Teeth are not made of keratin, a common misconception. Instead, they are specialized organs primarily composed of mineralized tissues: enamel, dentin, and cementum, along with the soft inner pulp. This unique composition provides their hardness and durability, allowing them to perform essential functions like chewing and speech.
The Primary Components of Teeth
A human tooth consists of four main components.
Enamel
The outermost layer of the tooth crown is enamel, the hardest substance in the human body. It is primarily composed of hydroxyapatite crystals, a calcium phosphate mineral. This mineralized structure provides hardness and resistance to wear, protecting against damage from chewing and acids.
Dentin
Beneath the enamel lies dentin, forming the bulk of the tooth. This mineralized connective tissue is harder than bone but softer than enamel. It contains tubules that transmit sensations like temperature and pressure. Dentin supports the enamel, protects the pulp, and contributes to the tooth’s shape.
Cementum
Cementum covers the tooth root, anchoring it to the jawbone. This bone-like tissue facilitates the attachment of periodontal ligaments, which connect the tooth root to its socket. Cementum is essential for maintaining the tooth’s stability.
Pulp
The innermost part of the tooth is the pulp, a soft tissue in the pulp chamber and root canals. It contains nerves and blood vessels, nourishing the dentin and enabling the tooth to sense pain, temperature, and pressure. The pulp also forms dentin throughout a tooth’s life.
Understanding Keratin
Keratin is a family of tough, fibrous structural proteins found in vertebrates. These proteins are known for their strength and protective qualities, being highly insoluble in water and organic solvents. Keratin monomers assemble into bundles to form intermediate filaments, which contribute to the durability of the tissues where they are found.
Keratin is the primary structural component of various biological materials. Examples include human hair, fingernails, and the outer layer of skin. In animals, keratin forms structures such as claws, hooves, horns, and feathers. Its function in these tissues often involves providing mechanical protection, structural support, or other specialized roles like insulation in hair or flight in feathers.
Why Teeth and Keratin are Different
The composition and biological roles of teeth and keratinous structures are fundamentally different. Teeth are primarily mineralized tissues, designed to withstand forces involved in chewing. Their hardness and rigidity come from their high mineral content, particularly hydroxyapatite. This mineral-based structure is optimized for mechanical strength and resistance to wear.
In contrast, keratinous structures are protein-based and, while tough, often exhibit properties like flexibility and elasticity. Hair, for instance, provides insulation and flexibility, while nails offer a durable but adaptable surface for gripping or scratching. The distinct functions of teeth necessitate a composition that prioritizes unyielding hardness for mastication, a requirement that protein-based keratin cannot fully meet. Therefore, the body employs different primary building blocks to suit the specific demands placed on these varied biological structures.