Lec.
Or
alHi
st
ol
ogy
ﺳ
ﺤ
ﺮ
ﻏ
ﺎ
ﻧ
ﻢ
.
ﺩ
PERI
ODONTALLI
GAMENT(
PDL)
Theper
i
odont
i
um i
sdef
i
nedast
hoset
i
ssuessuppor
t
i
ngandi
nvest
i
ngt
het
oot
h
andconsi
stofcement
um ,per
i
odont
all
i
gament
,bonet
hel
i
ni
ngal
veol
us(
socket
)
andt
hatpar
tt
heofgi
ngi
valf
aci
ngt
het
oot
h.
PERI
ODONTALLI
GAMENT(
PDL)
defi
neasi
st
hedensef
i
br
ousconnect
i
vet
i
ssuet
hatoccupi
est
heper
i
odont
alspace
bet
weent
her
ootoft
het
oot
handbonef
or
mi
ngt
hesocketwal
l
.
Rangesi
nt
hi
cknessbet
ween0.
15and0.
38mm andi
st
hi
nnesti
nt
hemi
ddl
epor
t
i
on
oft
her
oot
.
Or
i
gi
nandDevel
opmentOfPer
i
odont
all
i
gament
PDLi
sder
i
vedfr
om t
hedent
alf
ol
l
i
cl
et
hatenvel
opst
hedevel
opi
ngt
oot
hger
m.
Somedel
i
cat
ef
i
berbundl
esoft
hef
or
mi
ngPDLappearasr
ootfor
mat
i
onbegi
ns.
Thei
nnermostcel
l
sneart
hef
or
mi
ngr
ootdi
f
fer
ent
i
at
ei
nt
ocement
obl
ast
sandl
ay
downcement
um,whi
l
et
heout
er
mostcel
l
sdi
f
f
er
ent
i
at
ei
nt
oost
eobl
ast
sandf
ur
ni
sh
t
hel
i
ni
ngoft
hebonysocket
.Themor
ecent
r
al
l
yl
ocat
edcel
l
sar
edi
f
f
er
ent
i
at
edi
nt
o
fi
br
obl
ast
swhi
chsynt
hesi
zet
hef
i
ber
sandt
hegr
oundsubst
anceoft
hePDL.The
fi
ber
soft
hePDLbecomeembeddedi
nnewl
ydevel
opedcement
um andal
veol
ar
bone(
Shar
pey’
sfi
ber
s).
Hi
st
ol
ogi
calst
r
uct
ur
eoft
heper
i
odont
all
i
gament
ThePDLconsi
stoffi
ber
s,cel
l
s,gr
oundsubst
ance,andot
herst
r
uct
ur
es
suchasbl
oodvessel
sandner
ves.
A.
fi
ber
soft
heper
i
odont
all
i
gament
(
1)Col
l
agenfi
ber
s
Col
l
agenoft
heper
i
odont
all
i
gament
■
Theper
i
odont
alcol
l
ageni
smost
l
yt
ypeI
,col
l
agenTypeI
I
Icol
l
agen(
about20%)
.
■
Much of t
he col
l
agen i
s gat
her
ed t
oget
her t
o for
m bundl
es whi
ch ar
e
appr
oxi
mat
el
y5µm i
ndi
amet
er
.
■
Thesebundl
esar
et
er
medt
hepr
i
nci
palf
i
ber
soft
heper
i
odont
all
i
gament
.
■
Thepr
i
nci
palf
i
ber
sappearmor
enumer
ousatt
hei
rat
t
achment
st
ocement
um
t
hanatt
heal
veol
arbone.
Thepr
i
nci
palf
i
ber
soft
heper
i
odont
all
i
gamentwhi
char
eembeddedi
ncement
um
andi
nt
hebonel
i
ni
ngt
het
oot
hsocketar
et
er
medShar
pey’
sfi
ber
s.
Thehor
i
zont
all
i
nesi
nt
heboneandcement
umr
epr
esentt
heShar
pey’
sfi
ber
s.
Thepr
i
nci
palf
i
ber
s:Theyar
ef
or
medofcol
l
agenbundl
es,whi
char
ewavyi
ncour
se
andar
ear
r
angedi
nt
hr
eegr
oups
a)Gi
ngi
valfi
ber
s:
1-Dent
o-
gi
ngi
valfi
ber
s:
-
2-Al
veol
o-
gi
ngi
valgr
oup:
3-Ci
r
cul
argr
oup:4-Dent
o-
per
i
ost
ealf
i
ber
s.
b)Thet
r
anssept
all
i
gament
:I
tconnect
st
woadj
acentt
eet
h.Thel
i
gamentr
unsf
r
om
t
hecement
umofonet
oot
hovert
hecr
estoft
heal
veol
ust
ot
hecement
umoft
he
adj
acentt
oot
h.
Funct
i
on:Resi
st
smesi
alanddi
st
alt
oot
hsepar
at
i
on.
c)Theal
veol
odent
all
i
gament
:
1-
Al
veol
arcr
estgr
oup:at
t
achedt
ot
hecement
umj
ustbel
owt
hecementenamel
j
unct
i
onandr
unni
ngdownwar
dandoutwar
dt
oi
nser
ti
nt
ot
her
i
m oft
heal
veol
us.
Funct
i
on:r
esi
st
sver
t
i
calandi
nt
r
usi
vefor
ces.
2-
Hor
i
zont
algr
oup:j
ustapi
calt
ot
heAl
veol
arcr
estgr
oupandr
unni
ngatr
i
ght
angl
est
ot
hel
ongaxi
soft
het
oot
hfr
om cement
umt
obonej
ustbel
owt
heAl
veol
ar
cr
est
Funct
i
on:r
esi
st
shor
i
zont
alandt
i
ppi
ngfor
ces.
3-Obl
i
quegr
oup:t
hemostnumer
ousi
nt
hepdlandr
unni
ngf
r
omt
hecement
umi
n
an
obl
i
quedi
r
ect
i
ont
oi
nser
ti
nt
obonecor
onal
l
y.
Funct
i
on:Per
for
mst
hemai
nsuppor
toft
het
oot
hagai
nstmast
i
cat
or
y
f
or
ces.
*Resi
st
sver
t
i
calandi
nt
r
usi
vef
or
ces.
4-Api
calgr
oup:Thebundl
esr
adi
at
i
ngf
r
om t
hecement
umar
oundt
heapexoft
he
r
oott
ot
hebonefor
mi
ngt
hebaseoft
hesocket
.
Funct
i
on:r
esi
st
sver
t
i
calf
or
ce.
5-I
nt
err
adi
cul
argr
oup:f
oundonl
ybet
weent
her
oot
soft
hemul
t
ir
oot
edt
eet
h.And
r
unni
ngf
r
omcement
umi
nt
ot
hebonef
or
mi
ngt
hecr
estoft
hei
nt
err
adi
cul
ar
sept
um.
Funct
i
on:r
esi
st
sver
t
i
calandl
at
er
alf
or
ces.
(
2)Oxyt
al
anfi
ber
s
Theoxyt
al
anfi
ber
sar
eoft
ent
er
mi
nat
ear
oundbl
oodvessel
s.
Theoxyt
al
anfi
ber
svar
yi
nsi
zef
r
om 0.
5-
2.
5mm i
ndi
amet
erandconst
i
t
ut
enomor
e
t
hanabout3%oft
heext
r
acel
l
ul
arf
i
bercomposi
t
i
on.Theyneedspeci
alst
ai
nst
obe
demonst
r
at
edThesear
eel
ast
i
cf
i
ber
sr
uni
n obl
i
quedi
r
ect
i
ononeendbei
ng
embeddedi
nboneorcement
um andt
heot
heri
nt
hewal
lofbl
oodvessel
s.Att
he
api
calr
egi
ont
heyfor
macompl
exnet
wor
k.
Funct
i
onhasnotbeendet
er
mi
nedf
ul
l
yt
heyar
et
houghtt
o1.r
egul
at
evascul
arfl
ow
i
nr
el
at
i
ont
ot
oot
hfunct
i
onbecauset
heyar
eel
ast
i
c,2.
suppor
tt
hebl
oodsvessel
si
n
t
heper
i
odont
all
i
gament
.3-Hel
pf
i
br
obl
ast
smi
gr
at
i
on.
B.
Thecel
l
sofper
i
odont
all
i
gamentar
e
1.Synt
het
i
cCel
l
sa) Fi
br
obl
ast
sb) Ost
eobl
ast
s c)Cement
obl
ast
s
2.
Resor
pt
i
veCel
l
sa) Ost
eocl
ast
sb) Cement
ocl
ast
sc)
Fi
br
obl
ast
s
3.
Undi
ffer
ent
i
at
edmesenchymalcel
l
s(
Pr
ogeni
t
orCel
l
s)
4.
Epi
t
hel
i
alCel
lr
est
sofmal
assez
5.
Connect
i
veTi
ssuecel
l
s
a)Mastcel
l
sb)Macr
ophages
(1) Synt
het
i
ccel
l
s:
a)Fi
br
obl
ast
scel
ls
Per
i
odont
alf
i
br
obl
ast
s,bei
ngact
i
vecel
l
s,havel
ownucl
ear
-
cyt
opl
asmi
cr
at
i
os,and
eachnucl
euscont
ai
nsoneormor
epr
omi
nentnucl
eol
i
.
Fi
br
obl
ast
sar
et
hemostcommoncel
l
si
nper
i
odont
all
i
gament
.Theyconst
i
t
ut
e
about65%oft
ot
alpopul
at
i
on.
Theyappearasovoi
dorel
ongat
edcel
l
swi
t
hpseudopodi
al
i
kepr
ocess.
Theyar
eusual
l
yfoundpar
al
l
elt
ocol
l
agenf
i
ber
s.
Funct
i
ont
heyhel
pi
nsynt
hesi
sandr
esor
pt
i
onofext
r
acel
l
ul
arconnect
i
vet
i
ssue.
b)Ost
eobl
ast
scel
l
s
Al
ayerofost
eobl
ast
sl
i
ni
ngt
heal
veol
arbone.
Theyar
ebonef
or
mi
ngcel
l
s.
C)Cement
obl
ast
scel
l
s
Theyhel
pi
nfor
mat
i
onofcement
um.
(2)
Resor
pt
i
vecel
l
s
a)Cement
ocl
ast
scel
l
s
Ascement
umnotr
emodelt
hesecel
l
sar
enotnor
mal
l
yf
oundi
nl
i
gment
.Thesecel
l
occuronl
yi
ncer
t
ai
npat
hol
ogi
calcondi
t
i
ons,
dur
i
ngr
esor
pt
i
onofdeci
duoust
eet
h
anddur
i
ngor
t
hodont
i
ct
her
apy.
b)Ost
eocl
ast
scel
l
s
Theyar
eboner
esor
bi
ngcel
l.Ani
ncr
easei
nnumberofOst
eocl
ast
sar
eseenwher
e
bonei
sundergoi
ngact
i
ver
esor
pt
i
on.
(
3)Undi
ffer
ent
i
at
edmesenchymalcel
l
s(
Pr
ogeni
t
orcel
l
s)
Canunder
gomi
t
ot
i
cdi
vi
si
on,Candi
f
f
er
ent
i
at
et
odi
f
f
er
entt
ypesofcel
l
s,havesmal
l
,
cl
osed-f
acenucl
eus,l
i
t
t
l
eamountofcyt
opl
asm,f
oundcl
oset
obl
oodvessel
s.
(
4)Epi
t
hel
i
alr
estofMal
assez’
st
hesegr
oupsofepi
t
hel
i
alcel
l
sbecomel
ocat
edi
n
t
hemat
ur
ePDLaf
t
ert
hedi
si
nt
egr
at
i
onofHer
t
wi
gepi
t
hel
i
alr
ootsheat
hdur
i
ngt
he
f
or
mat
i
onoft
her
oot
.
(
5)Connect
i
vecel
l
s
Def
encecel
l
s:Mastcel
l
s,Macr
ophagest
hatder
i
vedf
r
ommonocyt
esar
epr
esenti
n
l
i
gament
.
C.Gr
oundsubst
ance
Thegr
oundsubst
ancei
sananamor
phousbackgr
oundmat
er
i
alt
hatbi
ndst
i
ssue
andf
l
ui
ds.
i
t
consi
st
smai
nl
yofpr
ot
ei
nsandpol
ysacchar
i
des.gr
oundsubst
ance
cont
ai
nsabout70%wat
er
.
Al
lcomponent
soft
heper
i
odont
all
i
gamentgr
ound
subst
ancear
epr
esumedt
obesecr
et
edbyf
i
br
obl
ast
s.
Thegr
oundsubst
ancei
s
t
houghtt
ohavemanyi
mpor
t
antfunct
i
ons:
1.
hel
psi
nt
r
anspor
t
i
ngi
onandwat
er
br
i
ngandexchangeandal
sohel
psi
ncar
r
i
ngt
hewastpr
oduct
sfr
omcel
lt
obl
ood
vessel
s,
2.cont
r
olofcol
l
agenf
i
br
i
l
l
ogenesi
sandf
i
beror
i
ent
at
i
on.
D.
I
nt
er
st
i
t
i
alt
i
ssue
t
heyar
efoundbet
weent
hef
i
ber
soft
hePDL
Theyar
ear
east
hatcont
ai
nsomeoft
hebl
oodvessel
s,l
ymphat
i
c,andner
ves.They
sur
r
oundedbyl
ooseC.
T
E.
Bl
oodvessel
s
Thebl
oodvessel
st
r
avelfr
om api
calt
ooccl
usal
.
Mai
nbl
oodsuppl
yi
sf
r
omsuper
i
orandi
nfer
i
oral
veol
arar
t
er
i
es.Thebl
oodvessel
s
ar
eder
i
vedfr
omt
hefol
l
owi
ng:
1.Br
anchesfr
omapi
calvessel
s:vessel
st
hatsuppl
yt
hedent
alpul
p.
2.Br
anchesfr
omi
nt
r
a-
al
veol
arvessel
s:
-Vessel
sr
unhor
i
zont
al
l
yandpenet
r
at
et
he
al
veol
arbonet
oent
eri
nt
ot
heper
i
odont
all
i
gament
3.Br
anchesf
r
omgi
ngi
valvessel
s:
-Thear
t
er
i
ol
esandcapi
l
l
ar
i
esr
ami
f
yandf
or
ma
r
i
chnet
wor
k.Ri
chvascul
arpl
exusi
sf
oundatt
heapexandi
ncer
vi
calpar
tof
l
i
gament
..
Adensevenousnet
wor
ki
spar
t
i
cul
ar
l
ypr
omi
nentar
oundt
heapexoft
heal
veol
us.
F.
Lymphat
i
cs
Anet
wor
kofl
ymphat
i
cvessel
sf
ol
l
owi
ngt
hepat
hoft
hebl
oodvessel
spr
ovi
dest
he
l
ymphdr
ai
nageoft
heper
i
odont
all
i
gament
.
G.
Ner
vesofper
i
odont
all
i
gament
Thener
vesar
et
hebr
anchesofsecondandt
hi
r
ddi
vi
si
onoffi
f
t
hcr
ani
alner
ve
(
t
r
i
gemi
nalner
ve)andf
ol
l
ow samepat
hasbl
oodvessel
s.Thesener
vefi
ber
s
pr
ovi
desenseoft
ouch,pr
essur
e,pai
nandpr
opr
i
ocept
i
ondur
i
ngmast
i
cat
i
on.The
ner
vef
i
ber
sent
er
i
ngt
heper
i
odont
all
i
gamentar
eder
i
vedf
r
om t
wosour
ces.Some
ner
vebundl
esent
erneart
her
ootapexandpassupt
hr
ought
heper
i
odont
all
i
gament
.
Ot
her
sent
ert
hemi
ddl
eandcer
vi
calpor
t
i
onsoft
hel
i
gamentasf
i
nerbr
anches
t
hr
oughopeni
ngi
nt
heal
veol
arwal
l
s.Per
i
odont
alner
vef
i
ber
sar
ebot
hmyel
i
nat
ed
andunmyel
i
nat
ed.
Funct
i
onsofper
i
odont
all
i
gament
1.Suppor
t
i
vefunct
i
on
byat
t
achi
ngt
het
oot
ht
ot
hesur
r
oundi
ngal
veol
arbonepr
oper
.
Thi
sf
unct
i
oni
s
medi
at
edpr
i
mar
i
l
ybyt
hepr
i
nci
palf
i
ber
soft
heper
i
odont
all
i
gamentt
hatf
or
m a
st
r
ongf
i
br
ousuni
onbet
weent
her
ootcement
um andt
hebone.
Theper
i
odont
al
l
i
gamental
soser
vesasashock-
absor
berbymechani
smst
hatpr
ovi
der
esi
st
ancet
o
l
i
ghtaswel
lasheavyfor
ces.
Li
ghtf
or
cesar
ecushi
onedbyi
nt
r
avascul
arfl
ui
dt
hat
i
sfor
cedoutoft
hebl
oodvessel
s.
Moder
at
ef
or
cesar
eal
soabsor
bedbyext
r
a
vascul
art
i
ssuefl
ui
dt
hati
sf
or
cedoutoft
heper
i
odont
all
i
gamentspacei
nt
ot
he
adj
acentmar
r
ow spaces.
Theheavi
erf
or
cesar
et
akenupbyt
hepr
i
nci
palf
i
ber
s.
Bl
oodvessel
sandal
lt
hecomponent
soft
hel
i
gamentactt
oget
herasahydaul
i
c
damper
orshockabsor
berwi
t
h t
hegr
ound subst
anceand t
het
i
ssuefl
ui
d.
t
he
gr
oundsubst
ancepr
esentbet
weent
hef
i
ber
sofpdli
sr
i
chi
nwat
ercont
entand
t
her
ef
or
eaddupt
ot
hesuppor
t.
2.Remodel
i
ngfunct
i
on
bypr
ovi
di
ngcel
l
st
hatar
eabl
et
of
or
m aswel
lasr
esor
bal
lt
het
i
ssuest
hatmakeup
t
heat
t
achmentappar
at
us,i
.
e.bone,cement
um andt
heper
i
odont
all
i
gament
Undi
f
f
er
ent
i
at
ed ect
omesenchymalcel
l
s,l
ocat
ed ar
ound bl
ood vessel
s,can
di
f
f
er
ent
i
at
ei
nt
ot
hespeci
al
i
zedcel
l
st
hatfor
m bone(
ost
eobl
ast
s)
,cement
um
(
cement
obl
ast
s)
,and connect
i
vet
i
ssuefi
ber
s(
fi
br
obl
ast
s).and r
esor
bi
ng cel
l
s
(
ost
eocl
ast
sandcement
ocl
ast
)
.
3-Sensor
yfunct
i
on:Theper
i
odont
all
i
gamentpr
ovi
desanexcel
l
entpr
opr
i
ocept
i
ve
mechani
sm whi
chhel
psi
nest
i
mat
i
ngt
heamountofpr
essur
eon mast
i
cat
i
onand
el
i
ci
t
sevent
hemi
l
destf
or
ceact
i
nguponat
oot
h.
4-Nut
r
i
t
i
vefunct
i
on:Thebl
oodvessel
si
nt
heper
i
odont
all
i
gamenthasagoodbl
ood
suppl
ywhi
chpr
ovi
denut
r
i
entforcel
l
soft
hel
i
gament.
5-Pr
ot
ect
i
ve funct
i
on The pr
ot
ect
i
ve f
unct
i
on oft
he per
i
odont
all
i
gamenti
s
achi
evedby:
a-Thepr
i
nci
palf
i
ber
s.
b-Thebl
oodvessel
s.
c-Thener
ves.
a-Thepr
i
nci
palfi
ber
s:Thear
r
angementoft
hef
i
berbundl
esi
nt
hedi
ff
er
entgr
oups
i
swel
ladapt
edt
oful
f
i
l
lt
hef
unct
i
onsoft
heper
i
odont
all
i
gament
.
Theal
veol
odent
al
l
i
gamentt
r
ansfor
mst
hemast
i
cat
or
ypr
essur
eexer
t
edont
het
oot
hi
nt
ot
ensi
onor
t
r
act
i
onont
hecement
um andbone.
I
ft
heexer
t
edf
or
ceonat
oot
hi
st
r
ansmi
t
t
edas
pr
essur
et
hi
swi
l
ll
eadt
odi
f
f
er
ent
i
at
i
onofost
eocl
ast
si
nt
hepr
essur
ear
eaand
r
esor
pt
i
onofbone.
b-Thebl
oodvessel
s:
Thecapi
l
l
ar
i
esfor
m ar
i
chnet
wor
k,t
heyar
ear
r
angedi
nf
or
m
ofacoi
landat
t
achedt
oboneandcement
um t
hr
ought
heoxyt
al
anf
i
ber
s.Thi
s
ar
r
angementmakesi
tpossi
bl
ewhenpr
essur
ei
sexer
t
edont
het
oot
h,t
hebl
ood
doesnotescapei
mmedi
at
el
yf
r
om t
hecapi
l
l
ar
i
esandt
husbuff
er
i
ngt
hepr
essur
e
act
i
onbefor
ei
tr
eachest
hebone.Thebehavi
oroft
hebl
oodi
nt
hecapi
l
l
ar
i
esmaybe
si
mul
at
edt
oahydr
aul
i
cbr
ake
c-Thener
ves:Byi
t
smechanor
ecept
or
sner
ves.
Cl
i
ni
calconsi
der
at
i
ons
1.Thel
i
gamenti
st
hi
ckeri
nfunct
i
oni
ngt
hani
nnon-
f
unct
i
oni
ngt
eet
h,andi
nar
eas
oft
ensi
ont
hani
nar
easofcompr
essi
on
.
2.Excessi
vef
or
cescancausel
ocal
i
zednecr
osi
s(
cel
ldeat
h)oft
hel
i
gamentby
cut
t
i
ngof
ft
henor
malbl
oodsuppl
yt
ot
hecel
l
s.Thi
ssi
t
uat
i
oni
mmedi
at
el
yr
esul
t
si
n
st
oppageofr
emodel
i
ngatt
heaf
f
ect
edsi
t
e.
Ther
ef
or
e,or
t
hodont
i
ct
oot
h
movementi
snol
ongerpossi
bl
e.
Repai
roccur
svi
aemi
gr
at
i
onofcel
l
sfr
om
adj
oi
ni
ngvi
t
alper
i
odont
all
i
gament
.
I
nt
heeventt
hel
i
gamentcont
i
nui
t
yi
snotr
est
or
ed,l
ocal
i
zedr
esor
pt
i
onand
ankyl
osi
smayoccur
.
3.Acci
dent
al
l
yexfol
i
at
edt
eet
hcanber
epl
ant
ed.
Compl
i
cat
i
onsi
ncl
udeext
er
nal
r
ootr
esor
pt
i
onandankyl
osi
smayoccur
ei
fpor
t
i
onsoft
hel
i
gamentar
e
per
manent
l
ydamaged.Thesecanbemi
ni
mi
zedbyavoi
di
ngexcessi
vehandl
i
ngof
t
het
or
nl
i
gamentpr
i
ort
or
epl
ant
at
i
on.
TheAgeChangesofper
i
odont
all
i
gament
*Theper
i
odont
all
i
gamentt
hr
oughagi
ngshowsvasucl
ar
i
t
y,
cel
l
ul
ar
i
t
y,t
hi
ckness.
*I
tmaycont
ai
ncement
i
cl
es.