Our teeth are complex structures. While the outermost layer, enamel, often receives the most attention for its hardness, an important component lies beneath it: dentine. This internal tissue plays an important role in the health and resilience of our teeth, acting as a foundation that supports and protects.
What Dentine Is: Location and Makeup
Dentine is a hard, mineralized tissue that forms the bulk of a tooth’s structure. It is situated directly beneath the enamel in the crown and under the cementum in the root, encapsulating the soft inner dental pulp. Unlike enamel, dentine is composed of both inorganic and organic materials. Approximately 70% of dentine consists of the mineral hydroxyapatite, while about 20% is organic material, primarily collagen, and roughly 10% is water.
This composition gives dentine a semi-hard, yellowish appearance, influencing the overall color of the tooth because enamel is translucent. A distinctive feature of dentine is the presence of microscopic channels known as dentinal tubules. These tubules radiate outward from the pulp chamber towards the outer surface of the dentine, containing fluid and extensions of specialized cells called odontoblasts.
The Vital Role of Dentine
Dentine provides the primary structural support for the tooth, acting as a foundation for the more brittle enamel. Its elasticity and tensile strength allow it to absorb and distribute chewing forces, preventing the enamel from fracturing under pressure. This resilience helps maintain the tooth’s integrity.
Beyond structural support, dentine acts as a protective barrier for the sensitive dental pulp, which contains nerves and blood vessels. It insulates the pulp from temperature changes and external irritants. Dentine also contributes to tooth longevity by continuously forming new dentine throughout life, maintaining its protective qualities.
Dentine and Tooth Sensitivity
Dentine plays a direct role in tooth sensitivity. When the protective outer layers of enamel or cementum are lost, the underlying dentine becomes exposed. This exposure allows external stimuli, such as hot, cold, sweet, or acidic foods and drinks, to directly affect the dentinal tubules.
The “hydrodynamic theory” explains that these stimuli cause rapid fluid movement within the exposed dentinal tubules. This fluid movement then triggers nerve endings at the pulp’s periphery, resulting in a short, sharp pain. Common causes of dentine exposure include gum recession, aggressive brushing, teeth grinding, and enamel erosion from acidic substances.
Dentine’s Response to Damage and Wear
Dentine is a living tissue with an ability to respond to various forms of damage and wear. Throughout life, dentine continually forms a type known as secondary dentine. This physiological process, occurring after tooth development is complete, leads to a gradual reduction in the size of the pulp chamber, providing additional protection to the pulp.
In response to specific injuries, such as dental decay, abrasion, or trauma, dentine can produce another type called tertiary dentine. This is a localized protective mechanism. If the stimulus is mild, existing odontoblasts can form reactionary dentine. If the damage is more severe and original odontoblasts are destroyed, new odontoblast-like cells can differentiate to form reparative dentine, which helps to wall off the advancing lesion and protect the pulp.