ISBN 9783843936583

978-3-8439-3658-3, Reihe Materialwissenschaften

Ezgi Deniz Yılmaz
Ultrastructural and mechanical characterization of bovine enamel at multiple length scales

133 Seiten, Dissertation Technische Universität Hamburg-Harburg (2018), Softcover, A5

Zusammenfassung / Abstract

Ancestral animals exhibit a simple enamel structure made of parallel aligned nm-sized hydroxyapatite (HAP) fibers and a little amount of soft matrix, which has evolved over time into a complex hierarchical composite. In the course of evolution, the magnitude of biting load imposed on teeth has increased. And also the type and direction of stresses generated in enamel have become far more complex. Thus, the hierarchical microstructure of enamel is believed to have evolved to enhance its mechanical properties. But which mechanical properties are improved and how exactly? A number of studies using advanced fracture mechanical methods were undertaken in the last decade revealing an increasing trend in the fracture toughness of enamel with increasing hierarchical levels. However, there is still no general agreement on how hierarchical structuring affects the stiffness and strength of enamel. The main aim of this study was to identify how and to which extent the compressive mechanical properties of enamel (considered as a biological composite) depend on its structural architecture, focusing on the aspects of hierarchy and direction. For this, extensive structural analyses and site-specific/size-dependent uni-axial compression tests were performed with bovine enamel. Bovine enamel is chosen for its easy availability and larger size compared to human enamel.