Enamel Composition and Properties

The incomplete sheath surrounding enamel rods, resisting decalcification and staining darker than enamel.

The material that cements enamel rods together, having a higher refractive index than the rods themselves.

Optical bands on enamel resulting from changes in enamel rod direction. Appear as dark and light alternating bands.

Transverse striations in enamel rods, marking daily enamel formation segments of approximately 4 microns.

Dark bands in enamel reflecting rhythmic enamel formation, showing periods of ameloblast rest and activity.

Brown striations in enamel, marking the separation between enamel formed before and after birth due to nutritional changes.

The pattern of enamel rod direction affects visual appearance of Hunter-Shreger bands; important pattern is visible under reflected light, and not under transmitted light.

Enamel is primarily made up of inorganic substances (96%), mostly hydroxyapatite crystals, and a smaller amount of organic substances (4%) including proteins, carbohydrates, and water.

Enamel color ranges from yellowish-white to grayish-white, depending on factors like translucency, calcification, and homogeneity.

Enamel is thickest at the tips of teeth (cusps and incisal edges) and thins out towards the gumline (cervical region).

Enamel is the hardest tissue in the human body, due to high calcification and crystal arrangement.

Despite its hardness, enamel can break easily if the underlying dentin (the softer tissue underneath) is damaged.

Enamel functions like a semi-permeable membrane, allowing certain substances to pass through.

In baby teeth, enamel rods are vertical at the tips, become oblique, and horizontal near the gumline.

In permanent teeth, enamel rods are similar to deciduous teeth (vertical-oblique), but near the gumline, they point towards the root.

Enamel rods initially start straight near dentin but become wavy before becoming straight again towards the outer surface.

The diameter of enamel rods increases as you move from the dentin-enamel junction towards the surface, in a 1:2 ratio.

Enamel rods can have hexagonal, oval, round, or 'fish scale' shapes in cross-sections.

In a longitudinal view, enamel rods resemble cylinders with striations.

The number of enamel rods varies between teeth, from 5 million in some lower incisors to 12 million in upper first permanent molars.

Enamel formed before birth is generally better quality due to protected fetal conditions and consistent nutrition.

The final product secreted by ameloblasts; structurally similar to a basement membrane (viewed with electron microscopy).

Hypocalcified enamel rods and inter-rod substance, resulting from stress during formation; appear as thin sheets extending from the enamel surface to the DEJ (dentinoenamel junction).

Poorly calcified enamel rods/inter-rod substance, confined to the enamel.

Pre-eruption enamel crack filled by adjacent tissues (epithelial cells or connective tissue).

Post-eruption enamel crack, often containing saliva; can extend to dentin.

Hypocalcified enamel prisms/inter-prismatic substance, appearing as tufts in transverse sections, originating from the DEJ toward the enamel.

Odontoblastic process extending between inner dental epithelium cells before enamel formation; appears black in ground sections due to preparation process.

A short, conical projection of the ameloblast cell, involved in enamel secretion.

Cytoplasmic condensation at the distal end of ameloblasts, separating Tomes' process from the cell body.

First stage of enamel creation, 25-30% of total enamel mineral is formed during matrix formation.

Second stage of enamel formation, mineralizing enamel to 96% inorganic substance

Enamel changes after tooth eruption that deposits ions from saliva, further increasing inorganic matter to 98%.

Physiological tooth wear, due to mastication.

The ability of substances to pass through enamel. Lower in older, older teeth.

Enamel's resistance to wear. Influenced by ionic exchange (e.g., nitrogen, fluorine).

A thin, highly mineralized layer of enamel on the tooth surface, lacking enamel prisms. Typically found at the neck of the tooth.

Tiny, wave-like grooves on the enamel surface, parallel to the cemento-enamel junction. They reflect incremental enamel growth lines.

Concave depressions on the enamel surface, varying in depth and shape. Deeper towards the incisal/occlusal region

Fissure-like structures on enamel surfaces, extensions of enamel lamellae, showing a variable length.

A thin layer of organic material on the outer enamel surface, mostly formed by the reduced enamel epithelium as the tooth erupts.

A type of cementum found along short portions of the cervical enamel area.

Initial stage of ameloblast development, establishing the enamel-dentin junction and cell shape.

Ameloblasts become taller and polarize, the cell free zone disappears, and dentin formation begins.

Ameloblasts continue to produce the enamel matrix as dentin formation is already well established

Long cells that form enamel in teeth; they have a proximal nucleus and an increasing Golgi complex.

The process where cells change shape and function to become specialized.

Cells influencing each other's development.

The elongated projection of ameloblasts, important for enamel formation.

The process of creating the initial enamel structure, which precedes enamel mineralization.

The hardening of the enamel matrix after formation.

A protective layer of epithelium that safeguards the enamel; forms 3-4 layers.

Enzymes secreted to break down tissue, aiding tooth eruption.

Stage of enamel formation marked by ameloblast shrinkage & organelle removal.

Ameloblasts become indistinguishable from the reduced enamel epithelium, completing enamel function.

Epithelial cells facilitate tooth eruption through tissue breakdown.