Tooth enamel of humans is made up of:

Human tooth enamel is the hardest substance in the body and is primarily composed of calcium hydroxyapatite, which is a crystalline form of calcium phosphate [1]. Enamel is a highly mineralized dental tissue, consisting of approximately 96% to 97% calcium phosphates by weight [4]. Chemically, these minerals exist as hydroxyapatite crystals with the formula Ca10(PO4)6(OH)2, where calcium (Ca) and phosphate (PO4) are the principal inorganic components. While enamel lacks collagen, it contains a small percentage of water and organic proteins like enamelins that provide a framework for mineralization. Tooth decay occurs when the pH in the mouth drops below 5.5, causing the calcium phosphate structure to corrode or demineralize [2]. Because hydroxyapatite is the primary inorganic mineral in both teeth and bones, it is frequently used in dental treatments for remineralization and repair.

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
2. [4] https://www.ncbi.nlm.nih.gov/books/NBK513314/
3. [2] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Dental caries > p. 86