Enamel, dentine, cementum and pulp: histology and defects
- Anatomy and histology
Enamel is made once by cells that then disappear; dentine keeps growing all life. Defects in how they form show as spots, stains and weak teeth.
What it is
Enamel is made by ameloblasts, which derive from the oral ectoderm and are lost when the tooth erupts, so enamel can never be rebuilt by the body. It is about ninety-six percent hydroxyapatite arranged in rods (prisms). Dentine, cementum and pulp come from neural crest–derived mesenchyme. Odontoblasts make dentine and keep their processes in the dentinal tubules; they can lay down new (secondary and reparative) dentine in response to age, wear or caries. Cementum resembles bone and anchors the ligament fibres.
Clinical anatomy
- Enamel: hydroxyapatite rods; no cells, nerves or vessels after eruption.
- Dentine: about seventy percent mineral; tubules with odontoblast processes and fluid.
- Reparative (tertiary) dentine: laid down under a cavity or worn area, protecting the pulp.
- Cementum: bone-like tissue covering the root; can be cellular near the apex.
- Fluoride replaces hydroxyl groups to form fluorapatite, which resists acid better.
Clinical correlation
- Enamel hypoplasia and hypomineralisation (from illness, preterm birth or nutritional deficit while the teeth form) appear as pits, bands or chalky spots and decay easily.
- Too much fluoride while teeth form causes fluorosis: white streaks or, in severe cases, brown pitted enamel.
- Tetracyclines given to pregnant women or young children bind to forming teeth and stain them grey-brown permanently.
- Genetic defects (amelogenesis imperfecta of enamel, dentinogenesis imperfecta of dentine, the latter with osteogenesis imperfecta) cause weak, discoloured teeth.
Next step / Initial management
- Discoloured or pitted teeth: ask about fluoride sources, tetracycline exposure, preterm birth and family history.
- Avoid tetracyclines in pregnancy and in young children while the teeth are forming, unless no alternative exists.
- Refer to the dentist for weak or defective enamel, which needs protection (sealants, fluoride, restorations).
Test yourself
Think of the answer, then tap the question to see it.
Which cells make enamel and why can enamel not be rebuilt?
Ameloblasts, derived from oral ectoderm; they are lost when the tooth erupts.
Which antibiotic class stains developing teeth?
Tetracyclines, when given in pregnancy or to young children while the teeth are mineralising.
How does fluoride make enamel more resistant to acid?
It is incorporated into the crystal as fluorapatite, which dissolves less easily than hydroxyapatite.
Elsewhere in DurgiPedia
Connections
In Pharmacology2
Educational content; it does not replace assessment by a dentist or doctor and is not a clinical instruction. For facial or neck swelling with difficulty swallowing or breathing, a knocked-out tooth or bleeding that will not stop, go to an emergency department at once.
Sources: Histology, Tooth (StatPearls Publishing (NCBI Bookshelf), 2023); Developmental Disturbances of the Teeth, Anomalies of Structure (StatPearls Publishing (NCBI Bookshelf), 2023); Dental Fluorosis (StatPearls Publishing (NCBI Bookshelf), 2023).
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Representative model, for educational purposes only.