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61 Cards in this Set
- Front
- Back
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Enamel is what percent inorganic & what percent organic?
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96% inorganic-- hydroxyapatite
4% organic & water |
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Enamel is thickest where?
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Over crown
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Enamel is thinnest where?
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Toward cervical margin
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Enamel rods run in which direction?
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From DEJ to surface
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What is located between the enamel rods?
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Inter-rod layer of enaml
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What is the rod sheath?
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Interface between rod & inter-rod enamel
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Do inner & outer layers of enamel have rod structure?
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No
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What are enamel striations?
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Regular bands in enamel
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Which way do enamel striations run?
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Roughly parallel to DEJ
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What causes enamel striations?
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Daily, rhythmic deposition pattern by ameloblasts
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Dark irregular bands in enamel known as?
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Striae of Retzius
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What causes Striae of Retzius?
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Systemic disturbances during amelogenesis
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Light & dark bands in enamel seen w/ incident light known as?
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Hunter-Schreger Bands
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Hunter-schreger bands run in which direction?
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Perpendicular to DEJ
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What causes hunter-schreger bands?
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Slight bending of enamel rods
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Where are hunter-schreger bands located & what type of phenomenon are they?
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Inner 4/5 of enamel-- purely optical phenomenon
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What is gnarled enamel?
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Enamel rods appear gnarled or intertwined at cusp region
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What causes gnarled enamel?
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Small radius of curvature at cusp region
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Where are enamel tufts located?
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Arise at DEJ & extend into enamel
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Where are enamel lamellae located?
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Arise at enamel surface & extend toward or past DEJ
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Enamel lamellae are filled w/ ?
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Enamel protein or organic debris
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Are enamel lamellae a route for caries attack?
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No
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What are enamel spindles?
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Tip of odontoblast process within enamel
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How are enamel spindles formed?
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Odontoblast processes extend between ameloblasts prior to enamel formation
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What are perikymata?
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Shallow valleys & ridges that are seen horizontally across tooth surface
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What causes perikymata?
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Termination of striae of retizius
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Where is the nucleus located in ameloblasts?
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proximal end
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How many steps are involved in amelogenesis?
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2
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What happens in the 1st step of amelogenesis?
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Ameloblasts produce full thickness of organic matrix-- mineralized to 30%
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2nd step of amelogenesis?
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Some of organic material is removed & mineralization proceeds to 96%
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Largest group of proteins made by ameloblasts?
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Amelogenins
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Remaning 10% of proteins that ameloblasts make? (3)
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1. tuftelin
2. enamelin 3. amelin |
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Ameloblast proteins are collagenous or non-collagenous?
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NON-COLLAGENOUS
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What are amelogenins degraded into during amelogenesis? (2)
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1. Tyrosine rich amelogenin peptide
2. leucine rich amelogenin peptide |
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Enamel mineralization is immediate, what does that mean?
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No unmineralized phase
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What iniatiates enamel mineralization?
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Dentin crystallites & tuftelin
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What happens to hydroxyapatite crystals once deposited?
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THey grow rapidly in length
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What cell type are ameloblasts?
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Columnar cells
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How is Tomes' process formed?
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Migration of ameloblasts away from new enamel during amelogenesis
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What occurs at Tomes' process?
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Enamel proteins are released by exocytosis
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Function of terminal bar apparatus?
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Maintains cellular alignment & regulates intercellular permeability
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What is amelogenesis & where does it occur?
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PRocess of ameloblast differentiation & enamel production
occurs w/ in enamel organ |
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5 stages of amelogenesis?
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1. morphogenesis
2. Differentiation 3. Secretory 4. Maturation 5. Protection |
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What occurs during morphogenesis?
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Crown pattern is established by inner enamel epithelium
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When does morphogenesis occur?
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Late bell stage
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What occurs during differentiation stage?
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Inner enamel epithelial cells differentiate into ameloblasts?
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What happens to the inner enamel epithelial cells as they differentiate?
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shape: Cuboidal --> Columnar
Nucleus shifts proximally Increase in Golgi, RER & Glycogen Junctional complexes develop |
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What occurs during the secretory stage?
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Ameloblasts begin enamel protein synthesis
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During secretory stage, ameloblasts migrate in what direction? What is formed due to this migration?
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Ameloblasts migrate away from new enamel & Tomes' process is formed
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Before Tome's process is formed enamel is _____?
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structureless
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What type of enamel is formed at proximal region of Tomes' process?
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Interrod enamel
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What type of enamel is formed at distal face of Tomes' process?
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Rod enamel
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Where happens with the stellate reticulum during onset of amelogenesis
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stellate reticulum collapses
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What occurs during the maturation stage of amelogenesis?
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Reduction in ameloblast high & organelle content
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Function of smooth border in maturation stage?
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Removes protein & water from enamel matrix
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What type of distal & proximal junctions are located at the smooth border?
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Distal -- leaky
Proximal -- impermeable |
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Function of ruffled border in maturation stage?
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For mineral deposition
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What type of junctions are located at distal & proximal ends of ruffled border?
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DIstal-- impermeable
Proximal-- leaky |
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What occurs during protection stage?
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Ameloblasts secrete primary cuticle for protection
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What attaches ameloblasts to cuticle?
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Hemidesmosomes
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What are the remaining cells of epithelial enamel organ which cover enamel called?
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Reduced enamel epithelium
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