Ch 7 Enamel

Question 0

Gnarled Enamel

Answer 0

Located at cusp tips where rods are twisted, bent, and intertwined

Question 1

Enamelin

Answer 1

Organic protein component in enamel

Like keratin in skin

Question 2

Hydroxyapatite

Answer 2

Inorganic compound that makes up the enamel, cementum, dentin, and bone
A crystalline calcium phosphate

Question 3

Hunter-Schreger bands

Answer 3

Alternating light and dark bands in enamel (when light is projected onto tooth)

Question 4

Lines (Striae) of Retzius

Answer 4

Incremental lines (like cross section of tree)

Question 5

Lamellae

Answer 5

Cracks in surface of enamel that are visible to naked eye (from surface to DEJ)
Path for caries
Caused by “stress” cracks (temp change)

Question 6

Neonatal Line

Answer 6

Notable/accentuated incremental line that occurs at birth

SPECIFIC Line of Retzius

Question 7

Perikymata

Answer 7

Imbrication lines

Fine ridges on surface of enamel caused by termination of the Lines of Retzius

Question 8

Prismless Enamel

Answer 8

Enamel formed without any prism pattern from the rods
Near surface
No Hunter-Schreger band effect

Question 9

Spindles

Answer 9

Extensions of dentinal tubules that arise at the DEJ and extend into the enamel
Shorter than tufts

Question 10

Tufts

Answer 10

Defects/spaces between rods
Filled with organic matter (enamelin and H2O)
Located at DEJ
Broader and longer than spindles

Question 11

Physical properties of enamel

Answer 11

Very hard
Brittle
Subject to fracture (esp if dentin is carious)
96% inorganic = hydroxyapatite
4% water and organic matter (enamelin: protein)
Grayish white and translucent
Thickness varies: thin at cervical region, 2.5 mm at incisal/occlusal surfaces
After formed, no more can be deposited

Question 12

Enamel rods…

Answer 12

Extend from DEJ to outer surface

Question 13

How many ameloblasts form each rod?

Answer 13

4
1-Head
2-Neck
1-Tail

Question 14

Size of rods

Answer 14

Size of RBC

Question 15

Rods are filled with..

Answer 15

Crystals

Question 16

Rods interlock to..

Answer 16

Prevent fracture and splitting

Question 17

Surface of rod

Answer 17

Rod sheath

More organic material

Question 18

Center of rod

Answer 18

Rod core

Less organic material

Question 19

Rods run..

Answer 19

Perpendicular to enamel surface at cervical region

Gnarled and intertwined near tip

Question 20

Light and dark bands appear when light is projected at surface (rods)

Answer 20

Hunter-Schreger bands

Question 21

“Growth Lines”

Answer 21

Incremental lines

Result of rhythmic recurrent deposits of enamel

Question 22

Permeability caused by..

Answer 22

1 Leakage around faulty restorations
2 Dental decay
3 Lamellae, cracks, tufts, spindles
4 Microlamellae- minutes spaces between rods
5 Surface irregularities

Question 23

Hydroxyapatite crystals in enamel are ___X bigger than in dentin

Answer 23

30X

Larger the crystal, harder the tissue

Question 24

Etching

Answer 24

Alters enamel surface
Usually Phosphoric Acid
Helps adherence of sealants