out. Enamel was deproteinized by chemical treatment and by heat treatment. Advanced microscopy techniques such as FIB and TEM revealed that the interfaces between single HAP crystallites likely cannot accommodate organic structures due to their narrow gap size of often <1 nm. Furthermore, the boundaries between enamel rods are discontinuous, porous structures and there is no complete organic layer engulfing the rods. In untreated enamel frequent bridging filaments could be found that might be of organic origin and were not present in the deproteinized enamel. While chemical treatment did not affect the crystal structure and arrangement, heating enamel leads to decomposition of inorganic components and sintering of the HAP crystallites. Additionally, at high temperatures large cracks are formed in the sample which lead to a largely reduced elastic modulus and hardness. Chemical treatment on the other hand did not affect the modulus and hardness, showing that the protein content is not the decisive factor for those properties. Nanoindentation creep studies confirmed that the protein content does not have a large influence on the mechanical behavior of dental enamel, as virtually no differences could be observed between deproteinized and untreated enamel. However, a pseudo-elastic behavior of enamel and a noticeable influence of water on the mechanical properties of enamel could be observed. Wet enamel, both deproteinized and untreated, had a lower elastic modulus and showed considerably more creep (~10% of the complete deformation) and recovery than dry enamel on both the first and second hierarchical level. It is proposed that the predominant creep mechanism in dental enamel is frictional sliding of the HAP crystallites which is facilitated by the water that is present in the pores and interfaces.