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The teeth of Arctodus pristinus transition between undulating to acute-angled Hunter-Schreger bands while Arctodus simus exhibited a transition between undulating to zigzag bands, demonstrating an evolution towards reinforced tooth enamel. This has been convergently evolved with giant pandas, agriotheriin bears, and Hemicyon. [9]
The enamel on primary teeth has a more opaque crystalline form and thus appears whiter than on permanent teeth. The large amount of mineral in enamel accounts not only for its strength but also for its brittleness. [6] Tooth enamel ranks 5 on Mohs hardness scale (between steel and titanium) and has a Young's modulus of 83 GPa. [4]
Hydroxyapatite, also known as hydroxylapatite, is the major component of tooth enamel and bone mineral. A relatively rare form of apatite in which most of the OH groups are absent and containing many carbonate and acid phosphate substitutions is a large component of bone material. [13]
An enamel prism, or enamel rod, is the basic unit of tooth enamel. Measuring 3-6 μm in diameter in primates, [ 1 ] enamel prism are tightly packed hydroxyapatite crystals structures. The hydroxyapatite crystals are hexagonal in shape, providing rigidity to the prism and strengthening the enamel.
This process begins during tooth development after the initial formation of dentin (dentinogenesis), the layer beneath the enamel. [2] The inner enamel epithelium (IEE), a layer of cells within the developing tooth, plays a crucial role by signaling the differentiation of specialized cells called ameloblasts , [ 3 ] which then secrete the ...
Enamel and dentin do not regenerate after they mineralize initially. Enamel hypoplasia is a condition in which the amount of enamel formed is inadequate. [59] This results either in pits and grooves in areas of the tooth or in widespread absence of enamel. Diffuse opacities of enamel does not affect the amount of enamel but changes its appearance.
The enamel on primary teeth has a more opaque crystalline form and thus appears whiter than on permanent teeth. The large amount of mineral in enamel accounts not only for its strength but also for its brittleness. [7] Tooth enamel ranks 5 on Mohs hardness scale and has a Young's modulus of 83 GPa. [5]
The AMELX gene encodes for the structural modeling protein, amelogenin, which works with other amelogenesis-related proteins to direct the mineralisation of enamel. This process involves the organization of enamel rods , the basic unit of tooth enamel, as well as the inclusion and growth of hydroxyapatite crystals.