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26 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What is the composition of enamel? |
96% hydroxyapatite crystals, 4% organic material (enamelin/tuftlein smeared on surface of crystals)
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What color is enamel? Dentin?
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Enamel is light blue; Dentin is yellow – THE HARDER THE ENAMEL, THE MORE TRANSLUCENT = YELLOW TEETH
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How does enamel change with age?
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More dense; Less permeable to water, ions, etc.
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What is the basic structure of enamel
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Enamel rods
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What are the units that ameloblasts lay down? How are they oriented?
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Rod segments that are parallel to each other but perpendicular to the enamel surface and DEJ
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What path do rods follow? Why?
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They go from DEJ to tooth surface like spokes on a wheel but are curved 2 +/- 10 degrees from each other; THIS ARRANGEMENT PREVENTS CLEAVAGE
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What is the shape of the enamel rod and how is it formed?
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Bulbous head and long skinny tail (looks like keys packed together); 1 ameloblast makes the head and 3 make the tail = 4 ameloblasts to make an enamel rod; TAIL IS CALLED INTER-ROD ENAMEL
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Describe arrangement of crystals at the center of the rod, periphery of the rod, and center of the tail
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CENTER – parallel to longitudinal axis of rods, PERIPHERY – Oblique angle to long. Axis, CENTER OF TAIL – perpendicular to long axis of rod
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Why is this arrangement important?
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Helps us differentiate between rod and tail in imaging
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What is the Striae of retzius called after birth? What can happen to it?
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Neonatal line (can become larger due to trauma during birth)
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Perikymata
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parallel shallow grooves on enamel surface formed by striae overlapping (“peri” is around; grooves around the striae)
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Imbrication Lines of Pickerill
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parallel elevations on enamel surface formed by striae overlapping
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What happens to these structures?
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disappear with age
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How many tails surround a head?
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4
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What is the shape of DEJ?
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Scalloped so that convexity of enamel fits into the concavity of dentin
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What are the 3 structures of the DEJ?
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Enamel Spindles, Enamel Tufts, and Enamel Lamellae
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Enamel spindles
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short-spindle-like structures at ends of dentinal tubules that are stuck in enamel
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Enamel Tufts
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hypocalcified enamel that extends 1/3 of way into enamel from DEJ
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Enamel lamellae
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other hypocalcified enamel rods
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FALSE Enamel lamellae
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Enamel cracks that extend from the DEJ into the dentin
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TRUE Enamel lamellae
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Poorly calcified enamel from developmental distubrances of ameloblasts that starts at enamel surface and ends at DEJ
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Gnarled enamel? Function?
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Located deep to cusps and made of enamel rods that intertwine as they pass from DEJ to tooth surface; protects enamel from cleavage
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Hunter-Schreger bands
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light (PARA
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ONES) and dark (DIA
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Fluoridation
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1ppm of fluoride to keep teeth resistant to acid/caries
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Fluorosis
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too much fluoride kills ameloblasts, leading to hypocalcifiation of enamel/mottling
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Chronologic enamel hypoplasia
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Childhood fever can cause band of hypocalcified enamel for the period of illness |
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