Tooth enamel is made up of which one of the following calcium compounds?

Tooth enamel is the hardest substance in the human body and serves as the outer protective layer of the teeth [1]. It is primarily composed of inorganic mineral salts, specifically calcium hydroxyapatite, which is a crystalline form of calcium phosphate [1]. Approximately 95% to 96% of the enamel's weight consists of these highly organized hydroxyapatite crystals, represented by the chemical formula Ca10(PO4)6(OH)2. While trace amounts of other minerals like carbonate, sodium, and fluoride can be incorporated into the crystal lattice, the fundamental structural component remains calcium phosphate. This mineral composition provides the enamel with its remarkable hardness and resistance to mechanical wear, although it remains susceptible to corrosion and demineralization when the mouth's pH drops below 5.5 due to bacterial acid production [1].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > pH change as the cause of tooth decay > p. 27