Download - Oral Histo 5th Lec 2
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We stopped at the peritubular dentine , we said this dentine
is the walls of
the dentinal tubules ( peri means: around the tubule ) ,
- hl2 the Synonym is also intratubular dentine , tab3an this is
deposited by
the process , not by the cell itself , this dentine is given by
the odontoblastic
process not by the cell itself , not by the odontoblastic cell ,
deposited by
the processes on the walls and narrowing the dentinal
tubules , tab3an
each time they build the peri tubular dentine , the dentaltubule becomes
narrower .
-It lacks collagenous fibrous matrix , this actually is not
collagenous , ya3ne
the organic matrix is not collagenous ok .
-Increased radiodensity , if u actually expose this toradiation , ya3ne if you
want to take a micro x-ray for this one , itll appear more
radio dense , this
Peritubular dentine :-
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means that its more mineralized than intertubular dentine ,
this is 15 %
more mineralized .
-The crystals are carbonated apatite , not hydroxyapatitecrystals , thats
why they are more mineralized & these are smaller than
those of
intertubular dentine ( the crystals )
** mmken fe el emte7an ajebelkom what are the
differences
between peritubular dentine and intertubular dentine ???
first of all
peritubular dentine is deposited by the odontoblastic
processes ,
intertubular dentine is deposited by the cell itself , now
peritubular dentine
lacks collagenous fibrous matrix , but intertubular dentine
is collagenous or
the organic matrix is collagenous , peritubular dentine is
more radio dense
and more mineralized and the crystals are made of carbon ,carbonated
apatite , and also the crystals are smaller than those of
intertubular dentine
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-this is actually scanning electron microscopic slide showing
the dentinal
tubules , and showing the walls of the dentinal tubules , this
is the area ofthe peritubular dentine and this irregular area is the
intertubular dentine .
-Odontoblastic processes becomes embedded in the extra-
cellular matrix ,
ya3ne as the tooth gives dentine , tab3an it sends an
odontoblastic
processe that remains embedded within the matrix
deposited , becomes
embedded in the extra-cellular matrix elongates as the
odontoblast moves
Peritubular dentine
deposited on the tubule
Intertubular
Odontoblasts andprocesses :-
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toward the pulp ( ya3ne if i consider myself now as an
odontoblast , i start
depositing dentine and i send an extension , this extension is
theodontoblastic process that extends actually inside the
dentine deposited .
odontoblastic process stimulates differentiation of
ameloblasts , its very
important the odontoblast and the odontoblastic process
especially the
odontoblastic process is important in the stimulation action
or the
differentiation of ameloblast , its actually the part of the
odontoblastic cell
, that actually sends and receives information from the cells
of internal
enamel epithelium .
Tab3an in the crown we have different layers compared to
the root , in the
crown we have mantle dentine , interglobular dentine and
circumpulpal
dentine .
In the root we have the hyaline layer , granular layer of
tomes and
* Layers of dentine :-
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circumpulpal dentine (Circum means surrounding , ya3ne
circumpulpal
dentine is that part of dentine that surrounds the pulp ) .
- Lets take the mantle dentine , which is the top layer , the
first layer of
dentine , near the enamel dentine junction , its the outer
layer and
because its the outer layer its the first formed layer , its
about 20 to 150
micrometer in thickness and its 5 % less mineralized than
the other parts
of dentine , tab3an collagen fibers are here perpendicular to
DEJ .
More dentinal tubules branching in this layer , ya3ne here in
this layer as you see ,
these are dentinal tubules , tab3an you see many branching
( ya3ne
tafaro3at ktere mn el dentinal tubules ) they occur in the top
layer of
dentine , which is the mantle dentine , tab3an hay el sora
3ebara 3n organic
* Mantle dentine :-
Dentine enamel junction
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material , ya3ne this is actually a microscopic picture after
removing all the
minerals , so after we remove the minerals what remain is
theodontoblastic process , so we see that the odontoblastic
processes have
many branches in mantle dentine but they dont have
branches in dentine
located beneath tha mantle dentine .
tab3an the process of mineralization in mantle dentine is
called matrix
vesicle mineralization , remember DPP mediated
mineralization can also
occur in mantle dentine but matrix vesicle mineralization
only occurs in
mantle dentine .
Interglobular dentine is the layer just under the mantle
dentine , its
called interglobular because we have globules that fail to
fuse completely ,
as we said dentine is actually deposited or mineralization
occurs as
spherical bodies that tend to increase in size until they fuse
together , we
* Interglobular dentine
(IGD) :-
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call them calcospherites , when these calcospherites fail to
fuse completely
in certain areas of dentine , they give the interglobular
dentine , sointerglobular dentine is actually where calcospherites fuse
incompletely or
fail to fuse completely .
- in general , much of the mineral in dentine is deposited as
globules (
calcospherites ) that eventually fuse together , hl2 when thay
fail to fuse or
when they fuse incompletely , they produce the interglobular
dentine , its
located beneath mantle dentine and also in the root , this
layer is located
-beneath the mantle dentine in the coronal pulp and its the
actual granular
layer of tomes in the radicular dentine , ( ya3ne btkon ta7et
el mantle
dentine fe el crown bs bl root btkon esmha heyye nafsha el
interglobualr
elle heye nafsha el granular layer of tomes ) .
Tom is the name of the scientist who discovered theprocesses of
ameloblast that we call tomes processes of ameloblast .
-now interglobular dentine appears dark in transmitted light ,
because light
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has to pass through spaces thats why it appears dark .
- tubules pass through the interglobular dentine without
deviation .
-peritubular dentine is also absent ya3ne in the interglobulardentine we
dont have peritubular dentine , we only have intertubular
dentine which is
even not completely fused .
this is
actually a slide showing the mineralization of dentine , we
say
mineralization of dentine is 70 % by weight , but this doesnt
mean that its
70 % in each region , the average mineralization is 70 % , itcan be very
mineralized in certain areas , like these dark areas , can be
less mineralized
Calcification is not always
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in light areas like these ones , laken in general the average
mineralization in
dentine is 70 % by weight or 50 % by volume , so
calcification is not alwayseven , its not the same in different areas .
Now lets talk about the different layers in root dentine , the
first one is
called the hyaline layer which is the white layer , we said this
is very narrow
, non tubular structureless band , the origin is obscure , some
people say
that they are dentinal , from the odontoblastic cells and
some people say
that these are from cementum , so thats why the origin is
not very secure ,
a third group of people say that these are from the epithelial
root sheath
that assist in forming the root .
* Hyaline layer :-
Granular
Hyaline
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under the hyaline layer we have the dark layer here ( the
picture above )
thats called the granular layer of tomes , in the root its
located just
beneath the hyaline layer and cementum , tab3an this layer
is produced by
two reasons : the first reason is branching and looping of
the dentinal
tubules ( el dentinal tubules betser teltaf 3ala ba3dha ,
bta3mel spirals ) ,
the second reason could be because of incomplete fusion
of calcospherites
( elle e7na samenaha nafs el process elle bte7doth fe el
interglobular
dentine in the crown ) .
In the crown beneath mantle and interglobular dentine , in
the root its
located beneath the granular layer of Tomes ( ya3ne most of
remained
dentine is circumpulpal dentine ) .
* Granular layer of Tomes :-
* Circumpulpal dentine
:-
*Pre dentine:-
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- hl2 predentine is the unmineralized part of dentine , ya3ne
the first
dentine that is deposited for 24 hours ok , before being
mineralized iscalled predentine , and all the time we find predentine layer
at the pulpal
front ( da2eman fe 3nde predentine layer bestemrar , btkon
tab3an b jehat
el pulp because this is the most inner layer of dentine )
-10 to 40 micrometer in thickness , tab3an if i return the next
day , ill find
that this layer becomes mineralized and a new layer of
predentine is
deposited ( da2eman kol 24 sa3a beser fe mineralization w
btkawan bardo
3nde a new layer of un-mineralized dentine w ba3den
beserlo
mineralization w hakatha ) .
this is the process , in
enamel this
doesnt occur because enamel undergoes immediate
mineralization , But in
dentine there is actually a duration of time between
deposition of the
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organic matrix and the mineralization of that matrix .
its non-mineralized because matrix deposition precedes
mineralization (
the deposition of the matrix yasbek el mineralization process) ,
- tab3an predentine is secreted by odontoblast by way of
golgi apparatus
and mitochondria , these are the intracellular changes .
-it appears pale compared to dentine because its un-
mineralized , thats
why it appears pale .
-mineralization front may show a globular or linear outline
**( hl2 fe 3nna mmken nes2al so2al , it appears although in
this slide( the
previous pic) even dentine is decalcified and this layer is notcalcified at all
ya3ne fa bl tale how they appear different ??? because the
organic matrix
when it gets mineralized and when u remove the minerals ,
its not the
same as the organic matrix which has not been mineralized
at all , ya3ne
eshe ana a3mallo mineralization w ba3den ashel mnno el
minerals fe
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3amaleyat el decalcification la ta7der el slide ra7 ybayen
mo5talef 3n she
aslan ma sarlo mineralization ) , eza bdkom afaserha tafser
a5ar ( thedecalcification involves removal of minerals from mineralized
tissues and
also involves some changes in un-mineralized tissues w bl
tale sar 3nde
shwayet changes bl predentine fa bayanat me5telfe 3n el
dentine )
- mineralization front may show a globular or linear outline
( el
mineralization front howe el 5at el fasel ma ben el
predentine w el dentine
) , it can be smooth ya3ne the junction between the dentine
and
predentine can be linear and can be globular .
We have incremental lines : lines associated with primary
curvatures and
lines associated with secondary curvatures , lets start with
the incremental
lines , we have short period incremental lines , and long
period incremental
lines , similar to the incremental lines of enamel , y3ne
odontoblast are
*Structure lines in
dentine :-
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similar to ameloblast , they dont function continuously , they
have actually
to take a quiescent phase ( ya3ne lazem tmor fe mar7alet
hodo2 , ya3neaction and then quiescence , la2eno bdhom wa2et la el
estera7a ) , this is
actually the short period incremental lines , they are
produced because of
this daily rhythmic quiescence , we have also the weekly ,
the long term
quiescence producing the long term incremental line .
Short incremental lines are called von Ebners lines and
long period lines
are called Andresen lines , and these are 16 to 20
micrometers apart , but
the short period lines are less than that , ya3ne up to 4
micrometers
between each other
- hl2 associated with changes in collagen fibrils orientation
( why the long
period lines appear ? because we have some change in the
orientation of
collagen fibers ) .
- hl2 we have exaggerated line one of the long period lines
can be
exaggerated , can be yan3e very very well demarcated line ,
its caused by
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the disturbance in metabolism at birth ( 3nd el welade
yata`3ayer el
environment w bl tale beser 3nde line ) , we call it neonatal
line , neonatalline also occurs in enamel .
regarding the structure lines , lines associated with primary
curvatures ,
if we have a group of dentinal tubules having the same
primary curvature
which is sigmoidal and another layer with a different
orientation ( yan3e
mmken enha nafs el sigmoidal bs different convexities and
concavities ) ,
they will be different in orientation , this actually produces
structural lines
we call them Schreger lines like for example this line here ,
This line is produced by the difference of the amount of
convexities
in the primary curvatures of the dentinal tubules , we have
also structural
A: Schreger lines
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lines related to the secondary curvatures ( y3ne some groups
of dentinal
tubules have the same secondary curvatures and in other
layers they areslightly different , this produces lines we call them Contour
Lines Of Owen
this is an example of contour lines of Owen
Y3nee when a group of dentinal tubules share the same
convexities and
Concavities they form contour line, these are perpendicular
to the long axis
Of the dentinal tubule
- Dentine folds after complete formation of the root is called
secondary
Dentine ,
do we have secondary enamel ?? no, because once enamel
is formed the
cells that produce enamel are lost and they're not actually
active
*Secondary dentine
:-
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but in dentine the cells are still existing and any dentine
that's formed after
the completion of the root is called secondary dentine.
- Increased crowding of odontoblasts: as dentine is formingand forming
The volume of the pulp becomes smaller and this produces
crowding in the
population of odontoblasts , because these are crowded they
will not
produce similar dentine to the dentine that they produced
before being
crowded because the space becomes limited and that's why
secondary
dentine is different from primary dentine
* Slower deposition than primary dentine
* less regular pattern of deposition than primary dentine
* also there will be change in orientation and curvature of
tubules
- Secondary dentine forms most rapidly in the pulpal roof and
floor : in the
Pulp chamber we have the roof of the pulp chamber and the
floor of the
pulp , this area is where they actually produce dentine fast ,
why ???
because this area isn't affected by decreasing the volume
( lao faradna
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enno 3endee 7ojret pulp the population in the lateral sides
decreases the
volume there, but in the upper and lower sides there will be
a spaceremains f ma bietza7amo b kathra ).
- Forms with aging that means when we become older we'll
have tubule
occlusion , that tubules that are open and contain theodontoblastic
processes they become occluded (y3ne betsakker) , when
they become
occluded it becomes very difficult for bacteria to penetrate
through dentine
that's why caries rate becomes less and less
- it's occluded by the peritubular dentine , why becomes
occluded ??
because peritubular dentine is deposited more and more
and more and
more and deposited against the walls of the tubules so the
tubules become
narrower and may be closed completely.
- This actually is very pronounced at the root apex
*Translucent
dentine:-
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This is a transversection through a
Tooth , notice the translucent
dentine because of a block or
occlusion in the dentinal tubules
- It's important to remember that this is used in forensic
dentistry in age
Termination : sometimes we can make a cross section in the
tooth , we
Examine the tooth under the microscope , we see the
amount of occlusion
in the dentinal tubules and by this we determine the age of
this person.
- we said sever stimuli lead to pulp necrosis , if these stimuli
are less sever
they lead to a reaction in the pulp this reaction causes the
odontoblasts to
produce a new layer of dentine called tertiary dentine .
- Formed by odontoblast newly differentiated from the pulpal
mesenchymal cells after original cells have died.
- Varies in appearance and composition : it can be regular
and may
contain tubules which is similar to secondary dentine, and
sometimes it can
*Tertiary
dentine:-
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be irregularly arranged so the tubules are irregular not
regular so it will not
be very similar to secondary dentine and it can be atubular (
without anytubules )
It is important to remember the difference between
reactionary and
reparative dentine ,
"halla hai assignment o ra7 yejee 3aleiha so2al bel
emte7an bs la2enkmkwaiseen o dalleitkm ma3ee hon r7 ne7kelkm eyaha bs la
te7koha ll ba2ee "
Reparative dentine : when all the odontoblastic cells die
( y3nee we have
Carries, very severe trauma outside , they killed most of the
cells that are
Defending and we don't have cells , now we call
undifferentiated cells
to go and differentiate and to build this new dentine we call
it reparative
dentine
Reactionary dentine: if the stimulus was not very sever and
instead of
killing the odontoblasts it injured them , so the odontoblasts
now are
injured but they are still able to function so they produce
tertiary dentine
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that is called reactionary
- Sclerotic dentine is when the tubules are occluded not by
aging but by a
Stimulus
( so when the tubules are occluded because of aging
we call it
Translucent dentine , when they are occluded due to a
stimulus we call it
sclerotic dentine )
- similar appearance to translucent dentine but related in site
to the
Stimulus ( y3nee betkoon mobasharatan 3nd el stimulus
amma el
Translucent because of aging you can't relate it to anystimulus because it
Occurs due to aging )
*Sclerotic dentine
:-
*Dead tracts:-
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Dead tracts is the opposite of tubule occlusion ( el tubule ma
sakkar laken
tafarra3' mn mo7tawah) ,tubule normally contains theodontoblastic
process , if the odontoblastic process dies , the tubule
becomes open
( empty) we call it dead tract
- Odontoblastic processes killed by a stimulus leading to
empty tubules ,
this appears dark under transmitted light microscope.
dead tracts
Why it appears in black ?? because the light passes through
spaces that is
why it becomes dark .
halla a5er shee bedna n7ke 3ano hoa el Tetracycline
*Tetracycline:-
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tetracycline is an antibiotic , it was commonly prescribed but
now it's not
very common and much avoided for pregnant ladies and for
children in theage of development of teeth cause it has affinity towards
calcium , it binds
calcium and produces a colored area appears on the teeth
become the
yellowish to brownish in color.
- tetracycline discolors dentine so u can't remove this stain
If you actually bring a tooth subjected to tetracycline and u
see it under
Florescent light microscope you see these lines ( the
yellowish lines ) that
Represent areas where tetracycline is deposited
"***anything related to tetracycline in the book eventhe pictures is
included . kl shee2 yata3ala2 bel tetracycline bel
ketaab matloob 7atta
lao ma 7akeito"
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**** anytooth that was forming at the time the
tetracycline was being
used will be affected .. but the upper canine is thelast tooth to be formed
so it is the least to be effected
So2al mohem feeh rab6 ma3 el dental anatomy :-
A child started to use tetracycline at the age of 6 and
stoped at the age of 9,
where can we see the discoloration???
You have to think what are the teeth that were forming
during that period :
Definitely in the second molars , lower canine and
premolars , definitely it
will not show in the third molars or in the first molars or inthe incisors
Done by: Last Years