**Enamel: The Hardest Substance in the Animal Kingdom**

Enamel refers to the hard, outermost layer of the teeth in vertebrates. It is considered the hardest substance found in the animal kingdom due to its exceptional strength and durability. This unique characteristic of enamel can be attributed to several factors, including its mineral composition, structure, and formation process.

**Mineral Composition**

Enamel primarily consists of a mineral called hydroxyapatite, which is a crystalline calcium phosphate. This mineral provides enamel with its remarkable hardness. Hydroxyapatite crystals align in an organized pattern, contributing to the dense structure of enamel. Additionally, enamel contains a small amount of organic material, primarily proteins, which help in the formation and maintenance of its structure.

**Structure**

The structure of enamel plays a significant role in its hardness. Enamel is composed of tightly packed, tightly bonded hydroxyapatite crystals. These crystals are aligned perpendicular to the tooth surface, forming long, parallel rods known as enamel prisms. The arrangement of these prisms adds to the overall strength of enamel.

Moreover, the prisms are surrounded by a protein-rich matrix called interprismatic substance. This substance acts as a cementing agent, further enhancing the structural integrity of enamel. The compact arrangement of hydroxyapatite crystals and the presence of interprismatic substance contribute to the hardness and resistance of enamel against wear and tear.

**Formation Process**

The formation of enamel, known as amelogenesis, occurs during tooth development. Ameloblasts, specialized cells in the tooth germ, secrete enamel matrix, which gradually mineralizes into mature enamel. During this process, the ameloblasts undergo structural changes and ultimately degenerate, leaving behind the fully formed enamel.

The unique formation process of enamel allows for the deposition of hydroxyapatite crystals in a highly organized manner. The gradual mineralization and structural changes ensure the formation of a dense, solid structure that resists mechanical stress and protects the underlying dentin and pulp of the tooth.

**Conclusion**

Enamel, as the hardest substance in the animal kingdom, possesses remarkable strength and durability. Its exceptional hardness can be attributed to the mineral composition of hydroxyapatite, the compact arrangement of enamel prisms, the presence of interprismatic substance, and the organized formation process during tooth development. Understanding the characteristics and structure of enamel is crucial in appreciating its significance in oral health and the overall functioning of the animal kingdom.

enamel is hardest part bcz it is made of calcium phosphate which is a hard mineral. also the strength of enamel is due to the highest percentage of mineral content ( about 96%)