Hygiene Atlas

Atlas · Plate III · Histology and Embryology · 03

Enamel

Enamel is about 96% mineral, mostly hydroxyapatite, and is the hardest tissue in the body. It is laid down as rods that run from the dentinoenamel junction to the surface. Because ameloblasts are lost once the tooth erupts, enamel cannot regrow. Growth lines called lines of Retzius end on the surface as perikymata, and enamel is thickest over the cusps.

High-yield facts · 7

  1. Enamel is about 96% inorganic hydroxyapatite by weight; it is the hardest tissue in the body.S44
  2. Ameloblasts form enamel; they are lost after eruption, so enamel cannot regenerate.S52
  3. The enamel rod (prism) is the basic structural unit; it runs from the DEJ to the surface.S52
  4. Lines of Retzius are incremental growth lines; they end on the surface as perikymata.S52
  5. The neonatal line marks birth in teeth forming at that time (primary teeth and first permanent molars).S52
  6. Enamel is thickest over cusps (about 2.5 mm) and thinnest at the CEJ.S52
  7. Enamel lamellae, tufts and spindles are normal structural features near the DEJ.S52

Facts are written in our own words; each tag links to its source. Values marked "sources vary" differ between references, so check the one your program uses.