Enamel

Enamel is a term used for two distinct hard, protective surfaces. In mammals, dental enamel is the outermost layer of teeth, covering the crown and serving as the first line of defense against mechanical wear and chemical attack. In materials science, enamel refers to a vitreous glaze fused to metal or ceramic surfaces to provide a smooth, durable coating.

Dental enamel is the body’s hardest substance, about 96% mineral by weight, predominantly hydroxyapatite crystals, with small amounts of water and organic components. It is acellular and aneural and contains no collagen. The mineral crystals are organized into enamel prisms (rods) and interprismatic enamel, with a thin boundary, the dentinoenamel junction (DEJ), where enamel meets underlying dentin. The enamel is translucent and appears white or yellowish due to light scattering and thickness.

Enamel forms during tooth development through secretion of enamel matrix by ameloblasts, followed by mineralization. After eruption, it cannot regenerate if damaged. It is extremely hard and wear resistant but brittle and prone to chipping and fracture. It is avascular, receiving nutrients via diffusion through the dentin.

Clinical considerations include susceptibility to dental caries and acid erosion; once minerals are lost, remineralization can occur with fluoride and calcium/phosphate ions, especially in early lesions. Enamel thickness varies by tooth type and location, typically around 1–2.5 mm on crowns but thinner at cusps or high-wear areas.

Glazes or enamels in industry are glassy coatings applied to metals or ceramics and fused in a kiln to create smooth, glossy surfaces. Industrial enamel compositions differ from dental enamel and are engineered for chemical resistance, color, and durability.