Histology of Enamel Quiz (ODS Learning Outcomes)

Enamel Composition and Structure

• Enamel is primarily composed of 96% inorganic minerals, predominantly calcium hydroxyapatite.
• Minor components include carbonate and fluoride.
• The remaining 4% is organic, including fibrous material (collagen), water, and proteins.
• Enamel is structured from enamel rods (prisms).
• These rods are tightly packed, creating a cross-sectional shape resembling a head and tail configuration (head towards occlusal/incisal surface, tail to cervical).
• Each rod contains millions of calcium hydroxyapatite crystallites.
• Enamel thickness varies significantly, thickest at cusp tips and thinnest at cervical margins.
• enamel crystallites are millions of hydroxyapatite packed crystallites arranged in a key-hole shape.
• Enamel shows incremental lines (striae of Retzius).
• Perikymata is the edge of the striae of retzius.
• Prismless enamel, found at the dento-enamel junction, features a scalloped appearance, enhancing bonding strength.

Enamel Function and Relationship to Structure

• Enamel is the hardest biological tissue, protecting the tooth and pulp.
• It covers the entire crown of the tooth and its thickness varies based on the location (thicker at cusps for biting and chewing).
• Enamel lacks cellular repair mechanisms.
• Its mineralized structure enables ion exchange for demineralization and remineralization processes (e.g., response to acids).
• Enamel is translucent and aesthetically pleasing.

Clinical Appearance of Enamel Throughout Life

• Enamel can experience wear from abrasion, attrition, and erosion.
• Changes in translucency can alter its colour.
• Demineralisation and remineralization cycles occur.
• Enamel's micropores can reduce its permeability (over time).
• Demineralisation can expose the underlying dentine, potentially causing a yellowish appearance.

Clinical Significance of Enamel in Health and Disease

• Enamel defects during amelogenesis (enamel hypoplasia or hypomineralisation) can have adverse effects.
• A common example is molar-incisor hypomineralisation influencing caries vulnerability and sensitivity.
• Enamel defects from local disturbances (e.g., trauma) or systemic factors (e.g., fluorosis, tetracycline exposure, nutritional deficiencies).
• Genetic factors (e.g., amelogenesis imperfecta) also contribute to enamel problems.