histo - amelogenesis

8/17/2019 histo - amelogenesis

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DR. SAMIHA J. SAMARA


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At bell stage of tooth development4 distinct layers is observed :

1. Outer enamel epithelium

2. Stellate reticulum

3. Stratum intermedium

4. Inner enamel epithelium


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- uboidal

cells- !ighly

vasculari"ed

- Has villi,

cytoplasmicvesicles andnumerousmitochondria


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- Star shaped cells with long processesseparated yintercellularsustance

- Renders the enamelorgan elastic andresistant to

physical !orces thatmay disturamelogenesis


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- #lat andcuboidal cells

- ontrols fluiddiffusion intoand out o!amelolasts and

contriution o!!ormativeelements oren"ymes


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- olumnarshaped cells

- Di!!erentiatesintoameloblast

that actuallyproducesenamel


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- #here the outer and

inner enamelepithelium meet at

the rim o! the enamel

organ

- uboidal cells thatelongates to !orm the

!ert$ig%s epithelial

root sheath


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1. &orphologic

2. Organi"ing

3. #ormative

4. &aturative'. (rotective

). *esmolytic


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- +o$ columnar cells with large centrallylocated nucleus

- $olgi apparatus andcentrioles are atpro,imal portion o!cells

- Separated !rom dental

papilla y delicate basallamina

- Amelolast receivenutrients !rom dentalpapilla

pro%imal

distal


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- *ifferentiation o!

odontolasts andamelolasts

- -eversal offunctional polarity

- -eversal ofnutritional source


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- mutual interaction etween enamel anddentin

- &rganelles are active

!or secretion- Amelolasts migrate

away !rom D'J asenamel matri, is laid

do$n and has a luntprocess on thepro%imal end (omes process


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- &inerali"ation stage- Starts a!ter !ull thic)ness o!

enamel has een laid down- Development o! microvilli/

numerous vacuoles andstriated border at thepro%imal ends o!amelolast

- * processes in !ull

minerali"ation+. removal o! water andorganic material*. addition or deposition o!inorganic material


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- ormation o! -00reduced enamelepithelium from O00

and I00- R'' separates mature

enamel !orm surroundingconnective tissue as

tooth erupts- rea) in R'' may

produce anomalies in theenamel


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- R'' produceen"yme to destroyconnective tissueas tooth erupts

- #usion of -00and oral

epithelium


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1. 0namel matri, formation2. &inerali"ation and

maturation

1st stage

2nd stage


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- Starts after thin layer ofdentin is formed

1. *entinoenamel membrane

2. omes processes

3. *istal terminal bars


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1st stage

- Immediate partialminerali"ation

- 2''5 o! mineral content isdeposited down as theenamel is laid down

2nd stage

- &aturation stage

- /ompletion o! minerali"ation

- urther decrease o! inorganic

content


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. actors that can disturb enamelformations 0systemic diseases, nutritionalde!iciencies, endocrinopathies, !erile

diseases and chemical into%ications1- maye in a !orm o!+

!6(O(+ASIA ( disturance in enamel

matri% !ormation!6(OA+I#IAIO7 ( lac)ing orincomplete maturation


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Maye +

+OA+

&8+I(+0S6S0&I

!0-0*IA-6


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2. 0,cess of fluoride content in the

enamel $ill cause fluorosis that maymanifest as a moth eaten appearance inthe enamel.


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3. etracycline may also producediscoloration of enamel and dentin.


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07A&0+

'mryology tissue ectoderm

/ells in mature tissue noneormative cells amelolasts

Degradative cells odontoclasts

&rganic matri% 'namelin, amelogeninsMineral Apatite 234

Aility to repair 5o repair, reminerali"ation

Sensitive 5oIncremental lines Ret"ius, neonatal line

lood supply avascular

Age change 6oss o! tissue, increase stain

histo - amelogenesis

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