periodontal ligament

2. Presented by:
Dr.Ayesha Taha
JR I
Department of Pedodontics
and Preventive Dentistry
SPPGIDMS, Lucknow

4. •Periodontal ligament is a part of the Periodontium.
• Periodontal Ligament is a dense fibrous connective
tissue that occupies the periodontal space which is
located between the cementum and the alveolar bone.
• It extends coronally to the most apical part of
lamina propria of gingiva .
• At apically it extends till the apical part foramen and
is continuous with the dental pulp.
• The average width of periodontal ligament space is
documented to be about 0.2 mm, though considerable
variation exists.

5. Periodontium
Gingiva
Periodontal
Ligament
Alveolar
Bone
Cementum

6. •It is thinnest around the middle third of the root, with an hour
glass appearance.
•The ligament appears as a radiolucent area between the
radiopaque lamina dura of the alveolar bone and cementum.

7. • Immediately before tooth eruption and for sometimes
thereafter, active fibroblasts adjacent to cementum of
the coronal third of root, appear to become aligned in an
oblique direction to long axis of the tooth
•Later the first collagen fiber bundles of the ligament
becomes discernible.
•These are the precursors of the alveolar crest fibre
bundle group.
•Cemental and alveolar fibers continue to elongate towards
each , to meet and fuse .

8. •As the first occlusal contact of the tooth occurs with its
antagonist the principal fibres around the coronal third of
root, horizontal group are almost completely developed .
•Oblique fibres are still being developed in middle third of
root.
•With the formation of Apical fibre group, the definitive
periodontal ligament architecture is established.

9. The Periodontal Ligament is formed of
• Synthetic cells
• Resorptive cells
• Progenitor cells
• Cells rests of Malassez
• Defense cells
CELLS
• Fibers
• Ground substances
• Blood vessels, Nerves &
Lymphatics.
EXTRACELLULAR
SUBSTANCES

10. CELLS
Synthetic
cells
Fibroblasts
Cementoblasts
Osteoblasts
Resorptive
cells
Osteoclasts
Cementoclasts
Progenitor
cells
Epithelial
rest cells
Defense
cells
Neutrophils
Lymphocytes
Macrophages
Mast cells
Eosinophils

11. •Predominant cell in the pdl .
•These fibroblasts origin from
the Ectomesenchyme of
investing layer of dental papilla
and from the dental follicle.
•These fibroblasts are
regularly distributed
throughout the ligament and
are oriented with their long
axis parallel to the direction
of collagen fibrils .

12. • Fibroblasts of pdl generate an
organizational pattern as they
have ability to both synthesize
and shape the proteins of the
extracellular matrix .
• Certain Fibrils form bundles
get inserted into tooth and
bone and are known as
SHARPEY’S fibers .
• Once embedded in the wall of
alveolus or tooth, these fibers
calcify to a certain degree and
are associated with an
abundance of non collagenous
proteins found in the bone i.e.
osteopontin and bone
sialoprotein .

13. •These cells covers the periodontal
surface of the alveolar bone.
•These are the cells lining the tooth
socket and are cuboidal in shape with
a prominent round nucleus at the basal
end of the cell.
•Rough endoplasmic reticulum ,
mitochondria , and vesicles are
abundant in active cells.
•These cells appear basophilic due to
the presence of abundant Rough
endoplasmic reticulum.
•The cells contact one another
through desmosomes and tight
junctions.

14. • Its distribution is similar to that of
Osteoblasts on the bone surface.
•These cells line the surface of
cementum.
•They are cuboidal with a large
vesicular nucleus , with one ore more
nucleoli and abundant cytoplasm.
•All the organelles are required for
protein synthesis and secretion are
present.
•Cells actively depositing cellular
cementum exhibit abundant
basophilic cytoplasm and cytoplasmic
processes.

15. •These resorb bone and tend
to be large and multinucleated
but can also be small and
mononuclear .
•Multinucleated Osteoclasts
are formed by fusion of
precursor cells similar to
circulating monocytes.
•The part of plasma membrane
lying adjacent to bone that is
being resorbed is raised in
characteristic folds and is
termed the Ruffled or
Striated border.

16. •The osteoclasts are found against
the bony surface occupying shallow
depression called Howship’s lacunae.
•The ruffled border is separated
from the rest of plasma membrane
by a zone of specialized membrane
that is closely applied to the bone
the underlying cytoplasm of which
tends to be devoid of organelles and
has been called The Clear Zone.

17. •As cementum does not remodel,
Cementoclasts are not usually found in
the ligament.
•These cells only occur in certain
pathologic conditions, during resorption
of deciduous teeth and when regressive
forces are applied on a tooth such as
orthodontic therapy.
•These Cementoclasts resembles
Osteoclasts and are located in
depressions in cementum resembling
Howship’s lacuna.
•These cells not only resorb cementum,
they can destroy dentin and enamel as
well thus they are also called
Odontoclasts.

18. •All connective tissues including
periodontal ligament contain
progenitors cells that have the
capacity to undergo mitotic division .
•If they were not present there
would be no cells available to replace
differentiated cells lying at the end
of their life span or as a result of
trauma.
•These are undifferentiated
mesenchymal cells.

19. •The ligament contains epithelial
cells that are found close to the
cementum.
•At the time of cementum formation
the continuous layer of epithelium
that covers the surface of newly
formed dentin breaks into lacelike
strands.
•The epithelial rests persist as a
network of strands islands or tube
like structures near and parallel to
the surface of the root.
•Their function is not yet clear but
they could be involved in periodontal
repair and regeneration .

20. •These cells rests can be
distinguished from fibroblasts in pdl
by the close packing of their
cuboidal cells and their nucleus
stains more deeply .
•They are more numerous in older
individuals and more numerous in
children .
•These cells may proliferate to form
cysts and tumors.
•These cells may undergo
calcification to become
CEMENTICLES.

21. •Neutrophils are the most abundant
(40% to 75%) type of white blood
cells in mammals and form an
essential part of the innate immune
system.
•Neutrophils are a type
of phagocyte.
•Neutrophils are recruited at the
site of injury within minutes
following trauma, and are the
hallmark of acute inflammation.

22. •A lymphocyte is subtypes
of white blood cell in
a human’s immune system.
•These are agranulocytes.
•The three major types of
lymphocyte are T cells, B
cells and natural killer (NK) cells.
•Lymphocytes can be identified by
their large nucleus.

23. •Found in the ligament and are
predominantly located adjacent to
blood vessels.
•Are capable of phagocytosis.
•Derived from blood monocytes.
•It has a nucleus, horseshoe or
kidney shaped with peripheral
chromatin.
•In periodontal ligament
macrophages play dual role:-
•1. Phagocytosing dead cells
2. Secreting growth factor that
regulate the proliferation of
adjacent fibroblasts.

24. •These are relatively small round
or oval cell having a diameter of
about 12 to 15 um .
•These cells are characterized by
numerous cytoplasmic granules
called Histamine.
•Mast cells histamine plays a role
in the inflammatory reaction and
have been shown to de granulate
in response to antigen – antibody
reaction on their surface .

25. Occasionally seen in the
periodontal ligament.
These are granulocytes.
They possess granules that consist
of one or more crystalloid
structures.
The cells are capable of
phagocytosis.
Increases in case of parasitic
infections.

26. Extracellular
Substance
Fibers Ground
Substances
Nerves,
vessels,
Lymphatics

27. Fibers
Collagen
Elastic
Reticular Secondary
Indifferent
plexus
Oxytalan

28. •The main types of collagen in the pdl are
TYPE I and TYPE III.
•More than 70 % of pdl is TypeI .
•Type I is uniformly distributed in the ligament .
•Type III collagen accounts for about 20 % of
collagen fibers
•Type IV and VII are associated with epithelial
cell rests and blood vessels.
•Type XIII collagen is believed to occur within
the pdl only when ligament is fully functional .

29. •The collagen is gathered to form bundles
approximately 5 um in diameter. These bundles are
termed as PRINCIPAL FIBERS.
•Within each collagen bundle , subunits are present
called collagen fibrils.
Principal
Fibers
Alveolar
Crest
Horizontal Oblique Apical
Inter
radicular

30. Extend obliquely from the
cementum just beneath the
junctional epithelium to the
alveolar crest.
These fiber resist tilting,
intrusive, extrusive and
rotational force.

31. These fiber run at right angles
to the long axis of the tooth
from cementum to bone and are
roughly parallel to the occlusal
plane of the arch.
Found immediately apical to the
alveolar crest fiber group.
These fiber resist horizontal
and tipping force.

32. Oblique group are more
numerous and occupy 2/3rd of
the ligament.
These fibers are inserted
into the alveolar bone at a
position coronal to their
attachment to cementum,
thereby resulting in their
oblique orientation within the
periodontal space.
These fiber resist vertical
and intrusive forces.

33. Apical group radiating from
cementum around the apex of
the root to the bone, forming
the base of the socket.
The apical fiber resist the
forces of luxation.
These fibers are not seen in
the incompletely formed root.

34.  The principal fibers of this
group are inserted into
cementum from the crest of
interradicular septum into
multirooted tooth.
These fiber resist tooth
tipping, torquing and luxation.
These fiber are lost, if age
related gingival recession
proceeds to the extent, that
the furcation area are
involved.

35. •There are three types of elastic fibers which are
histochemically and ultrastructurally different.
•Mature Elastic fibers , Eulanin fibers and the
Oxytalan fibers .
•Eulanin fibers and Oxytalan fibers have been
described as immature elastic fibers.
•Mature elastic fibers consist of microfibrillar
component surrounding an amorphous core of elastin
protein .

36. These are immature collagen fibers with argyrophilic
staining properties and are related to basement
membrane of blood vessels and epithelial cells which lie
within the periodontal ligament.

37. Located between and among the principal
fibers.
Fibers are relatively non-directional and randomly
oriented.
Appear to transverse the periodontal ligament space
coronoapically and are often associated with path of
vasculature and nervous elements.

38. Small collagen fiber associated with the large collagen
fibers.

39. Oxytalan fibers are bundles of microfibrills.
These fibers are approximately 0.5μm to 2.5 μm in
diameter.
They tend to run in axial direction one end being
embedded in cementum or possibly bone, and other in
the wall of blood vessels.
They have found to be thicker and more numerous in
teeth that are subjected to high load.

40. •Amorphous background material that binds tissues and fluids.
•Major constituent of the Periodontal ligament.
•Similar to most connective tissue ground substance.
•Dermatan sulfate is the major glycosaminoglycan.
•When function of pdl increases, its size increases.
•However, in reduction of function, Pdl narrows and fiber
bundles decreases in number and thickness.

41. •The blood supply is rich because
the PDL has a very high turnover
as a tissue.
•The posterior supply is more
prominent than the anterior.
•The mandibular is more
prominent than the maxillary.

42. •A network of lymphatic vessels, following the path of
blood vessels, provides the lymph drainage of the
periodontal ligament.
•The flow is from the ligament towards and into the
adjacent alveolar bone.

43. •Generally follow the blood vessels.
•Nerve are derived from the second and third divisions of
the fifth cranial nerve.
•Nerve fibers can be large myelinated or small non
myelinated fibers.
•Nerve end as knobs or spindles.
•Large nerve are responsible for discerning touch while
the smaller ones perceives pain.

44. Supportive
Sensory
Nutritive
Homeostatic
Eruptive

45. Supportive
Whenever a tooth is moved in its socket, the
periodontal ligament that is found around the root,
gets compressed and therefore provides support for
the tooth.
The numerous collagen fibers that occur in the
periodontal ligament act as a cushion to withstand
masticatory forces.
The periodontal ligaments are so arranged that
functional pressure on the teeth from any direction
produces tension of certain fibers.

46. Therefore pressure on the
tooth crown is transmitted to
the bone of the socket.
Thus PDL behaves as
suspensory ligament
The ground substances present
between the fibers of
periodontal ligament is rich in
water and therefore add up to
the support.

47. Sensory
Periodontal ligament is richly innervated.
It provides an excellent Proprioceptive mechanism
which helps in estimating the amount of pressure on
mastication, and detect even the mildest force acts
upon a tooth.

48. Nutritive
The periodontal ligament has a good blood supply
which provides nutrition for various cells of the
periodontium such as the cementocytes and the
superficial osteocytes.
Whenever heavy forces are applied on a tooth the
periodontal ligament may get necrosed.

49. Homeostatic
Its is evident that the cells of pdl have the ability to
resorb and synthesize the extracellular substance of the
connective tissue of the ligament , alveolar bone and
cementum
Pressure on the periodontal ligament tends to cause bone
resorption.
Although the cementum is more resistant to resorption, it
can neverthless exhibit resorption under severe pressure.
These Resorptive processes are brought about by cells
present in the periodontal ligament.

50. Eruptive
During the development of the tooth, the cells of
periodontal ligament produce cementum and bone of
the tooth socket.
The periodontal ligament contains Cementoblasts and
Osteoblasts that can form new cementum and bone
respectively.

51. The periodontal ligament ages as in all other tissues
of the body.
Cell number and cell activity changes with aging.
One of the prominent age changes is seen in the
calcified tissue of the periodontium, the bone and the
cementum is scalloping and the periodontal ligament
fibers are attached to the peaks of this scalloped
than over the entire surface as seen in the younger
periodontium.

52. With aging the activity of the periodontal ligament
tissue decreases because restricted diets and
therefore normal functional stimulation of the tissue
is diminished.
Any loss of gingival height related to gingival and
periodontal diseases promotes destructive changes in
the periodontal ligament.

53. •The periodontal ligament is made up of collagen
fibers in a proteoglycans stroma and many types of
connective tissue cells as in any other soft fibrous
connective tissue elsewhere in the body .
•But it has cells that form and resorb cementum and
bone and the collagen fibers in a specific orientation
connecting the two mineralized tissues that makes it
unique.

54. •The tissue hydrostatic pressure is high. The tissue is
extremely cellular with fibroblast showing many
intercellular contacts well innervated with many
mechanoreceptors and highly vascular unlike any other
connective tissue in the adult.
•The features being high cellularity, very high rates of
turnover and with significant amount of type III collagen.
•The collagen fibers are also sharp with unimodal size and
frequency.
•The ground substance of pdl occupies large volume with
high content of glucornate rich proteoglycans and
glycoprotein- tenascin and fibronectin .

55. The primary role of the periodontal socket is to support
the tooth in the bony socket. Its thickness varies in
different individuals in different teeth in the same
person and in different locations on the same tooth .
1)Acute trauma to the periodontal ligament, accidental
blows, or rapid mechanical separation may produce
pathologic changes such as -
Fractures or
resorption
of cementum
Tear of fiber
bundles
Hemorrhage
Necrosis

56. •2. Orthodontic tooth movement depends on resorption
and formation of alveolar bone and periodontal
ligament. These activities can be stimulated by
properly regulated pressure and tension.
•If the movement of teeth is within physiologic limits
the initial compression of pdl on the pressure side is
compensated for by bone resorption whereas on the
tension side bone apposition is seen .
•ResorptionCOMPRESSION
SIDE
•DepositionTENSION
SIDE

58. 3. Application of large forces results in necrosis of
pdl and alveolar bone on the pressure side and
movement of the tooth will occur after the necrotic
bone has been resorbed by Osteoclasts located on its
endosteal surface.
4 . Inflammatory diseases of the pulp progress to
the apical periodontal ligament and replace its fiber
bundles with granulation tissue. This lesion is called a
periapical granuloma may contain epithelial cells
•These may undergo proliferation and produce a
periapical cyst.

59. 5 . Chronic inflammatory disease such as
Periodontitis is common pathology related to pdl .
The toxins released from the bacteria in the dental
plaque and metabolites of the host’s defense
mechanism destroy the pdl and the adjacent bone
very frequently. This leads to tooth mobility and
further loss of tooth .
6 . To repair the existing destruction of pdl can be
quite challenging. It involves limiting the disease
process and to regenerate the host tissues to their
original form in such a way that reattachment of pdl
to bone becomes possible.

60. •The periodontal ligament is a fibrous connective
tissue forming important part of the Periodontium.
•Without it tooth is support less.
•Cell of the periodontal ligament are Pluri-potent and
helps in the regeneration of all the components of
Periodontium lost in the periodontal disease process.

61. •A better understanding of cell and molecular biology
of developing and regenerating periodontium offers
newer avenues to regenerate the pdl.
•Newer options of treatment are made available from
time to time.
•Yet safeguarding the integrity of the pdl and
alveolar bone is still one of the most important
challenge .

62. •FerminA, Carranza, Newmann, Takei; clinical periodontology
;9thedition;45–51.
•FerminA.Carranza,Newmann,Takei;clinicalperiodontology;10thedition;6
8–92.
•R.Tencate,AntonioNanci;oralhistology,development,structure&function;
6thedition;111–143
•Hagel-Bradway S, Dziak R: Regulation of bone cells metabolism, J Oral
Pathol Med 18:344,1989
•Junqueria LC, Carneiro J, Kelley RO: Basic Histology, ed6, Norwalk,
Conn, 1989, Appleton & Lange.

63. • Nanci A. Periodontium: Ten Cate’s Oral Histology. 6th Edition.
Elsevier; 2005. 145-200.
• Avery J K, Histology of Periodontal ligament, Oral Development
and Histology.2nd Edition. Thieme Medical Publications 1994. 153-
172.
• Bhaskar S N, Periodontal ligament, Orban’s Oral Histology And
Embryology. 12th Edition. Elsevier publications 2008.45-84
• Bhalaji SI. Periodontal ligament. Dental Anatomy histology and
development. 1st Edition. Arya publications; 2003. 295-302.
•Kumar GK. Periodontal ligament. Orban’s Oral Histology and
Embryology. 12th Edition. Elsevier Publications; 2006. 137-154.

64. Perfection is not attainable
But
If we chase Perfection we
can achieve Excellence