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40 Cards in this Set
- Front
- Back
does enamel contain collagen? |
no |
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describe the enamel blood vessels and innvervation |
it has none |
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what secretes/forms enamel |
ameloblasts |
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where is enamel thickest? |
in areas exposed to attrition and risk of fracture |
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Why do teeth turn yellow as we age? |
enamel translucency increases with age allowing the darker yellow colour of dentine to be transmitted |
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what is contained in an enamel prism? |
several million HA crystaliites |
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where do enamel prisms run from? |
amelodentinal junction to tooth surface |
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why do enamel prism arrangements have a keyhole appearance? |
the prism are arranged in staggered rows such that the tail of the prism lies between two heads in the row below |
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what causes sinusoidal lines in enamel? |
prisms path bending |
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what creates hunter-schreger bands? |
periodic changes in prism direction that make the enamel more resistant to fracture |
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Where is gnarled enamel found? |
near cusps and incisal regions |
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what is the arrangement of prisms in gnarled enamel? |
spirals |
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where is prismless enamel found? |
first few microns of formed enamel adjacent to dentine and the outer 20-70 micrometres of enamel |
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what are the features of prismless enamel? |
the absence of prism boundaries means that there is less organic material present and the highest degree of mineralisation occurs |
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where and when do cross striations form in enamel? |
formed every 24 hours, they cross prisms at right angles |
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what are the straie of retzius? |
prominent dark lines running obliguely across enamel prisms to the surface (in longitudinal sections) |
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what are perikymata ridges formed by? |
the straie of retzuis at tooth surface creat a series of fine grooves running around the tooth crown. Perikymata grooves are separated from each other by perikymata ridges |
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what sort of patten is the amelodentinal junction? |
scalloped |
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what are enamel spindles? |
seen in longitudinal sections as narrow round tubules extending up enamel, not aligned with prisms. Thought to be odontoblast processes |
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what are enamel tufts? |
resemble tufts of grass, tubules extending from amelodentinal junction travelling with prisms |
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what is contained in enamel tufts? |
tuftelin - a non-amelogenin protein of enamel |
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In which section are lamellae distinguishable from enamel cracks? |
decalcified sections as cracks disappear |
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what are enamel lamellae? |
sheet-like structural fault across entire thickness of enamel in transverse sections. Hypomineralised and filled with debris. |
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what happens to enamel as we age? |
increased wear and tear, darkening colour, equilibrates with oral environment |
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when does amelogenesis occur? |
during bell stage of tooth development, process begins at amelodentinal junction |
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what does crystal formation of enamel begin with? |
an organic matrix secreted by ameloblasts moving away from Amelodentinal junction |
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what are the 5 stages of the life cycle of the ameloblast? |
presecretory, secretory, transition, maturation, post-maturation |
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what occurs when ameloblasts are in the pre-secretory phase? |
resorption of basal lamina |
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what occurs when ameloblasts are in the secretory phase? |
Secrete aprimsmatic Enamel. Cells become polarised. Rings of webs form via tight junctions and desmosomes in ameloblast layers. Extensions of cytoplasm: Tomes process develops. Enamel laid down. |
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what forms prisms? |
one ameloblast contributes to the formation of one prism core. |
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What are tomes processes responsible for in enamel formation? |
they secrete the matrix and are therefore responsible for the prism structure of enamel |
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What are 90% of enamel matrix proteins? |
amelogenins |
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what role do the enamel matrix proteins play? |
regulate the formation of long enamel crystals and prism pattern/structure. |
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What happens to amelogenins in maturation phase of enamel? |
virtually all removed by controlled extracellular degradation |
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What role do ameloblasts play in maturation phase? |
they move calcium, phosphate and carbonate ions into the immature matrix and move water/degraded proteins out of it |
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when are mature ameloblasts ruffled ended? |
secretory phase: calcium phosphate and carbonate ions |
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when are mature ameloblasts smooth ended? |
resorptive phase: water and degraded proteins |
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what is formed when reduced post-maturation phase ameloblasts merge with the enamel organ? |
reduced enamel epithelium |
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what forms reduced enamel epithelium? |
merging of post-maturation ameloblasts and enamel organ. |
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What is amelogenesis imperfecta? |
hereditary disorders affecting only enamel, via malfuntion of enamel proteins. Teeth are abnormal in colour, have a high risk of dental caries and are hypersensitive to temperature changes |