Our teeth are biological structures that enable us to chew, speak clearly, and form expressions. While they might appear to be simple, solid objects, teeth are intricately designed. They are composed of several distinct materials, each playing a specialized role in their function and durability.
The Tooth’s Outer Defenses: Enamel
The outermost layer of the tooth, visible above the gum line, is enamel. It is the hardest substance in the human body, surpassing even bone in its mineral density. Enamel’s composition is primarily inorganic, consisting of approximately 95% hydroxyapatite, a crystalline form of calcium phosphate. The remaining percentage includes water and organic materials.
Its extreme hardness allows it to withstand the forces of chewing and biting. It acts as a protective barrier, shielding the softer internal structures of the tooth from temperature fluctuations, physical damage, and acidic attacks from bacteria. Unlike other body tissues, enamel is non-living and cannot regenerate once damaged or eroded.
The Bulk and Its Vital Core: Dentin and Pulp
Beneath the enamel lies dentin, which constitutes the majority of the tooth’s structure. Dentin is a calcified tissue that is less mineralized than enamel but harder than bone, providing support and flexibility to the tooth. Its composition includes about 70% hydroxyapatite, 20% organic material (primarily collagen), and 10% water.
Dentin has a yellowish hue, and its translucency influences the overall shade of the tooth. A distinguishing feature is the presence of microscopic channels called dentinal tubules, which extend from the pulp to the outer surface. These tubules contain fluid and cellular extensions, enabling the transmission of sensations like temperature and pressure, which can result in sensitivity if the dentin becomes exposed. Dentin also continues to form throughout life, responding to stimuli like wear or decay by producing new layers.
The dental pulp is a soft tissue nestled within the innermost part of the tooth, encased by dentin. It occupies the pulp chamber within the crown and extends into the root canals. This living tissue is rich in blood vessels, nerves, and connective tissue.
The dental pulp serves several functions, including providing nourishment to the dentin through its blood supply, maintaining its hydration, and forming new dentin. The nerves within the pulp are responsible for sensing pain, temperature changes, and pressure. The pulp also contains specialized cells that can initiate the formation of new dentin in response to damage, helping to protect the tooth’s core.
Anchoring the Tooth: Cementum
The root of the tooth, which extends into the jawbone, is covered by a specialized hard tissue called cementum. This bone-like substance is less hard and less mineralized than dentin. Cementum is composed of approximately 45-50% inorganic material (primarily hydroxyapatite) and about 50-55% organic material (largely collagen), along with water.
Cementum’s primary function is to serve as an attachment point for the periodontal ligament fibers. These fibers are strong connective tissues that bridge the gap between the tooth root and the surrounding jawbone, anchoring the tooth within its socket. Cementum can also undergo repair and regeneration throughout life, adapting to changes and helping to maintain the tooth’s stability within the jaw.