1. The
periodontal
Ligament

2. Periodontium:
Is the investing and supporting attachment system of the
teeth.
:It consists of
Two soft tissues Two hard tissues
Gingiva -1 Cementum -1
That part covers the neck of the
tooth and part of the alveolar covers the anatomical root
.bone Alveolar Bone -2
The bone of the jaw that
Periodontal Ligament -2 surrounds the root of the tooth
Strong ligament that attaches
the tooth to the alveolar bone

3.  Definition: The periodontal
ligament is the dense fibrous
connective tissue that occupies
the periodontal space between
the root of the tooth and the
alveolus.
•Inflammation from the dental pulp
and gingiva could spread to involve
the PDL and other apical supporting
tissues.

4. Width of the periodontal ligament:
It ranges from 0.15-0.21 mm.
The narrowest area is at the mid-root ( Fulcrum ).
The region at the alveolar crest is the widest area
followed by the apical region.
The width generally reduced in:
•Non-functional teeth.
•Un-erupted teeth.
While increased in:
Bone Dentin
*Teeth subjected to an occlusal stress
within the physiological limits .
*Deciduous teeth

5. The periodontal ligament resembles
immature, fetal-like connective tissues in
the following features:
1- High rate of turnover.
2- Large volume of ground substance.
3- The presence of oxytalan fibers.
4- High cellularity.
5- Similar biomechanical propereties.

6. Knocked out tooth
The length of time before a tooth is reimplanted (within half an
hour) and how it is transported to the dentist (in saline) are
critical in successfully saving and re-implanting the tooth.
The periodontal ligament will regenerate and revascularize.
A tooth that is replaced within half an hour has a 90% chance of
successful re-implantation.

7. Development
Of PDL:
•Dental follicle consists of
1-Dense fibrous and cellular
tissues immediately
encapsulate the developing
tooth
(Cementum)
2-Perifollicular mesenchyme
(PDL ,Alveolar bone)

8. Histological structure
The periodontal ligament is formed of :
Intercellular
cells substances
Synthetic Fibers,
Resorptive
ground substances
Progenitor
blood vessels,
Defensive nerves & lymphatics.

9. A- The principal fibers:
They are formed of collagen bundles, which
are wavy in course and are arranged in three
groups.
a) Gingival fibers.
b) Transseptal or interdental ligament.
c) Alveolodental ligament which is subdivided
into the following five groups:
1- Alveolar crest group.
2- Horizontal group.
3- Oblique group.
4-Apical group.
5- Interradicular group.

10. A- The principal fibers:
a- The gingival fibers:
1- Dento-gingival fibers: extend from
the cervical cementum into the Dento-
gingiva. gingival
Alveolo-
2- Alveolo-gingival group: extends gingival
from the alveolar crest into the
gingiva. Circular
fibers
3- Circular group: a small group of
fibers that encircles the tooth and
interlaces with the outer fibers.
4- Dento-periosteal fibers: they Dento-
extend from the cementum directed periosteal
over the bone crest and then incline Alveolar
apically between the periosteum of bone
the alveolar bone and the gingiva.

11. Function of gingival fibers:
They form a rigid cuff around the
tooth that can add stability and resist
gingival displacement.

12. b- The transseptal ligament:
*It connects two adjacent
teeth.
Dentin
*The ligament runs from the
cementum of one tooth
over the crest of the
alveolus to the cementum
of the adjacent tooth.
Bone
*Function: Dentin
Resists mesial and distal
tooth separation.

13. c- The alveolodental ligament:
1-Alveolar crest group:
radiate from the crest of the
alveolar process and attach
themselves to the cervical
part of the cementum.
Function: resists vertical and
intrusive forces. Bone Dentin
2-Horizontal group:
The fiber bundles run from the
cementum to the bone at right
angle to the long axis of the
tooth.
Function: resists horizontal
and tipping forces.

14. 3- Oblique group:
The fiber bundles run obliquely.
Their attachment in the bone is
somewhat coronal (higher)
than the attachment in the
cementum. bone
The greatest number of fiber dentin
bundles are found in this group.
Function:
*Performs the main support
of the tooth against masticatory
forces.
*Resists vertical and intrusive
forces.

15. 4- Apical group:
The bundles radiate from the dentin
apical region of the root to
the surrounding bone
bone
Function: resists vertical
force.
5- Interradicular group:
dentin
The bundles radiate from the
interradicular septum to the
furcation of the multirooted
tooth. bone
Function: resists vertical
and lateral forces.

18. B- Accessory fibers:
They are collagenous in nature and run from bone
to cementum in different planes, more tangentially to
prevent rotation of the tooth and found in the
region of the horizontal group.

19. 2- Oxytalan fibers
These are immature elastic (pre-
elastic) fibers.
They need special stains to be
demonstrated.
They tend to run in an axial
direction, one end being embedded
in bone or cementum and the
other in the wall of blood vessels.
At the apical region they form a
complex network.

20. The functions of oxytalan fibers:
1-Support nerves.
2- Support blood vessels.
3- Help fibroblasts migration.

21. Histological structure
The periodontal ligament is formed of :
cells Intercellular
substances
Synthetic
Fibers,
Resorptive
ground substances
Progenitor
blood vessels,
Defensive nerves & lymphatics.

22. The cells
Synthetic
fibroblasts, osteoblasts and cementoblasts.
cells
Resorptive
cementoclasts , osteoclasts and fibroclasts.
cells
Note that fibroblasts perform both
synthetic and resorptive activities.
Progenitor undifferentiated mesenchymal
cells cells Epithelial cells
remnants of the epithelial
Defensive macrophage, lymphocytes root sheath of Hertwig
cells and mast cells

23. Synthetic Cells of PDL
 Fibroblasts
 Cementoblasts
 Osteoblasts

24. PDL Fibroblasts
• Oriented parallel to collagen fibers
•Are motile due to contractile properties
•Show numerous microtubules &
microfilaments
•Assembles procollagen molecules
•Perform fibroclastic function
•Ingestion collagen fibers
•Contains intracellular collagen profiles
& vacoules
•Contains lysosomal system

25. Cementoblasts Osteoblasts
Both are rich in alkaline phosphatase activity.

26. Resorptive Cells of PDL
• osteoclasts
• cementoclasts
Both are rich in acid phosphatase
activity.

27. Progenitor cells
.U. M. C
• Can undergo mitotic
devision
• Can differentiate to
different types of cells
• Have small, closed-
face nucleus
• Little amount of
cytoplasm
• Found close to blood
vessels

28. Defensive Cells of PDL
Macrophages Mast cells
lymphocytes
Note: There are no plasma cells.

29. Epithelial Cells: remnants of the epithelial
.root sheath of Hertwig
•They are separated from the
surrounding connective tissue by a
basal lamina.
•They show low cells turnover,
although they may proliferate to form
cysts or tumors.

31. Histological structure
The periodontal ligament is formed of :
cells Intercellular
substances
Synthetic
Fibers,
Resorptive
ground substances
Progenitor
blood vessels,
Defensive nerves & lymphatics.

32. Interstitial tissues
*They are found between the
fibers of the periodontal
ligament.
*They are areas that
contain some of the blood
vessels, lymphatic and
nerves.
*They are surrounded
by loose connective tissue.

33. Blood supply
The arterial blood supply of the periodontal
ligament is derived from 3 sources:
1- Branches from the gingival vessels.
2- Branches from the intra-alveolar
vessels, these branches run
horizontally and these constitute the
main blood supply.
3- Branches from the apical vessels that supply the dental pulp.

34. Nerve supply:
The nerve supply of periodontal ligament comes from
either the inferior or superior dental nerves.
1- Bundles of nerve fibers run from the apical region of
the root towards the gingival margin.
2- Nerves enter the ligament horizontally through multiple
foramina in the bone.

35. Are responsible for
Small nerve fibers pain sensation
Are responsible for
Large nerve fibers touch & pressure
(mechanoreceptors)
•Stimulation of the mechanoreceptors initiates a reflex jaw
opening.
•This reflex is a protective mechanism to prevent forces
applied to the teeth from reaching damaging levels.

36. Functions of the periodontal
ligament:
1- Supportive: Through the collagen fibers and the blood vessels.
[
*Periodontal ligament permits the teeth to withstand
the considerable forces of mastication.
*As the force is applied on the teeth, the wavy course
of the collagen fibers gradually straightening out and
then acting as inelastic strings.
*Also periodontal fibers being non elastic prevent the
tooth from being moved too far.

37. *Blood vessels and all the components of the
ligament act together as a hydraulic damper
or shock absorber with the ground
substance and the tissue fluid.

38. Dental implants lack periodontal ligament fibers
and they have a rigid connection to bone
(Osseointegration).

39. Periimplant tissues
Titanium implant
Sulcular epithelium
Juunctional epithelium
Connective tissue
Bone

40. 2- Sensory:
The periodontal ligament having the mechanoreceptors
contributes to the sensation of touch and pressure on
the teeth.
proprioceptive reflex
sudden overload inhibition of the activity
of the masticatory muscles
Opening the mouth

41. 3- Nutritive:
The blood vessels in the periodontal ligament provide
nutrient supply required by the cells of the ligament and
to the cementocytes and the most superficial osteocytes.
4- Formative:
The fibroblasts are responsible for the formation of new
periodontal ligament fibers and dissolution of the old
fibers
Cementoblasts and osteoblasts are essential in building up
cementum and bone.

42. 5- Protective
The protective function of the periodontal ligament is achieved by:
a- The principal fibers.
b- The blood vessels.
c- The nerves.
a- The principal fibers:
The arrangement of the fiber bundles in the different groups is well
adapted to fulfill the functions of the periodontal ligament.
The alveolodental ligament transforms the masticatory pressure
exerted on the tooth into tension or traction on the
cementum and bone.
If the exerted force on a tooth is transmitted as pressure this will lead to
differentiation of osteoclasts in the pressure area and resorption of
bone.

43. b- The blood vessels:
The capillaries form a rich network, they are arranged in
form of a coil and attached to bone and cementum
through the oxytalan fibers.
This arrangement makes it possible when pressure is exerted
on the tooth, the blood does not escape immediately
from the capillaries and thus buffering the pressure action
before it reaches the bone.
The behavior of the blood in the capillaries may be simulated
to a hydraulic brake.
c- The nerves:
By its mechanoreceptors nerves.

44. The Age Changes of periodontal
ligament
*The periodontal ligament through aging shows
Vasuclarity
Cellularity
Thickness
*It may contain cementicles.

45. The cementicles appear near the
surface of cementum may be
free , attached or embedded in
the cementum.
They have nidus favoring the
deposition of concentric layers of
calcosphrite as degenerated cells, area
of hemorrhage and epithelial rest's of
Malassez.
Cementicles are usually seen in
periodontal ligament by aging but
in some cases they may be seen in
a younger person after local
trauma.

46. Thank you
&
good luck