Enamel & Amelogenesis Flashcards
Dentine is of ectomesenchymal origin. Enamel however, is from ectodermal origin. True or False?
True
Where would you find the thickest layer of enamel over teeth? Thinnist?
Thickest over cusps.
Thinnest over cervical region
What does Birefringent mean? What substance is birefringent?
Refracts light in different directions
Enamel
What would you expect to have lower translucency? Enamel from primary or permanent dentition?
primary
Enamel is resistant to abrasion, fractures, and cannot regenerate. It also has high tensile strength and is generally hard, but brittle.
True or false?
False, low tensile strength.
Rest is of the paragraph is true.
What are the benefits of a ground section vs demineralized section for observing enamel?
Ground section loses soft tissue, but you can actually see enamel.
Enamel is completly lost in demineralized sections.
What are the 3 prism patterns of enamel? Which one is predominant in humans?
Circular
Parallel
Keyhole
Keyhole for humans
What are hunter-schreger lines?
10-13 layers of prisms that follow the same direction with blocks below and above that follow different directions.
Prisms that are cut tranversely, known as diazones, show up are dark banding while the prisms that are cut longitudally, known as parazones, show up as white lines
Hunter Schreger Bands are useful because?
The complex pattern confers resistance to fracture
What part of enamel is most susceptible to fracturing?
The outer 1/3 layer. Hunter Schreger bands do not reach the outer 1/3 of enamel.
Where would you see gnarled enamel? What is it?
Enamel over cusps and incisal edges that appear to have some coiling of prisms
What is aprismatic enamel? Where do you usually see it?
90 degree angled crystallites from the surface that don’t have a prism structure. Usually see it in newly erupted teeth although it in on the outermost layer of enamel from both primary and perm dentition
What are incremental lines and how are they important?
During development changes in the enamel secretory rhythm, chemical composition and/or the position of the developing enamel front are recorded as incremental features.
Short period are cross striations 24 hour period
Long period are striae of retzius - weekly
SOR run obliquly down enamel
What is perikymata?
Ridges and drooves seen in perm teeth and cervical enamel of primary 2nd molars
What are these rings?
Striae of Retziuss (transverse section)
What are theses lines?
Striae of Retziuss (longitudinal section)
What are enamel tufts?
Hypomineralized protein rich (tuftellin) areas of enamel. Same directions as prisms and only within inner third of enamel.
