Term
| Physical and Chemical Characteristics of Enamel |
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Definition
-most mineralized biological tissue (96% inorganic) -translucent -semipermiable to water and low-MW compounds -inarganic = hydroxyapatie crystals (crystalline calcium phosphate) -organic = amelogenin (TRAP) and other proteins |
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Term
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Definition
1. Enamel rods 2. Incremental lines 3. Hunter-Schreger bands 4. Gnarled enamel 5. Enamel tufts 6. Enamel lamellae 7. Enamel Spindles |
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Term
Structure of Enamel Enamel Rods |
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Definition
-basic structural unit -densly packed hydroxyapatite crystals -interrod = area surrounding rod where crystals oriented in different direction from those of the rod -rod sheath = interface between rod and interrod contains HIGHEST protein content -no rod structure adjacent to dentin -no rod structure at enamel surface (sometimes) due to lack of Tomes' process at begining + end of amelogenisis -diameter increases towards enamel surface -rods mantain undulating coarse through enamel -arranged perpendicular to dentinal surface -bend toward cusp tip -mechanically locked into dentin |
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Term
Structure of Enamel Incremental Lines (4 types) |
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Definition
-due to variations in secretory activity, strucutre, and mineralization -visible on ground sections 1. Striae of Retzius 2. neonatal line 3. cross striation 4. perikymata |
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Term
Structure of Enamel Incremental Lines Striae of Retzius |
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Definition
-primarily in perminent teeth (less evident in primary) -represent constriction of Tomes' process coupled with increased production of interrod enamel -result = prominent alteration alonf entire front =roughly parallel =no clinical sig
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Term
Structure of Enamel Incremental Lines neonatal lines |
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Definition
-exaggerated stria of Retzius -reflects physiologic changes that occur at birth |
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Term
Structure of Enamel Incremental Lines cross striations |
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Definition
-represent either daily changes in secretory activity by ameloblasts or -differing orientations by hydroxyapatite crystals within a single rod |
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Term
Structure of Enamel Incremental Lines Perikymata |
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Definition
-surface irregularities -represent termination of striae of Retzius -horizontal bands encircle crown of tooth; absent on occlusal surface Imbercation Lines pf Pickerel = troughs inbetween crests of enemel |
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Term
Structure of Enamel Hunter-Shreger bands |
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Definition
-optical phenomenon -changes in rod orientation -appear as alternating broad light and dark bands |
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Term
Structure of Enamel Gnarled enamel |
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Definition
-disarrayed enamel rods -present at the cusp tips -due to crowding anf twisting of rods in a small area |
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Term
Structure of Enamel Enamel Tufts |
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Definition
-small, branchinf defects at DEJ -projecting into enamel -contain lareger % of enamel protein -short flame shaped -no clinical sig |
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Term
Structure of Enamel Enamel lamellae |
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Definition
-prominent linear enalem defects -start at tooth surface -sometimes penetrate DEJ -high concentration of enamel protein -sometimes contain material from oral cavity -no clinical sig |
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Term
Structure of Enamel Enamel Spindles |
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Definition
-short, linear defects -found at DEJ -extend into the enamel -more prevalent at cusp tip -formed by entrapment of odonoblast processes b/w ameloblasts prior to and during amelogenesis -no clinical sig |
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Term
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Definition
1. Attrition 2. Discoloration 3. Reduced permeability -tooth most porus whrn youn -less permeable over time as you add Ca+ 4. Changes in surface structure -imbercation lines wear away 5. Modification of the surface layer -often due to dental procedures
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Term
Clinical Implications Fluoridation |
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Definition
-enamel can become resistant to acid dissolution -facilitates calcium phosphate percipitation fluoride ions incorporated into hydroxyapatite crystals |
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Term
Clinical Implications Acid Etching |
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Definition
-used to increase mechanical retention of restoritives -makes enamel surface irregular -removes plaque, organic debris, and surface enamel -increased porosity of exposed enamel -rod orientation at enamel determines specific pattern of etching
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Term
Clinical Implications Acid Etching (3 types) |
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Definition
Type I = removal of rod core
Type II = removal of rod periphery Type II = irregular removal of enamel structure |
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