%0 Journal Article
%T Mechanical Properties of Enamel Nanocomposite
%A Nilormi Biswas
%A Arjun Dey
%A Saugata Kundu
%A Himel Chakraborty
%A Anoop K. Mukhopadhyay
%J ISRN Biomaterials
%D 2013
%R 10.5402/2013/253761
%X For adult Indian premolar teeth, we report for the first time ever the simultaneous evaluations of nanohardness, Young's modulus, and fracture toughness of the enamel nanocomposite. The nanohardness and Young's moduli were evaluated from near the beginning of the middle enamel region to within 10£¿¦Ìm of the dentino-enamel junction (DEJ) and in the dentin region using the nanoindentation technique. The fracture toughness from near the middle of the enamel region to near the DEJ zone was measured using the microindentation technique. The deformation was studied using scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM). The relative differences in the extents of biomineralization in the enamel and dentin regions were studied by the energy dispersive X-ray (EDS) technique. The variations of the toughness of the enamel as a function of the toughness of the protein matrix phase have been analyzed which showed that the predicted value of the toughness of the protein present in the nanocomposite was comparable to that of other bioproteins reported in the literature. Further, the work of fracture estimated from the measured value of toughness of the enamel nanocomposite agreed well with the experimental data reported in the literature. 1. Introduction Tooth is a microscopically functionally graded calcium phosphate based natural biocomposite material (Figure 1). Furthermore, tooth has also a hierarchical architecture, for example, from macrostructure to microstructure to nanostructure (Figure 1). The tooth is composed of mainly the hard enamel, the more ductile dentin, and a soft connective tissue, the dental pulp. Enamel is the hardest structure in the human body with approximately 95£¿wt% hydroxyapatite (HAP). On the other hand, dentine possesses a porous structure and is made up of 70% inorganic material (i.e., HAP), 20% organic materials (i.e., collagen fiber), and 10% water by weight. The enamel microstructure shows different orientations of closely packed enamel prisms or rods. These rods are encapsulated by an organic protein called enamel sheath. Further, the prisms or rods consist of nanosize inorganic HAP crystals with different orientations inside. On the other hand, the dentine has a collagen matrix reinforced with HAP nanocrystal retained as layer by layer. The composite bed of dentine also has dentine tubules and channel-like microstructures which supply the nutrition from the pulp region to the crown part of the teeth. In contrast, the interface between the enamel and dentin junction (DEJ) is arranged with
%U http://www.hindawi.com/journals/isrn.biomaterials/2013/253761/