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37 Cards in this Set
- Front
- Back
Enamel
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Acellular and Avascular
96% inorganic 4% water Thin near junction and Root hard and brittle most highly mineralized tissue in body |
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Cells of the inner enamel epithelium differentiate into
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ameloblasts
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Tomes process
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-Shovel shaped
-responsible for the orientation of the enamel rod |
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What shape are ameloblasts in a cross-section?
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Hexagonal
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Formation of enamel?
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Amelogenesis
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2 Stages of Amelogenesis?
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1 Secretory
2 Resorbing |
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Secretory Stage
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deposition of enamel matrix that contains both organic and inorganic material
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Resorbing stage
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Removal by ameloblasts of most of the water and the organic matter
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Enamel rods
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Interlocking rods that help resist masticatory forces to prevent fracture between rods
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Rod Sheath
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Formed by a change in the angulation of the crystals formed by the ameloblasts as they move
*Outline around the periphery of the rod, especially noticable in the head region of the rod |
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Rod Sheath resists______more than Rod core.
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demineralization
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Enamel rods extend from the DEJ to ?
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outer enamel surface-appear wavy due to the path of ameloblasts as they migrate
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Enamel rods are _____shape?
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keyhole
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One rod is formed by?
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4 different ameloblasts
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hunter-schreger bands
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alternating light and dark bands in the enamel due to configuration of the enamel rods
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Rodless enamel
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found on all deciduous teeth and 70% of the permanent teeth
-found at the cervical area of enamel -less frequently found over the cusp tips -structureless layer of enamel about 30 microns thick |
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gnarled enamel
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*formed by enamel rods that have bent in exaggerated ways
*found near the dej over areas of the cusp tips |
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Enamel is unable to
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remodel or repair
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amelogenesis occurs during which stage of tooth development?
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Late Bell Stage
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incremental lines
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a result of rhythmic deposition of enamel
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3 types of incremental lines?
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1 cross striations
2 striae retzius 3 neonatal line |
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Perikymata
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small ridges on the tooth surface
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cross striations
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daily apposition lines
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striae of retzius
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more prominent growth lines may reflect major interruptions in deposition of enamel
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neonatal
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a significant striae of retzius
distinguishes prenatal enamel from postnatal enamel |
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Enamel spindle
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single extension of dentinal tubules into the enamel
*shorter than tufts* |
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Enamel tufts
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hypomineralized inner ends of some enamel rods
*defect in enamel*Bigger than spindle |
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Enamel lamellae
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cracks in the surface of the enamel visible to the eye
*extend from the DEJ to the surface of the enamel *possible pathway for dental caries to spread no greater chance for fracture/ is greater risk for caries |
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Tetracycline Stain
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Appear as dark bands through the enamel especially near the cervix of the tooth
*Does not affect enamel *Binds to dentin and bone *cannot bleach/caused by dentin *Darkend dentin that shows through translucent enamel, giving tooth a darker appearance |
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2 functions of cementum
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1Seals the tubules of root dentin
2 serves as attachment for periodontal fibers to suspend tooth in the socket |
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Cementum is
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*less mineralized than enamel and dentin
*continues to grow throughout life *thinnest near the cervix *thickest at the apex *no nerves *not sensitive |
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_______is SHiny; _______is not shiny
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Enamel; cementum
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Bone
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Vascular
nerves lacunae cells canaliculi incremental lines |
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Cementum
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avascular
no nerves lacunae cells canaliculi incremental lines more resistant to resorption and demineralization than bone |
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Hertwigs epithelial root sheath is formed by______
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joining of OEE and IEE
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Hertwigs epithelial root sheath degenerates and the remnants are called?
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epithelial rests of mallasez
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Cells from the _____________differentiate into cementoblasts?
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dental follicle
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