oral histo 5th lec 2

8/2/2019 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

oral histo 5th lec 2

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