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16 Cards in this Set
- Front
- Back
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What are the five stages of amelogenesis?
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Presecretory
Secretory Transitional Maturation Post-maturational |
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What are the two main events of presecretory phase of amelogenesis?
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Differentiation
Resorption of basal lamina |
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Differentiation in Presecretory phase of amelogenesis refer to what?
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morpho-differentiation and cytodifferentiation
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Describe the presecretory phase of amelogenesis
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IEE cells initially cuboidal differentiation into pre-ameloblast (taller, columnar and polarised)
Secrete enzyme to degrade basal lamina Dental-papilla-odontoblast lay down first layer of dentin matrix |
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Describe the secretory phase of amelogenesis
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Tome's process develop at the distal end
Secretions made at TP One enamel rod involves 4 TPs (1 head and 3 tails) This stage ends when full thickness enamel is laid down and TP retracts and a thin layer of aprismatic enamel is laid |
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Describe the transitional stage of amelogenesis
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Enamel secretion stops
ameloblast shortens and the no is reduced to 50% Protein synthesising organelle are destroyed |
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Describe the maturation stage
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Part 1
initial mineralisation 30% Crystals increase in size Tome's process lost Part 2 Distal membrane becomes ruffled and alternates with smooth end ruffled end: tight junctions for secretion and CaPO4 influx and resorptive Smooth end: no tight junction, allow organic matrix/water to pass between ameloblasts |
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When does maturation stage of amelogenesis end?
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When all organic material is absorbed
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What are the phases involved in Post maturation stage of amelogenesis?
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Protective phase
Desmolytic phase |
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Describe protective and desmolytic phase of post-maturation stage of amelogenesis
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Protective phase:
Distal end of ameloblast becomes flat 1mm thick protein layer laid on enamel surface REE is formed Ameloblast protects nascent enamel from surrounding tissue Desmolytic: REE secretes enzymes to degrade overlying connective tissue during eruption REE forms dentogingival junction as the tooth erupts |
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Enamel rods are often not straight. These enamel are referred to as what? Where are these located?
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Gnarled enamel
Located close to dentine |
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Explain the formation of cross striations found in enamel
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Reflects variations in the density of mineralisation
Indicates a daily variation in the secretory activity of the ameloblasts |
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Explain the formation of Striae of Retzius.
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During development of enamel, variations in the metabolic activities cause variations in the density of organic material in the enamel. Hence alternating dark and light lines can be seen. Dark lines are high in organic material and light lines are lesser in organic content
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What is neonatal line?
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An accentuated Stria of Retzius that occurs at the time of birth due to stress of birth
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What are Hunter-Schreger Bands?
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Optical phenomenon due to changes in rod direction. Can be seen on longitudinal ground section as alternating light and dark bands
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What are enamel tufts and enamel lamellae?
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Hyponineralised stria perpendicular to DEJ. If it's just inner third from DEJ then it is enamel tuft. If the stria goes right through the enamel, it's enamel lamellae
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