Periodontal Ligament

1. GOOD
MORNING

2. PERIODONTAL LIGAMENT
A SEMINAR
Presented By- Dr. Sneha Sharan
MDS 1st year
Department of Periodontology
Seema Dental College & Hospital, Rishikesh

3. CONTENTS
1. Introduction
2. Definitions Of PDL
3. Synonyms
4. Structure
5. Average Width
6. Development Of PDL
7. Structural Components Of The PDL
8. Periodontal Fibers
9. Development Of Periodontal Fibers
10.Cellular Elements
11.Functions
12.Blood Supply
13.Nerve Supply
14.Clinical Correlation
15.References

4. Introduction
● Specialized fibrous connective tissue
● Surrounds & attaches roots of teeth to the alveolar bone
● Composed of complex vascular & highly cellular connective tissue
● Continuous with the connective tissue of the gingiva
● Avg. Width - 0.2mm
● Diminished around teeth that are not in function & in unerupted teeth

5. DEFINITIONS OF PDL
➢ Periodontal Ligament is composed of soft complex vascular & highly
cellular connective tissue that surrounds the tooth roots & connects to
the inner wall of the alveolar bone
(Mc Culloch CA, Lekic P, Mc Kee MD Periodontal 2000 24:56, 2000)
➢ It is that soft, specialized CT situated between the cementum covering
the root of the tooth & bone forming the socket wall.
(A.R Tencate 1971)
➢ It is a narrow & highly cellular CT that form is the interface between
alveolar bone & cementum.
( Periodontal 2000, vol. 3, 1993)

6. ➢Soft ,richly vascular & cellular connective tissue which
surrounds the roots of the teeth & joins the root
cementum with the socket wall.
(Jan Lindhe 5th ed)
➢The periodontal ligament occupies the periodontal space,
which is located between the cementum & the
periodontal surface of alveolar bone & extends coronally
to the most apical part of the lamina propria of the
gingiva.
(Orban’s)

7. SYNONYMS
❏ Gomphosis
❏ Desmodent
❏ Pericementum
❏ Dental Periosteum
❏ Alveo-dental ligament
❏ Periodontal membrane

8. Structure
● Hourglass shaped
● Widest cervically
● Dense, fibrous connective tissue
● Bears heavy occlusal stress
● Thickness decreases with age

9. AVERAGE WIDTH
● DEPENDING ON AGE:
AGE AVERAGE WIDTH
11-16yrs 0.21mm
32-52yrs 0.18mm
51-67yrs 0.15mm

10. AVERAGE WIDTH
● According to the functional state of the tissues:
Functional State AVERAGE WIDTH
Time of eruption 0.1-0.5mm
At Function 0.2-0.35mm
Hypo Function 0.1-0.15mm

11. As the root formation continues, cells in the perifollicular
mesenchyme gain their polarity, cellular volume & become
widely separated
Actively synthesize and deposit collagen fibrils &
glycoproteins in developing PDL
Type I Collagen is secreted
Assembles as collagen bundles on the bone and
cementum surface
Establish Continuity across the ligament space
DEVELOPMENT
OFPDL

12. DEVELOPMENT OF PDL
Jan Lindhe, Niklaus P.Lang, Thorkild Karring
Clinical Periodontology & Implant Dentistry 5th Edition

13. Cellular Elements Periodontal Fibers Ground Substance
1. Synthesizing Cells:
Fibroblasts,
Cementoblasts,
Osteoblasts
1. Principal Fibers
Alveolar Crest Fibers ,
horizontal fibers, oblique
fibers, apical fibers,
interradicular fibers
1. Glycosaminoglycans
a. Hyaluronic acid
b. Proteoglycans
2. Resorptive cells: fibroblasts,
cementoblasts, osteoclasts
2. Other Fibers
Oxytalan fibers, elaunin fibers
2. Glycoproteins
a. water
b. fibronectin
c. c. laminin
3. epithelial cell rests of
malassez, progenitor cells,
defense cells, such as mast
cells & macrophages
The structural components

14. Periodontal Fibers
● Most important element of PDL- Principal Fibers
● PRINCIPAL FIBERS: - Collagenous
- arranged in bundles
- follow wavy course (when viewed in LS)

15. Originate at surface of newly formed root dentin in close
relation to highly polarized fibroblasts
Nascent fiber bundles are tightly packed by action of
cementoblasts during initial development of Acellular
extrinsic fiber cementum.
As PDL Matures, fringe fibers merge
across the width of ligament to form
principal fiber bundles
Closely related to root
formation
DEVELOPMENT
OF
PRINCIPAL
FIBERS

16. DEVELOPMENT OF PRINCIPAL
FIBERS

17. DEVELOPMENT OF PRINCIPAL
FIBERS….
❏ Terminal portions of principal fibers that insert into cementum and
bone are termed as Sharpey’s fibers.
❏ The principal fibers embedded in the cementum have a small diameter
but are more numerous than those embedded in the alveolar bone
proper.
❏ In addition to these fiber types, small collagen fibers associated with
larger principal fibers have been called as “Indifferent fiber plexus of
Shefforfold”

18. ❏ Terminal portions of the principal fibers that are inserted into the
cementum & bone are termed as - SHARPEY FIBERS

20. SHARPEY FIBERS
● Calcify to a significant degree
● associated with abundant noncollagenous proteins-typically found in bone

21. ALVEOLAR CREST GROUP
● Extend obliquely from the cementum just beneath the
JE to the alveolar crest
● Prevent extrusion of the tooth and resist lateral tooth
movements.

22. Transseptal Fibers
● Extend interproximally over the alveolar bone crest
● Embedded in cementum of adjacent teeth
● reconstructed even after destruction of alveolar bone
● do not have osseous attachment

23. Horizontal Fibers
● Extend at right angles to the long axis of the tooth from
the cementum to the alveolar bone.
● Prevent Lateral tooth movement

24. Oblique Fibers
● Comprise the largest group in periodontal ligament
● Extend from cementum in a coronal direction obliquely to
the bone
● Bear vertical masticatory stresses
● Transform such stresses into tension on the alveolar bone

25. Apical Fibers
● Radiate in irregular manner from cementum to the bone at
the apical region of the socket
● Do not occur on incompletely formed roots.
● Prevent tipping
● Resist forces of luxation
● Protect blood, lymph & nerve supply

26. Interradicular Fibers
● Fan out form the cementum to the tooth in the furcation
areas of multirooted teeth.
● Resist tipping of tooth.
● Forces of luxation & rotation

27. ● Other well-formed fiber bundles interdigitate at right
angles between regularly arranged fiber bundles.
● Less regularly arranged collagen fibers are found in the
interstitial connective tissue between the principal fiber
groups; this tissue contains the blood vessels, lymphatics
& nerves.

29. ● PDL does not contain mature elastin, 2 immature forms are found: oxytalan &
elaunin
● OXYTALAN FIBERS: - Run parallel to root surface in a vertical direction
- bend to attach to the cementum in the cervical third of
the root
- Regulate vascular flow
● Principal Fibers are remodeled by PDL cells to adapt to physiologic needs &
in response to different stimuli.

30. ELASTIN FIBERS
Restricted to walls of blood vessels in humans
PDL fibers do not contain mature elastin but
two immature forms are found oxytalan and
eulanin.

31. OXYTALAN FIBERS
● Are micro fibrils
● Run in apico-coronal direction to bend and attach at cervical third of root
(Fulmer et al. 1974)
● Diameter – 0.5-2.5mm
● Volume – 3%
● No cross banding seen
● Function - regulate vascular flow - play a role in tooth support - guides cell
migration

32. Oxytalan fibers(stained dark purple) running in the apico occlusal direction. Note
that their course does not correspond with that of the collagen fibers in the
periodontal ligament.

33. ELUANIN FIBERS
● Are immature elastic fibers consisting of micro fibrils within
small quantity of elastin
● An elastic meshwork has been described in the PDL as being
composed of many elastin lamellae with peripheral oxytalan &
eulanin fibers
● Functions - Regulate vascular flow - Role in tooth support -
Facilitate fibroblast attachment and migration

34. RETICULIN FIBERS
● Reticular fibers, reticular fibres or reticulin is a type of fiber in connective tissue
composed of type III collagen secreted by reticular cells. Reticular fibers crosslink
to form a fine meshwork (reticulin). This network acts as a supporting mesh in soft
tissues such as liver, bone marrow, and the tissues and organs of the lymphatic
system.
● Reticular fiber is composed of one or more types of very thin and delicately woven
strands of type III collagen. These strands build a highly ordered cellular network
and provide a supporting network. Many of these types of collagen have been
combined with carbohydrate. Thus, they react with silver stains and with periodic
acid-Schiff reagent but are not demonstrated with ordinary histological stains such
as those using hematoxylin. The 1953 Science article mentioned above concluded
that the reticular and regular collagenous materials contains the same four sugars
– galactose, glucose, mannose, and fucose – but in a much greater concentration
in the reticular than in the collagenous material.

35. RETICULIN FIBERS

36. CELLULAR ELEMNTS

38. FIBROBLASTS
● Most common cells in the PDL
● Appear as ovoid / elongated
cells oriented along the
principal fibers
● Exhibit pseudopodia-like
processes.
● Synthesize collagen
● Regulates collagen turnover

39. SEM IMAGE OF PDL
FIBROBLASTS

40. FIBROBLASTS...
● Most common cells in PDL
● Occupies about 30% of the volume of the periodontal ligament space
in rodents (Beertsen W, Brekelmans M, Everts V. 1978)
● Appear as ovoid or elongated cells oriented along the principal fibers,
exhibiting pseudopodia like processes.
● In cross section, they may exhibit a stellate appearance with
cytoplasmic process segregating individual fiber bundles of collagen
fiber.

41. FIBROBLASTS...
● Phenotypically distinct & functionally different sub populations of
fibroblasts exist in adult PDL.
● They may have different functions like secretion of different collagen
types & production of collagenase.
● Importantly in inflammatory situations, an increased expression of MMP
occurs that aggressively destroys collagen.
● Thus attractive therapies for controlling this may include host
modulators to inhibit MMP.

42. FIBROBLASTS...
● The PDL fibroblasts are large cells with an extensive cytoplasm
containing in abundance, all organelles associated with protein
synthesis and secretion.
● They also have well developed cytoskeleton with a particularly
prominent actin network.
● ATTACHMENTS The fibroblasts of PDL are interconnected by gap
junctions or adherence type of junctions.
● The cells may attach to collagen via a fibro nexus type of attachment
plaque and are likely to have the capacity to orient extracellular matrix.

43. FIBROBLASTS...
● The migratory and contractile activity of fibroblast is because of the
presence of contractile protein actin and myosin in their cytoskeleton.
● It may:
-Remain stationary and pull on adjacent structures
-Crawl and cause the environment in which it lies to wrinkle.

44. FIBROBLASTS...
● Chemoattractants produced locally or by the hard tissues bordering the
ligament may have a role in this process.
● Directed migration of cells is associated with polarity of organelles, the
nucleus usually in the trailing portion of cell and golgi apparatus and
centrioles are towards the leading edge of the cells.
● They appear to be rich in alkaline phosphatase activity an enzyme
along outer plasma membrane that plays a key role in phosphate
metabolism, probably in the mineralization process and in Acellular
cementum formation.

45. Add Text
Add Text
Epithelial Rests Of Malassez
● Form a latticework in the PDL
● Appear as either isolated clusters of cells/interlacing strands
● Considered remnants of the hertwig’s root sheath
● Distributed close to the cementum
● Diminish in no. with age by undergoing calcification
● Surrounded by a distinct lamina
● Participates in formation of periapical cysts & lateral root cysts

47. ● Osteoblasts, Cementoblasts,
osteoclasts & odontoclasts are
also seen in the cemental &
osseous surfaces of the PDL
● Defense Cells in the PDL
include neutrophils,
lymphocytes, macrophages,
mast cells & eosinophils

48. Osteoblasts & Cementoblasts
● Although technically situated within the PDL, bone and
cementum cells are properly associated with the hard
tissues they form.
● Osteoblasts line the bone surface of the ligament and may
be either functional or resting, depending on the functional
state of the ligament.
● Cementoblasts are responsible for formation of cellular
cementum.

50. Resorptive Cells
● Fibroblasts :
- Exhibit lysosomes that contain
fragments of collagen that appear
to be undergoing digestion.
- Dual action
● Osteoclasts & Cementoclasts:
- Osteoclast cells resorb bone and
tend to be large and
multinucleated.
- Cementoclasts resemble
osteoclasts and are occasionally
found in normal functioning PDL.

51. Progenitor Cells
● Cell division ---- daughter cell ---- undifferentiated
progenitor
CHARACTERISTICS
❏ Small cells
❏ Close faced nucleus
❏ Very little cytoplasm
❏ Highest concentrations' close to blood vessels
❏ Burst of mitosis occurs when pressure is applied

52. Defense Cells
❏ Include neutrophils, lymphocytes, macrophages,& eosinophil's.
MAST CELLS
● Small round or oval cell; Diameter 12-15µm.
● Contain numerous cytoplasmic granules(0.5-1 µm) that stain
metachromatically with dyes like azure A and positively by PAS
reaction.
● Contain heparin & histamine.
● Role of heparin is not clear. Histamine plays a role in
inflammatory reaction. Occasionally seen in healthy PDL. It
may cause proliferation of endothelial & mesenchymal cells.

53. Defense Cells

54. Macrophages
CHARACTERISTICS
● Found adjacent to the blood vessels
● Nucleus has a regular contour and may be horse shoe or
kidney shaped with a dense peripheral layer of chromatin.
● Surface may be raised in microvilli.
● Sparse RER with widely spaced polysomes.
● Golgi apparatus is not well developed
● DUAL ROLE
1. Phagocytosing dead cells
2. Secreting growth factors that regulate the proliferation of
adjacent fibroblasts.

55. Cementicles
● Calcified masses, adherent to or detached
from the root surfaces (O.J. Mikola, Wm.H.
Bauer,1949)
● Represent dystrophic calcification (example
of regressive or degenerative change)
● Develop from: calcified epithelial rests,
calcified Sharpey’s fibers, Calcified,
thrombosed vessels within the PDL, around
small spicules of cementum or alveolar
bone traumatically displaced into the PDL

56. Cementicles...
● Too small to be seen on IOPA, seldom being larger than 0.2-
0.3 mm. in diameter.
● No clinical significance.
● Actually a variety of calcified bodies may occur in the PDL, not
all of which have the morphologic characteristics of cementum.
Nevertheless, they have all been commonly known as
cementicles.
● The pattern of calcification often gives the appearance of a
circular lamellated structure.

57. EXTRACELLULAR COMPONENTS
FIBERS GROUND SUBSTANCE
Collagen Proteoglycans
Elastic Glycoproteins
Reticular
Secondary
Indifferent Fiber Plexus
Oxytalan

58. COLLAGEN
● Is derived from the French word collagene to designate
connective tissue constituents that produce glue.
● Collagen molecule is rigid and resists stretching. Therefore it is
utilized in tissues where mechanical forces should be
transmitted without loss.
● Organization of collagen depends upon the specific functional
requirements in various tissues.

59. COLLAGEN...
STRUCTURE
● All collagens are composed of 3 polypeptide chains coiled
around each other to form the typical triple helix configuration.
Variations are brought about by
● Differences in assembly of the basic polypeptide chains
● Different lengths of helix
● Various interruptions in helix
● Differences in the terminations of the helical mains

60. UNIQUE STRUCTURAL PROPERTIES THAT
DISTINGUISH COLLAGEN FROM OTHER
PROTEINS
● Made up of 3 polypeptide chains
● α chains that are left handed chains assembled into a triple helix with a right handed twist.
May be a homo-trimer or hetero-trimer.
● Has a repeating gly-X-Y amino acid sequence in which X and Y are usually amino acid
other than glycine.
● Contain 2 unique amino acid hydroxy proline and hydroxy lysine along with glycine &
proline (Carneiro J, Fava de Moraes F , 1955)
● Collagen molecules are covalently linked through lysine derived intra and inter chain
crosslink.

61. COLLAGEN...
● The amount of collagen in a tissue is determined by its hydroxy
proline content.
● There are at least 19 recognized collagen species encoded by at
least 25 separate genes, dispersed among 12 chromosomes
(Embery et al 2000)
Collagen classes
a. Interstitial collagens ---- Type I,II,III
b. Basement membrane type ---- Type IV,VI,VII
c. Short chain collagens ---- Type IX,X

62. COLLAGEN...
● Type I, III, V, XII – Periodontal Ligament
● Type VI, II – cartilage
● Type IV - Basement membrane
● Type VI – Ligaments, skin, bone
● Type VII - Anchoring fibrils of basement membrane
● Type IX - Cartilage
● Type X, XI - Cartilage, Bone
● Type XIII - Epidermis Cartilage

64. COLLAGEN...
● The ligament fibers and Sharpey’s fibers are composed of
interstitial collagen type III and I
● Collagen V is associated with these fibrils and is either buried
within these fibrils or is found in the spaces between the fiber
bundles.
● Type VI - microfibrillar component associated with oxytalan fiber
system.
● Type XII contribute to the construction of 3-dimensional fibril
arrangement- hence closely associated with regeneration of PDL

65. Formation Of Collagen Fiber
Synthesized by - Fibroblasts, chondroblasts,
osteoblasts, odontoblasts and other cells.
The steps involved in biosynthesis of collagen fiber
involve
- Intra cellular pro collagen synthesis
- Extra cellular collagen biosynthesis & fibril/fiber
formation.

66. GROUND SUBSTANCE
● The ground substance is the gel like matrix
synthesized by the fibroblasts family & fills the space
between the fibers & cells.
COMPOSITION
● Consists of a biochemically complex , highly hydrated
semi solid gel.
● Water content of 70%
● Glycosaminoglycans- hyaluronic acid,
● Proteoglycans(versican,decorin)
● Glycoproteins-fibronectin,laminin,vibronectin,tenascin

67. GROUND SUBSTANCE
● Fills the space between the fibers and cells
● Overlooked possibly because difficult to investigate and not
recognized in routine methods
COMPOSITION
● Consists of a biochemically complex, highly hydrated, semisolid
gel.
● Water content of 70% Glycosaminoglycan's – hyaluronic acid,
proteoglycans( versican , decorin )
● Glycoproteins -- fibronectin , laminin , vibronectin , tenascin

68. PROTEOGLYCANS
● Large group of anionic macromolecules that consists of a
protein core to which are attached hexose amine
containing polysaccharide called gag chains.
● Distribution in PDL is similar to gingival tissue.
FUNCTIONS
a. Cell adhesion
b. Cell-cell & cell- matrix adhesion
c. Cell repair
d. Binding to various growth factors

69. GLYCOPROTEINS
● The primary function of these molecules is to bind cells to
extracellular elements.
● Most widely studied is FIBRONECTIN
● Exists in one form as an insoluble connective tissue matrix protein
which promotes the attachment and subsequent spreading of cells
that bind to a fibronectin – collagen complex.
● The attachment and spreading of cells within the PDL collagen
matrix is a pre requisite for both alignment of collagen fibers and for
cell migration.

70. GLYCOPROTEINS...
● TENASCIN is an adhesive glycoprotein synthesized at specific
times and location during embryogenesis.
● In adult its distribution is specific and restricted.
● It binds to fibronectin and to proteoglycans.
● It blocks the binding capacity of syndecan and thereby enables the
cell to move freely

71. ➢PHYSICAL FUNCTIONS
➢FORMATIVE & REMODELING FUNCTION
➢NUTRITIONAL & SENSORY FUNCTIONS
➢REGULATION OF PERIODONTAL LIGAMENT WIDTH
FUNCTIONS OF PDL

72. PHYSICAL FUNCTIONS
● Provision of a soft-tissue “casing” to protect the vessels & nerves from injury by
mechanical forces.
● Transmission of occlusal forces to the bone
● Attachment of the teeth to the bone
● Maintenance of the gingival tissues in their proper relationship to the teeth
● Resistance to the impact of occlusal forces (i.e, shock absorption)

73. RESISTANCE TO IMPACT OF OCCLUSAL FORCES ( Shock Absorption):
Two theories pertaining to the mechanism of tooth support have been
considered:
1) TENSIONAL THEORY
❖ States that the principal fibers of the PDL are the major factors in supporting the tooth &
transmitting forces to the bone
❖ When a force is applied to the crown,the principal fibers first unfold & straighten, & then they
transmit forces to the alveolar bone, thereby causing an elastic deformation of the bony socket.
❖ Finally, when the alveolar bone has reached its limit, the load is transmitted to the basal bone.

74. 2) VISCOELASTIC THEORY
❖ States that the displacement of the tooth is largely controlled by fluid movements,
with fibers having only a secondary role. (Bien SM,1996 & Bim H, 1966)
Force applied on tooth
Extra-cellular fluid from PDL escapes to marrow spaces
Depletion of fluid, Fibers absorb slack & tigthen
Blood vessels stenosis
Arterial back pressure created
Balloning of vessels
Passage of blood ultra filtrates
Lost fluid replenished

76. TRANSMISSION OF OCCLUSAL FORCES TO BONE
❏ Arrangement is like suspension bridge/Hammock
❏ The oblique fibers alter their wavy pattern & sustain the
major part of the axial force
AXIS OF ROTATION:
● Single rooted tooth at junction of middle & apical 3rd of
the root.
● Multirooted tooth in the bone between the roots below
furcation

78. ❏The apical portion of the root moves in a
direction opposite to the coronal portion
❏Areas of tension- Principal fibre bundles are
taut rather than wavy
❏Areas of pressure- Fibres are compressed,
the tooth is displaced & a corresponding
distortion of bone exists in a direction o
tooth movement.(Picton DC, 1967)

79. Formative & Remodelling Function
● Occur during physiologic tooth movement, during the accomodation of the
periodontium to occlusal forces, & during the repair of injuries.
● Variations in cellular enzyme activity are correlated with the remodelling process.
● PDL is constantly undergoing remodeling.
● Old cells & fibres are broken down & replaced by new ones.
● Rate of formation & differentiation of the fibroblasts affects the rate of formation of
collagen, cementum & bone.
● Rate of collagen synthesis is twice as fast as that in the gingiva & four times as fast
as that in the skin.

80. NUTRITIONAL
❏ Supplies nutrients to cementum, bone & gingiva by way of the blood vessels
❏ Provides lymphatic drainage
❏ PDL is highly vascularized tissue
❏ Rich network of arcades are more evident in the PDL space adjacent to the
bone and cementum.

81. SENSORY
❏ PDL provides the most efficient proproceptive mechanism.
❏ 4 types of neural transmissions are seen
1) Free nerve endings-pain
1) Ruffini like mechanoreceptors(apical area)
1) Meissner's Corpuscles- mechanoreceptors (middle 3rd)
1) Spindle like pressure & vibration endings (apex)

82. REGULATION OF PDL WIDTH
❏ Adaptability to rapidly changing applied force
❏ Capacity to maintain its width at constant dimensions
throughout its lifetime.
❏ Ability of PDL cells to synthesize & secrete a wide
range of regulatory molecules is an essential
component of tissue remodeling & PDL homeostasis.

83. BLOOD SUPPLY
● Branches of the intraseptal
vessels-perforate the lamina
dura & enter the ligament.
● After entering the PDL
perforating rami anastomose
& form a polyhedral network
which surrounds the root like
a stocking

84. ● Inferior & superior alveolar arteries
to the mandible & maxilla reaches
the PDL from 3 source:
1)Apical vessels (Dental Artery)
2)Transalveolar vessels( rami
perforates - penetrating vessels
from alveolar bone)
3)Intraseptal vessels
(anastomosing vessels from the
gingiva)

85. NERVE SUPPLY
● The nerve follow almost the same course as
the blood vessels.
● Nerve bundle divide
- myelinated fibers
- lose their myelin sheath - end in one of the 4
types of neural termination

86. 1. Free nerve endings
- terminal arborization of thick/fine myelinated fibers
-0,21 um in diameter
- fine, nonmyelinated fibers only type of ending in
tooth
pulp - classic model of pure nociception.
1. Ruffini- like - apical area
1. Meissner’s corpuscles- mid-root, for tactile perception
1. Spindle shaped(Krause type end bulbs)- temperature
receptor, present at apex of the tooth

87. ● Development of a new technique in which the axons can be
radioactively labeled & visualized by radioautography
● The PDL has double innervation:
➢Axons arising both from the mesencephalic nucleus
- Unconscious reflex pathways & proprioceptors- position
control of the mandible
➢Axons from the trigeminal ganglion
- Conscious sensation of touch, pain & temperature

88. CLINICAL CORRELATION
❏ Trauma to the ligament due to mechanical separation can produce
pathological changes such as fracture or resorption of the
cementum, tears of fiber bundles, hemorrhage and necrosis.
❏ This result in resorption of bone and periodontal ligament is
widened, so the teeth become loose.
❏ Orthodontic tooth movement depends on resorption and
formation of both bone and periodontal ligament- ->stimulated by
both tension and pressure Application of large forces->necrosis of
periodontal ligament(28)

89. CLINICAL CORRELATION
❏ In SCLERODERMA, the periodontal ligament is uniformly widened
at the expense of surrounding alveolar bone.
❏ Malignancy, both primary and metastatic, can affect the alveolar
ridge and often presents as periodontal disease.
❏ A uniform widening of the periodontal ligament can be an early
sign of osteosarcoma. Irregular destruction of the periodontal bone
without tooth displacement is frequently the result of squamous cell
carcinoma or metastatic carcinoma.

90. PDL Relationship With Implants
● Implants do not employ a gomphosis to provide support & attachments to the jaw
bones as does the PDL, but still it serves as a replacement for natural teeth
.
● The absence of PDL around implants- absence of resilient connection between
teeth & jaw bones thus any occlusal disharmony will have repercussions at bone
to implant interface.
● No intrusion or migration can compensate for the eventful presence of a
premature contact.
● Absence of PDL leads to: reduced tactile sensitivity reduced reflex functions
● Even if certain degree of perception is present- Osseoperception

92. PDL WITH IMPLANTS
Periodontitis is the inflammation of hard and soft tissues of periodontal
structures; if left untreated may lead to the tooth loss. Replacement of the
missing tooth with an implant has gained immense popularity in the last few
decades. Currently, development of a periodontal ligament (PDL) attachment
around dental implants has now become an important new therapeutic tool to
replace lost teeth. PDL houses various vital cells that are all important in the
dynamic relationship between the tooth and the bone. Thus, ligaplants are now
an available option to improve the biological performance and to prolong the life
of the prosthesis.

93. CONCLUSION
● The periodontal ligament is a fibrous connective tissue forming
important part of periodontium.
● The PDL is a physically small, but functionally important tissue in
tooth support,proprioception, & regulation of alveolar bone volume.
● The PDL is an absolute requirement for rapid remodelling of
alveolar bone when forces are applied to the teeth.
● Cell of the periodontal ligament are pluripotent & helps in the
regeneration of all the components of the Periodontium lost in the
periodontal disease process.

94. REFERENCES
● Carranza’s Clinical Periodontology, 10th Edition
● Clinical Periodontology and Implantology by Jan Lindhe,
5th edition
● Oral Histology and Embryology by Orban, 11th edition
● Tencate oral histology, 5th edition
● Fundamentals of Periodontics, 2nd Edition, by Thomas G.
Wilson, Kennath S. Kornman
● Hassel TM. Tissues and cells of periodontium.
● Periodontol 2000, Vol. 3, 1993, 9-38. The Periodontium -
Hubert E Schroeder