Understanding the Periodontal Ligament in Dental Sciences

 
 
        
SIBAR INSTITUTE OF DENTAL SCIENCES
   DEPARTMENT OF PERIODONTICS
 PERIODONTAL LIGAMENT
DR. K. KISHORE KUMAR, 
PROFESSOR
 
 
 
 
 
 
 
 
 
 
 
 
 
 
P
E
R
I
O
D
O
N
T
I
U
M
C
o
n
n
e
c
t
i
v
e
 
t
i
s
s
u
e
 
o
r
g
a
n
 
t
h
a
t
 
a
t
t
a
c
h
e
s
 
t
h
e
 
t
e
e
t
h
 
t
o
 
t
h
e
 
j
a
w
 
b
o
n
e
 
 
&
s
u
p
p
o
r
t
s
 
d
u
r
i
n
g
 
f
u
n
c
t
i
o
n
.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
C
e
m
e
n
t
u
m
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2
 
m
i
n
e
r
a
l
i
z
e
d
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
A
l
v
e
o
l
a
r
 
b
o
n
e
C
o
n
s
i
s
t
s
 
o
f
 
4
 
t
i
s
s
u
e
s
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
P
e
r
i
o
d
o
n
t
a
l
 
l
i
g
a
m
e
n
t
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2
 
s
o
f
t
 
t
i
s
s
u
e
s
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
L
a
m
i
n
a
 
p
r
o
p
r
i
a
 
o
f
g
i
n
g
i
v
a
 
Periodontal ligament
 
Is a soft, richly vascular &
cellular connective tissue that
surrounds the roots of the teeth
and joins the root cementum
with socket wall
 
Extends from base of the
socket to apical portion of the
lamina propria of gingiva
 
 
Development of P.D.L
 
Pdl fibroblasts have their origin
in DF &begin to differentiate
during root development
(TENCATE et al  1971)
 
 
The outer & inner enamel
epithelia fuse & proliferate to
form 
Hertwig's epithelial root
sheath
 
As and when cementum and PDL begin their formation, osteoblasts
also differentiate from 
parafollicular
 cells and lay down Alveolar
bone
 
These fibers embed themselves into the newly formed cementum laid
down by cementoblasts at one end, and into the bone laid down by
osteoblasts at their other end.
 
 
FORMATION  OF  PERIODONTAL
LIGAMENT FIBERS
 
 
Initially the fibers become embedded in the cementum as
SHARPEYS FIBERS
 and are laid in coronal direction within the
region identified as developing PDL
The fibers deposited apical to the CEJ ultimately form the fibers of
PDL.
By the time 
approximately 1/3 rd of root formation 
is complete,
fibers are inserted within a cementum matrix from CEJ & traverse in a
coronal direction following outline of newly formed crown
Both root surface derived & bone derived fibers ultimately coalesce in
middle third of ligament to form  
INTERMEDIATE PLEXUS
 
 
 
 
Structure of periodontal ligament
 
Average width of periodontal ligament space 
0.25 mm
(0.2 - 0.4 mm).
 
PDL has a shape of  
HOURGLASS
 and is narrowest at mid root
level .
PDL space diminished around teeth that are not in function &
unerupted teeth.
 
PDL has 
a wavy course 
when viewed in longitudinal section
 
Components
 
Fibers
Cells
Ground substance
 
FIBROBLAST
 
TROPOCOLLAGEN MOLECULES
 
MICRO FIBRILS
 
FIBRILS
 
FIBER
 
BUNDLE
             
COLLAGEN
    It is a protein composed of different aminoacids, most important of
them
            
Glycine
            Proline
            Hydroxyproline
            Hydroxylysine
Amount of collagen in the tissue can be determined by its
hydroxyproline
 content
 
Collagen Responsible For
              Maintenance Of frame work
              Tone Of Tissue
Collagen fibrils have transverse striations with a characteristic
periodicity of 64 nm
This is due to the overlapping arrangement of  
tropocollagen
molecules
Collagen Fibers are chiefly type I &
some type III
Type I
 More than 
70% 
is 
type I.
Uniformly distributed in the
ligament.
Two identical 
α
 1chains and a
chemically different 
α
2 chain.
It is low in hydroxylysine and
glycosylated hydro-lysine.
Type III
Accounts for about 20% of collagen fibers.
Three identical 
α
1 chains
.
It is high in hydroxyproline, low in hydroxylysine and contains
cysteine.
It is found in the periphery of sharpey's fiber attachments into
alveolar bone.
Other than collagen several other proteins also occur
              proteoglycans
              glycoproteins  (Undulin & fibronectin)
Although PDL doesnot contain mature elastin  it has
            two immature forms  . oxytalan
                                               . Eluanin     oxytalan fibers
 
 
 
 
 
 
O
x
y
t
a
l
a
n
 
f
i
b
e
r
s
 
 
r
u
n
 
p
a
r
a
l
l
e
l
 
t
o
 
t
h
e
 
r
o
o
t
 
s
u
r
f
a
c
e
 
i
n
 
v
e
r
t
i
c
a
l
 
d
i
r
e
c
t
i
o
n
 
&
t
h
e
y
 
b
e
n
d
 
a
t
t
a
c
h
 
c
e
m
e
n
t
u
m
 
a
t
 
c
e
r
v
i
c
a
l
 
t
h
i
r
d
 
o
f
 
t
o
o
t
h
I
n
 
a
d
d
i
t
i
o
n
 
t
o
 
t
h
e
s
e
 
f
i
b
e
r
s
 
s
m
a
l
l
 
c
o
l
l
a
g
e
n
 
f
i
b
e
r
s
 
a
r
e
 
a
s
s
o
c
i
a
t
e
d
 
w
i
t
h
l
a
r
g
e
r
 
f
i
b
e
r
s
 
,
t
h
e
y
 
r
u
n
 
i
n
 
a
l
l
 
d
i
r
e
c
t
i
o
n
s
 
f
o
r
m
i
n
g
 
I
N
D
I
F
F
E
R
E
N
T
F
I
B
E
R
 
P
L
E
X
U
S
 
PRINCIPLE FIBRES OF PERIODONTAL LIGAMENT
 
 Subdivided into 6 categories
 
 
1.
Transseptal group
2.
Alveolar crest group
3.
 Horizontal group
4.
Oblique group
5.
Apical group
6.
Interradicular fibers
 
 
Transseptal group
      
Extend interproximally over alveolar bone crest and are embedded
into adjacent tooth
    
  Reconstructed even after destruction
 
 
Alveolar crest group
      Arise from crest of alveolar bone & attached to cementum.
      Resist tilting, extrusive and lateral forces.
 
 
 
Horizontal group
     
 Alveolar bone to cementum right angles to long axis
      Resist lateral forces
 
Oblique group
      Occupy 2/3
rd
 of the ligament
      Extend obliquely from cementum to alveolar bone coronally
      Bear vertical masticatory forces
      oppose axially directed forces
 
 
Apical group
       
Fibers radiate in different directions from apex of the tooth
      Not seen on incompletely formed roots.
      prevent tooth tipping and extrusion
 
 
Interradicular group
      Extend from the crest of the interradicular bone to the furcation area
 
of the multirooted tooth.
     Fibers are lost – if gingival recession extends &  the furcation area is
 
exposed.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
C
e
l
l
s
 
a
r
e
 
d
i
v
i
d
e
d
 
i
n
t
o
 
4
 
m
a
i
n
 
c
a
t
e
g
o
r
i
e
s
:
1
.
 
 
S
y
n
t
h
e
t
i
c
 
c
e
l
l
s
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
a
.
 
F
i
b
r
o
b
l
a
s
t
s
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
b
.
 
O
s
t
e
o
b
l
a
s
t
s
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
c
.
 
C
e
m
e
n
t
o
b
l
a
s
t
s
2
.
 
 
R
e
s
o
r
p
t
i
v
e
 
c
e
l
l
s
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
a
.
 
O
s
t
e
o
c
l
a
s
t
s
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
b
.
 
F
i
b
r
o
b
l
a
s
t
s
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
c
.
 
C
e
m
e
n
t
o
c
l
a
s
t
s
3
.
 
 
P
r
o
g
e
n
i
t
o
r
 
c
e
l
l
s
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
E
p
i
t
h
e
l
i
a
l
 
r
e
s
t
s
 
o
f
 
M
a
l
a
s
s
e
z
4
.
 
D
e
f
e
n
s
e
 
c
e
l
l
s
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
a
.
 
m
a
s
t
 
c
e
l
l
s
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
b
.
 
m
a
c
r
o
p
h
a
g
e
s
    
FIBROBLAST
Ovoid/elongated, oriented along
principal fibers.
c/s of fibroblast - stellate appearance
 Fibroblast are connected by numerous
junctions
         .  
Gap junction
         .  Adherence type of junction
 
(tight junction)
Communication b/n the cells by mutual
interaction are facilitated via
          . Junctional complexus
          . Electric coupling
GROUND SUBSTANCE
 
 
 
 
 
 
 
 
 
 
 
 
T
h
e
 
p
e
r
i
o
d
o
n
t
a
l
 
l
i
g
a
m
e
n
t
 
a
l
s
o
 
c
o
n
t
a
i
n
s
 
a
 
l
a
r
g
e
 
p
r
o
p
o
r
t
i
o
n
 
o
f
 
g
r
o
u
n
d
s
u
b
s
t
a
n
c
e
 
f
i
l
l
i
n
g
 
t
h
e
 
s
p
a
c
e
s
 
b
e
t
w
e
e
n
 
c
e
l
l
s
 
a
n
d
 
f
i
b
e
r
s
I
t
 
c
o
n
s
i
s
t
s
 
o
f
 
t
w
o
 
m
a
i
n
 
c
o
m
p
o
n
e
n
t
s
1.
G
l
y
c
o
s
a
m
i
n
o
g
l
y
c
a
n
s
 
-
 
 
H
y
a
l
u
r
o
n
i
c
 
A
c
i
d
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
P
r
o
t
e
o
g
l
y
c
a
n
s
2
.
 
 
 
G
l
y
c
o
p
r
o
t
e
i
n
 
 
 
 
 
 
 
F
i
b
r
o
n
e
c
t
i
n
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
L
a
m
i
n
i
n
A
l
s
o
 
h
a
s
 
a
 
h
i
g
h
 
w
a
t
e
r
 
c
o
n
t
e
n
t
(
7
0
%
)
Functions of PDL
 
 
1.
Provision of soft tissue
 
casing
 
to protect the vessels and nerves from
injury by mechanical forces
 
2.
Transmission of occlusal forces to bone
 
3.
Attachment of teeth to bone
 
4.
Maintenance of gingival tissues  in their proper relationship to teeth
 
5.
Resistance to impact of occlusal forces (shock absorption)
 
 
Resistance to impact of occlusal forces (shock absorption)
 
Tensional theory
Viscoelastic system theory
 
 
Tensional theory
 
Principle fiber first unfold ,straighten and then transmit forces to
alveolar bone ,causing an elastic deformation of bony socket
 
Finally when bone  has reached its limit the load is transmitted to the
basal bone
 
Viscoelastic theory
 
States that displacement of tooth is largely controlled by fluid
movements with fibers having  only a secondary role
 
When force is transmitted to tooth the extra cellular fluid passes from
pdl into marrow spaces of bone through  foramina in cribriform plate.
 
The 
perforations of the plate 
link the pdl with cancellous portion of
alveolar bone  and more abundant in cervical third
 
 
 
After depletion of tissue fluids the fiber bundles absorb slack& tighten
 
This leads to 
blood vessels stenosis
 
Arterial back pressure causes the ballooning of vessels and passage of
blood ultra filtrates into tissues and replenish the tissue fluids
 
 
Transmission of occlusal forces to bone
when an axial force is applied to a tooth  a tendency towards
displacement of root in to alveolus occurs
The oblique fibers alter their wavy, untensed pattern and assume their
full length and sustain major part of axial force
 
 
 
 
 
 
 
 
W
h
e
n
 
a
 
h
o
r
i
z
o
n
t
a
l
 
w
o
r
k
 
o
r
 
t
i
p
p
i
n
g
 
 
i
s
 
a
p
p
l
i
e
d
T
w
o
 
p
h
a
s
e
s
 
o
f
 
t
o
o
t
h
 
m
o
m
e
n
t
 
o
c
c
u
r
 
t
h
e
 
f
i
r
s
t
 
i
s
 
w
i
t
h
 
i
n
 
t
h
e
 
c
o
n
f
i
n
e
s
 
o
f
p
d
l
 
a
n
d
S
e
c
o
n
d
 
p
r
o
d
u
c
e
s
 
 
t
h
e
 
d
i
s
p
l
a
c
e
m
e
n
t
 
o
f
 
 
t
h
e
 
f
a
c
i
a
l
 
a
n
d
 
l
i
n
g
u
a
l
 
b
o
n
y
p
l
a
t
e
s
T
h
e
 
t
o
o
t
h
 
r
o
t
a
t
e
s
 
a
b
o
u
t
 
a
n
 
a
x
i
s
 
t
h
a
t
 
m
a
y
 
c
h
a
n
g
e
 
a
s
 
t
h
e
 
f
o
r
c
e
 
i
s
i
n
c
r
e
a
s
e
d
 
 
 
 
 
 
 
 
 
T
h
e
 
a
p
i
c
a
l
 
p
o
r
t
i
o
n
 
o
f
 
r
o
o
t
 
m
o
v
e
s
 
i
n
 
a
 
d
i
r
e
c
t
i
o
n
 
o
p
p
o
s
i
t
e
 
t
o
 
c
o
r
o
n
a
l
p
o
r
t
i
o
n
I
n
 
a
r
e
a
s
 
o
f
 
t
e
n
s
i
o
n
 
t
h
e
 
p
r
i
n
c
i
p
l
e
 
f
i
b
e
r
s
 
a
r
e
 
t
a
u
t
 
r
a
t
h
e
r
 
t
h
a
n
 
w
a
v
y
I
n
 
a
r
e
a
s
 
o
f
 
p
r
e
s
s
u
r
e
 
t
h
e
 
f
i
b
e
r
s
 
a
r
e
 
c
o
m
p
r
e
s
s
e
d
,
 
t
h
e
 
t
o
o
t
h
 
i
s
 
d
i
s
p
l
a
c
e
d
C
o
r
r
e
s
p
o
n
d
i
n
g
 
d
i
s
t
o
r
t
i
o
n
 
o
f
 
b
o
n
e
 
e
x
i
s
t
s
 
i
n
 
t
h
e
 
d
i
r
e
c
t
i
o
n
 
o
f
 
r
o
o
t
m
o
v
e
m
e
n
t
Single rooted tooth-between –
apical third and middle third
Root apex and coronal half of clinical root are other locations of axis
of rotation
In multirooted tooth axis of rotation is located in bone 
between the
roots
Pdl is thinner on mesial surface
 
Nutritional and sensory functions
 
Pdl supplies nutrients to the cementum ,bone and gingiva by way of
blood vessels and also lymphatic drainage
 
pdl  is 
highly vascularized tissue 
(almost 
10%
 of the volume in
rodent molar is blood vessels)
 
This relatively high blood vessel content may provide hydrodynamic
damping to applied forces as well as high perfusion rates  to pdl
Nerve bundles pass into pdl from
the PA area & through channels
from the alveolar bone that follow
the course of blood vessels
The bundles 
divide into single
myelinated fibers 
which
ultimately lose their myelin sheath
& end in one of the 4 types of
neural termination
 
 
1.
Free endings 
tree like configuration –carry pain sensation
 
2.
Ruffini like 
mechano receptors –apical area
 
3.
Coiled meissners corpuscles 
–mechano receptors- midroot region
 
4.
Spindle like 
pressure and vibration endings which are surrounded by
fibrous capsule located at apex.
Blood supply
Blood vessels
 – 3 sources
1.
Vessels that enter the tooth to supply
the dental pulp, prior to entry give
branches that supply the PDL
2.
Intra alveolar vessels traverse
horizontally within alveolar bone to
enter PDL
3.
Gingival vessels supply the P.L from
the coronal end
 
 
Arterioles and capillaries of microcirculation ramify in   Pdl and form
a rich network of arcades
 
It is possibly involved that the circulation plays in supporting teeth
during function
 
Venous vessels drain axially to drain to the apex
 
Nerves
 
They are associated with blood vessels and pass through foraminae in
the alveolar bone including apical foramen to enter Pdl
 
They run along the length of the root they branch and run coronally &
apically
 
Large diameter myelinated
 
Small diameter may or may not be
 
 myelinated
 
 
 
 
 
 
 
 
 
 
 
S
m
a
l
l
 
f
i
b
e
r
s
 
a
p
p
e
a
r
 
t
o
 
e
n
d
 
i
n
 
f
i
n
e
 
b
r
a
n
c
h
e
s
 
t
h
r
o
u
g
h
o
u
t
 
t
h
e
 
l
i
g
a
m
e
n
t
L
a
r
g
e
 
f
i
b
e
r
s
 
m
a
y
 
e
n
d
 
k
n
o
b
 
l
i
k
e
 
,
 
s
p
i
n
d
l
e
 
l
i
k
e
 
,
 
m
e
i
s
s
n
e
r
 
l
i
k
e
L
a
r
g
e
 
d
i
a
m
e
t
e
r
-
-
c
o
n
c
e
r
n
e
d
 
w
i
t
h
 
p
r
e
s
s
u
r
e
S
m
a
l
l
 
d
i
a
m
e
t
e
r
 
 
c
o
n
c
e
r
n
e
d
 
w
i
t
h
 
p
a
i
n
L
y
m
p
h
a
t
i
c
s
L
y
m
p
h
 
v
e
s
s
e
l
s
 
p
r
o
v
i
d
e
 
l
y
m
p
h
a
t
i
c
 
d
r
a
i
n
a
g
e
 
o
f
 
t
h
e
 
P
.
L
.
 
i
n
t
o
 
a
d
j
a
c
e
n
t
a
l
v
e
o
l
a
r
 
b
o
n
e
 
 
 
Clinical considerations
 
 
Pdl thickness varies in different individuals
 
The fact that Pdl 
is thinnest in middle region of root 
--- fulcrum of
physiologic tooth movement
 
 Supporting tissues of tooth long out of function are poorly adapted to
carry load suddenly placed on tooth by a restoration
 
 
 
 
 
 
 
 
 
 
 
E
g
;
T
e
e
t
h
 
o
p
p
o
s
i
n
g
 
b
r
i
d
g
e
s
 
o
r
 
d
e
n
t
u
r
e
s
T
e
e
t
h
 
u
s
e
d
 
a
s
 
a
n
c
h
o
r
a
g
e
 
f
o
r
 
r
e
m
o
v
a
b
l
e
 
b
r
i
d
g
e
s
T
h
i
s
 
w
i
l
l
 
a
c
c
o
u
n
t
 
f
o
r
 
i
n
a
b
i
l
i
t
y
 
o
f
 
a
 
p
a
t
i
e
n
t
 
t
o
 
u
s
e
 
a
 
r
e
s
t
o
r
a
t
i
o
n
i
m
m
e
d
i
a
t
e
l
y
 
a
f
t
e
r
 
i
t
s
 
p
l
a
c
e
m
e
n
t
I
n
 
o
r
t
h
o
d
o
n
t
i
c
 
t
r
e
a
t
m
e
n
t
 
a
n
 
a
d
j
u
s
t
m
e
n
t
 
p
e
r
i
o
d
 
m
u
s
t
 
b
e
 
p
e
r
m
i
t
t
e
d
Cysts derived from epithelial cell rests of Malassez 
Periapical cyst
Residual cyst
Lateral periodontal cyst
Tumours derived from epithelial rests of Malassez 
Ameloblastoma
Primary intra alveolar epidermoid carcinoma
Squamous odontogenic tumour
 
Slide Note
Embed
Share

The periodontal ligament (PDL) is a vital connective tissue that supports teeth by attaching them to the jaw bone. It consists of various tissues including cementum and alveolar bone, and is rich in vascular and cellular components. The development of PDL fibers plays a crucial role in tooth support and function. Fibers embed in cementum forming Sharpey's fibers and eventually traverse in a coronal direction, forming the intermediate plexus. The structure of PDL includes an hourglass shape with a narrowest point at mid-root level. This ligament's space decreases in non-functional or unerupted teeth.


Uploaded on Aug 03, 2024 | 1 Views


Download Presentation

Please find below an Image/Link to download the presentation.

The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author. Download presentation by click this link. If you encounter any issues during the download, it is possible that the publisher has removed the file from their server.

E N D

Presentation Transcript


  1. PERIODONTAL LIGAMENT DR. K. KISHORE KUMAR, PROFESSOR SIBAR INSTITUTE OF DENTAL SCIENCES DEPARTMENT OF PERIODONTICS

  2. PERIODONTIUM Connective tissue organ that attaches the teeth to the jaw bone & supports during function. Cementum 2 mineralized Alveolar bone Consists of 4 tissues Periodontal ligament 2 soft tissues Lamina propria of gingiva

  3. Periodontal ligament Is a soft, richly vascular & cellular connective tissue that surrounds the roots of the teeth and joins the root cementum with socket wall Extends from base of the socket to apical portion of the lamina propria of gingiva

  4. Development of P.D.L Pdl fibroblasts have their origin in DF &begin to differentiate during root (TENCATE et al 1971) development The outer & inner enamel epithelia fuse & proliferate to form Hertwig's epithelial root sheath

  5. As and when cementum and PDL begin their formation, osteoblasts also differentiate from parafollicular cells and lay down Alveolar bone These fibers embed themselves into the newly formed cementum laid down by cementoblasts at one end, and into the bone laid down by osteoblasts at their other end.

  6. FORMATION OF PERIODONTAL LIGAMENT FIBERS

  7. Initially the fibers become embedded in the cementum as SHARPEYS FIBERS and are laid in coronal direction within the region identified as developing PDL The fibers deposited apical to the CEJ ultimately form the fibers of PDL. By the time approximately 1/3 rd of root formation is complete, fibers are inserted within a cementum matrix from CEJ & traverse in a coronal direction following outline of newly formed crown Both root surface derived & bone derived fibers ultimately coalesce in middle third of ligament to form INTERMEDIATE PLEXUS

  8. Structure of periodontal ligament Average width of periodontal ligament space 0.25 mm (0.2 - 0.4 mm). PDL has a shape of HOURGLASS and is narrowest at mid root level . PDL space diminished around teeth that are not in function & unerupted teeth. PDL has a wavy course when viewed in longitudinal section

  9. Components Fibers Cells Ground substance

  10. FIBROBLAST TROPOCOLLAGEN MOLECULES MICRO FIBRILS FIBRILS FIBER BUNDLE

  11. COLLAGEN It is a protein composed of different aminoacids, most important of them Glycine Proline Hydroxyproline Hydroxylysine Amount of collagen in the tissue can be determined by its hydroxyproline content

  12. Collagen Responsible For Maintenance Of frame work Tone Of Tissue Collagen fibrils have transverse striations with a characteristic periodicity of 64 nm This is due to the overlapping arrangement of tropocollagen molecules

  13. Other than collagen several other proteins also occur proteoglycans glycoproteins (Undulin & fibronectin) Although PDL doesnot contain mature elastin it has two immature forms . oxytalan . Eluanin oxytalan fibers

  14. Oxytalan fibers run parallel to the root surface in vertical direction & they bend attach cementum at cervical third of tooth In addition to these fibers small collagen fibers are associated with larger fibers ,they run in all directions forming INDIFFERENT FIBER PLEXUS

  15. PRINCIPLE FIBRES OF PERIODONTAL LIGAMENT Subdivided into 6 categories 1. Transseptal group 2. Alveolar crest group 3. Horizontal group 4. Oblique group 5. Apical group 6. Interradicular fibers

  16. Transseptal group Extend interproximally over alveolar bone crest and are embedded into adjacent tooth Reconstructed even after destruction Alveolar crest group Arise from crest of alveolar bone & attached to cementum. Resist tilting, extrusive and lateral forces. Horizontal group Alveolar bone to cementum right angles to long axis Resist lateral forces

  17. Oblique group Occupy 2/3rd of the ligament Extend obliquely from cementum to alveolar bone coronally Bear vertical masticatory forces oppose axially directed forces Apical group Fibers radiate in different directions from apex of the tooth Not seen on incompletely formed roots. prevent tooth tipping and extrusion Interradicular group Extend from the crest of the interradicular bone to the furcation area of the multirooted tooth. Fibers are lost if gingival recession extends & the furcation area is exposed.

  18. Cells are divided into 4 main categories: 1. Synthetic cells a. Fibroblasts b. Osteoblasts c. Cementoblasts 2. Resorptive cells a. Osteoclasts b. Fibroblasts c. Cementoclasts 3. Progenitor cells Epithelial rests of Malassez 4. Defense cells a. mast cells b. macrophages

  19. FIBROBLAST Ovoid/elongated, oriented along principal fibers. c/s of fibroblast - stellate appearance Fibroblast are connected by numerous junctions . Gap junction . Adherence type of junction (tight junction) Communication b/n the cells by mutual interaction are facilitated via . Junctional complexus . Electric coupling

  20. GROUND SUBSTANCE The periodontal ligament also contains a large proportion of ground substance filling the spaces between cells and fibers It consists of two main components 1. Glycosaminoglycans - Hyaluronic Acid Proteoglycans 2. Glycoprotein Fibronectin Laminin Also has a high water content(70%)

  21. Functions of PDL Provision of soft tissuecasingto protect the vessels and nerves from injury by mechanical forces 1. 2. Transmission of occlusal forces to bone 3. Attachment of teeth to bone 4. Maintenance of gingival tissues in their proper relationship to teeth 5. Resistance to impact of occlusal forces (shock absorption)

  22. Resistance to impact of occlusal forces (shock absorption) Tensional theory Viscoelastic system theory Tensional theory Principle fiber first unfold ,straighten and then transmit forces to alveolar bone ,causing an elastic deformation of bony socket Finally when bone has reached its limit the load is transmitted to the basal bone

  23. Viscoelastic theory States that displacement of tooth is largely controlled by fluid movements with fibers having only a secondary role When force is transmitted to tooth the extra cellular fluid passes from pdl into marrow spaces of bone through foramina in cribriform plate. The perforations of the plate link the pdl with cancellous portion of alveolar bone and more abundant in cervical third

  24. After depletion of tissue fluids the fiber bundles absorb slack& tighten This leads to blood vessels stenosis Arterial back pressure causes the ballooning of vessels and passage of blood ultra filtrates into tissues and replenish the tissue fluids

  25. Transmission of occlusal forces to bone when an axial force is applied to a tooth a tendency towards displacement of root in to alveolus occurs The oblique fibers alter their wavy, untensed pattern and assume their full length and sustain major part of axial force

  26. When a horizontal work or tipping is applied Two phases of tooth moment occur the first is with in the confines of pdl and Second produces the displacement of the facial and lingual bony plates The tooth rotates about an axis that may change as the force is increased

  27. The apical portion of root moves in a direction opposite to coronal portion In areas of tension the principle fibers are taut rather than wavy In areas of pressure the fibers are compressed, the tooth is displaced Corresponding distortion of bone exists in the direction of root movement

  28. Single rooted tooth-between apical third and middle third Root apex and coronal half of clinical root are other locations of axis of rotation In multirooted tooth axis of rotation is located in bone between the roots Pdl is thinner on mesial surface

  29. Nutritional and sensory functions Pdl supplies nutrients to the cementum ,bone and gingiva by way of blood vessels and also lymphatic drainage pdl is highly vascularized tissue (almost 10% of the volume in rodent molar is blood vessels) This relatively high blood vessel content may provide hydrodynamic damping to applied forces as well as high perfusion rates to pdl

  30. Nerve bundles pass into pdl from the PA area & through channels from the alveolar bone that follow the course of blood vessels The bundles divide into single myelinated fibers which ultimately lose their myelin sheath & end in one of the 4 types of neural termination

  31. 1. Free endings tree like configuration carry pain sensation 2. Ruffini like mechano receptors apical area 3. Coiled meissners corpuscles mechano receptors- midroot region 4. Spindle like pressure and vibration endings which are surrounded by fibrous capsule located at apex.

  32. Blood supply Blood vessels 3 sources 1. Vessels that enter the tooth to supply the dental pulp, prior to entry give branches that supply the PDL 2. Intra alveolar vessels traverse horizontally within alveolar bone to enter PDL 3. Gingival vessels supply the P.L from the coronal end

  33. Arterioles and capillaries of microcirculation ramify in Pdl and form a rich network of arcades It is possibly involved that the circulation plays in supporting teeth during function Venous vessels drain axially to drain to the apex

  34. Nerves They are associated with blood vessels and pass through foraminae in the alveolar bone including apical foramen to enter Pdl They run along the length of the root they branch and run coronally & apically Large diameter myelinated Small diameter may or may not be myelinated

  35. Small fibers appear to end in fine branches throughout the ligament Large fibers may end knob like , spindle like , meissner like Large diameter--concerned with pressure Small diameter concerned with pain Lymphatics Lymph vessels provide lymphatic drainage of the P.L. into adjacent alveolar bone

  36. Clinical considerations Pdl thickness varies in different individuals The fact that Pdl is thinnest in middle region of root --- fulcrum of physiologic tooth movement Supporting tissues of tooth long out of function are poorly adapted to carry load suddenly placed on tooth by a restoration

  37. Eg; Teeth opposing bridges or dentures Teeth used as anchorage for removable bridges This will account for inability of a patient to use a restoration immediately after its placement In orthodontic treatment an adjustment period must be permitted

  38. Cysts derived from epithelial cell rests of Malassez Periapical cyst Residual cyst Lateral periodontal cyst Tumours derived from epithelial rests of Malassez Ameloblastoma Primary intra alveolar epidermoid carcinoma Squamous odontogenic tumour

Related


More Related Content

giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#