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86 Cards in this Set
- Front
- Back
What is the hardest substance in the body?
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enamel
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Enamel is (cellular/acellular) and is mostly devoid of ____________.
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acellular, organic material
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What accounts for 96% of enamel?
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hydroxyapatite
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What are the percentages of water and organic material in enamel?
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3%; 0.5-1%
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10% HCl will result in _____________ of the enamel?
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decalcification
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What is the basic structural unit of enamel?
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enamel rods
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The organic component of enamel is what percent protein?
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90-95%
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What are the two major proteins in enamel?
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enamelin and amelogenin
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Ground substance of enamel is composed of what three substances?
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1. polysacchrides
2. glycoproteins 3. phospholipids |
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the length of an enamel rod depends on its location in the ___________?
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crown
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T or F: the length of an enamel rod may exceed the thickness of the enamel
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true
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average enamel is rod is ________ in length and __________ in width?
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2mm, 5um
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rods are thicker towards the (surface/DEJ)?
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surface
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What portion of the enamel rods are wavy?
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first 1/3 of the enamel rods (near DEJ)
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enamel rod density is higher at the DEJ or surface of the tooth?
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DEJ
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Daily deposition of enamel results in what structure?
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cross striations
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a cross section of an enamel rod has what shape?
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key-hole
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enamel rods consist of what two regions?
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head and tail
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enamel rod sheaths are distinct around _____________ but blurred around _____________?
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the head, tails
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enamel rods are (parallel/perpendicular) to the long axis of the tooth, while interrod enamel is (parallel/perpendicular).
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parallel, perpendicular
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Interrod enamel is (more/less) mineralized than enamel rods.
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less
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Lack of a Tome's process will result in what kind of enamel?
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prismless
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Tome's process pit produces the rod _______?
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head
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__ ameloblasts make a core, but __ make a tail?
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1,3
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____________ is randomly dispersed the a tome's process while ___________ is not.
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amelogenin, enamelin
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_______________ serves as a template for HA deposition in enamel?
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enamelin
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T or F: maturation of enamel involves the addition in number of HA crystals?
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False, number and length do not change, only width of the crystals.
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Removal of what protein allows HA crystal to increase in size?
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amelogenin
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Name two places where prismless enamel occurs?
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DEJ, surface
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HA crystal in the enamel rod are arranged parallel to the _____________ of the rod.
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long axis
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HA crystals in the rod tail are arranged ____________ to the rod.
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obliquely
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Interrod enamel is located between a rod ______ and a rod ______?
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head, tail
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greatest amount of matrix in enamel is found in the _______________?
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enamel rod sheath
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enamel rod sheath is approx. _____ um in width?
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0.2
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The only way to distinguish between enamel rod head and rod sheath by determining the amount of ______________________?
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matrix and calcification
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Enamel rod ______ is almost exclusively HA crystals while the enamel rod _______ is almost exclusively matrix.
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head, sheath
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name the 3 zones of an enamel HA crystal.
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1. hydration shell
2. crystal surface 3. cyrstal interior |
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The hydration shell on an HA crystal is formed on the outside of what layer?
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crystal surface by incorporation of water
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Which layer of an HA crystal interacts with ions?
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crystal surface
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Most ions which interact with the crystal surface of an HA crystal (soften/harden) the enamel? The exception is (Na, Mg, F, Sr, Ra, CO3, citrate)?
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soften, F
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An HA crystal is _____nm thick x ___nm wide x ____um long?
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30,65,2
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space between HA crystal is less than ___ nm?
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2
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Enamel runs ____________ at the DEJ, ____________ in the middle zone and ______________ in the outer zone.
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perpendicular, helically, perpendicular
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Enamel appears wavy in the 1/3 portion nearnest the (DEJ/surface of the tooth)?
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DEJ
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______________ are regions in enamel where groups of enamel rod curve up and out while others curve in and down.
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Hunter Schreger bands
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Hunter Schreger bands appear as ______ and _______ bands within the enamel.
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light, dark
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If you were to section a tooth longitudinally, what band would you see in the enamel? How would they appear?
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Hunter Schreger bands; you would see some bands coming towards you and some running longitudinally
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More organic content allows (more/less) light to penetrate the structure?
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more
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T or F: enamel lamellae extend the length of the enamel?
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True
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Enamel lamellae are ____________ mineralized enamel?
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improperly
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What are A, B and C?
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A - lamella
B - tuft C - spindle |
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Name the 3 causes of enamel lamella formation.
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1. Uncalcified enamel
2. crack formed and filled with enamel organ cells (before eruption) 3. crack formed after eruption and filled with salivary proteins |
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T or F: enamel lamellae are more common with age?
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True, due to unequal loading on teeth
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T or F: enamel tufts extend the whole length of the enamel.
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False, they extend only through the inner 1/3
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Enamel tufts are (normal/abnormal) structures in enamel?
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normal
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Enamel tufts are (more/less) calcified than surrounding enamel?
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less
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Enamel tufts increase the organic content of enamel near the DEJ to _x other enamel?
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3
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Enamel tufts have a __________ appearance.
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grass-like
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"Leaves" of the enamel tufts are due to the _______________?
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curvature of enamel in this region
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Tension planes will cause (increased/decreased) calcification?
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decreased
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An enamel spindle is an ___________ ___________ that gets stuck in enamel.
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odontoblastic process
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DEJ is ____________ (shape) with (concave/convex) portion towards the DEJ?
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scalloped;concave
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The number of concavities in the DEJ roughly corresponds with the number of what?
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enamel rods
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cross striations are in (enamel/dentin)?
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enamel
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cross striations are (parallel/perpendicular) to enamel rods?
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perpendicular
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cross striations represent the ________ growth increment and are approx. __ - __ um apart?
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daily; 4,5
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Cross striations are synonamous with what what lines in dentin?
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inbricaiton lines of von Ebener
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Cross striations have dark and light lines. Dark lines represent areas of (more/less) calcification?
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less
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Stria of Retzius are due to _______?
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stress
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Stria of Retzius are formed because of a retraction of ______ ____________?
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tome's process
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Stria of retzius formed at birth is called a _________________?
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neonatal line
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Stria of retzius are (more/less) calcified than surrounding enamel?
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less (dark = less)
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Perikymata are surface manifestations of _____________?
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stria of retzius
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Perikymata are interspersed __________ and _______ and are located near the ______ of the tooth?
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grooves, ridges; cervix
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T or F: perikymata will eventually wear down?
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True
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T or F: Gnarled enamel is present near the DEJ?
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False, it is found in cuspal regions
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T or F: Gnarled enamel may extend through entire enamel region?
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True
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Gnarled enamel (strengthens/weakens) the tooth structure?
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strengthens
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Enamel in pits and fissures is (stronger/weaker) than at the cusps?
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weaker
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Ameloblasts often cannot complete maturation of the enamel in pits and fissures due to?
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crowding and strangulation
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Margins of restorations should be placed in (gnarled/non-gnarled enamel)?
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non-gnarled (good luck!)
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Precarious enamel lesions involve the dissolution of what part of the enamel?
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crystal cores
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In carious lesions the length of the enamel crystals is ____________ but it it isn't in precarious lesions.
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shortened
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Etching of enamel preferentially dissolves enamel rod ________?
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head (core)
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When enamel is etched, what can fill the areas of dissolved enamel?
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restorative material (composite)
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Etching will not roughen enamel surface where the enamel is ____________?
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prismless
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