Upload By : Ahmed Ali Abbas Babylon University College of Dentistry  download this file from Website on google theoptimalsmile.wix.com/dentistry Oral histology

1. PDL
Upload By : Ahmed Ali Abbas
Babylon University College of Dentistry
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2. The
Periodontal
Ligament
By :Ahmed Ali Abbas

3. Periodontium:
Is the investing and supporting attachment system of the
teeth.
It consists of:
Two soft tissues Two hard tissues
1- Gingiva
2- Periodontal Ligament
1- Cementum
2- Alveolar Bone :

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

5. Width of the periodontal ligament 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.
DentinBone
The width generally reduced in:
• Non-functional teeth.
• Un-erupted teeth.
While increased in:
• Teeth subjected to an
occlusal stress within the
physiological limits .
• Deciduous teeth

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

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

9. 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.
A-The principal fibers:
They are formed of collagen bundles, which are wavy
in course and are arranged in three groups.

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

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

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

13. 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.
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.
c- The alveolodental ligament:
Bone Dentin

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

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

18. 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.
B- Accessory fibers:

19. 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.
2- Oxytalan fibers

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

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

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

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
lymphocytes
Mast cells
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. Interstitial tissues

32. *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.
Interstitial tissues

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

34. 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.
Nerve supply:

35. (mechanoreceptors)
Large nerve fibers
Small nerve fibers pain sensation
touch & pressure
Are responsible for
Are responsible for
•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. Function of PDL

37. 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.
Functions of the periodontal
ligament:

38. *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.

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

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

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

42. 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.
3- Nutritive:

43. 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.
5- Protective

44. 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.

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

46. 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.