Enamel is the hard calcified tissue which covers the dentine of a tooth. It is
the hardest substance produced by vertebrates.
Enamel is composed almost entirely of inorganic calcium phosphate (apatite),
most of which is arranged in a crystalline lattice structure.
Cross-sectional view of a tooth
Sam Fentress Tooth section (GNU Free Documentation license)
Dental fluorosis - Dentine - Fluoride
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