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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