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20 Cards in this Set
- Front
- Back
Why is enamel the hardest substance in the body?
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because of the number and arrangement of hydroxyapatite crystals
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How are fluorapatite crystals made?
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Fluoride replaces OH of CaOH forming the more insoluble fluorapatite crystal
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what is amelogenin secreted by?
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ameloblasts, odontoblasts and cementoblasts
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Appear as small nanospheres that control spacing of hydroxyapatite crystal
May determine how wide and thick each crystallite will become (keeps the crystals thin) |
Amelogenin
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Found in surface layers of enamel (rod sheath)
Control saturation of enamel fluid Maintain the sheath space as an escape route of enamel proteins Prevent growth of interrod (tail) crystals into rod (head) |
Ameloblastin
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Present only at the mineralization front directly beneath the secretory face of Tomes’ process
Involved in crystal elongation and shape By binding to sides of crystallites, inhibits growth in thickness and width |
Enamelin
also noteand another thing that may be important to know is that enamelin is associated with hypoplastic amelogenesis imprefecta and kallikrein with hypomaturation AI |
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What is the difference between interrod substance and the rod?
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the orientation of the hydroxyapatite crystals
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Hypomineralized sheath surrounding each enamel rod
Allows etching of teeth for sealants |
Rod Sheath
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twisted rods of enamel under the cuspal tips that provide greater strength against forces of mastication
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gnarled enamel
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Concentric dark bands that follow the contour of the tooth surface
Hypomineralized areas of rods resulting from several days of growth during physiological stress such as sickness (hypomineralized so they show up darker) |
Striae of Retzius
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Accentuated hypomineralized line associated with child birth (large Striae of Retzius due to child birth)
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neonatal line
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Where will the neonatal line be found?
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All primary teeth and first molars of the secondary teeth (teeth being formed during child birth)
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Viewed only with reflected light
Alternating light & dark bands Results from the arrangement of hydroxyapatite crystals |
Hunter-Schreger Bands
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Fusion lines between 2 growth centers of cusps
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Fissure
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Area where 2 fissures cross
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Pit
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Clinical significance of pits and fissures?
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Enamel over pits and fissures is thin & less protective
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Horizontal grooves on the surface of the tooth
Surface manifestations of the striae of Retzius Termination of striae of Retzius |
Perikymata
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Appear as dark lines extending from the DEJ to the surface
Hypomineralized Weak area of resistance to organic acids Represents cracks in the enamel due to stress |
Enamel Lamellae
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Appear like tufts of grass
Hypomineralized These are also more resistant to organic acids Represents optical effect caused by the movement of ameloblasts from the DEJ |
enamel tufts
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Odontoblast cell processes which have crossed the DEJ – odontoblast, so these are not from the enamel – these are from the dentin
Surrounded by enamel – this forms when dentin & enamel are forming – cannot form after formation is complete Believed to be responsible for the sensitivity of the tooth near the DEJ |
enamel spindles
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