Periodontal Ligament

1. PERIODONTAL LIGAMENT
A SEMINAR
Presented by: Dr. Abhishek Gakhar
Department of Periodontics
At
I.T.S DENTAL COLLEGE,HOSPITAL &RESEARCH
CENTRE,GREATER NOIDA
26th Sep 2012
Moderator - Dr. Kanwarjit Singh Asi

2. Introduction
1) Structure
2) Evolution
3) Development
4) Constituents of the pdl
5) Blood supply
6) Nerve supply
7) Functions
8) Clinical Corelations
9) Conclusion
10)References

3.  Soft fibrous specialised connective tissue
present in periodontal space b/w cementum of
root &bone forming the socket wall.(1)
 Other names
 Gomphosis
 Desmodent
 Pericementum
 Dental Periosteum
 Alveo-dental ligament
 Periodontal membrane

4.  Hour-glass shaped
 Widest cervically
 Is the dense, fibrous connective tissue
 Average width is 0.2mm
 Nonfunctional ,unerupted
 Bears Heavy occlusal stress
 Thickness decreases with age

5.  Reptiles teeth are ankylosed to bone & growth is
by sutures
 Teeth fixed to bone
 Mammals teeth are suspended by ligaments in sockets &
growth is by cartilage.
 The teeth are independent of bone- individual tooth
movement

6.  Hertwigs Epith Root Sheath
 Epithelial Rests of Malassez
 Cells of dental follicle migrate to root
dentin
 Migrated follicular cells - cementoblast
lay cementum
 Other cells of dental follicle differentiate
into fibroblast, synthesize fibers & extra
cellularsubstance of PDL(2)

7. PDL
Cells
Resorptive
Synthetic Progenitor
Defence
Extracellular
substance
Fibers
Ground
substance

8. The characteristic of synthetic cells are:
 Should be actively synthesizing ribosomes.
 Increase in rough endoplasmic reticulum and golgi
apparatus.
 Large open faced or vesicular nucleus with
prominent nucleoli.(2)

9.  Uninucleated cells
 Cuboidal in shape
 Basophilic cytoplasm
 Numerous orgenelles
 Get incorporated as osteocytes(2)

10.  Synthesize both collagenous and
noncollagenous bone proteins.(3)
 Osteoblasts also synthesize the enzyme
alkaline phosphatase, which is needed locally
for the mineralization of osteoid.
 The precursor cell of the osteoblast is the
preosteoblast. (4)
 Osteoblasts have all the characteristics of
hard tissue-forming cells.
 When the bone is no longer forming, the
surfaces of the osteoblasts become inactive
and are called Lining cells.

11. Function:
Osteoblasts help in the synthesis of alveolar bone.

12.  Constitute 65% of total cell population
 Remodeling of collagen
 Parallel to the collagen fibres
 Well developed cytoskeleton
 Interconnected by desmosomes.
 Appear as elongated cells with pseudopodia like
process.(5)

13. Extensive cytoplasm
Prominent nucleus- flat, disc
shaped
Occupys 30% of cell space
Cell organelles-protein synthesis,
Numerous Cytoplasmic processes
Mitochondria numerous,
Lysosomes large , membrane
bound vesicles

14. • The fibroblast is stellate shaped cell which produces:
1. COLLAGEN FIBERS
2. RETICULIN FIBERS
3. OXYTALAN FIBERS
• Various stages in the production of collagen fibers
are as follows:
The first molecule released by fibroblasts is
tropocollagen which contains three polypeptide chains
intertwined to form helix. Tropocollagen molecules are
aggregated longitudinally to form protofibrils, which
are subsequently laterally arranged parallel to
form collagen fibrils. (6)

15. FUNCTION:
PRODUCTION OF VARIOUS TYPES OF FIBERS & IS ALSO
INSTRUMENTAL IN THE SYNTHESIS OF CONNECTIVE TISSUE
MATRIX

16.  Observed during phases of active cementum
deposition(7)
 Oval to cuboidal shape
 Basophilic due to high %membrane bound and free
ribosomes.
 large nuclei
 Structure depends on activity
 After some cementum has been laid down, its
mineralization begins with the help of calcium and
phosphate ions.

17. FUNCTION:
Cementoblasts synthesize the organic
matrix of the cementum

18.  Large & multinucleated gaint cells
 Located in Howships lacunae.
 Seen adjacent to the bone surface
 Irregular distribution
 Appear only in active resorption / deposition
 Cytoplasm-vacuolated ,numerous mitochondria

19.  Derived from a monocytic-macrophage
system, which are responsible for bone
resorbtion.(8)
 They are multinucleated cells with fine,
fingerlike cytoplasmic processes and are rich
in lysosomes that contain tartrate-resistant
acid phosphatase (TRAP).(9)
 Osteoclasts lie in resorbtion craters known
as Howship’s lacunae on bone surfaces or in
deep resorption cavities called cutting cones.
 These bone cells can only resorb mineralized
bone matrix.

20.  The surface of an osteoclasts which is in contact
with bone has a ruffled border.
 Resorption occurs in two stages:
 The mineral is removed at bone margins and
then exposed organic matrix disintegrates.

22.  Cementoclasts are found in periodontal ligament
but not remodeled like alveolar bone and
periodontal ligament.
 These are found on the surface of cementum.

23.  Progenitor cells are the undifferentiated
mesenchymal cells, which have the capacity to
undergo mitotic division and replace the
differentiated cells
 Located in perivasular region and have a small
cnucleus and little cytoplasm(5).
 When cell division occurs, one of the daughter cells
differentiate into functional type of connective tissue
cells. The other remaining cells retain their capacity to
divide.

24.  These cells are the remnants of the epithelium of
Hertwig’s Epithelial Root Sheath close to cementum.
 These cells exhibit monofilaments and are attached to each
other by desmosomes.
 They are round to ovoid cells with central darkly stained
nuclei.
Can develop into pathological cysts.
Normal function is unknown.
 The epithelia cells are isolated from connective tissue by a
basal lamina.

25.  Although seen in longitudinal sections as
isolated cell clusters surrounded by a
basement membrane, which separates them
from the surrounding connective tissue, they
apparently form a continuous network
ensheathing the root at a certain distance.
Although the number of epithelial rests of
Malassez decreases with age, cell mitotic
Activity has also been observed. (2,4)

26. Periodontal ligament showing
epithelial cell rests of
malassez, indicated by arrows

27. MAST CELLS
 Small round or oval.
 Numerous cytoplasmic granules, which mask its small,
indistinct nucleus.
 The diameter of mast cells is about 12 to 15 microns.
 The granules contain heparin and histamine. The
release of histamine into the extracellular compartment
causes proliferation of the endothelial and
mesenchymal cells.

28. FUNCTION:
Degranulate in response to antigen- antibody formation
on their surface

29. MACROPHAGES
 Derived from blood monocytes
 Present near the blood vessels.
 These cells have a horse-shoe shaped or kidney
shaped nucleus with peripheral chromatin and
cytoplasm contain phagocytosed material.

30. FUNCTION
1. Phagocytosis of dead cells .
2. Secretion of growth factor, which help to regulate
the proliferation of adjacent fibroblasts

31. Extra cellular substance comprises the following:
1. Fibers
a) Collagen b) Oxytalan
2. Ground Substance
a) Proteoglycans b) Glycoproteins

32.  The most important element of periodontal ligament -
principal fibers
 The principal fibers are collagenous in nature and a
arranged in bundles
 Follow a wavy course
 Dia-5 µm
 Primarily composed of type I & III collagen fibrils.

33. COLLAGEN
 Collagen is a high molecular weight protein.
 Composed of 3 polypeptide α-chain coiled around each
other- Triple helix
 Individual fibril diameter = 50 – 60 nm
 Half life : 3 - 23 day
 collagen imparts a unique combination of flexibility
and strength to tissue.
 Vitamin C help in formation and repair of collagen

34.  Collagen macromolecules are rod like and are
arranged in form of fibrils. Fibrils are packed side by
side to form fibers.

35. Alveolar crest group
Horizontal group
Oblique group
Apical group
Interradicular group

37. These fibers extend obliquely from the cementum over the
alveolar crest to alveolar crest.
The alveolar crest fibers prevent extrusion of tooth and resist
lateral tooth movements.
.These fibers resists vertical and intrusive forces

38. Horizontal fibers extend at right angles to long axis of
tooth from the cementum to alveolar bone.
These fibers are located apical to the level of alveolar
bone crest.
 These fibers resists horizontal and tipping forces.

39.  The main attachment of the tooth.
They run obliquely in coronal
direction.
These fibers mainly resists the
vertical and intrusive forces.
They bear the brunt of vertical
masticatory stresses and transfer
them on to the alveolar bone

40. The apical fibers radiate in a rather irregular manner f
They do not occur on incompletely formed roots.
 These fibers resist vertical forceps.

41. These fibers are seen mainly in multi-rooted teeth with
bifurcations and trifurcations ,fanning out from cementum into
bone.
These fibers resists vertical and lateral movements

42.  Do not have osseous attachment
 Run from cementum to cementum
 Reconstructed even after destruction

44.  These are elastic fibres found in the PL
 Restricted to the walls of the blood vessels.
 They originate from cementun or bone & are embedded into walls
of the blood vessels.
 Function- support blood vessels & regulate vascular flow
 These oxytalan fibers run perpendicular to the collagen fibres .

45.  Represents another form of elastic tissue consisting of
bundles of microfibrils embedded within a small quantity of
elastin.
 They form a network together with oxytalan fibers,
extending from cementum to bone & sheathing the collagen
fibers of PDL.

46.  It is a zone of loose not well oriented collagen fibers in the
center of the periodontal space.
 In this zone the fiber radiating from bone and cementum
intermingle to form lattice network.
 Earlier it was thought that this is zone of rapid remodeling
of fibers and necessary for tooth movement.
 It is presently believed/ concluded that this is just an
artifact arising out of plane of section. In completely
erupted tooth these fibers are no longer exist.

47.  Collagen fibers bundles are anchored in cementum at
one end of PDL space and alveolar bone at other end.
 These fibers do not run in straight line but have a
wavy course.

48. It mainly consists of-
 GAG’s such as hyaluronic acid
 Proteoglycans
 Glycoprotein i.e. fibronectin and tenascin.
 It also consists of water 70%.
They are present between cells & fibers of the PDL.

49. Main blood supply is from superior and inferior
alveolar arteries. The blood vessels are derived
from the following:
1. BRANCHES FROM APICAL VESSELS
Vessels supplying the pulp.
2. BRANCHES FROM INTRA-ALVEOLAR
VESSELS:- Vessels run horizontally and penetrate
the alveolar bone to enter into the periodontal
ligament.

50. 3. BRANCHES FROM GINGIVAL VESSELS:- The
arterioles and capillaries ramify and form a rich
network. Rich vascular plexus is found at the apex and
in cervical part of ligament.

51.  Nerves pass through apical foramen to enter the PL.
 Finer branches enter middle & cervical
portions of the PL through openings in the alveolar
bone
 Nerves supplying the PDL are : Superior Alveolar
Nerve & Inferior Alveolar Nerve
• Branches of trigeminal nerve
 These nerve fibers provide sense of touch, pressure,
pain and proprioception during mastication

52. There are four types of neural terminations in the PDL that
have been described:
 1- Free endings- Sensory, pain perception
 2- Ruffini’s Corpuscles- knob-like, mechanoreceptors
 3- Tactile (meissner’s) corpuscles –mid root,
mechanoreceptors
 4- Spindle type nerve endings -apex

53.  Small calcified bodies
 Remain free or fused into large calcified mass.
 They may be joined with cementum to form
excementoses.
 Degenerated epithelial cells form the nidus for their
calcification.
 Old age

54. 1. PHYSICAL FUNCTION
A) Provision of soft tissue ‘casing” in order to protect
the vessels and nerves from injury due to
mechanical forces.
B) Transmission of occlusal forces to bone.
 Depending on type of force applied, axial force
when applied causes stretching of oblique fibers of
periodontal ligament.

55. C) Attaches the teeth to the bone.
D) Maintains the gingival tissues in their proper
relationship to the teeth.
E) “Shock absorption” resists the impact of occlusal
surfaces.

56.  Two theories have been explained for mechanism
of tooth support.
A. TENSIONAL THEORY
B. VISCOELASTIC THEORY

57. • According to it, principal fibers play a major role
in supporting tooth and transmitting forces to
bone.
• When forces are applied to tooth, principal fibers
unfold and straighten and then transmit the
forces to alveolar bone, causing elastic
deformation of socket.

58. A. Tooth in a resting state
B. The periodontal ligament
fibers are compressed in areas
of pressure and stretched in area
of tension.

59. • According to it, the fluid movement largely controls the
displacement of the tooth, with fibers playing a secondary
role.
• When forces are transmitted to the tooth, the extracellular
fluid is pushed from periodontal ligament into marrow
spaces through the cribriform plate.
• After depletion of tissue fluids, the bundle fibers absorb
the shock and tighten.

60. • Cells of the periodontal ligament have the capacity
to control the synthesis and resorption of
cementum, ligament and alveolar bone.
• Periodontal ligament undergoes constant
remodeling, old cells and fibers are broken down
and replaced by new ones.

61. • Blood vessels of periodontal ligament provide nutrition
to the cells of periodontium, because they contain
various anabolites and other substances, which are
required by cells of ligament.
• Compression of blood vessels (due to heavy forces
applied on tooth) leads to necrosis of cells.
• Blood vessels also remove catabolites.

62. • The nerve bundles found in periodontal ligament,
divide into single myelinated nerve, which later on
lose their myelin sheath and end in one of the four
types of nerve termination:
1. Free endings, carry pain sensations.
2. Ruffini like mechanoreceptors located in the
apical area.
3. Meissener’s corpuscles are also
mechanoreceptors located primarily in mid-root region.
4. Spindle like pressure endings, located mainly in
apex.
 Pain sensation is transmitted by small diameter
nerves, temperature by intermediate type; pressure
by large myelinated fibers.

63. • The resorption and synthesis are controlled procedures.
• If there is a long term damage of periodontal ligament,
which is not repaired, the bone is deposited in the
periodontal space.
• This results in obliteration of space and ankylosis
between bone and the tooth.
• The quality of tissue changes if balance between
synthesis and resorption is disturbed.

64. • If there is deprivation of Vit. C which are essential
for collagen synthesis, resorption of collagen will
continue.
• So there is progressive destruction and loss of
extra cellular substance of ligament.
• This occurs more on bone side of ligament.
• Hence, loss of attachment between bone and tooth
and at last, loss of tooth.

65.  The primary role of periodontal ligament is to support
the tooth in the bony socket.
AGE CHANGES
 The width of periodontal ligament varies from 0.15 to
0.38mm. The average width is:
- 0.21mm at 11 to 16 years of age.
- 0.18mm at 32 to 50 years of age.
- 0.15mm at 51 to 67 years
1. width of periodontal ligament decreases as age
advances
2. Aging results in more number of elastic fibers and
decrease in vascularity, mitotic activity, fibroblasts and in
the number of collagen fibers and mucopolysaccharides.

66. PERIAPICAL LESIONS
 Periapical area of the tooth is the main pathologic site.
Inflammation of the pulp reached to the apical periodontal
ligament and replaces its fiber bundles with granulation
tissue called as granuloma, which then progresses into
apical cyst.

67.  Chronic periodontal disease can lead to infusion of
microorganisms into the blood stream.
 The pressure receptors in ligament have a
protective role. Apical blood vessels are protected
from excessive compression by sensory apparatus of
the teeth.
 The rate of mesial drift of tooth is related to health,
dietary factor and age. It varies from 0.05 to 0.7mm
per year

68. Trauma:
The trauma can be result from number of ways:
 Abnormal occlusal function,Accidental blows.
 Premature contacts from high points in restoration.
 Excessive orthodontic forces.
All of the above leads to pulpal injury result in periapical
changes.
 Over instrumentation during RCT causes profuse periapical
haemorrhage and dissemination of dentin debris beyond the
apical foramina. It result in edematous PDL, intense neutrophil
inflammatory infiltrate.

69. Surface resorption:
When there is very less damage to PDL – Adjacent PDL is
proliferates.
 Inflammatory resorption: When there is infection is there –
inflammation of bone and PDL – which is replaced by
granulation tissue.
 Replacement resorption : When there is severe damage to
PDL, resorption of bone, cementum, PDL it is replaced by the
bone. Results in ankylosis of tooth

70. Orthodontic tooth movement
 Depends on resorbtion and formation of bone and periodontal
ligament (i.e. remodelling).
 when a orthodontic force is applied through PDL to the tooth
there is a initial compression of PDL on pressure side followed
by the bone-resorbtion, whereas in tension side there is bone
apposition.
 Application of large amount of force result in necrosis and
death of PDL

71.  Carranza FA, and Saglie, 1984 :The PDL acts as a shock
absorber & a means of transmitting occlusal forces to bone
 GriffinCJ 1968:Presence of unnmyelinated nerve endings in
the periodontal membrane
 Grant DA, Stern, Listgarten,1988: PDL plays an active role
in the resorption and formation of collagen and cementum
and the fibroblasts of the PDL may develop into
cementoblasts and osteoblasts.
 ButlerWT,Birkedal-hansen,Beegle et al ,1975:studied the
proteins in the periodontium,concluded with the
identification of type I & III collagen.
 Genco R, Goldman, HM., and Cohen, 1990: Periodontal
regeneration is defined as restoration of the periodontal
attachmentapparatus, which includes periodontal
ligament, cementum, and alveolar bone, and gingival

72.  Nyman S, Gottlow J, Karring T, et al. 1982:cells from the
periodontal ligament (PDL) are responsible for the
reestablishment of periodontal attachment.
 A study done on Dogs by Isaka et. al. concluded that dogs
periodontal ligament cells retain capability to differentiate
into osteoblast lineage & may act in periodontal
regeneration of periodontal ligament with new cementum
formation .

73. The diseases of PDL are often irreversible once
destroyed the PDL is difficult to regenerate and
damage of PDL result in loss of tooth. So, all
operative procedures must be performed so as to
maintain and restore the PDL is optimum health and
function.

74. 1) Glossary of Periodontal Terms
2) FerminA, Carranza, Newmann, Takei; clinical periodontology ;9thedition;45–51.
3)R.Tencate,AntonioNanci;oralhistology,development,structure&function;6thediti
on;111–143.
4)FerminA, Carranza, Newmann, Takei; clinical periodontology ;9thedition;45–51.
5)Junqueria LC, Carneiro J, Kelley RO: Basic Histology, ed6, Norwalk, Conn, 1989,
Appleton & Lange.
6) Hagel-Bradway S, Dziak R: Regulation of bone cells metabolism, J Oral Pathol
Med 18:344,1989
7)Sicher H, DuBrul EL: Oral Anatomy, ed6, St Louis, 1975

75. 8)Chambers TJ: The cellular basis of bone
resorption, Clin J Periodontal Res 1:120,
1966.
9)Bernard GW, Ko JS: Osteoclast formation
in vitro form bone marrow, mononuclear
cells in osteoclast-free bone, Am J Anat
161:415, 1981