Ch 7 Enamel Flashcards
(25 cards)
Gnarled Enamel
Located at cusp tips where rods are twisted, bent, and intertwined
Enamelin
Organic protein component in enamel
Like keratin in skin
Hydroxyapatite
Inorganic compound that makes up the enamel, cementum, dentin, and bone
A crystalline calcium phosphate
Hunter-Schreger bands
Alternating light and dark bands in enamel (when light is projected onto tooth)
Lines (Striae) of Retzius
Incremental lines (like cross section of tree)
Lamellae
Cracks in surface of enamel that are visible to naked eye (from surface to DEJ)
Path for caries
Caused by “stress” cracks (temp change)
Neonatal Line
Notable/accentuated incremental line that occurs at birth
SPECIFIC Line of Retzius
Perikymata
Imbrication lines
Fine ridges on surface of enamel caused by termination of the Lines of Retzius
Prismless Enamel
Enamel formed without any prism pattern from the rods
Near surface
No Hunter-Schreger band effect
Spindles
Extensions of dentinal tubules that arise at the DEJ and extend into the enamel
Shorter than tufts
Tufts
Defects/spaces between rods
Filled with organic matter (enamelin and H2O)
Located at DEJ
Broader and longer than spindles
Physical properties of enamel
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
Enamel rods…
Extend from DEJ to outer surface
How many ameloblasts form each rod?
4
1-Head
2-Neck
1-Tail
Size of rods
Size of RBC
Rods are filled with..
Crystals
Rods interlock to..
Prevent fracture and splitting
Surface of rod
Rod sheath
More organic material
Center of rod
Rod core
Less organic material
Rods run..
Perpendicular to enamel surface at cervical region
Gnarled and intertwined near tip
Light and dark bands appear when light is projected at surface (rods)
Hunter-Schreger bands
“Growth Lines”
Incremental lines
Result of rhythmic recurrent deposits of enamel
Permeability caused by..
1 Leakage around faulty restorations 2 Dental decay 3 Lamellae, cracks, tufts, spindles 4 Microlamellae- minutes spaces between rods 5 Surface irregularities
Hydroxyapatite crystals in enamel are ___X bigger than in dentin
30X
Larger the crystal, harder the tissue